Inhibiting fretting wear and sequentially altering its mechanism in TiAl alloy via laser-induced coupled gradient structure

Fretting wear frequently occurs between turbine blade tenons and disk dovetails fabricated from TiAl alloys, leading to fatigue failure of structural components. To investigate the fretting wear damage progression and reinforcement mechanisms of TiAl alloy exposed to laser shock peening with coating (LSPwC), multiple LSPwC treatments were applied to the alloy, and cyclic interrupted fretting wear tests were performed. The findings indicate that LSPwC treatment induces the creation of a coupled gradient structure composed of an ablation-remelted layer and a hardened layer in TiAl alloys, thereby changing the wear behavior of the alloy across various fretting cycles. Firstly, the ablation-remelted layer provided lubrication and protection within the first 200 cycles, which reduced the wear volume. Subsequently, at 10,000 cycles, the ablation-remelted layer fractured rapidly due to structural defects, causing the wear volume of the specimen at this stage to increase by 22.8% compared to the original. Finally, after the remelted layer fractures, the hardened layer takes a dominant role. This layer contains numerous stacking faults and a few twin structures, which facilitated the development of a stable debris layer, transitioning the primary wear mechanism from fatigue to abrasive wear. As a result, the wear volume of the strengthened specimens decreased from 25,000 cycles onward; by the time it reached 100,000 cycles, the wear volume of the strengthened specimen is reduced by 24.4%.