Grain-boundary engineering markedly reduces susceptibility to intergranular hydrogen embrittlement in metallic materials

The feasibility of using grain-boundary engineering techniques to reduce the susceptibility of a metallic material to intergranular embrittlement in the presence of hydrogen is examined. Using thermo mechanical processing, the fraction of special grain boundaries was increased from 46% to 75% (by length) in commercially pure nickel samples. In the presence of hydrogen concentrations between 1200 and 3400 appm, the high special fraction microstructure showed almost double the tensile ductility; also, the proportion of intergranular fracture was significantly lower and the J(c) fracture toughness values were some 20-30%, higher in comparison with the low special fraction microstructure. We attribute the reduction in the severity of hydrogen-induced intergranular embrittlement to the higher fraction of special grain boundaries, where the degree of hydrogen segregation at these boundaries is reduced. Published by Elsevier Ltd on behalf or Acta Materialia Inc.