Effects of laser polishing on surface morphology and mechanical properties of additive manufactured TiAl components

The laser deposition manufacturing (LDM) is a free-form metal deposition process, which allows generating a prototype or small series of near net-shape structures. Despite numerous advantages, one of the most critical issues of the technique is that produced pieces have a deleterious surface quality which requires post machining. Traditional machining methods such as milling and grinding have been used to improve the surface quality of the LDM components. However, these methods have some drawbacks such as tool wearing and narrow-area difficult machining. In this paper, the CW laser and the pulsed laser was applied to polish the surface of LDM TiAl alloy samples. The difference between these two polishing processes on the surface morphology, microstructures, corrosion resistance, micro-hardness and wear resistance were investigated. Results revealed that the surface roughness of CW laser polished TiAl can be reduced to about 1.76 μm, which is comparable to a precise machining surface. It was also found that a hardened layer about 600 μm was produced on the TiAl alloy surface after laser polishing, which can improve the mechanical properties of the component. The micro-hardness of the laser polished sample was improved about 8% compared with the initial TiAl alloy, the wear resistance and corrosion resistance were also improved compared with the as-received TiAl surface.