INITIATION AND GROWTH OF INTERGRANULAR STRESS-CORROSION CRACKS FOR SENSITIZED 304 STAINLESS-STEEL DEPENDING ON NAF CONCENTRATION OF AQUEOUS-SOLUTION

Using a slow strain rate technique, SSRT, with CCD camera system, init iation and growth behavior of intergranular stress corrosion cracking, IGSCC, for sensitized 304 stainless steel in aqueous solution contain ing various concentrations of NaF has been investigated. The largest d ecrease in maximum stress indicating the highest IGSCC susceptibility was found at 10(3) ppm NaF. And at the same concentration of 10(3) ppm NaF, the highest density of crack number and the shortest crack gener ation time was found. On the other hand, threshold stress intensity fa ctor for IGSCC was independent of concentration of NaF. Crack growth r ate showed a little dependence on NaF concentration, exhibiting a decr ease at 10(3) ppm. It was obvious from the results that the highest IG SCC susceptibility at 10(3) ppm NaF was caused by increasing the numbe r of cracks and decreasing the crack generation time, not by a change in threshold stress intensity factor for SCC or crack growth rate.