Surface Morphology and Wear Analysis of Stellite 6 Deposited on 9Cr-1Mo Steel Substrate by Laser Cladding

Stellite 6 was deposited by laser cladding on a 9Cr-1Mo (P91) substrate with energy inputs of 1 kW (P91-1) and 1.8 kW (P91-1.8). 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 evaluated using a pin-on-plate (reciprocating) wear testing machine. The results showed less cracking and pore development for Stellite 6 coatings applied to the 9Cr-1Mo (P91) steel substrate with the lower heat input (P91-1). Further, the Stellite coating for P91-1 was significantly harder than that obtained for P91-1.8. The wear test results indicated that the weight loss for P91-1 was much lower than for P91-1.8. The surface topography data indicated that the surface roughness for P91-1 was much lower than for P91-1.8. It is concluded that the lower hardness of the coating for P91-1.8, together with the softer underlying substrate structure, markedly reduced the wear resistance of the Stellite 6 coating.