Effects of process variables on interfacial quality of laser cladding on GH4133 alloy

Abstract

The microstructure and mechanical properties of interface between GH4133 substrate and laser cladding were investigated experimentally. It was found that the process variables for laser cladding can result in the formation of incomplete fusion between the cladding layer and substrate or reheat cracking along the grain boundary in the coarse grain zone of the heat-affected zone (HAZ) during ageing treatment. The SEM and EDS analysis demonstrates that the chemical compositions in the crack and substrate are very similar and there is not precipitation in the crack. Therefore, the reheat cracking has nothing to do with liquid film on the grain boundaries, the possible cause of the formation of reheat cracking is that the plastic deformation caused by residual stress formed during thermal cycle of laser cladding concentrates on the coarse grain boundary in HAZ because precipitations precipitating in the grain during ageing treatment strengthen grain. The laser cladding layer with integrated melt interface and without reheat cracking can be obtained by optimizing laser power, scanning velocity and powder thickness. The experimental results of microhardness have shown that the microhardness of laser cladding layer is the same with that of GH4133 base metal after ageing treatment, thus the properties of the clad layer and the substrate are homogeneous.