Matching and strengthening between Inconel718 cladding and K418 alloy blades by laser remanufacturing

The cladding layer of K418 alloy blade after remanufacturation was easy to crack and the mechanical properties of bonding interface were poor. In order to solve these problems, the pulsed laser with the advantages of adjustable input, controllable heat input and lower temperature of molten pool and heat affected zone was used. Good metallurgical bonding was formed between K418 matrix and Inconel718 cladding layer under the conditions of laser power 2.5kW, powder feeding rate 37.5g/min, scanning rate 8mm/s and carrier gas flow 3L/min. The results show that the microstructure of the cladding layer is composed of plane crystal at the interface, cell crystal at the bottom, dendrite in the middle and equiaxed crystal at the top. Under the optimized process parameters, Inconel718 cladding layer with good forming quality and without obvious cracks and pore defects is obtained. After the test of the hardness of the matrix and the coating, overall hardness of the coating is about 300HV and the distribution is uniform. Average hardness of the matrix is above 400HV, and the hardness of the bonding interface is 460.46HV, which is 12% higher than that of the matrix. Phase analysis shows that, the properties of Inconel718 cladding layer and matrix K418 match well. The solidification process of laser remanufacturing is L→γ→(γ+MC)→(γ+laves). Solid solution and precipitation of γ′ phase in heat affected zone of matrix K418 alloy are completed by heat input of the pulsed laser. A small amount of secondary precipitates is precipitated along the grain boundary at the interface. Laves phase and MC phase can pin the grain boundary and hinder the slip of the cladding layer and the grain boundary at the interface. The related process and parameters can be used for reference and analysis of K418 blade laser remanufacturing.