材料期刊网

利用Thermo-Calc软件并结合金相显微镜, 定性研究了2205双相不锈钢在800 ℃下敏化不同时间后的微观组织演变过程. 通过研究扫描速率、介质成分、介质温度和试样表面状态优化了双环电化学动电位再活化法(DL-EPR), 并用该优化方法研究了2205双相不锈钢晶间腐蚀敏感性. 结果表明: DL-EPR法能定量评价σ相对2205双相不锈钢晶间腐蚀敏感性的影响, 随敏化时间延长, σ相含量增多, 晶间腐蚀敏感性也随之增加. 腐蚀形貌的观测验证了这一规律.

Duplex stainless steels (DSS), consisted of ferrite and austenite, are widely used in oil, chemical, petrochemical, nuclear and marine industries because of their attractive combination of higher mechanical strength and corrosion resistance in various aggressive environments. However, precipitations of detrimental phases, such as chromium carbides, nitrides, intermetallic phases (χ, σ) inevitably occur when manufacturing conditions and welding procedure heat these duplex stainless steels to temperature ranging from 300 to 1000 ℃, which results in a reduction in corrosion properties due to the presence of chromium-depleted zones around these precipitates. In this paper, the microstructure evolution of 2205 DSS was studied qualitatively at 800 ℃ by using Thermo-Calc coupled with optical microscope. The double-loop electrochemical potentiokinetic reactivation (DL-EPR) was optimized through studying the influences caused by four factors (scan rate, temperature, the concentration of the electrolyte and the surface finish). Then the susceptibility to intergranular attack (IGA) of 2205 DSS was tested by optimized DL-EPR. The results indicated that σ phase will be precipitated in the ferrite phase when 2205 DSS aged at 800 ℃, and the volume fraction would increase with the aging time increasing. The optimized DL-EPR test can evaluate the susceptibility to IGA of 2205 DSS both quantitatively and qualitatively, which is proved by the morphologies of the sample after D--EPR test.