Table 3: Erosion test parameters Erosion test was done using sand blasting equipment, Fig. 1, with parameters given in Table 3. Table 4: Macro view of investigated samples before and after erosion test The macro view of the damage following erosion tests has an elliptic shape with clearly visible edges in the samples with the metallization deposited coatings. In the samples with a welded layer, the damage zone has an irregular shape and uneven dimples most probably as a result of geometry of welded layers. Considering that the testing conditions for all three samples were the same, the observed difference in the damage features can be correlated with the coating density, cohesion strength between the grains as well as the erosion mechanism itself. Figures 1. EDAX analyse of 502 metallized layer Fi Figures 2. EDAX analyse of 595 metallized layer For the given testing conditions, the weight loss in the unprotected metal and the weld overlay samples are lower than in the samples with metallization protection. Based on these results, it should not be concluded that the metalized layers are of not so good quality characteristics, but rather that for the given erosion parameters the higher density materials have the advantage in erosion resistance. Figures 1-3 depict the EDAX analyses of the samples with the 502 and 595 coatings, that is, with the welding overlayers. In all cases it is apparent that in the micro zones the presence of a complex type of material in the sense of chemical composition with numerous carbide-forming elements is noted. Table 5: Weight changes of investigated samples after erosion test 4. MICROSTRUCTURAL CHARACTERIZATION From the SEM images of the CDP sample with a weld overlay shown in Figs. 8-9 it is clear that there are 3 distinguished regions: base material, heat affected zone and weld overlay. Even with this type of protection, the materials removal is not uniform due to the presented phases (matrix and carbides) with different hardness values and thus erosion resistance.
