1984 Volume 25 Issue 6 Pages 411-419
Carbon tends to suppress the grain boundary fracture of α-iron, which is promoted by the segregation of phosphorus and other impurities to grain boundaries. This effect of carbon is due to its grain boundary segregation. It is shown in the present paper that the same effect of carbon is observed when hydrogen promotes the grain boundary fracture. Iron specimens with and without carbon addition are tensile tested while being charged with hydrogen electrolytically at low temperatures. A specially prepared high purity iron fractures along grain boundaries after a few percent elongation when tested during hydrogen charging, otherwise it is completely ductile. The same iron is ductile even under hydrogen charging, if it is doped with carbon of about 20 mass ppm. The carbon effect is further investigated with fine grained specimens made from a commercial high purity iron. Tests are performed on as-quenched and on aged specimens with precipitates of ε-phase and Fe3C. The results show that carbon segregated at grain boundaries has the effect to prevent the grain boundary fracture.
