Numerical and experimental study of temperature, residual stresses, and microstructural evolution on multi-layer and multi-pass laser cladding of 6061Al alloy

Multi-layer and multi-pass laser cladding is a promising and important process for repairing and strengthening Al alloy parts, whereas the temperature and residual stresses have a great influence on the properties of the laser cladding layer. In this paper, a nonlinear transient thermo-mechanical coupling finite element model of multi-layer and multi-pass cladding of 6061Al alloy was established. Meanwhile, the DFLUX user subroutine was developed using Fortran code to define the movement of the three-dimensional heat source model. From there, the distribution and evolution of temperature and stresses at different times were investigated. In addition, the micro-morphology and micro-hardness after cladding were also analyzed in detail. The results show that both the maximum residual tensile and compressive stresses decrease with increasing the number of cladding passes. At the same time, due to the reheating effect of each cladding on the previous cladding, a few bubbles appear at the top, middle and bottom of the overlap surfaces. Moreover, the micro-hardness of the overlap surfaces decreases slightly. This study can provide a theoretical basis for further research into multi-layer and multi-pass laser cladding of 6061Al alloy.