Modelling of corrosion fatigue crack initiation on martensitic stainless steel in high cycle fatigue regime

Abstract

This paper presents an analytical model for assessing the corrosion fatigue crack initiation life on a martensitic stainless steel X12CrNiMoV12-3 in high cycle fatigue regime (between 10 5 and 10 7 cycles). Based on in-situ electrochemical measurements during corrosion fatigue tests in NaCl aqueous solution, the corrosion fatigue crack initiation mechanism was identified. Two main stages were investigated: (i) the fracture of the passive film by slip bands and (ii) the free dissolution of the metal developing fatigue crack initiation from a critical corrosion defect. The depassivation stress threshold corresponds to the median fatigue strength at 10 7 cycles for fatigue corrosion tests. For an applied stress range less than this threshold, the depassivation phenomenon was not observed at 10 7 cycles and no crack initiation occurred. The proposed model takes into account the depassivation process induced by the slip bands emergence at the specimen surface and the corrosion rate under cyclic loading. The experimental results are compared to the proposed model taking into account mechanical and electrochemical material parameters.

Observations on the influence of process and corrosion related defects on the fatigue strength of 316L stainless steel manufactured by Laser Powder Bed Fusion (L-PBF)

“…The corrosion fatigue coupling could also be particularly harmful for some materials [13,30,52]. Different coupling mechanisms were pointed out in the literature, such as local persistent slip bands inducing pit initiation [14,23], loading driving pit growth morphology [40,52], corrosion at crack tip [31] or hydrogen embrittlement [11]. These coupling mechanisms could potentially decrease the lifetime more drastically than it could be predicted by considering corrosion and fatigue phenomena independently.…”

Monitoring of corrosion‐fatigue degradation of grade R4 steel using an electrochemical‐mechanical combined approach

“…Another powerful electrochemical technique, which allows measurement of corrosion rates and learning about corrosion mechanisms is electrochemical impedance spectroscopy (EIS), in which an alternating potential or current signal is applied to an electrochemical cell and the resulting current (or potential) is measured. The technique has been successfully applied on stainless steel under corrosion‐fatigue degradation …”

“…Electrochemical variables such as corrosion current density and corrosion potential have been used to assess the damage evolution in corrosion-fatigue experiments. [21][22][23][24][30][31][32] Although current response gives valuable information about the electrochemical kinetics of the corrosion-fatigue system, its measurement commonly requires the application of a certain level of polarization leading to a condition that does not represent the free corrosion behaviour of the material. Meanwhile, some studies 30,31 have shown that the growth of oxide on the surface of the material and the nucleation of microcracks can change the shape of the corrosion potential response during corrosion-fatigue tests of magnesium alloys.…”

“…The technique has been successfully applied on stainless steel under corrosion-fatigue degradation. 32 Because degradation of offshore metallic structures is a major issue in the oil extraction industry, it is crucial to understand the mechanisms and the influence of environmental variables on the degradation process. The focus of this study is on monitoring the mechanisms of degradation of martensitic steel of offshore mooring chains, under corrosion-fatigue condition.…”

“…The electrochemical behaviour of the steel surface in the marine environment has a decisive role on fatigue life. Electrochemical variables such as corrosion current density and corrosion potential have been used to assess the damage evolution in corrosion‐fatigue experiments . Although current response gives valuable information about the electrochemical kinetics of the corrosion‐fatigue system, its measurement commonly requires the application of a certain level of polarization leading to a condition that does not represent the free corrosion behaviour of the material.…”