Effect of short-time gradient nitriding on the surface microstructure and tribological behaviors of Ti–48Al–2Cr–2Nb alloy

TiAl alloys offer Ni-based-superalloy-like high-temperature strength at significantly lower density; however, their application is often limited by poor resistance to sliding wear and solid-particle erosion. In this study, short-time gradient nitriding (800–1000 °C for 1h) was applied to a Ti–48Al–2Cr–2Nb alloy to investigate its effect on surface microstructural evolution and tribological behavior. Sliding wear was evaluated using a ball-on-disk configuration, and solid-particle erosion tests were conducted using Al₂O₃ as both the counterbody and erodent; therefore, the results are discussed within the context of the Ti–48Al–2Cr–2Nb/Al₂O₃ tribosystem. Microstructural analyses indicated the formation of nitrogen-enriched surface regions accompanied by nitride phases, with the dominant surface features varying with nitriding temperature. At 800 °C, a thin TiN-rich surface layer was suggested, whereas nitriding at 900–1000 °C resulted in more complex nitride-containing surface regions with increased nitrogen penetration depth, consistent with the appearance of TiN- and Ti₂AlN-related diffraction features. Although high-temperature nitriding induced partial microstructural coarsening near the surface, the nitrided specimens exhibited reduced coefficients of friction and lower wear volumes compared with the as-received alloy. Under identical Al₂O₃ erodent conditions, the nitrided alloy treated at 1000 °C showed a reduced total mass loss and a lower initial erosion rate relative to the untreated state. These results suggest that short-time gradient nitriding can modify the near-surface microstructure of TiAl alloys and provide a beneficial balance between surface hardening and tribological performance, highlighting its potential as a surface-modification route for TiAl components operating in erosive and sliding environments.