Investigation on the effect of laser remelting for laser cladding nickel based alloy

Laser cladding is a recently developed additive manufacturing technique, which is widely used in remanufacturing and sustainable manufacturing fields. However, the surface roughness of laser cladding layer often fails to meet the tribological functions and assembly requirements. In order to improve the surface finish quality of laser cladding, various techniques such as manual polishing, grinding, abrasive blasting, and chemical polishing were adopted. However, these methods have certain disadvantages, such as secondary positioning and polluting the environment. Laser remelting is an eco-friendly technology, which is based on remelting of a thin surface layer and can improve surface quality without the secondary positioning. In this paper, the high-power continuous-wave carbon dioxide laser was first used for preparing laser cladding layer of nickel-based alloy and then used for laser remelting process. Design of experiments based on orthogonal arrays was employed for optimization of process parameters. Both surfaces of laser cladding and laser remelting, as well as the cross-sectional subsurface, were analyzed to investigate the variation of surface roughness. Scanning electron microscopy and energy dispersive spectrometer were used to analyze the microstructure of the remelted sample. It was shown that the average surface roughness of laser cladding layer was reduced more than 2 μm after laser remelting process. Microstructure and microhardness of laser remelting zone were investigated in order to examine the thermal effect of laser remelting processing on the laser cladding layer. It can be induced that laser remelting process is an effective method to improve the surface quality of laser cladding.