Abstract

In this study, warm shot peening was applied to Ti-Al coatings to investigate its effect on high-temperature oxidation behavior at 800–1000 °C. WSP induced severe plastic deformation and thermal effects, resulting in grain refinement, increased lattice distortion, and TiAl-to-Ti3Al phase transformation, thereby enhancing the structural stability of the coating matrix. Cyclic oxidation kinetics revealed a two-stage process transitioning from reaction-controlled to diffusion-controlled behavior. WSP delivered prominent protective effects at intermediate temperatures, substantially reducing oxidation weight gain and rate constants by promoting the formation of dense, stable Ti2O3 and Al2O3 protective layers with finer, more uniform oxide-scale morphology. However, this beneficial effect progressively weakened with increasing temperature and sharply diminished at 1000 °C, where massive generation of porous, thermally unstable TiO2 dominated the oxidation process. The loose TiO2 structure provided channels for inward oxygen diffusion, offsetting the microstructural optimization advantages of WSP and compromising oxide-scale barrier effectiveness. These findings establish a clear structure–performance correlation for WSP-modified Ti-Al coatings and elucidate the temperature-dependent failure mechanism of surface modification under ultra-high-temperature oxidation conditions.

Keywords