Cavitation erosion and drain erosion are major causes of failure of mechanical devices in fluid handling systems. The authors investigated the application of plasma spraying technique to the formation of coatings with high resistance against the cavitation and drain erosion damage. By using low pressure plasma spraying, some coatings of cermet and metallic alloy materials were prepared and tested for the cavitation erosion behavior. Cobalt base alloy coating shows much more excellent resistance to the erosion than that of Stellite-6, which has been widely used as the wrought product to shield a steam turbine blade from the damage. In spite of the similar chemical composition of the Co alloy to that of stellite-6, the erosion-performance is different. Microscopic characterization of the deposite reveals that the superiority of the coating is caused by the extended solid solubility of carbon resulted from the rapid solidification of the sprayed droplets.