Effect of laser power on microstructure and wear properties of laser cladding Stellite 6 alloy coating

Stellite 6 alloy coating was prepared on 0Cr17Ni4Cu4Nb stainless steel by laser cladding technology. The microstructure of the coating was characterized by optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), electron backscatter diffraction (EBSD), and confocal laser scanning microscopy (CLSM). The hardness and wear resistance of the sample were tested. The coatings prepared with different laser power parameters had no obvious defects such as pores and cracks. The coating of all samples had good metallurgical bonding with the substrate. Therefore, all 5 laser powers were reasonable process parameters. The microstructure of the coatings mainly consisted of coarse columnar dendrite at the bottom, coarse dendritic crystals at the middle, and fine equiaxed dendrite at the top. The hardness of the coating (420~510 HV) was significantly higher than that of the substrate (206 HV), and the hardness gradually decreased from the top of the coating to the substrate. The sample with a laser power of 1400 W exhibited the smallest and most uniform microstructure, while there were more hard phases (carbides) between dendrites. Therefore, the 1400 W sample exhibited the highest hardness. After wear experiment testing, all sample surfaces showed parallel furrows along the sliding direction, without obvious accumulation of debris, which belongs to the abrasive wear mechanism. The sample with a laser power of 1400 W had the lowest friction coefficient (0.353) and wear rate (0.954 m3sN-1), while the 1400 W sample had the narrowest wear scar width (928.463 μm) and the minimum depth of wear marks (45.087 μm), exhibiting the best wear resistance.