Tribological behaviour of plasma sprayed diamond reinforced molybdenum coatings

Thermally sprayed molybdenum coatings have widespread applications in automotive, aerospace, paper and plastics processing industries owing to their high scuffing resistance and wear resistance under sliding contact conditions as well as their high-temperature strength. However, plasma-sprayed molybdenum coatings are reported to be soft and need reinforcing agents to improve their coating performance. The present work envisages the tribological performances of a 10 and 20 wt% diamond reinforced plasma sprayed molybdenum coating fabricated using a ball-milled powder. Some important mechanical properties like hardness and elastic modulus of the coating surface were evaluated. A maximum increase of similar to 20% and similar to 32% in hardness and elastic modulus was observed upon addition of diamond reinforcements up to 20 wt%. Tribological performance of these coatings was evaluated in sliding mode using ball-on-disc configuration under 1- 3 kg normal load range and a sliding speed range of 50- 150 mm/s. Microstructural features of the coating were identified and correlated to the tribo-performance of the coatings. A pure molybdenum coating was used for benchmarking purpose. The diamond reinforced coatings demonstrated an improved wear characteristic. An improvement in wear resistance by up to 2.7 times and 8 times were observed in the case of 10 and 20 wt% diamond reinforced coatings, respectively. Wear in these coatings is attributed to localized plastic deformation.