Effect of two different energy inputs for laser cladding of stellite 6 on P91 and P22 steel substrates
Stellite 6 was deposited by laser cladding of two different chromium-bearing steel substrates (P91 and P22). The chemical compositions, microstructures and surface roughnesses of these coatings were characterized by atomic absorption spectroscopy, optical microscopy, scanning electron microscopy and atomic force microscopy. The microhardness of the coatings was measured and the wear mechanism of the coatings was examined using a pin-on-plate (reciprocating) wear testing machine. The results showed less cracking and pore development for Stellite 6 coatings applied to the P22 steel substrate. Further, the Stellite coating on P22 steel was significantly harder than that deposited on the P91 steel. The wear test results showed that the weight loss for the coating on P22 steel was significantly lower than for the P91 steel substrate. The surface topography data showed that the surface roughness for the coating on P22 steel was much lower than for the P91 steel substrate. It is concluded that the residual C content for the deposit on P22 was higher, mainly because the lower concentration of strong carbide formers, compared to P91, reduced the extent of carbon loss in the deposit.