The Influence of Second Particals on Grain Boundary Sliding

The effect of second particles on the grain boundary deformation in 304 type austenitic stainless steel was studied. Flat tensile samples with marker scratches on the surface were strained at slow rate at intermediate temperatures (300-500 °C) at ambient pressure. It seems that the sensitized material decreased creep rate and needed more stress to generate deformation of grain boundary, suggesting Cr carbides decreased the grain boundary sliding. Thus, the resistance to SCC crack propagation could be improved. The Charpy tests suggested that sensitized material had lower fracture toughness; this was due to the GB carbides that acted as nucleation sites for brittle fracture. Characterizations of the tensile samples were carried out using a secondary electron microscope in order to understand whether second phases can affect the creep behavior and grain boundary sliding.