Hydrogen Embrittlement Mechanism in Fatigue Behavior of Austenitic and Martensitic Stainless Steels

Abstract

In the present study, the influence of hydrogen on the fatigue behavior of the high strength martensitic stainless steel X3CrNiMo13-4 and the metastable austenitic stainless steels X2Crni19-11 with various nickel contents was examined in the low and high cycle fatigue regime. The focus of the investigations were the changes in the mechanisms of short crack propagation. Experiments in laboratory air with uncharged and precharged specimen and uncharged specimen in pressurized hydrogen were carried out. The aim of the ongoing investigation was to determine and quantitatively describe the predominant processes of hydrogen embrittlement and their influence on the short fatigue crack morphology and crack growth rate. In addition, simulations were carried out on the short fatigue crack growth, in order to develop a detailed insight into the hydrogen embrittlement mechanisms relevant for cyclic loading conditions. It was found that a lower nickel content and a higher martensite content of the samples led to a higher susceptibility to hydrogen embrittlement. In addition, crack propagation and crack path could be simulated well with the simulation model.

Modeling of hydrogen effects on short crack propagation in a metastable austenitic stainless steel (X2CrNi19-11)

“…Cracks predominantly initated at grain boundaries in the uncharged specimen and in specimen in 10 MPa hydrogen atmosphere as often observed in uncharged austenitic stainless steels [22,23]. In precharged specimens, the crack initation site shifted towards triple junctions [24]. As earlier mention, hydrogen residing at grain boundaries could weaken the interfacial strength leading to premature fracture.…”

“…It can also be seen that during cyclic loading a localization of plastic strain occurs as indicated by the emerging slip markings on the specimen surface as often observed for steels with low stacking fault energies. To determine the influence of hydrogen on the slip morphology, the average slip band heigth and average distance between slip bands were determined in the vicinity of the crack [24]. It could be observed that the maximum slip band heigth in precharged specimens (0.14 µm) was significantly increased as compared to measurements in uncharged specimens (0.08 µm).…”

Effect of Hydrogen Content and Strain Rate on Hydrogen-induced Delay Cracking for Hot-stamped Steel

“…In addition, martensitic steels have a high density of movable dislocation [24]. Therefore, hydrogen could be transported to the prior austenite grain boundary by movable dislocations during the stretching process and, consequently, the cohesion of grain boundary would be reduced, due to hydrogen segregation (i.e., a HEDE-type mechanism) [9,23,[38][39][40]. When the cohesion was less than the critical stress, it would lead to inter-granular fracture, as shown in Figure 15b.…”

Analysis of Hydrogen-Induced Changes in the Cyclic Deformation Behavior of AISI 300–Series Austenitic Stainless Steels Using Cyclic Indentation Testing

“…In previously published fatigue tests on AISI 300-series austenitic stainless steels the presence of hydrogen led to an earlier crack initiation and a change of the crack initiation site, as well as crack morphology [4]. Moreover, the hydrogen resulted in higher extruded slip bands, showing a wider distance between each other in relation to the slip band observed at the hydrogen-free reference condition.…”

“…Hydrogen behaves as a Cotrell cloud inside the stress field of a dislocation, shielding the dislocation from the distorted lattice. This effect causes a reduction of the interaction energy between the dislocation and obstacles [3], resulting in a decreasing external stress level required for dislocation movement [4]. The HEDE mechanism is based on the weakening effect of the accumulated hydrogen on interatomic metal bonds.…”