| 17-4PH precipitation-hardening stainless steel is widely used in chemistry, aerospace, oil, nuclear, energy fields owing to its good corrosion resistance, excellent inoxidizability, good machinability, high strength and high toughness. In this paper, as the impeller material of core component in centrifugal compressor,17-4PH precipitation-hardening stainless steel usually serves in corrosive media, which requires very good stress corrosion resistance. To meet the requirement of good comprehensive properties, four methods of heat treatment:480℃aging treatment,585℃aging,600℃aging and600+605"Caging were used to improve the structure of17-4PH steel. This article took the slow strain rate test(SSRT) on the aged specimen to analysis the impact of heat treatment and corrosive media on the stress corrosion property by combining with the test curve, microstructure, mechanical properties and fracture characteristics.The optimization of structure and strengthening phase’s distribution caused by aging treatment can improve the stress corrosion resistance of17-4PH steel. It obtained the best stress corrosion resistance after the aging treatment at600+605℃. Many researches indicate that H+is the major factor leading to the stress corrosion in H2S medium and H+had a high solubility in reverse austenite. As the increasing of aging temperature, reverse austenite content becomes higher which reduces the gathering and diffusion of H+in17-4PH steel, and ultimately results in the improvement of the stress corrosion resistance.In different corrosive media, there are obvious differences on the SCC sensitivity. Specimen in2#medium have a higher SCC sensitivity than in3#medium showing up as the reduce of elongation, yield strength and tensile strength. Cl-can promote the corrosive effect of H2S by damaging the passive film of the steel and preventing its self-healing effect, therefore specimen in H2S-CI-medium have a higher SCC sensitivity than that in the H2S medium. |
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