A comparative study on slurry and dry erosion behaviour of HVOF sprayed WC–CoCr coatings

In the present study, slurry and dry erosion behavior of HVOF sprayed WC–CoCr cermet coatings has been studied. The coatings were developed using the powders feedstock having WC grains in conventional and fine structured sizes. The slurry erosion testing was performed using a laboratory made pot-type slurry erosion tester. The dry erosion testing was carried out using air-jet erosion test rig (ASTM G76-07), at an impact velocity of 60 m/s and 90° impact angle. The rate of dry erosion was significantly high as compared to that of slurry erosion and it was mainly due to the particle-target impact velocities and impact angle. The mechanism of material removal in slurry and dry erosion was studied and discussed on microstructural investigations and was found to be different in both the erosion conditions. The morphology of eroded surface shows crater, lip and groove formation in the binder matrix, carbide fracturing, chipping, and pullout as visible mechanism of material removal. It was observed that the cermet coating with fine WC grain exhibits higher erosion resistance as compared to conventional cermet coating due to its improved properties like micro-hardness and fracture toughness.