구리합금에 대한 WC-27NiCr 초고속화염용사 코팅층의 해수내 캐비테이션 특성 평가
Evaluation of Cavitation Characteristics in Seawater on HVOF Spray Coated Layer with WC-27NiCr Material for Cu Alloy
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초록
Copper alloys are commonly applied to ship's propellers, pumps and valves which are serviced in seawater due to their good castability and corrosion resistance. In the environment of high flow velocity, however, erosion damage predominates over corrosion damage. In particular, the cavitation in seawater environment accelerates surface damage to copper alloys, resulting in degradation of products and economic losses and also threatening safety. The surface was coated with WC-27NiCr by high velocity oxygen fuel(HVOF) spraying technique to attain durability and cavitation resistance of copper alloys under high velocity/pressure flow. The cavitation test was performed for the WC-27NiCr coating deposited by HVOF in seawater at the amplitude of 30 μm with seawater temperature. The cavitation at 15 ℃ caused exfoliation of the coating layer in 17.5 hours while that of 25 ℃ caused the exfoliation in 12.5 hours. When the temperature of seawater was elevated to 25 ℃ from 15 ℃, more damage was induced by over 160%. Although WC-27NiCr has good durability, corrosion resistance and eletrochemical stability, the cavitation damage rate of the coating layer could remarkably increase at the elevated temperatures under cavitation environments.
Abstract
Copper alloys are commonly applied to ship's propellers, pumps and valves which are serviced in seawater due to their good castability and corrosion resistance. In the environment of high flow velocity, however, erosion damage predominates over corrosion damage. In particular, the cavitation in seawater environment accelerates surface damage to copper alloys, resulting in degradation of products and economic losses and also threatening safety. The surface was coated with WC-27NiCr by high velocity oxygen fuel(HVOF) spraying technique to attain durability and cavitation resistance of copper alloys under high velocity/pressure flow. The cavitation test was performed for the WC-27NiCr coating deposited by HVOF in seawater at the amplitude of 30 μm with seawater temperature. The cavitation at 15 ℃ caused exfoliation of the coating layer in 17.5 hours while that of 25 ℃ caused the exfoliation in 12.5 hours. When the temperature of seawater was elevated to 25 ℃ from 15 ℃, more damage was induced by over 160%. Although WC-27NiCr has good durability, corrosion resistance and eletrochemical stability, the cavitation damage rate of the coating layer could remarkably increase at the elevated temperatures under cavitation environments.
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