Investigation on cracking behavior of Ni-based coating by laser-induction hybrid cladding

Based on the experiments of laser-induction hybrid cladding by powder feeding, the cracking behavior of Ni-based coating and solidification characteristic in molten pool were investigated. The results indicate that the hybrid cladding is effective to prevent from cracking in Ni-based coating. With the increase of induction energy density, the tensile stress and crack rate decrease obviously. When the induction energy density arrives at 36 J/mm2, the free-cracks coating can be achieved. In laser-induction hybrid cladding, the martensite can be eliminated in the heat affected zone and the phase transformation stress is little. Moreover, the molten pool is solidified through two directions such as the coating surface and coating/substrate interface, i.e., firstly the top and bottom in molten pool are solidified, and then the middle in molten pool is solidified. Therefore, in hybrid cladding, the peak value of tensile stress is located in the middle of coating, which is different from that in laser cladding. This distribution status of residual stress is greatly helpful to restrict the cracks of Ni-based coating in laser-induction hybrid cladding.