Microstructure characterization in domestically-made TP310HNbN austenitic stainless steel after creep test

Microstructure characterization of domestically-made TP310HNbN austenitic stainless steel after creep test was investigated by means of transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The results revealed that M₂₃C₆ carbides precipitated both inside grains and at the grain boundaries and NbCrN particles were located inside grains for creep-rupture samples. It was clear that sigma phase and NbC particles precipitated inside grains for the creep-rupture sample at 670 C. M₂₃C₆ carbides with lattice parameter of three times of the austenite matrix grow in a cube to cube orientation relationship with the matrix. The amount of M₂₃C₆ carbide particles obviously increased with the testing time prolonged. Deformation hardening induced an enhanced hardness nearby rupture surface for the creep-rupture samples with a short testing time. For the domestically-made TP310HNbN steel, great attention should be paid to the distribution, size and amount of sigma phase and M₂₃C₆ during service.