Residual stresses in Stellite 6 layers cladded on AISI 420 steel plates with a Nd:YAG laser

Abstract

Clad tracks/layers with good geometry, desirable dilution, and hardness can be produced using optimal process parameters. However, cracking and deformation can occur in the laser cladded products. The tensile residual stress is mainly responsible for the failure of the cladded products. Therefore, different residual stresses’ control strategies during laser cladding were investigated, such as preheating the substrate, using an intermediate layer, and using different energy inputs. The residual stresses in clad layers were measured with layer removal and hole drilling techniques. The depth residual stress distributions obtained from both techniques show a good agreement. The residual stresses acting along the cladding direction σx and the maximum residual stresses within the clad layer were analyzed. The cooling rate and thermal gradient were simulated from our previously developed 2D thermal model. The relationships among the cooling rates, thermal gradients, maximum residual stresses, and absorbed energy were investigated and the results are discussed. Thermal gradients, cooling rates, and the maximum residual stresses decrease with energy input. The decay factors between maximum residual stress and absorbed energy and between the cooling rate and absorbed energy are close to each other indicating that a correlation between the maximum residual stress and cooling rate exists. An empirical relation is used to describe such a correlation.