Hydrogen Embrittlement of the Additively Manufactured High-Strength X3NiCoMoTi 18-9-5 Maraging Steel

Abstract

The main aim of this study was to determine the susceptibility of the additively manufactured high strength X3NiCoMoTi 18-9-5 maraging steel to hydrogen embrittlement. For this purpose, samples produced by selective laser melting technology, before and after heat treatment, were used. The examined samples were electrochemically charged with hydrogen in NaCl + NH4SCN solution at a current density of 50 mA/cm2 for 24 h. The H content increased from about 1 to 15 ppm. Heat treatment did not affect the amount of H trapped in the maraging steel. Tensile testing revealed that the tensile strength of the H-charged samples was much lower than that of the uncharged samples. Moreover, the material became brittle after charging compared to the ductile as-printed and heat-treated samples with elongation values of 7% and 2%, respectively. The loss of plasticity was confirmed by fractography, which revealed transformation of the fracture surface morphology from dimple-like in the as-produced state to a brittle one with smooth facets in the H-charged state.

Hydrogen Embrittlement as a Conspicuous Material Challenge─Comprehensive Review and Future Directions

“…Li et al suggested that H decreases the critical stress needed for martensitic transformation of retained austenite in L-PBFed 300 steel, leading to premature phase transformation and higher HE susceptibility. Similarly, Strakosova et al reported substantial HE in L-PBFed X3NiCoMoTi 18-9-5 maraging steel with a fully martensitic microstructure after heat treatment, H trapping at defects was suspected to be the main cause. HE of a 18Ni-300 maraging steel produced by SLM was also attributed to H trapping, in particular due to retained austenite.…”

Hydrogen embrittlement in micro-architectured materials

“…More recently, the research on this topic has extended to additively manufactured bulk materials, e.g. see [28], [29] and [30]. There exist two prevailing theories for hydrogen embrittlement, namely the hydrogen enhanced decohesion (HEDE) mechanism and the hydrogen enhanced localized plasticity (HELP) mechanism.…”