Crack healing of hydrogen-attacked cracks in carbon steel under hot plastic deformation

Healing of hydrogen - attacked (HA) cracks in carbon steel was studied by using hot press treatment. Under hot plastic deforming at 1000°C and the deformation rate of 40%, the most of HA cracks can be recovered completely within 15 min. Partial HA cracks, which has not been recovered by hot - press treatment, present the spherical cap - shaped with the length of about 4 μm ∼ 8 μm. Comparing with the results of high temperature treatment without press (cyclic heat treatment between room temperature and 1000 °C for 10 h), both the healing degree and speed under hot plastic deforming are improved obviously. There are not distinct difference of healing results between the direct hot - press healing and pre - heated treatment before hot - press healing. That means the decomposition of methane in HA cracks is not the key step during the whole healing process.