Abstract
Plasma-sprayed NiCrBSi–graphite coatings have been subjected to solid particle erosion at elevated temperatures. The work reports the erosion resistance of NiCrBSi coatings with 4, 6 and 8 wt-% addition of graphite and optimum graphite content for erosion resistance. The coatings were analyzed using optical microscopy, XRD and scanning electron microscopy. Testing was carried out using air-jet erosion test rig, at an impact velocity of 70 m s−1 and at 45° and 90° angles with sand flow rate of 1 g min−1 at RT, 500°C and 650°C. Morphology of eroded surface shows crater, lip, groove formation and chipping as visible mechanism of material removal. Coating with 4wt% distribution of graphite exhibits higher erosion resistance as compared to the coating without graphite addition and improved microhardness. Microstructure images reveal that increase in graphite content above 4% results in the segregation of graphite and leading to soft islands in the coatings thereby decreasing the erosion resistance.
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