On the influence of microstructure evolution and wear mechanism of direct laser deposited Ti-Al-Si coatings with different Si contents

In response to the problem of low hardness and poor wear resistance of TC4 coatings prepared by laser additive manufacturing, three titanium alloy coatings with different Si contents were prepared on a TC4 substrate by direct laser deposition (DLD) technology. The evolution of the microstructure and wear mechanism of the coatings were studied. The addition of the Si element facilitated the formation of Ti5Si3 hard phase, which exhibited a uniform mesh form. The strengthening effect of the hard phase in the prepared coating increased with its proportion, demonstrating a positive correlation with the incremental addition of an Si element. However, the excessive addition of the Si element resulted in the surface cracking of the coating. The optimal DLD Ti-Al-Si coating was obtained when the Si content was 10 wt. %, with an average microhardness of 801 ± 24 HV0.2, 2.5 times greater than that of the TC4 substrate. The average friction coefficient of the Ti-Al-Si coating was 0.39, and the wear rate was 1.9%. The hard phase was uniformly distributed in a mesh form, which not only refined the wear debris and suppressed the shear force of the wear debris during wear but also slowed down the continuous wear of debris on the worn surface. The results of this study could provide a reference for preparing high-hardness and wear-resistant titanium alloy coatings by DLD.