Metallurgical and Materials Engineering

This book is dedicated to our parents and to all people close to us who supported us so far and keep on supporting us every day. 'Tis the custom of pedagogues to be eternally thundering in their pupil's ears, as they were pouring into a funnel, whilst the business of the pupil is only to repeat what the others have said: now I would have a tutor to correct this error, and, that at the very first, he should according to the capacity he has to deal with, put it to the test, permitting his pupil himself to taste things, and of himself to discern and choose them, sometimes opening the way to him, and sometimes leaving him to open it for himself; that is, I would not have him alone to invent and speak, but that he should also hear his pupil speak in turn. Socrates, and since him Arcesilaus, made first their scholars speak, and then they spoke to them. 1. WHAT ARE STAINLESS STEELS? Stainless steel is an iron-based alloy with a significant chromium content; in many cases, together with chromium, other special chemical elements are intentionally added, such as nickel and molybdenum. The main characteristics of this family of steels is resistance to wet corrosion, or electrochemical corrosion, in aggressive environments such as fresh water, sea water, contaminated water based solutions, acidic and basic environments, industrial environments, etc. Another important characteristic of this category of steel is the resistance to high temperature oxidation as typically occurs in hot gases. The typical fields of application for stainless steel are in the chemical industry, oil industry, foodstuff and paper manufacturing, the pharmaceutical, biomedical and transport sectors, in offshore structures, household appliances, and the construction and urban furnishing sectors. In accordance with the European standard EN 10088, steel is classed as stainless when its chemical composition has a minimum chromium content of 10.5%. However, it should be noted that all grades of stainless steel available on market, show a chromium content greater than this value, normally ranging from 13% to 18%; in practice, a chromium content of at least 12% is needed to obtain satisfactory resistance to corrosion in water based solutions. Chromium ensures the possibility of creating a very thin layer of oxide (also known as passive film) on steel surface, mainly made up of chromium oxides and hydroxides Cr 2 O 3 and Cr(OH) 3 : this film is insoluble, compact and adheres well to the substrate thereby protecting the base material. The passive film does not only comprise chromium oxides and hydroxides: tests performed using XPS 1 techniques have also revealed iron and molybdenum (in form of oxides and hydroxides) and have shown how nickel tends to accumulate in the interface between passive film and steel substrate (figure 1). The film of chromium oxide/hydroxide is extremely thin-just a few nanometres-and transparent to luminous radiation, and therefore gives stainless steel its typical grey-silver metal finish, as clearly seen in cooking utensils, pans, cutlery and metal watch straps. All the above properties are consequence of rapid reaction of chromium with oxygen. Oxidation of stainless steel, also known as passivation, occurs naturally and spontaneously in neutral oxidating environments, such as in contact with air. Otherwise, as normally occurs in industrial processes, it is induced by immersion of the semi-finished product in diluted nitric acid solution. The chromium oxide/hydroxide film acts as a sealant and creates a barrier between material and external environment. In a certain sense the term "stainless" is not appropriate; steel is, in fact, highly "oxidizable" and as it is in a stable oxide/hydroxide state, it is also highly resistant to corrosion from surrounding environment.

This research was funded by, and implemented within, a UK national research organisation, while the author was the KE and Impact Evaluation Manager responsible for assessing impact on a £15m UK government-funded research programme.

This work was also submitted as the authors MBA dissertation which was accepted and awarded in 2009.

ABSTRACT: A methodology and methods ‘toolbox’ is proposed for conducting impact research and assessment from within research programmes. The emphasis is upon how to clarify and assess the wider impacts from the early stages onwards.

The approach explicitly acknowledges, and attempts to address, the known issues and challenges of impact assessment while drawing upon the resources and opportunities available to research managers and researchers within such programmes.

The study has two triangulating foundations. Firstly, it examines the academic literature to help identify and design the pilot methodology and methods. Secondly it trials these in a real programme to both test and improve them.

The study was conducted over one year within one leading UK research organisation, where two research programmes (and around 60 research projects of £15m total value) were being assessed for their impacts. The study draws upon actual impact management experience and reflection, prospective (ex ante) and retrospective (ex post) assessments, participatory contributions from leading researchers undergoing assessment, and consultation with external users. The findings of this study outline the pilot and its first iteration. Recommendations are made for improvement to the methodology and methods.

A subsequent follow-on bid to UK government incorporating the impacts identified from implementing this methodology, successfully led to a further £15m of government funding.

It is expected the pilot methodology and methods will be applicable to other organisations, conducting and funding such research programmes, required to research and assess the wider research impacts.

Although primary focus of implemetation trials was upon research in physical sciences, technology, high-tech engineering, computing/IT, and environment, the wider literature study, the methodology design and justification, the methods proposed and used, and the resulting general recommendations and lessons are expected to apply more broadly to many other research areas, where the impact is to be found more widely in the society, economy, government or public sector or within organizations, policies, professions or the public.

Interest in this work is expected from research programme managers, impact managers and assessors, management consultants advising in this area, and government funding managers, all seeking to embed a developing approach to understand, capture, and enhance wider impact.

Paper ini merupakan sebuah pengantar untuk mempelajari berbagai macam proses-proses pengolahan material di bidang metalurgi. Mulai dari pemrosesan mineral, pengerjaan logam, pengujian material, dan perlindungan korosi. Sangat cocok untuk mahasiswa baru maupun orang awam yang ingin mempelajari ilmu metalurgi.

The paper provides an overview of tribological properties of nanocomposites with aluminium matrix. Nanocomposites represent a new generation of composite materials with better properties than conventional composite materials. The paper presents and explains the most common methods of nanocomposites production. In addition, the overview of tribological properties is presented through the equipment used for testing; amount, size and type of reinforcement; matrix material and manufacturing process; and test conditions.

This paper analyses wear behaviour of Al-Si alloy A356 (AlSi7Mg) based composite reinforced with 10 wt. % SiC, and compare it with the base A356 alloy. Composite are obtained using the compocasting procedure. Tribological testing have been conducted on a block-on-disc tribometer with three varying loads (10, 20 and 30 N) and three sliding speeds (0.25, 0.5 and 1 m/s), under dry sliding conditions. Sliding distance of 300 m was constant. The goal of the paper was to optimize the influencing parameters in order to minimize specific wear rate using the Taguchi method. The analysis showed that the sliding speed has the greatest influence on specific wear rate (39.5 %), followed by the load (23.6 %), and the interaction between sliding speed and load (19.4 %). A regression analysis and experiment corroboration was conducted in order to verify the results of the optimization. Specific wear rate prediction was done using artificial neural network (ANN).

The metal 3-D printing market is currently dominated by high-end applications, which make it inaccessible for small and medium enterprises, fab labs, and individual makers who are interested in the ability to prototype and additively manufacture final products in metal. Recent progress led to low-cost open-source metal 3-D printers using a gas metal arc welding (GMAW)-based print head. This reduced the cost of metal 3-D printers into the range of desktop prosumer polymer 3-D printers. Consequent research established good material properties of metal 3-D printed parts with readily-available weld filler wire, reusable substrates, thermal and stress properties, toolpath planning, bead-width control, mechanical properties, and support for overhangs. These previous works showed that GMAW-based metal 3-D printing has a good adhesion between layers and is not porous inside the printed parts, but they did not proceed far enough to demonstrate applications. In this study, the utility of the GMAW approach to 3-D printing is investigated using a low-cost open-source metal 3-D printer and a converted Computer Numerical Control router machine to make useful parts over a range of applications including: fixing an existing part by adding a 3-D metal feature, creating a product using the substrate as part of the component, 3-D printing in high resolution of useful objects, near net objects, and making an integrated product using a combination of steel and polymer 3-D printing. The results show that GMAW-based 3-D printing is capable of distributed manufacturing of useful products for a wide variety of applications for sustainable development.

PREFAZIONE "Metallurgia degli Acciai": l'opera per continuare a raccontare i nostri materiali e la nostra storia... perchè, da sempre, noi ci crediamo! Crediamo in quello che facciamo, con professionalità, impegno e dedizione. Crediamo nella cultura. Nella cultura di settore e nella cultura del sapere, rivolgendoci a chi, questo mestiere, lo vive con intensità e passione, o, a chi, più semplicemente è solo agli inizi. Crediamo che il nostro lavoro, a cui dedichiamo tutta una vita, non debba essere solo quotidianità, ma desiderio di continuità. Crediamo nella collaborazione tra le persone e nel valore dei progetti che nascono dalle collaborazioni. Crediamo che il futuro del nostro settore dipenda, alla fine, solo da noi. Ringrazio gli autori, grandi professionisti ma soprattutto grandi persone, e ringrazio tutti coloro che hanno reso possibile questa iniziativa. Giorgio Buzzi, Esine-BS-15 Aprile 2017 Credo di non far torto a nessuno dicendo che la prefazione di un libro viene normalmente scritta per ultima, nonostante il termine indichi esattamente il contrario. Nella prefazione di solito gli autori espongono i motivi per cui hanno deciso di scrivere quel libro, quale ne è l'utilità e per quali lettori è pensato e realizzato. Io, che di mestiere faccio l'insegnante (bello sarebbe poter dire il "maestro"... ma quello non è un mestiere), scrivo e insegno sempre con una tara mentale in testa: riuscirò a far capire quello che voglio dire o no? Proprio con questa idea mi accingo a consegnare alle stampe il volume che avete in mano. Volevo scrivere un libro semplice-ma non semplicistico-che spiegasse le basi della metallurgia degli acciai con un linguaggio comprensibile a tutti. Spesso, infatti, quando leggo dei testi tecnico-scientifici di questa disciplina (ma anche di altre) ho la spiacevole sensazione che l'autore stia parlando solo agli addetti ai lavori, ai cosiddetti "iniziati", a chi la metallurgia la sa già. Ecco, questo è proprio quello che non volevo fare. Io ho pensato ad un approccio "dal basso" dei problemi, qualcosa che potesse essere utile per i miei studenti e per tutti coloro che già lavorano nel settore metallurgico. Per i primi il desidero è quello di stuzzicare l'interesse per una materia non ancora conosciuta, per i secondi di colmare qualche lacuna teorica che permetta di spiegare la pratica quotidiana. Se si vuole scrivere bene, si deve avere un approccio altruistico; fare un libro è un atto d'amore per il lettore. Il bravo scrittore, come il bravo insegnante, non è quello che fa la somma di tutte le conoscenze possibili attorno ad un dato argomento o quello che sa trasmettere efficacemente tante informazioni. È invece quello che seduce, suggestiona, stimola. È colui che per trasmettere un sapere vero, genera in chi legge una specie di vuoto che, da quel momento in avanti, dovrà essere colmato. O, come ben osserva Massimo Recalcati, "I veri insegnanti non sono quelli che ci hanno riempito la testa con un sapere già costituito, dunque già morto, ma quelli che vi hanno fatto dei buchi al fine di animare un nuovo desiderio di sapere. Sono quelli che hanno fatto nascere domande senza offrire risposte precostituite. 1 " Chissà se sono riuscito in tutto ciò: solo i lettori potranno dirlo.

The common failures mechanisms of boiler components at elevated temperatures and monitoring techniques used in power plants to detect damaging or failures are generally well described in literature. Despite of different classification concerning the principal failure mechanisms of boiler thermal power plant components, it is necessary to emphasize that essential difference between these classification does not exist. Concerning the different failures mechanisms it is obvious that the most of them are completely explained and clear in physical sense of process but some of them are not still so explicit. Therefore, until today there is a great interest to investigate the failures of power plant boiler components especially having in mind the all peculiarities of particular events. This efforts are necessary while a full assessment of the failure mechanism(s) is required to prevent further failures due to the same causes. The numerous case studies presented in this paper were done as a contribution to this efforts.

Hydrogen evolution and permeation occur during electroplating, corrosion, and cathodic protection. Hydrogen accumulates in areas of high stress and may reach a critical concentration, potentially causing fractures and catastrophic damage. This chapter describes hydrogen permeation and hydrogen-induced damage in metals and alloys. It also discusses hydrogen evolution kinetics, theoretical diffusion solutions, and basic hydrogen permeation models. Models are used as a diagnostic tool to determine the effectiveness of various metals and alloys as hydrogen permeation inhibitors. It then explains experimental atomic hydrogen permeation transient determination and hydrogen absorption rate constants and diffusivity evaluation into metals using case studies. Hydrogen embrittlement, hydrogen-induced cracking, hydrogen blistering, and hydrogen stress cracking are also discussed to show the relationship to hydrogen permeation and hydrogen-induced cracking mechanisms. Finally, various techniques used to prevent and control hydrogen damage of metals and alloys are described.

Low­cost gas metal arc welding (GMAW)­based 3­D printing has proven effective at additive manufacturing steel and aluminum parts. Early success, however, was based on hand­writing G­code, which is inadequate for the majority of potential users. To enable automated slicing a 3­D model and generating G­code for an acceptable path for GMAW 3­D printing, this paper reports on upgrading of the free and open source CuraEngine. The new slicer, MOSTMetalCura, provides the following novel abilities necessary for GMAW 3­D printing: i) change the perimeter metric from width to track count, ii) avoid movement that overlaps previous weld beads, iii) have infill start immediately after the perimeter finished and in the direction that eliminates translations, iv) add a variable pause between layers to allow for substrate cooling, v) configure GPIO pins to turn on/off the welder, and vi) set optimized wire feed speed and voltage of the welder based on printing speed, layer height, filament diameter, and tool track width. The process for initiating these changes are detailed and the new slicer is used to help improve the function of the printer for ER70S­6 steel. To find the printing function with the smallest bead width based on volume of material, the line width, layer height, and printing speed are varied to provide wire feed speed calculated by MOSTMetalCura, then the settings are used to print 3­D models. The results of 3­D printing three case study objects of increasing geometric complexity using the process methodology improvements presented, which show resolution of 1mm bead widths.

Investigation of tribological behaviour of the hybrid composite, whose substrate is Al/Si alloy A356, reinforced with 10 wt. (%) of silicon carbide (SiC) and 0 and 5 wt. (%) of graphite (Gr) is presented in this paper by application of the Taguchi method. The composites are obtained by the compocasting procedure. The tribological investigations were realised on the tribometer with the block-on-disc contact pair in lubricating conditions and for the two values of the sliding speed, 0.25 and 1 m/s, two values of load 40 and 120 N and two values of the sliding path, 1200 and 2400 m. The wear traces were measured within the experiment, namely the wear intensities were calculated and results analysis was performed by application of the ANOVA technique. The strongest influence on the wear intensity was exhibited by the normal load (39.05%), then follow wt. (%) of the reinforcer (26.84%), the sliding speed (20.93%) and the sliding path (10.72%). The smallest wear appears in hybrid composite Al/SiC/Gr with 5 wt. (%) of the graphite reinforces, at the lowest load of 40 N, sliding speed of 1 m/s and along the sliding path of 2400 m. The main aim of their study is to provide new information and knowledge about the tribological behaviour of hybrid composites with a base of Al-Si alloy A356 reinforced with 10 wt. (%) SiC and with the addition of 0 and 5 wt.% Gr under lubricated sliding conditions.

Excavations of the Phoenician and Punic layers at the site of Bir Massouda in Carthage have provided evidence for ferrous metallurgical activity spanning several centuries. Archaeometallurgical analyses of slagged tuy eres, slag, and alloys using optical microscopy, portable X-ray fluorescence spectroscopy (pXRF), and variable pressure scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (VPSEM-EDS) show that Carthaginian smiths were conducting primary smithing and forging of wrought iron and steel. Although the majority of slag specimens are remnant from ferrous production, a few select finds are from bronze recycling. The corpus represents the earliest known ferrous metallurgy in North Africa. As a Phoenician colony then later as an independent imperial metropolis, Carthage specialized in centrally organized ferrous technology at the fringes of the settlement in areas such as Bir Massouda and the Byrsa Hill from before 700 to 146 BC.

http://www.sciencedirect.com/science/article/pii/S0305440316300036
dx.doi.org/10.1016/j.jas.2016.04.002

"Generally, in steel processing systems, steels are heated via induction or combustion furnaces. Natural gas fired furnaces have installation costs advantage
while the induction furnaces have the advantages of less scale formation on the surface of the workpiece as well as less environmental pollutions. The
operation cost of both systems is a vital argument to be solved. In this paper, a natural gas fired and induction heating furnaces of a forging process were
studied. Thermodynamic analysis was performed for the furnaces which heat the steel workpiece up to 1,300 °C. The energy performances of both
systems were analyzed and compared. It is concluded that, instead of a natural gas fired or an induction furnace, a hybrid furnace may save more energy
and cost."

Hydrogen embrittlement is a common, dangerous, and poorly understood cause of failure in many metal alloys. In practice, it
is observed that different types of damage to industrial components have been tied to the presence and localization of hydrogen in metals. Many efforts have been made at understanding the effects of hydrogen on materials, resulting in an abundance of theoretical models and papers. However, a fully developed and practically-applicable predictive physical model still does not exist industrially for predicting and preventing hydrogen embrittlement. The connection of microstructure-based behaviors of materials and effects on the macroscopic measurable characteristics (stress levels, hardness, strength, and impact toughness) is of the utmost importance to achieve a unified model for hydrogen embrittlement. This paper gives an overview of the application of a model for structural integrity analysis of boiler tubes made of
plain carbon steel exposed during operation to a local corrosion process and multiple hydrogen assisted degradation processes: hydrogen embrittlement and high-temperature hydrogen attack. The model is based on the correlation of mechanical properties to scanning electron microscopy fractography analysis of fracture surfaces in the presence of simultaneously active hydrogen embrittlement micromechanisms. The proposed model is practical for use as a predictive maintenance in power plants, as it is based on the use of standard macro-mechanical tests.

The Tektaş Burnu ship (440–425 BC) sank along a rough and desolate stretch of the Turkish Aegean coast. Archaeological excavation of the shipwreck site by the Institute of Nautical Archaeology at Texas A&M University resulted in the retrieval of hundreds of small fragments from the ship's wooden hull and its metal fasteners. Recent study of this artefact assemblage suggests that the coastal trader was built with pine planks and made-frames, and assembled by a shell-based construction method. Fasteners include pegged mortise-and-tenon joints and double-clenched copper nails, and the ship may have had laced extremities consistent with other contemporaneous shipwrecks.

Welding is a widely used process in industry because welding techniques have some striking features which are included in this project. In other way of saying, welding techniques will be so important in human life in the future because of their unique specialties. For this reason, researches and studies on welding are increasing day by day.
Welding is used in different areas in industry and it has various features. Welding is especially used in the manifacturing area, as a connector between materials in the existence of heat and pressure (with or without additional materials). The main targets in this process are; lowest cost, highest satisfaction in performance and longest life.
In this project, the importance of choosing a suitable production regarding to the intended features and how to improve the mechanical features, tried to be explained. Therefore, the welding process which is going to be applied to the materials which has different metal content, are virtually modelled by using Ansys Workbench software.
Parameters as, used materials and chosen welding techniques within this project are widely explained.  Experimental studies were done in order to help the project to enlighten the future studies and to make the project based on numerical data (simplifies prooving). In the other parts of the experimental studies, welding process is applied to the materials which have different metal contents by using Ansys Workbench software. Modelling a material using different welding techniques before production gives  more practical and more proactive vision.

Many efforts have been made to understand the effects of hydrogen on steels, resulting in an abundance of theoretical models and papers. However, a fully developed and practically applicable predictive physical model still does not exist industrially for predicting and preventing hydrogen damage. In practice, it is observed that different types of damages to industrial boiler components have been associated with the presence and localization of hydrogen in metals. In this paper, a damaged boiler tube made of grade 20 – St.20 (or 20G, equivalent to AISI 1020) was investigated. The experimental research was conducted in two distinctive phases: failure analysis of the boiler evaporator tube sample and subsequent postmortem analysis of the viable hydrogen embrittlement mechanisms (HE) in St.20 steel. Numerous tested samples were cut out from the boiler tubes of fossil fuel power plant, damaged due to high temperature hydrogen attack (HTHA) during service, as a result of the development of hydrogen-induced corrosion process. Samples were prepared for the chemical composition analysis, tube wall thickness measurement, tensile testing, hardness measurement, impact strength testing (on in-strumented Charpy machine), analysis of the chemical composition of corrosion products – deposit and the microstructural characterization by optical and scanning electron microscopy – SEM/EDX. The HTHA damage mechanism is a primary cause of boiler tube fracture. Based on the multi-scale special model, applied in subsequent postmortem investigations, the results indicate a simultaneous action of the hydrogen-enhanced decohesion (HEDE) and hydrogen-enhanced localized plasticity (HELP) mechanisms of HE, depending on the local concentration of hydrogen in investigated steel. The model is based on the correlation of mechanical properties to the SEM fractography analysis of fracture surfaces.

The experiment investigates the separation of materials of different densities on a shaking table. The variables that affect the efficiency of separation are the material feed rate, water flow rate, slope of the deck and the frequency of the vibration of the table. However, in this investigation, the feed rate is kept constant at 22.17 g/minute, the water flow rate at 0.21 litres/second and the slope of the deck at 19 • . For simplicity, the frequency is the only variable of the experiment.

The paper presents tribological behaviour of hybrid aluminium composite A356/10SiC/3Gr in dry-sliding conditions. Hybrid
composites were made with a modified compocasting procedure and tribological tests were conducted on a tribometer with a
block-on-disc contact geometry. An analysis of the effects of three sliding speeds ((0.25, 0.5 and 1) m/s) and two normal loads (10 N and 20 N) on the wear volume and wear rate was conducted for different sliding distances. The total sliding distance was
300 m. SEM and an EDS analysis of the wear surfaces of the tested material were also performed. The analysis of the wear
surfaces shows an intensive adhesive wear of hybrid composites. Also, the appearance of mechanically mixed layers (MMLs) was confirmed, i.e., an increase in the concentration of iron in the hybrid composite material.

Many efforts have been made to understand the effects of hydrogen on steels, resulting in an abundance of theoretical models and papers. However, a fully developed and practically applicable predictive physical model still does not exist industrially for predicting and preventing hydrogen damage. In practice, it is observed that different types of damages to industrial boiler components have been associated with the presence and localization of hydrogen in metals. In this paper, a damaged boiler tube made of grade 20 – St.20 (or 20G, equivalent to AISI 1020) was investigated. The experimental research was conducted in two distinctive phases: failure analysis of the boiler evaporator tube sample and subsequent postmortem analysis of the viable hydrogen embrittlement mechanisms (HE) in St.20 steel. Numerous tested samples were cut out from the boiler tubes of fossil fuel power plant, damaged due to high temperature hydrogen attack (HTHA) during service, as a result of the development of hydrogen-induced corrosion process. Samples were prepared for the chemical composition analysis, tube wall thickness measurement, tensile testing, hardness measurement, impact strength testing (on in-strumented Charpy machine), analysis of the chemical composition of corrosion products – deposit and the microstructural characterization by optical and scanning electron microscopy – SEM/EDX. The HTHA damage mechanism is a primary cause of boiler tube fracture. Based on the multi-scale special model, applied in subsequent postmortem investigations, the results indicate a simultaneous action of the hydrogen-enhanced decohesion (HEDE) and hydrogen-enhanced localized plasticity (HELP) mechanisms of HE, depending on the local concentration of hydrogen in investigated steel. The model is based on the correlation of mechanical properties to the SEM fractography analysis of fracture surfaces.

Corrosion is irreversible process of material degradation. Due to detrimental effects exerted on the operating material characteristics, especially in the boiler tube system, it is of one the most important issues in the operation of thermal plants and is considered to be the root cause of many outages. Besides common remaining life assessment methods, it is useful to apply a method of reliability evaluation of the thermal power plant boiler tubes with corrosion damages. Correlation of results obtained by these two methods makes possible to obtain a better knowledge of current tubes material states as well as a more accurate assessment of their behavior during future exploitation. Therefore, an integrated approach of remaining life assessment and reliability evaluation, on the first stage reheater tubes system example, is presented in this paper. Considerations of this kind are very important for the risk-based maintenance programs.

High-entropy alloys (HEAs) have recently become a vibrant field of study in the metallic materials area. In the early years, the design of HEAs was more of an exploratory nature. The selection of compositions was somewhat arbitrary, and there was typically no specific goal to be achieved in the design. Very recently, however, the development of HEAs has gradually entered a different stage. Unlike the early alloys, HEAs developed nowadays are usually designed to meet clear goals, and have carefully chosen components, deliberately introduced multiple phases, and tailored microstructures. These alloys are referred to as advanced HEAs. In this paper, the progress in advanced HEAs is briefly reviewed. The design strategies for these materials are examined and are classified into three categories. Representative works in each category are presented. Finally, important issues and future directions in the development of advanced HEAs are pointed out and discussed.

Limited material options, prohibitively expensive equipment, and high production costs currently limit the ability of small and medium enterprises to use 3D printing to prototype and manufacture metallic goods. A low-cost open-source 3D metal printer that utilizes gas metal arc welding technology has been developed that could make metal printing accessible to the average consumer. Unfortunately, this technology would demand access to expensive cutting tools for part removal from the substrate. This article investigates several substrate treatments to provide a low-cost method to easily remove 3D-printed 1100 aluminum parts from a reusable substrate. Coatings of aluminum oxide and boron nitride on 1100 aluminum and A36 low-carbon steel substrates were tested. Lap shear tests were performed to assess the interlayer adhesion between the printed metal part and the print substrate. No warping of the substrate was observed during printing. It was determined that boron nitride-coated low-carbon steel provided the lowest adhesion strength. Printing aluminum on uncoated low-carbon steel also allowed easy removal of the aluminum part with the benefit of no additional coating steps or costs.

Reliability centered maintenance (RCM) has a key role in the quality system of thermal power plants. Electricity production is definitely not only production of a product, but also becomes a customer service. Reliability is the top quality tier of this service. Incorporation in the Integrated energy system means fast transformations of organization on all levels. The reliability of modern generation components basically influences the efficiency and capacity of a power plant as a whole. This paper presents the results of RCM practice on Unit Two of The Thermal Power Plant ″Nikola Tesla -B″, 2x600 MW, Yugoslavia. RCM implementation on current problems during exploitation emphasized problems with the boiler tubing system. The methodological approach included outages analyses, marking of the most significant ones, determination of main causes of damage (determination of the material exhaustion state based on expert analyses), application of adequate remaining life assessment methodology and finally the recommendations. Based on these analyses, certain technical solutions were performed and as a result, the mean time between failures of the plant increased, as well as its reliability. According to cost efficiency, RCM methodology presented the most effective cost-benefit method for reliability upgrade.

""Hydrogen embrittlement (HE) of steels is extremely interesting topic in many industrial applications, while a predictive physical model still does not exist. A number of studies carried out in the world are unambiguous confirmation of that statement. Bearing in mind multiple effects of hydrogen in certain metals, the specific mechanism of hydrogen embrittlement is manifested, depending on the experimental conditions. In this paper structural, low carbon steel, for pressure purposes, grade 20 - St.20 (GOST 1050-88) was investigated. Numerous tested samples were cut out from the boiler tubes of fossil fuel power plant, damaged due to high temperature hydrogen attack and HE during service, as a result of the development of hydrogen-induced corrosion process. Samples were prepared for the chemical composition analysis, hardness measurement, impact strength testing (on instrumented Charpy machine) and microstructural characterization by optical and scanning electron microscopy - SEM/EDX. Based on multi-scale special approach, applied in experimental investigations, the results, presented in this paper, indicate the simultaneous action of the hydrogen-enhanced decohesion (HEDE) and hydrogen enhanced localized plasticity (HELP) mechanisms of HE, depending on the local concentration of hydrogen in investigated steel. These results are consistent with some models proposed in literature, about a possible simultaneous action of the HELP and HEDE mechanisms in metallic materials.

One of reinforcement bar treatment during delivery
transportation is to bend up or buckle in the middle of
the bar. This treatment will undermine the strength of the
reinforcement bar on buckle region due to its mechanical
properties have been changed and no longer within
specification . An important point of this study is to
knowing the rate of change of mechanical properties ,
especially strength. Concrete reinforcing steels are bent
with nine variations of the bending angle starting from
the angle ( α ) of 20 o  , 40 o , 60 o , 80 o , 100 o , 120 o , 140 o ,
160 o , and 180 o . The data obtained indicated that the yield
strength and ultimate tensile strenght increases and
decreases ductility. The i ncreasing percentage of the
yield strength is 14% and the tensile strength is 7%. The
maximum decreased elongation is 13.42% (α = 180º)
from 24.67% (α = 0º) and the reduction of area is
decreasing 1.93 %.

Based on very early occurring ruptures found in the first stage high pressure turbine blades of a turbo reactor in a local aviation company, this study has the aim to determine their safe life. The first stage blades are subjected to simultaneous action of gas pressure coming from the combustion chamber, centrifugal forces in the case of the rotor blades and to important temperatures transients, which progress in a very aggressive environment due to hot gases. These combined parameters cause a high state of stress involving several complex mechanisms of damage, such as: fatigue caused by mechanical stress fluctuations, thermo-mechanical fatigue caused by temperature variations and corrosion caused on the stressed elements. Life cycle determination asks for stress evaluation of blades regarding several variables which are approached deterministically in the study. Heat exchange between combustion gases and metal blades is considered. The total stress on two kinds of blades is calculated by the addition of the thermal effect and the mechanical loading. The stress cycle is then calculated for different steps of the engine function during the operation by considering the variation of the thermal and the mechanical properties of the system. Safe life determination is done by two different approaches: the safe life approach by the initiation model and the damage tolerance approach considering the defect growth mechanics and considering the pitting corrosion effect. The calculation is applied for stator and rotor blades of an aero engine high pressure turbine made of NI 738. Since these parts are high risk components from the point of view of potential failure consequences, the risk is assessed as well. The results obtained are studied to determine the solution to the problem, and to propose a safe decision to be taken about the design or maintenance procedures.

Damage of boiler tubes is a very serious problem in many utilities worldwide, including even in the most advanced countries. Preserve of boiler tube integrity present major part in maintenance programs centered to achievement of high levels of availability and reliability of thermal power plants. This is due to a very specific and complex interconnection of design and operating characteristics of the boiler unit. Based on the results of numerous boiler tube damages investigation performed on domestic thermal power plants it is concluded that the initiation of different damage mechanism was strongly influenced by tube weld geometry defects. In this paper particular attention was dedicated to this not well documented problem. Structural integrity of the boiler tubes are greatly affected by the weld excessive root penetration (melt-through) on the tube inner surface. This type of weld geometry defect, which occurred often on boiler tubing system, present local flow disruptor and also very strong stress riser. In the vicinity and downstream of excessive root penetration type disruptor initiation of different damage mechanisms (erosive and corrosive wear, under-deposit corrosion, stress corrosion, corrosion fatigue) occurred due to working fluid nucleate boiling destabilization (evaporator), or due to turbulent flow (superheater and reheater), followed by intensive suspended solids deposition.

The multi-scale complexity of lath martensitic microstructures requires scale-bridging analyses to better understand the deformation mechanisms activated therein. In this study, plasticity in lath martensite is investigated by multi-field mapping of deformation-induced microstructure, topography, and strain evolution at different spatial resolution vs. field-of-view combinations. These investigations reveal site-specific initiation of dislocation activity within laths, as well as significant plastic accommodation in the vicinity of high angle block and packet boundaries. The observation of interface plasticity raises several questions regarding the role of thin inter-lath austenite films. Thus, accompanying transmission electron microscopy and synchrotron x-ray diffraction experiments are carried out to investigate the stability of these films to mechanical loading, and to discuss alternative boundary sliding mechanisms to explain the observed interface strain localization.

Hydrogen embrittlement (HE) of steels is extremely interesting topic in many industrial applications, while a predictive physical model still does not exist. A number of studies carried out in the world are unambiguous confirmation of that statement. Bearing in mind multiple effects of hydrogen in certain metals, the specific mechanism of hydrogen embrittlement is manifested, depending on the experimental conditions. In this paper structural, low carbon steel, for pressure purposes, grade 20 - St.20 (GOST 1050-88) was investigated. Numerous tested samples were cut out from the boiler tubes of fossil fuel power plant, damaged due to high temperature hydrogen attack and HE during service, as a result of the development of hydrogen-induced corrosion process. Samples were prepared for the chemical composition analysis, hardness measurement, impact strength testing (on instrumented Charpy machine) and microstructural characterization by optical and scanning electron microscopy - SEM/EDX. Based on multi-scale special approach, applied in experimental investigations, the results, presented in this paper, indicate the simultaneous action of the hydrogen-enhanced decohesion (HEDE) and hydrogen enhanced localized plasticity (HELP) mechanisms of HE, depending on the local concentration of hydrogen in investigated steel. These results are consistent with some models proposed in literature, about a possible simultaneous action of the HELP and HEDE mechanisms in metallic materials.

The world yearly production of Silicon and Ferrosilicon is estimated in 2,4 1 and 8,2 mio 1 of tons respectively. China is responsible for 55% (Si) and 66% (FeSi) of the world production. The total amount of Submerged Arc Furnaces that could be used to produce Silicon in different grades (metallurgical for Aluminium Industry, chemical for Polysilicon and Silicones Industries, mainly) are estimate in 295 furnaces 2 divided between the main producers of Silicon product along Chinese country. Based on the updated marketing information, there are 64 of that Submerged Arc Furnaces 3 in the Northeast china region, which around 13 SAF 3 are in normal operation by the first quarter of 2016. The Silicon and Ferrosilicon processes have some similarities in terms of equipment. Since the raw material handling system, the batching and feeding process, stocking process in the top of the furnace, the main smelting process, the tapping, refining and casting as well as the crushing, milling, grinding, screening and packaging process have different environmental emissions, qualitatively and quantitatively speaking. The target of this technical article is to provide a review of the different techniques applied in the metallurgical industry towards reducing those environmental emissions, via efficiency increase or new process and equipment implementation. Also to give a general ideal about return on investment for each separated system. The outcome of those optimization and assets improvement are the positive environmental profile plants increase that could be capitalized via the microsilica quality increase, the NOx and SOx and other gas emissions reduction and the increase of the overall plant efficiency. Although there is an analogy of this article and the direction of the 13 th Five Year Plan (2016-2020), the coverage of the initiatives mentioned are applicable in any Silicon/FeSi plant worldwide; iincluding within the general context of the efficiency drive sustainable practices to all production process through an environmental management system. The global geographic distribution of production plants for ferrosilicon and metallurgical grade silicon is typically a function of the availability of low (and clean) electric energy, as well as the possibility of a long term contract with the local utility company; logistic access to the raw material such as the iron and silicon ore, carbon source (reducing agent called as " reductant ") and also access to potential customers and for example, regional off-takers within the respective processing industries which use Ferrosilicon and Silicon as feedstock. In the case of Ferrosilicon, mainly Carbon and others alloys, iron casting, magnesium industry (die casting for example and primary production process) and Stainless Steel are responsible for more than 99% of FeSi usage. In the case of Silicon, the main industries are respectively Chemical Industry (Silicones and Polysilicon) and Aluminium Industry, responsible together for more than 99% too. Besides the typical oscillation into those markets (due to the economic crisis in 2008 and lower demand in 2015), the forecast for both sectors are positively evaluated by the industry worldwide. For the case of Silicon production, better than Ferrosilicon:

The following is the first thermodynamically reasoned ancient metal system assessment intended for use by archaeologists and archaeometallurgists to aid in the interpretation of remelted/recycled copper alloys composed of arsenic and copper, and arsenic, copper, and nickel. These models are meant to fulfill two main purposes: first, to be applied towards the identification of progressive and regressive temporal changes in artifact chemistry that would have occurred due to recycling, and; second, to provide thermodynamic insight into why such metal combinations existed in antiquity. Built on well-established thermodynamics, these models were created using a combination of custom written software and published binary thermodynamic systems data adjusted to within the boundary conditions of 1200 °C and 1 atmosphere. Using these parameters, the behavior of each element and their likelihood of loss in the binaries As-Cu, As-Ni, Cu-Ni, and ternary As-Cu-Ni, systems, under assumed ancient furnace conditions, was determined.

This work investigates the effects of heat input
and  shielding gas composition on microstructure, ferrite
number, ultimate tensile strength, hardness, and impact of
austenitic stainless steels 304L. The shielding gases used in this
study are pure Argon and mixture of 98% Argon (Ar) and 2%
Nitrogen (N). Gas tungsten arc welding (GTAW) process was
applied to weld joints. The results of the present work showed
that the shielding gas composition has a significant effect on
microstructure,  ultimate tensile strength  and hardness.
Microstructure revealed changing in solidification structure
from ferrite to austenite when used shielding gas 98% Ar and
2% N and revealed when heat input increased the dendrite
size and inter-dendritic spacing in the weld metal also
increase. The ferrite number decreased with increasing the
heat input and using mixture of 98 % Ar and 2 % N.
Transverse tensile test revealed that the average ultimate
tensile strength (UTS) values increased with decreasing the
heat input, using mixture of 98 % argon and 2 % nitrogen as
shielding gas. furthermore Hardness values increased with
decreasing of heat input and using shielding gas of 98 % Ar
and 2% N.

Reliability centered maintenance (RCM) has a key role in the quality system of thermal power plants. Electricity production is definitely not only production of a product, but also becomes a customer service. Reliability is the top quality tier of this service. Incorporation in the Integrated energy system means fast transformations of organization on all levels. The reliability of modern generation components basically influences the efficiency and capacity of a power plant as a whole. This paper presents the results of RCM practice of one 620 MW thermal power plant. RCM implementation on current problems during exploitation emphasized problems with the boiler tubing system. The methodological approach included outages analyses, marking of the most significant ones, determination of main causes of damage (determination of the material exhaustion state based on expert analyses), application of adequate remaining life assessment methodology and finally the recommendations. Based on these analyses, certain technical solutions were performed and as a result, the mean time between failures of the plant increased, as well as its reliability. According to cost efficiency, RCM methodology presented the most effective cost-benefit method for reliability upgrade.

In this study, an attempt has been made to evaluate the complex correlations occurred between double pulsed gas metal arc welding (DP-GMAW) process parameters and weld bead geometry using two statistical methods: Taguchi orthogonal array design method and response surface methodology. The Taguchi method was applied to plan the design of experiments (DoE). Contour and surface plots were made using response surface methodology (RSM) to understand the effect of different parameters on the bead geometry. It was found that at a particular range of arc voltage higher mean current, higher pulse frequency along with lower thermal pulse frequency produced optimum conditions for high depth of penetration with low or moderate bead width and height. The optimization of process parameters was also conducted using RSM and the optimum parameters were compared with experimental trials. Three second-order statistical models were also developed using experimental results to predict the weld bead parameters from the process parameters. The model developed was checked for its adequacy using ANOVA. Results of confirmation experiments showed that the model can predict the bead geometry with reasonable accuracy.

""Hydrogen-induced fractures of metallic components of thermal fossil fuel power plants (TPP) presents very serious exploitation problem and often exert considerable influence on the loss of power plant availability. Hydrogen damage is one of the most disturbing of boiler tube failure mechanism, and from the international experience, remains as one of the leading causes of frequent outages of boiler tubing system. To clarify root causes and complexity of problems associated with hydrogen damages, it is necessary to apply a multidisciplinary approach which comprises research in the field of material quality, boiler design, operation and maintenance. The work reported here is based on the theory and, particularly, on the experimental tests performed on boiler evaporator tube samples, taken from a domestic 210 MW power plant, that had experienced hydrogen damages during service. Possible mechanisms for metal – hydrogen interaction are considered from materials point of view, fluid hydrodynamics in evaporator tubes and the complexity of structural – exploitation plant characteristics. The aim of this paper is to contribute to the analysis of hydrogen damaging in boiler evaporator tubes and to propose failure mechanism model based on ′′micro-departure from nucleate boiling′′ (micro-DNB) of working fluid. In addition, this paper elucidates some definitions of major root cause influences by proposing model for systematization of influencing and corresponding operating factors responsible for hydrogen damages of boiler evaporator tubes.""

Component failures due to the hydrogen embrittlement (HE) were observed in different industrial systems, including high-pressure hydrogen storage tanks, aircraft components, high-strength alloy components, and high-strength steel fasteners. The contemporary approach in studying the effects of hydrogen on the mechanical properties of steels and iron at different scales is based on the implementation of various multiscale (macro, micro-meso, and nano-atomic) modeling approaches and the applications of advanced experimental methods. A large number of contemporary studies confirmed the multiple effects and activity of different HE mechanisms in steels and iron. The coexistence and synergistic activity-concurrent action and effects in a cooperative manner of different HE mechanisms, including the hydrogen-enhanced localized plasticity (HELP) and the hydrogen-enhanced decohesion (HEDE), were recently detected and confirmed through computations-simulations, as well as experimentally in different grades of steel. However, the critical evaluation and quantification of synergy between the HELP and HEDE mechanisms, enhanced plasticity and decohesion, hydrogen-deformation/dislocation interactions and their simultaneous effect on the mechanical properties (hardening and softening), still do not exist. In this review paper, the multifaceted nature of the synergistic interplay of HE mechanisms is covered through extensive literature overview regarding the chronological development of ideas related to the HELP + HEDE concept and HELP mediated HEDE model. The particular emphasis is given to the proposal of the novel and unified HELP + HEDE model based on the specific microstructural mapping of the dominant HE mechanisms with implications on the fracture process and resulting hydrogen-assisted fracture modes. Most of up-to-date experimental and modeling approaches, current trends and future challenges in the investigation of the synergistic interplay of HE mechanisms in different grades of steel, including the most advanced, and iron, are also included and critically discussed.

Hybrid materials with the metal matrix are important engineering materials due to their outstanding mechanical and tribological properties. Here are presented selected tribological properties of the hybrid composites with the matrix made of aluminum alloy and reinforced by the silicon carbide and graphite particles. The tribological characteristics of such materials are superior to characteristics of the matrix – the aluminum alloy, as well as to characteristics of the classical metal-matrix composites with a single reinforcing material. Those characteristics depend on the volume fractions of the reinforcing components, sizes of the reinforcing particles, as well as on the fabrication process of the hybrid composites. The considered tribological characteristics are the friction coefficient and the wear rate as functions of the load levels and the volume fractions of the graphite and the SiC particles. The wear rate increases with increase of the load and the Gr particles content and with reduction of the SiC particles content. The friction coefficient increases with the load, as well as with the SiC particles content increase.

Quality has been variously defined, but fairly understood because of its complexity. In case of education, this haziness is further enhanced, especially because of the illusion at the boundary of quality of education
w.r.t education of quality – the two aspects of education quality. This paper attempts to clarify the haziness by citing the importance of each and underpinning how each contributes holistically to the excellence
working at the system level.
To analyze the two aspects this work draws on the three definitions of quality, as defined by ISO 9000 series standard, or by Gurus like Philip Crosby or Joseph Juran. The quality prescriptions are weighted
w.r.t the system of education that looks at approach of transformation, or outcomes or the customer’s demand. The three attributes are mandates of excellence of the Thareja’s AUM model, or of accrediting
bodies or of the employer. The latter attribute is sought after both by prospective customers of education institutions (students) and by employers – the consumers of the product.Finally, in this paper I prescribe improving the system requirements, addressing the constraints and holistically
transforming the student through various education processes. The implementation is prescribed to chase
objectives duly aligning with processes for performance improvement, using the transition tree approach.
This is done through determination of gaps between current reality and possible solutions (actions).

Keywords: Employability, Fitness to auality, Holistic education, Compettitude (competence+attitude), System approach (system of systems), Thareja’s AUM model

Abstract – The characteristics of zircon sand and how they affect foundry castings have been studied with respect to their surface finish, mechanical properties and the microstructure. Local and imported zircon sand was employed in the work and it was found that imported zircon sand showed better performance than the local zircon sand. From the study it was evident that the local zircon sand could be upgraded to make it suitable for castings under extreme temperature conditions.

Thick walled components such as high pressure (HP) steam turbine casings operating under high parameter conditions are subjected to a complex stress state. As a result of that stress state, some parts of HP turbine casing undergo to the creep fatigue caused by the combination of thermal fatigue resulted from repeated start/stop operation and the creep which occurs during long-term operation at high temperature and high-pressure. It is well known that domestic thermal power plants have been in use over 100000 h which means that significant cost is required not only for maintenance, but often for renewal of equipment. Based on comprehensive investigation, the results of residual life assessment of one high pressure steam turbine casing, which belongs to the older turbine generation, taking into account simultaneous action of thermal fatigue and creep, are presented in this paper. Also, the critical flaw crack size of HP turbine casing is determined because this parameter has a strong influence on casing integrity and residual life. The results of residual life assessment provide not only a basis for further maintenance, but also estimated time for reparation or renewal.

Bearing in mind the multiple effects of hydrogen in steels, the specific mechanism of hydrogen embrittlement (HE) is active, depending on the experimental conditions and numerous factors which can be grouped as environmental, mechanical and material influences. A large number of contemporary studies and models about hydrogen environment assisted cracking and HE in steels are presented in the form of critical review in this paper. This critical review represent the necessary background for the development of a multiscale structural integrity model based on correlation between simultaneously active HE micro-mechanisms: the hydrogen-enhanced localized plasticity (HELP) and the hydrogen-enhanced decohesion (HEDE) - (HELP+HEDE) and macro-mechanical response of material, unevenly enriched with hydrogen during service of boiler tubes in thermal fossil fuel power plant. Several different experimental methods and techniques were used to determine the boiler tube failure mechanism and afterwards also the viable HE mechanisms in the investigated ferritic-pearlitic low carbon steel, grade 20 - St.20 (equivalent to AISI 1020). That represent a background for the development of a structural integrity model based on the correlation of material macro-mechanical properties to scanning electron microscopy fractography analysis of fracture surfaces of Charpy specimens, in the presence of confirmed and simultaneously active HE micro-mechanisms (HELP+HEDE) in steel. The aim of this paper is to show how to implement what we have learned from theoretical HE models into the field to provide industry with valuable data and practical structural integrity model.

In President John F. Kennedy’s original Consumer Bill of Rights speech to the United States Congress he called for the “right to be informed”. At the time, materials science was in its infancy and only crude information technology was available, so the need for consumers to know what materials their products were made up of was outweighed by the difficulty of providing the information. Fifty-five years later the basic material ingredients are largely unknown for the vast majority of consumer products, making informed choices impossible. With the significant evolution in material science as well as information technology the ability to provide a materials ingredient list for every product is technically feasible, low-cost and straight forward. It is time for the Consumer Bill of Rights to be expanded to include digital access to a materials ingredient list. Freely accessible information about the material ingredients for all consumer goods would provide several advantages including: 1) creating new business opportunities for upselling products manufactured with superior materials, 2) improved consumer safety, 3) enabling socially responsible and ethical consumerism, 4) fostering advanced industrial as well as distributed recycling, and 5) expanding products to more valuable applications.

Self-cleaning properties have received significant attention for the importance of their potential. Coatings at Nano-scales offer possibilities of using materials for self-cleaning surfaces. Recent efforts have begun to focus on the kinds of materials including metals, semiconductors and polymers. Such materials can have enormous potential in only a few applications. Moreover, the production of these materials requires high costs with low photo activity. In this regard, TiO 2 and its derived materials have shown acceptable and effective suggestions for this application. Moreover, the mechanism of self-cleaning has been explained by the effect of hydrophilic and hydrophobic. Hydrophilic and hydrophobic can have many applications in different areas like water purification, microfluidics and photovoltaic. In this review, the application of self-cleaning in solar cells and environment as well as TiO 2 derived materials and their applications in water management have been briefly illustrated. In addition, it has been explained that a huge number of self-cleaning materials, applications and improvement in utilities have been essential. In short, we have conducted a comprehensive review of the new approach and to mention numerous materials with hydrophobic and hydrophilic properties would be promising for most environmental concerns. Bio-inspired surface respond in nature through hydrophobic (Cicada Wing, Butterfly Wing, Lotus Leaf, Rice Leaf) and hydrophilic (Fish Scale, Snail Shell, Shark Skin) properties was divided in 4 and 3 respectively. Anti reflective coatings with self-cleaning properties have drowned considerable attention for both their basic appearances and vast applied usages. Antireflective coatings with self-cleaning properties have been considered because of their fascinating features and vast diversity of empirical uses.

— The objective of the study is to investigate the effect of the welding parameters on the weldability of austenitic stainless steel 304L using 308L consumable electrodes (microstructure, ultimate tensile strength and hardness). The parameters used are: the Welding current, the travel speed and Shielding gases. The welding currents used in this study are: 90A, 110A and 130A.The travel speed used is 50mm/min and 100mm/min .The shielding gases used are: pure Argon and mixture of 98% Argon and 2% Nitrogen. The process of Gas tungsten arc welding (GTAW) was applied to weld the joints. The results indicated that; the shielding gases composition has a significant effect on the microstructure evolution, ultimate tensile strength and hardness. Microstructure revealed a change in the solidification structure during the transformation; from ferrite to austenite using shielding gases of 98% Argon and 2% Nitrogen also the microstructure showed an increasing of the dendrite size and inter-dendritic spacing in the weld metal when the electric current was increased. Transverse tensile test showed an increasing in the value of the average ultimate tensile strength (UTS).when used a shielding gases of 98 % argon and 2 % Nitrogen. The highest ultimate tensile strength was achieved when using current 90A, travel speed 100mm/min and shielding gas 98% argon and 2% nitrogen. When using shielding gases of 98 % argon and 2% N; the hardness values were lower than the case of using pure argon.

— The aim of this work is to conduct an optimized conditions of the post weld heat treatment of the GTAW(gas tungsten arc welding) and SMAW (shielded metal arc welding) weld joint between P11 (1.1 Cr) and P91 (8.5 Cr) steels; using E9018B3/ER90SB and E9015B9/ER90SB9 as filler metals. The post weld heat treatment was conducted at 750°C for holding times 0.5, 1 and 2 hours for the evolution of the microstructure, hardness and Tensile Strength ; required for high mechanical performance; at elevated temperatures. The investigated results showed that: the optimum conditions of the post weld heat treatment is 750°C for 1 hour with E9018B3/ER90SB as a filler metal and post weld heat treatment at 750°C for 0.5 hour with E9015B9/ER90SB9 as a filler metal are the proper conditions to reduce the hardness of heat affected zone (HAZ) of P91 steel and regular Hardness distribution.