A numerical-experimental investigation of heat distribution, stress field and crack susceptibility in Ni60A coatings

Abstract 3D finite element model (FEM) was built for the simulation of temperature and stress field induced by laser cladding. The proposed model was validated by experimental results. The numerical width and depth of coating matched well with the experimental cross-section of macrograph. The viscosity of molten pool versus the temperature field was also discussed, and the maximum difference of viscosity in different zones was approximately 32.8%. High temperature and sharp thermal gradient was generated in the vicinity of heat source, which was prone to produce residual stress. The heat distribution obtained from temperature field was in consistent with the thermocouple measurements. Due to large plastic tensile deformation of materials, the longitudinal residual stress was susceptible to crack propagation in the laser cladding. The measured maximum value of longitudinal residual stress reached 492 MPa, which was lower than predicts. The coatings were apt to crack along the vertical scanning direction. In addition, the crack susceptibility of coatings was not only depended on residual stress, but also the microsegregation of Cr, Ni and Fe elements. The calculation results are helpful for systematically understanding the melt pool, heat cycles, and stress, which related to laser cladding Ni-based materials.