Effect of laser power on microstructure and wear resistance of laser cladding Stellite 6 alloy coatings

Stellite 6 alloy coatings were prepared on 0Cr17Ni4Cu4Nb stainless steels by laser cladding technology. The microstructure of the coatings 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 samples were tested. In the results, all the coatings prepared with different laser powers have no obvious defects, such as pores and cracks, and show the good metallurgical bonding with the substrate. The microstructure of the coatings is mainly consisted of the coarse columnar dendrite at the bottom, the coarse dendritic crystals in the middle, and the fine equiaxed dendrite on the top. The hardness of the coatings (HV 420~510) is significantly higher than that of the substrate (HV 206), and the hardness gradually decreases from the top of coating to the substrate. The samples with the laser power of 1400 W exhibit the smallest and most uniform microstructure, while there are more hard phases (carbides) between dendrites. Therefore, the 1400 W samples exhibit the highest hardness. After the wear experiment testing, all the sample surfaces show the parallel furrows along the sliding direction without the obvious accumulation of debris, which belongs to the abrasive wear mechanism. The samples with the laser power of 1400 W have the lowest friction coefficient, while show the narrowest wear scar width (928.463 μm) and the minimum depth of wear marks (45.087 μm), exhibiting the best wear resistance.