Isothermal and dynamic oxidation behaviour of Mo−W doped carbon-based coating

The oxidation behaviour of Mo−W doped carbon-based coating (Mo−W−C) is investigated in elevated temperature (400°C−1000°C). Strong metallurgical bond between Mo−W−C coating and substrate prevents any sort of delamination during heat-treatment. Isothermal oxidation tests show initial growth of metal oxides at 500°C, however graphitic nature of the as-deposited coating is preserved. The oxidation progresses with further rise in temperature and the substrate is eventually exposed at 700°C. The performance of Mo−W−C coating is compared with a state-of-the-art coating, which shows preliminary oxidation at 400°C and local delamination of the coating at 500°C leading to substrate exposure. The graphitisation starts at 400°C and the diamond-like structure is completely converted into the graphite-like structure at 500°C. Dynamic oxidation behaviour of both the coatings is investigated using Thermo-gravimetric analysis carried out with a slow heating rate of 1°C/min from ambient temperature to 1000°C. Mo−W−C coating resists oxidation up to ~800°C whereas delamination of coating is observed beyond ~380°C. In summary, Mo−W−C coating provides improved oxidation resistance at elevated temperature compared to coating.