Improved wear resistance of TiAl composite coatings through NbC@(Ti,Nb)2AlC core-shell structure and nanoscale precipitation strengthening

TiAl metal-based composite coatings are fabricated by laser cladding on Ti-6Al-4V (TC4) surfaces to improve their wear resistance and expand its application rang. In this study, the NbC ceramic phase and the Cu alloying element are added to improve the performance of TiAl composite coatings. The results show that the microstructure is mainly composed of TiAl, Ti3Al matrix phase, core-shell structure is NbC or TiC as the core and (Ti,Nb)2AlC as the shell, and the (Nb, Ti)Al2Cu2 phase with increasing Cu content. The composite coating achieves a maximum hardness of 1048.8 HV0.2 and a minimum wear rate of 9.5 × 10−8 mm2/N, which respectively represents an increase of 3 times and 5.2 times compared with TC4. The wear mechanism is abrasive wear. The SEM and TEM analyses and the nanoindentation results show that the main reasons for the good friction properties are (i)the increased hardness; (ii)the good interfacial relationship of the core-shell structure; (iii) the presence of the (Nb,Ti)Cu2Al2 phase reinforced by nanoscale precipitates. A detailed explanation of the wear mechanism of composite coatings, counterbody of morphology and a systematic explanation of the role of wear debris in the friction process through experimental design are provided in this paper.