Characterisation of the laser-clad stellite layers for protective coatings

Stellite layers produced for protective coatings in a direct process by laser remelting of the powder SF6 on plates of a high-temperature resistive alloy in Ar environment are investigated experimentally. Microphotographs and EDS analysis reveal a metallurgical bond between the substrate and coating as well as the structural homogeneity along the depth of the layer which is characterised by a chemical composition close to that of the powder. The laser-clad layers show a dendritic and fine-grained structure with a minor presence of impurities. For the coatings an improvement of mechanical properties in comparison to the base material such as the behaviour in wear resistance comparable to that of TiN and values of microhardness up to approximately 1000 HV are observed. On the other hand, corrosion properties depended on the defects and appeared on the surface as a result of the laser process parameters.