关键词: 125 ksi钢级, 超级马氏体不锈钢, Cu含量, 组织, 力学性能

Abstract: To investigate the effect of Cu element on the microstructure and mechanical properties of 125 ksi grade 15Cr martensitic stainless steel, the changes in microstructure and properties of 1.00%-1.50%Cu tested steels tempered at 500-550 ℃ were studied by means of optical microscope (OM), scanning electron microscope (SEM), transmission electron microscope (TEM), Rockwell hardness tester, and electron universal testing machine. The results show that there is no obvious difference between the metallographic structure and SEM images of 1.00%-1.50% Cu tested steels. The TEM observation shows that with the increase of Cu content, the martensitic lath gradually coarsens, the strengthening effect increases, but the tempering resistance weakens. The precipitated phases in the tested steels are mainly Laves phase, χ phase, σ phase, a small amount of M₂₃C₆, and trace amounts of Cu-rich phase, and the austenite phase region gradually expands with the increase of Cu content. The precipitation temperature of the Cu-rich phase gradually increases from 667 ℃ to 706 ℃ with the increase of Cu content, and the precipitation amount increases from 0.008 to 0.012, transforming from ellipsoidal to rod-shaped. The increase of Cu content in the tested steel has little effect on the χ phase, Laves phase, and M₂₃C₆ phase. It is more appropriate to control the Cu content at 1.25%, and with a control range of 1.20% to 1.40%, which can adjust the strength and toughness within a wide range of tempering processes.

Key words: 125 ksi steel grade, super martensitic stainless steel, Cu content, microstructure, mechanical properties