Multi-scale tribological and nanomechanical behavior of cold sprayed Ti^sub 2^AlC MAX phase coating

Ti2AlC based MAX phase coatings were successfully deposited on Inconel 625 substrate by a cold spraying technique. A dense coating of 70 µm thickness was deposited. Ball-on-disk wear behavior of Ti2AlC coating at room temperature (25 °C), and high temperature (600 °C) were studied. The coefficient of friction (COF) and wear volume loss at 600 °C reduced by ∼ 21% and ∼ 40% respectively, due to the lubricious nature of oxide layer formed at a higher temperature. Mechanical properties of the Ti2AlC coating were also studied by carrying out nanoindentation and nano-scratch tests at room temperature and 300 °C and varying loads. For a low load of 7000 µN at room temperature, Ti2AlC coating exhibited a higher elastic modulus of 273 GPa compared to the elastic modulus of 191 GPa at high temperature (300 °C). The room temperature nano-scratch at 7000 µN displayed brittle behavior with fracture, chipping and wear debris formation along the scratch path. However, high temperature (300 °C) scratch path exhibited ductile nature with plowing, cutting and no wear debris formation. The wear volume loss was several orders of magnitude higher at 8 N load scratch. The overall wear behavior in MAX phase Ti2AlC coating at multiple load scales is elucidated in terms of the interaction volume varying from a single to several splats in the cold sprayed structure.