Processing of IN625-ZrB₂ composite coating by laser cladding through optimization and definition of line energy and powder feeding density parameters

This study used laser cladding technology to fabricate IN625-ZrB₂ coatings on the surface of GTD-111 Ni-based superalloy. The coating was used to apply two variables, line energy (LE) and powder feeding density (PFD), which were obtained through the relationships between laser power, powder feed rate, and scan speed. The properties of the processed coatings, including microstructural, coating profile, and mechanical investigations, were evaluated by optical and electron microscopes, X-ray diffraction, microhardness, and wear tests. The results showed that LE and PFD had the most significant effect on the depth of fusion and melting height, respectively. With increasing PFD, unmelted powders in the coating increased. However, with increasing LE, increasing dilution rate caused a decrease in the coating quality. The results showed that the appropriate range of LE and PFD for forming the optimal coating was 16–25 W.s/mm and 22–38 mg/mm, respectively. The coatings that were subjected to laser cladding in this parameter range had the highest hardness and wear resistance, with a coating consisting of equiaxed grains, without defects, and with a proper distribution of ZrB₂. The low coefficient of friction of the optimal coating due to its high hardness caused the formation of a tribe-oxide layer during wear, which played the role of a lubricant and increased the improvement of tribological behavior.