Hydrogen Embrittlement Cracking Produced by Indentation Test

Abstract

Indentation is a convenient method to evaluate mechanical properties of materials as well as to simulate contact fracture with locally plastic deformation. Indentation experiment has been widely used for brittle solids, including ceramics and glass, for evaluating the fracture properties. With the aid of computational framework, simulation of crack propagation (for quasi-static and dynamic impact) is conducted to characterize “brittleness” of materials. In this review, we explore the applicability of indentation method for hydrogen embrittlement cracking (HEC). HEC is an important issue in the development of hydrogen-based energy systems. Especially high-strength steels tend to suffer from HE cracking, which leads to a significant decrease in the mechanical properties of the steels, including the critical stress for crack initiation and resistance to crack propagation. For such materials integrity for HEC, convenient material testing is necessary. In this review, the first part describes new indentation methodology to evaluate threshold stress intensity factor K_ISCC, and the latter one is investigation into HEC morphology due to residual stress produced by indentation impression. Our findings will be useful for predicting K_ISCC for HE instead of conventional long-term test with fracture mechanics testing. It will also indicate the stress criterion of HE cracking from an indentation impression crater, when the formed crater (for instance due to shot peening or foreign object contact) is exposed to a hydrogen environment.