A hybrid laser surface modification technique: Microstructural and property regulation mechanisms of titanium alloy via laser shock forging

Abstract

In this study, a hybrid surface modification technique, Laser Shock Forging (LSF), was developed by integrating pulsed laser excitation with laser cladding (LC) using TA15 titanium alloy both as the substrate and the powder. Differences between LCed and LSFed coatings in microstructure, residual stress state, tribological properties, and electrochemical corrosion behavior were systematically analyzed. Results showed that the α-phase microstructure transformed from a typical basketweave morphology in the LCed coating to a refined columnar structure in the LSFed coating, with an average size reduction of approximately 32 %. A work-hardened layer and a compressive residual stress (CRS) layer formed in the LSFed coating, accompanied by high-density dislocation introduction, which collectively contributed to a microhardness increase of approximately 33.5 % compared to the LCed coating. In terms of wear performance, the LSFed coating demonstrated superior resistance, with abrasive and oxidative wear as the dominant mechanisms. X-ray photoelectron spectroscopy (XPS) further revealed that LSF promoted the formation of a dense and stable TiO₂-rich passivation film, significantly enhancing corrosion resistance. In summary, LSF improved the overall performance of the TA15 alloy through a combined mechanism of grain boundary strengthening and dislocation-induced hardening, offering an effective approach for advanced titanium alloy surface engineering.