Influence of heat-treatment on the sliding wear of thermal spray cermet coatings

Functionally graded WC-NiCrBSi coatings were thermally sprayed using a High Velocity Oxy-Fuel (JP5000) system and heat-treated at 1200 °C in argon environment. The relative performance of the as-sprayed and heat-treated coatings was investigated in sliding wear under different tribological conditions of contact stress, and test couple configuration, using a high frequency reciprocating ball on plate rig. Test results are discussed with the help of microstructural evaluations and mechanical properties measurements. Results indicate that by heat-treating the coatings at a temperature of 1200 °C, it is possible to achieve higher wear resistance, both in terms of coating wear, as well as the total wear of the test couples. This was attributed to the improvements in the coating microstructure during the heat-treatment, which resulted in an improvement in coating's mechanical properties through the formation of hard phases, elimination of brittle W2C and W, and the establishment of metallurgical bonding within the coating microstructure.