Process optimization of laser cladding Ni60A alloy coating in remanufacturing

•Linear energy density identifies threshold for elimination of large porosity.•A statistical model between process parameters and porosity area is developed.•Cracks are effectively eliminated with decreasing of molten pool cooling rate. The inherent problems associated with laser cladding remanufacturing process using NiCrBSi alloy powder are the formation of crack and porosity, which can be detrimental to the mechanical properties of the deposited material. In this paper, a comprehensive investigation of crack and porosity is carried out using Ni60A alloy. It is shown that the linear energy density can be used to identify a threshold for the elimination of large porosity. And statistical analysis is used to optimize process parameters leading to minimum porosity area, and the result shows that powder feed rate in the coating process is the most significant parameter considering the porosity area. The crack can be effectively eliminated by the combination of preheating up to 300 °C and placing insulated plank under the substrate. In this situation, one large-area crack-free and low porosity rate (0.027%) coating is obtained successfully and its average microhardness is about 2.7 times as much as that of the substrate. The other large-area crack-free coating with low porosity rate (0.01%) is prepared successfully without preheating, but its microhardness descends intensely because of high dilution of the coating.