The Effect of Hydrogen on Fatigue Properties of Metals used for Fuel Cell System

Abstract

The effect of hydrogen on the fatigue properties of alloys which are used in fuel cell (FC) systems has been investigated. In a typical FC system, various alloys are used in hydrogen environments and are subjected to cyclic loading due to pressurization, mechanical vibrations, etc. The materials investigated were three austenitic stainless steels (SUS304, SUS316 and SUS316L), one ferritic stainless steel (SUS405), one martensitic stainless steel (0.7C-13Cr), a Cr-Mo martensitic steel (SCM435) and two annealed medium-carbon steels (0.47 and 0.45%C). In order to simulate the pickup of hydrogen in service, the specimens were charged with hydrogen. The fatigue crack growth behaviour of charged specimens of SUS304, SUS316, SUS316L and SUS405 was compared with that of specimens which had not been hydrogen-charged. The comparison showed that there was a degradation in fatigue crack growth resistance due to hydrogen in the case of SUS304 and SUS316 austenitic stainless steels. However, SUS316L and SUS405 showed little degradation due to hydrogen. A marked increase in the amount of martensitic transformation occurred in the hydrogen-charged SUS304 specimens compared to specimens without hydrogen charge. In case of SUS316L, little martensitic transformation occurred in either specimens with and without hydrogen charge. The results of S-N testing showed that in the case of the 0.7C-13Cr stainless steel and the Cr-Mo steel a marked decrease in fatigue resistance due to hydrogen occurred. In the case of the medium carbon steels hydrogen did not cause a reduction in fatigue behaviour. Examination of the slip band characteristics of a number of the alloys showed that slip was more localized in the case of hydrogen-charged specimens. Thus, it is presumed that a synergetic effect of hydrogen and martensitic structure enhances degradation of fatigue crack resistance.

Effect of Hydrogen on the Mechanical Properties of Stainless Steels

“…This was done by Murakami and co-workers [70,71] for different steels in laboratory tests. Their main result was that "Role of hydrogen in metal fatigue is a mystery!"…”

Hydrogen embrittlement of grain boundaries in nickel: an atomistic study

“…1 Hydrogen in metallic containment systems, such as high-pressure vessels and pipelines can cause the degradation of their mechanical properties that can further result in a sudden and unexpected catastrophic fracture. [2][3][4][5] A wide range of hydrogen embrittlement phenomena was attributed to the loss of cohesion of interfaces (between grains, inclusion and matrix, or phases) due to interstitially dissolved hydrogen. 6 This concept and related models, [7][8][9] however, have not been made sufficiently predictive due to a lack of fundamental understanding of the chemomechanical mechanisms of embrittlement, despite considerable research effort.…”

Hydrogen Effect against Hydrogen Embrittlement

“…Among deleterious effects of hydrogen, ductility loss [8][9][10] is a well-known phenomenon. Hydrogen-induced degradation in fracture toughness, [11][12][13] fatigue strength, and fatigue crack growth properties [14][15][16][17][18][19][20] has also caused concern in various industrial sectors. With respect to the relationship between hydrogen and microstructure, localized plasticity due to hydrogen-enhanced dislocation mobility [3][4][5][21][22][23][24][25][26] and crystallographic slip localization by hydrogen [27][28][29] have also attracted considerable attention in the field of materials science.…”