Investigation of nickel-based alloys coatings on stainless steel by laser cladding

Two kinds of nickel-based alloy coatings were formed on 0Cr18Ni10Ti stainless steel surface by laser cladding. The hardness of the coating formed with nickel based alloy 1 was about HRC 34, no cracks existed in the coating. While the hardness of the coating with nickel based alloy 2 was as high as HRC 47, and this coating presented high tendency to crack. Introducing a layer of softer nickel based alloy 1 as a transition one to the coatings, the problem of crack presented in the coating with nickel based alloy 2 could be resolved. And thicker coatings with large area were prepared successfully. The microstructure of the large area coatings were characterized by means of optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscope (SEM) as well as energy-dispersive spectroscope (EDS). The results indicated that the upper area of the coating formed with nickel based alloy 2 was composed of γ-Ni matrix dendrite, 7-Ni lumps and reinforcing phase M12C carbides. The results of micro-hardness analysis along the coating thickness showed that the average hardness of the surface layer of the coatings could reach HV0.2583 and the hardness decreased gradually from the coating surface to the substrate.