Mitigating hydrogen embrittlement in CoCrNi alloy using a self-refilling nanoscale amorphous oxide layer

Designing hydrogen embrittlement-resistant materials exposed to extreme conditions has long been challenging. In this work, we introduced a strategy combining Si alloying with short-term oxidation to generate a nanoscale amorphous layer on CoCrNi alloy. The layer spontaneously formed in a high-temperature environment and was firmly bonded to the matrix. This nanoscale amorphous layer reduced the hydrogen penetration rate by 62 %. The hydrogen-charged CoCrNi alloy with amorphous layers still retained a high tensile strength of 890 MPa and a strain-to-failure of 57 %, while the embrittlement sensitivity is only 0.04 (which is 0.25 for bare CoCrNi), demonstrating an outstanding hydrogen embrittlement resistance. The nanoscale amorphous layer is an effective hydrogen barrier due to its dense structure, which lacks rapid hydrogen diffusion pathways such as dislocations and grain boundaries. Additionally, the amorphous layer reduces Cr depletion at subsurface grain boundaries and prevents the formation of pores induced by the Kirkendall effect. Compared to traditional coatings, the amorphous layer can be self-refilled at critical temperature after damage under external loading. This approach provides a long-run approach for designing hydrogen embrittlement-resistant alloys capable of withstanding extreme service conditions.