Abstract: Cu-bearing Cr13 martensitic stainless steels without La and with 0.012% La were taken as the test materials, which were subjected to solution treatment at 980 ℃, following by oil cooling, and aging at 500 ℃ for different time. Effect of rare earth addition on microstructure and mechanical properties of the steel was studied by means of optical microscope, scanning electron microscope, EBSD, combined with mechanical property tests. The results show that rare earth La significantly reduces the δ ferrite volume fraction in the steel, leading to an increase of martensite after quenching, which in turn leads to the increase of dislocations in the matrix, and thus improves the hardness and strength of the tested steel. During the aging process, by the continuous precipitation of Cu-rich particles, about 200 MPa can be contributed to the yield strength of the tested steels at the peak stage of aging strengthening, but the rare earth La has no significant effect on the precipitation kinetics of Cu-rich phases. At the same time, the plasticity of the tested steels is significantly improved due to the continuous reduction of low-angle grain boundaries and the increase of high-angle grain boundaries during the aging process.

Key words: Cr13 martensitic stainless steel, La, microstructure, precipitate, mechanical properties