해수 환경에서 듀플렉스 스테인리스강의 전기화학적 거동 및 캐비테이션 특성
Electrochemical and Cavitation-Erosion Characteristics of Duplex Stainless Steels in Seawater Environment
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A wet type scrubber for merchant vessel uses super austenitic stainless steels with pitting resistance equivalentnumber (PREN) of 40 or higher for operation in a harsh corrosive environment. However, it is expensivedue to a high nickel content. Thus, electrochemical behavior and cavitation erosion characteristics ofUNS S32750 as an alternative material were investigated. Microstructure analysis revealed fractions of ferriticand austenitic phases of 48% and 52%, respectively, confirming the existence of ferritic matrix andaustenitic island. Potentiodynamic polarization test revealed damage at the interface of the two phasesbecause of galvanic corrosion due to different chemical compositions of ferritic and austenitic phases. After a cavitation test, a compressive residual stress was formed on the material surface due to impact pressureof cavity. Surface hardness was improved by water cavitation peening effect. Hardness value was thehighest at 30 μm amplitude. Scanning electron microscopy revealed wave patterns due to plastic deformationcaused by impact pressure of the cavity. The depth of surface damage increased with amplitude. Cavitation test revealed larger damage caused by erosion in the ferritic phase due to brittle fracture derivedfrom different strain rate sensitivity index of FCC and BCC structures.
Abstract
A wet type scrubber for merchant vessel uses super austenitic stainless steels with pitting resistance equivalentnumber (PREN) of 40 or higher for operation in a harsh corrosive environment. However, it is expensivedue to a high nickel content. Thus, electrochemical behavior and cavitation erosion characteristics ofUNS S32750 as an alternative material were investigated. Microstructure analysis revealed fractions of ferriticand austenitic phases of 48% and 52%, respectively, confirming the existence of ferritic matrix andaustenitic island. Potentiodynamic polarization test revealed damage at the interface of the two phasesbecause of galvanic corrosion due to different chemical compositions of ferritic and austenitic phases. After a cavitation test, a compressive residual stress was formed on the material surface due to impact pressureof cavity. Surface hardness was improved by water cavitation peening effect. Hardness value was thehighest at 30 μm amplitude. Scanning electron microscopy revealed wave patterns due to plastic deformationcaused by impact pressure of the cavity. The depth of surface damage increased with amplitude. Cavitation test revealed larger damage caused by erosion in the ferritic phase due to brittle fracture derivedfrom different strain rate sensitivity index of FCC and BCC structures.
참고문헌 (23)
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