Stress corrosion crack growth rates in Type 304 stainless steel in simulated BWR environments

摘要

Stress corrosion cracking of Type 304 stainless steel has been studied with fracture-mechanics-type standard 25.4-mm-thick compact tension specimens in simulated boiling-water reactor environments at 289/sup 0/C and 8.3 MPa. Tests were performed with either constant or cyclic loading. The latter tests used a positive sawtooth waveform with an unloading time of 1 or 5 s, a load ratio R (minimum load to maximum load) of 0.2 to 0.95, and a frequency f of 8 x 10/sup -4/ to 1 x 10/sup -1/ Hz. Crack lengths and crack growth rates were determined by the compliance method; crack mouth opening displacement was measured with in-situ clip gauges. Fractography was used to examine the mode of cracking and to confirm the compliance method for crack length determination. The test environments were high-purity deionized water with 0.2- to 8-ppM dissolved oxygen, and water with 0.2-ppM dissolved oxygen and 0.1-ppM sulfate (as H/sub 2/SO/sub 4/). Two heats with a carbon content of 0.06 wt % were investigated in solution-heat-treated and furnace-sensitized conditions. Degree of sensitization varied from approx. 0 to 20 C/cm/sup 2/ as measured by the electrochemical potentiokinetic polarization method. 8 references, 7 figures, 5 tables.