Optimizing the Microstructure and Mechanical Properties of a Laser Clad Ti-6Al-4V Coating by Laser Shock Peening (LSP)
W-B. Ren, S-Y. Fang, J-H. Li, W-C. Yu and Y-J. Wang
In view of the difficulties such as coarse microstructure, performance degradation and excessive residual stress during the preparation of Ti-6Al-4V layers by laser cladding, the microstructure and mechanical properties of such a Ti-6Al-4V coating were optimized and improved based on the plastic deformation effect caused by laser shock peening (LSP). The characteristics of phase composition, changes in microstructure and morphology, grain plastic deformation and the influence of mechanical properties of the laser clad Ti-6Al-4V coating were studied pre- and post-LSP. The results indicate that the α/α′ phase content increases and the β phase content decreases after LSP. The β phase and acicular martensite α′ phase is refined significantly and divided, and the basket structure presents a more dense and staggered distribution after LSP. Laser cladding causes the grains in the Ti-6Al-4V coating to undergo plastic strain and the degree of grain refinement was significantly improved following LSP. The microhardness at the top of the laser clad Ti-6Al-4V coating increases from 23 to 30% compared after LSP. At the same time, the LSP promotes the transformation of residual tensile stress to compressive stress on the surface of the laser clad Ti-6Al-4V coating, with an average residual compressive stress value of about 339 MPa. This study provides theoretical and methodological references for optimizing the microstructure and properties of Ti-6Al-4V coatings.
Keywords: Fibre laser, Nd:YAG laser, Ti-6Al-4V, laser cladding