Stress Corrosion Screening Tests of Materials For Steam Generator Tubing in Nuclear Power Plants^*

Nuclear power plant steam generator tubing materials were tested for their susceptibility to chloride stress corrosion cracking. Stressed U-bend specimens were exposed for 24 hours in a tilting autoclave to both the liquid and vapor phases of a high pH synthetic boiler water solution containing oxygen, phosphate, and 500 ppm of chloride ion. The results indicate that AISI Type 347 stainless steel, the control material, and Carpenter 7Mo are about equally susceptible to stress corrosion cracking in this test environment. Carpenter 20Cb and Type 304 having low carbon and nitrogen content displayed improved resistance. Inconel, Monel, nickel, and titanium displayed complete resistance. Ferritic steels were crack resistant but they did suffer pitting attack. 3.5.8