Suppressing hydrogen embrittlement of a CrCoNi medium-entropy alloy by triggering co-segregation of carbon, boron, and Cr

The CrCoNi medium-entropy alloy has drawn extensive attention due to its outstanding mechanical properties, yet it suffers severe gaseous hydrogen embrittlement (HE). Here we report that co-doping of carbon and boron could greatly suppress such embrittlement, resulting in a significant reduction in ductility loss from 71 % to merely 16 %. The minor doping has no significant influence on the phase structure, grain size, and grain-boundary character. However, the co-segregation of carbon, boron, and Cr was triggered, which not only improves the grain-boundary cohesive strength but also hinders the diffusion and accumulation of hydrogen at GBs, thereby leading to improved HE resistance.