EFFECT OF TEMPERATURE, PH AND SULFIDE ON THE CAVITATION EROSION BEHAVIOR OF SUPER DUPLEX STAINLESS-STEEL

Cavitation erosion characteristics of super duplex stainless steel UNS S32760 in 3.5% NaCl solution with controlled temperature, pH value an d sulphide content have been studied by means of a 20 kHz ultrasonic v ibrator at a peak-to-peak amplitude of 50 mu m. The erosion behaviour was compared with that of austenitic stainless steel UNS S30400. It wa s found that the mean depth of penetration rate (MDPR) for S32760 and S30400 initially increased with temperature from 10 degrees C to 50 de grees C, and reached a maximum at about 50 degrees C and then decrease d with further increase in temperature to 70 degrees C. Results of MDP R versus pH at 23 degrees C indicated that S32760 is more sensitive to change of pH than is S30400 at 23 degrees C. Also, there exists a min imum MDPR at pH 9 for S32760. For S30400 and S32760 in 3.5% NaCl solut ion with various sulphide concentrations, the MDPR increased gradually as sulphide concentration was increased. S30400 was found to be more sensitive than S32760; to the effect of sulphide on cavitation erosion . The cavitation erosion behaviour of S32760 at varying temperature, p H and sulphide content is explained with the aid of polarisation studi es. (C) 1997 Elsevier Science S.A.