Study on laser clad cobalt-free nickel-based alloys coatings on stainless steel

To meet the cobalt-free requirement for a certain valve, thicker coating with gradient hardness distribution was prepared on 0Cr18Ni10Ti stainless steel by laser cladding two kinds of cobalt-free nickel-based alloy powder. The microstructure, hardness and the interface bonding strength of the coating were analyzed. The results showed that using nickel-based alloy with lower hardness as a transition layer, the problem of cracking for nickel-based alloy coating with higher hardness could be resolved. The interfaces between the coating and the substrate as well as these two nickel-based alloy coatings were smoothly transited. The hardness was also gradient along the cross-section of the coating. The hardness of the coating surface was about HRC47. The coating was metallurgically bonded with the substrate. And the interface bonding strength of the coating was higher than 565MPa. There was no de-bonding and cracking after bending and thermal shock test, indicating the good anti-thermal shock property of the coating.