Surface Quality Control and Pool Characterization of NiTi Alloy Single Track Formed by Selective Laser Melting

In order to investigate the forming law of NiTi alloy powders by laser selective melting(SLM) and obtain excellent process parameters, a series of single track forming experiments for NiTi alloy were carried out under different combination parameters of laser power and scanning speed. The influence mechanism of the process parameters on the formation of the molten track, the evolution of the molten pool and the formation of pores was systematically discussed by characterizing the forming surface of the molten track and the morphology of the molten pool. The results reveal that the depth of molten pool, the width and width uniformity of the molten track show an overall increasing trend with the increase of the laser power, and show a decreasing trend with the increase of the scanning speed. Under different process parameters, the cross-section profiles of the molten pool can be divided into four categories: lack of fusion, shallow bowl shape, deep bowl shape and keyhole shape. Too low energy density leads to incomplete fusion, and too high energy density leads to keyhole effect. In above cases, pore defects can be easily observed at the bottom of the molten pool.