Evolution of microstructure and mechanical properties of a 25Cr-20Ni heat resistant alloy after long-term service

This work investigated the effect of long-term service on the evolution of microstructure and properties of HR3C alloy. Its results show that large amount of discontinuous chromium carbide is accompanied by a chromium depletion area that is formed along the grain boundary. This depletion area promotes the crack nucleation and propagation at the carbide-matrix interface at the grain boundary, leading to a decrease in the alloy ductility at room temperature. However, this deteriorative effect is not obvious at high temperatures primarily because the fast drop of the grain strength. Therefore, the crack propagates easily across the grain during the alloy deformation at high temperatures.