WC-10Co4Cr으로 초고속 화염용사 코팅된 Cu 합금의 해수내 캐비테이션 손상 거동

Abstract

Due to the good corrosion resistance and machinability, copper alloy is commonly employed for shipbuilding, hydroelectric power and tidal power industries. The Cu alloy, however, has poor durability, and the seawater application at fast flow condition becomes vulnerable to cavitation damage leading to economic loss and risking safety. The HVOF(High Velocity Oxygen Fuel) thermal spray coating with WC-10Co4Cr were therefore introduced as a replacement for chromium or ceramic to minimize the cavitation damage and secure durablility under high-velocity and high-pressure fluid flow. Cavitation test was conducted in seawater at <TEX>$15^{\circ}C$</TEX> and <TEX>$25^{\circ}C$</TEX> with an amplitude of <TEX>$30{\mu}m$</TEX> on HVOF WC-10Co4Cr coatings produced by thermal spray. The cavitation at <TEX>$15^{\circ}C$</TEX> and <TEX>$25^{\circ}C$</TEX> exposed the substrate in 12.5 hours and in 10 hours, respectively. Starting from 5 hours of cavitation, the coating layer continued to show damage by higher than 160% over time when the temperature of seawater was elevated from <TEX>$15^{\circ}C$</TEX> to <TEX>$25^{\circ}C$</TEX>. Under cavitation environment, although WC-10Co4Cr has good wear resistance and durability, increase in temperature may accelerate the damage rate of the coating layer mainly due to cavitation damage.