Wear behaviour of laser clad NiCrBSi coating

The work is based on the dry sliding wear of NiCrBSi coatings deposited on the plates of grey cast iron (DIN GG30) using the laser cladding technique, the parameters of which were such as to provide almost crack-free coatings with minimum dilution and very low porosity. The post-laser treatment microstructure showed up as a dendritic structure matrix which is a solid solution of Ni and chromium-rich precipitates with an average microhardness of over 850 HV300 gf. Higher concentrations of precipitates are observed in the overlapped tracks, leaving the adjacent areas and some zones of the interface free of them. Wear behaviour was determined by using block-on-ring dry sliding linear contact at several loads (30–100 N) and sliding speeds (0.65–2.6 m/s). The density of the coating, friction coefficient and wear rate coefficient k (mm3/N m) were estimated using a method founded upon the PV factor theory. When load or speed increases, the friction coefficient diminishes. For a 30 N load, a superficial oxidation mechanism with loosening of the generated oxide layer predominated as the principle wear mechanism. Adhesion and oxidation were observed for higher loads.