The Ultrasonically Induced Cavitation Corrosion Behavior of UNS R31233 Alloy In Sea Water

ABSTRACT A vibratory induced cavitation facility was used to study the cavitation corrosion behavior of UNS R31233 alloy in seawater. The work included measurements of free corrosion potentials, and mass loss in the presence and absence of cavitation. The cavitation tests were made at a frequency of 20 KHz and at temperatures of 25°C. Cavitation conditions caused an active shift in the free corrosion potential for UNS R31233 alloy. Cavitation also very slightly increased the rate of mass loss of this alloy with respect to stagnant conditions. Another set of cavitation experiments was also carried out for this alloy in a nonconductive medium in order to distinguish between the mechanical and electrochemical factors that contribute to metal loss. Results indicated that the mechanical factor has an overriding role in metal loss of this alloy. Cavitation made the surface of this alloy slightly rough exhibiting very small cavity pits in the middle region of the attacked area as revealed by the scanning electron microscope (SEM). Mechanical factors were determined to be the leading cause of metal loss. INTRODUCTION UNS R31233 is a Co-26 Cr-9Ni (wt%) alloy which exhibits excellent resistance to both corrosion and wear and in a wide range of aqueous media. This alloy tends to maintain its corrosion resistance under high velocity conditions and show good wear resistance. Wrought cobalt-based UNS R31233 alloy provides excellent elevated-temperature strength, and resistance to various forms of wear and sulfidizing environments.¹ The alloy possesses high tensile strength combined with excellent impact toughness and ductility. The typical room-temperature yield strength of the alloy is 586 MPa. The tensile strength is 1000 MPa, and elongation is 39% (Ref). UNS R31233 alloy is an appropriate material for fabricating structural components, such as agitators, blenders, spray nozzles, screw conveyors, pumps, and valve parts.