Effect of Long-Term Aging at 350 ℃ on Dynamic Fracture Toughness of 17-4PH Stainless Steel

The variation of impact performance with the extension of aging time on the type of 17-4PH stainless steel at 350 ℃ was studied in the paper, and the variation of dynamic fracture toughness and fractographys of the type stainless steel for various holding time at this temperature were also researched by instrumental impact test and scanning electron microscope. All results indicate that the plastic deformation energy (E_PL), tearing energy (E_TE), absorbed in fracture energy (E_t) and dynamic fracture toughness (K_Id ) of this type alloy are decreased with the continuation of time at 350 ℃. The KK_Id falls fast at the forepart of aging test and then slowly. It shows that the toughness of the alloy is degraded and the degradation is mainly taken place at the forepart of aging test. The fractography of this alloy is changed from dimple fracture into cleavage fracture and inter granular rapture with the extension of aging time. Those show that the fracture toughness of this alloy has degraded with the extension of aging time at 350 ℃..