Evaluating the intergranular SCC resistance of sensitized Type 304 stainless steel in low-temperature water environments

The resistance of sensitized AISI Type 304 stainless steel to intergranular stress-corrosion cracking (IGSCC) in 320C water environments has been investigated using constant axial load (CAL), constant extension rate (CER), U-bend and crevice corrosion tests. Constant load tests were found to give a better simulation of a service failure and produced IGSCC under a wider range of conditions than CER or U-bend tests. Intergranular SCC of welded and furnace-sensitized Type 304 specimens was observed in CAL experiments in both deionized and borated water with ppM level chloride additions. Constant extension rate tests also produced IGSCC but only in welded pipe specimens with the original ground and welded surfaces intact. If the original ID and OD surfaces were removed, fracture surfaces showed ductile, microvoid coalescence appearances. No evidence of SCC or significant corrosive attack was found in U-bend or crevice corrosion tests after more than six months in dilute chloride environments at temperatures of 30 or 500C. However, intergranular cracking was observed in furnace-sensitized, high-carbon Type 304 U-bend specimens at 800C