HYDROGEN ASSISTED FRACTURE OF SPHEROIDIZED PLAIN CARBON-STEELS

Both initially smooth and circumferentially notched tensile specimens were electrochemically charged with hydrogen at various cathodic current densities and uniaxially strained various amounts. Comparisons with uncharged specimens showed that hydrogen promotes void initiation at cementite particles. Void growth and coalescence were also accelerated. Hydrogen induced losses in interfacial cohesion may account for void initiation, growth and coalescence at lower stresses and strains. A partial transition in fracture mode was observed in steels with a low particle-matrix and grain boundary interfacial area per unit specimen volume. This quasicleavage mode was generally associated with nonmetallic inclusions.