Environmentally Assisted Growth Rate Response of Nonsensitized AISI 316 Grade Stainless Steels in High Temperature Water Available to Purchase

Experiments were performed on a compact tension specimen of AISI⁽¹⁾ 316L stainless steel (SS) to determine its susceptibility to intergranular environmentally assisted cracking in 288 C water. Crack growth rates were measured using a reversing DC potential drop technique as a function of mechanical loading variables in 288 C water containing 200 ppb dissolved oxygen and 0.5 μS/cm Na₂SO₄. The specimen was tested in the as-received plus 650 C/1 h heat treatment condition. The crack propagation rate at constant stress intensity of 27.5 MPa $m$ was 4.2 × 10⁻⁹ cm/s (6.0 × 10⁻⁶ in./h), about a factor of 8 lower than the typical crack growth rate for sensitized AISI 304 SS (EPR = 15 C/crn²) under similar test conditions. Additionally, a database of crack growth rates on fracture mechanics specimens in high temperature water for AISI 316L and 316NG SSs was developed and compared with predictive modeling. The accuracy of the prediction algorithms has been demonstrated for sensitized AISI 304 SSs; an objective of this investigation was to validate the algorithms for nonsensitized SSs. The observed crack growth rates are in good agreement with predictions over more than three orders of magnitude variation resulting from various loading conditions, dissolved oxygen levels (≈10 to 8000 ppb) and solution conductivities (0.1 to 0.8 μS/cm).