Statistical approach for evaluating SCC initiation and propagation behavior of sensitized Type 304 stainless steel

The crack initiation and propagation behavior of a sensitized Type 304 stai nless steel in distilled water containing small amounts of Na2SO4 or Na2B4O 7 impurities was investigated by using slow strain rate technique (SSRT) wi th an insitu cracking observation system, and analyzed with a statistical a pproach. It was found that the crack initiation time for the steel in Na2SO 4 or Na2B4O7 solutions obeyed the exponential distribution, while K-ISCC an d crack velocity obeyed the Weibull distribution. An increase in Na2B4O7 co ncentration decreased the SCC susceptibility of the steel by delaying crack initiation time, reducing the crack initiation rate and increasing K-ISCC. In contrast, an increase in Na2SO4 concentration increased SCC susceptibil ity of the steel by shortening crack initiation time and accelerating crack propagation.