Characterization of Damage During Low Cycle Fatigue of a 304L Austenitic Stainless Steel as a Function of Environment (Air, PWR Environment) and Surface Finish (Polished, Ground)

Influence of mean stress and pressurized water reactor environment on the fatigue behavior of a 304L austenitic stainless steel

“…From Figures 8F and 9A, it is revealed that this crack initiation life is much lower in PWR water than in air. This detrimental effect of PWR water on the crack initiation stage is in agreement with previous research 40–42 …”

“…The values of C , m , N t , and a t for each investigated condition are assembled in Table 3. This transition in crack growth rate was previously observed in 304 stainless steel on striation spacing as on crack growth rates derived from direct current potential drop (DCPD) monitoring method, at diverse strain amplitudes and strain rates and in different media 6,34–36 . This can be attributed to a lower sensitivity to Δ K ε (or crack depth) during the propagation of short cracks than the macro‐crack propagation, firstly reported as a “short‐crack” effect 37 .…”

“…This is furthermore consistent with the variation observed in fatigue striation spacing on the crack propagation area of the fracture surface and as presented in Figure 11 as a function of Δ K ε . In Figure 11, the results for strain amplitudes equal to and lower than 0.2% are compared with results previously obtained for the same material and under the same strain rate but at significantly higher strain amplitudes (0.6%, 6,40 0.5%, 19 and 0.3% 40 ). It is found that for a given environment (air or PWR water), the effect of strain amplitude on fatigue crack growth rates is extremely limited and that the fatigue crack growth rate in air is always smaller than in PWR water.…”

“…The numbers of cycles required to make a surface crack grow to a certain depth are then calculated by using these values represented by the fitting curves in Figure 8F. In some previous research with Δ ε t /2 = 0.6%, 10–20 μm is frequently applied to define the depth of fatigue crack initiation for the 316 stainless steels 39 and for the investigated material 6,40 . However, at Δ ε t /2 = 0.2%, even after 50% of the fatigue life, a considerable proportion of cracks can be stopped by the first grain boundaries encountered 38 .…”

Environmental effect of PWR primary water on fatigue life of stainless steel (influence of loading rate on fatigue life reduction)

“…It has been shown that the fatigue crack growth rate in the PWR water environment is closely correlated with the strain intensity factor range ΔK ε. 17,28,32 The following equation can be used for predicting the growth rate da / dN : where D p and m are material constants. Because fatigue life N f corresponds with the number of cycles necessary for a crack to reach the critical size for specimen failure, it can be predicted by integrating Equation 4 from initial depth a i to final depth a f .…”