Effect of Artificial Defects on the Very High Cycle Fatigue Behavior of 316L Stainless Steel

Abstract

Widely used for structural materials in nuclear engineering, 316L austenitic stainless steel undergoes very high cycle fatigue (VHCF) throughout its service life. Since defects caused by service conditions are unavoidable in many engineering components during service life, the effects should be properly understood. In the present study, the effect of surface defects on the VHCF behavior were investigated on solution annealed (SA) and cold-worked (CW) 316L. Surface defects were artificially created using indentation. The VHCF test was conducted using an ultrasonic fatigue testing system. The results showed that the fatigue crack initiation was independent of the indent with the applied range of depth in this research. Furthermore, the critical depth of the indent was evaluated based on an empirical formula (Murakami’s model). In the case of SA 316L, the VHCF strength was not affected when the indent depth was less than 40 μm, which is consistent with the value obtained from the empirical formula. In the case of 20% CW 316L, the VHCF strength was not affected when the indent depth was less than 80 μm. The experimental results, i.e., the critical depth of the indent, were much larger than the results obtained from the empirical formula, and might have been caused by the plastic deformation, residual stress, and probable deformation-induced martensite transition around the indent.

Very High Cycle Fatigue Behavior of Additively Manufactured 316L Stainless Steel

“…S-N diagram of the L-PBF 316L stainless steel specimens, as well as the data obtained by Spierings et al[35], Leuders et al[36], and by Xiong et al[41] for cold-worked and solution-annealed 316L SS. The points indicated by the arrows correspond to specimens that were not disrupted during the tests.Materials 2020, 13, x FOR PEER REVIEW 6 of 12…”

“…As shown in Figure 3, the plotted S-N data corresponding to cold-worked specimens [41] shows higher endurance at similar stress levels than the data in the plot obtained for the AM specimens in HCF [36] and VHCF regimes. However, the AM specimens demonstrated almost the same fatigue behavior as the specimens heat treated at 1120 • C for 7.5 min followed by water quenching [41]. This indicated that the difference could be explained by assuming features of the damage-to-failure mechanism of the AM and routinely manufactured 316L stainless steel under fatigue loading.…”

“…The distance between the individual striations at this stage was approximately 2 µm. [36], and by Xiong et al [41] for cold-worked and solution-annealed 316L SS. The points indicated by the arrows correspond to specimens that were not disrupted during the tests.…”

Artificial Defects in 316L Stainless Steel Produced by Laser Powder Bed Fusion: Printability, Microstructure, and Effects on the Very‐High‐Cycle Fatigue Behavior

“…Although there are several works where artificial surface defects were used for VHCF studies, [ 12,32 ] there is only one very recent work in which it was used for AM materials. [ 33 ] The authors used spherical artificial defects of sizes in the range from 100 to 400 μm in Ti6Al4V.…”

Effect of Turning on the Surface Integrity and Fatigue Life of a TC11 Alloy in Very High Cycle Fatigue Regime

“…The VHCF properties are thus a vital indicator to assess the security of these aero-engine components. Therefore, the VHCF performance of titanium alloys and their damage mechanisms have received extensive attention over recent decades [2][3][4].…”