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 (400–1000◦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 perfor-mance of Mo–W–C coating is compared with a state-of-the-art DLC(Cr/Cr–WC/W:C–H/a:C–H) coating,which shows preliminary oxidation at 400◦C and local delamination of the coating at 500◦C leadingto 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 DLC(Cr/Cr–WC/W:C–H/a:C–H) coating is observed beyond ∼380◦C. In summary, Mo–W–C coating provides improved oxidation resistance at elevated temperature compared to DLC(Cr/Cr–WC/W:C–H/a:C–H)coating.