Cracking behavior of laser cladding forming nickel based alloys

The largest difficulty in laser cladding forming of nickel based alloy is the high cracking susceptibility, which greatly impedes the further and wider application of this alloy. In this paper, experiments of laser cladding forming NiCrFeSiB alloy Ni25, Ni45 and Ni60 have been carried out. The cracking behavior and phenomena of laser cladding forming nickel based alloy has been observed. The microstructure and phase composition is analyzed with optical microscopy (OM) and X-Ray diffraction (XRD). Cracking generating mechanism was investigated. Macro morphology observation, fracture and microstructure analysis with OM and SEM show that the cracks are mainly brittle cold cracks caused by the low ductility and residual internal stresses induced by hard brittle phases and high temperature gradients. Through the optimization of process parameters and adjustment of alloy composition, forming microstructures can be improved, plasticity and toughness can be enhanced, and residual stress can also be reduced. Therefore, cracking susceptibility can be effectively reduced and cracks can even be eliminated.