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1、西安建筑科技大学硕士论文 时效处理对超级奥氏体不锈钢组织性能的影响 专 业： 材料加工工程 硕 士 生： 刘小花 指导教师： 邹德宁 教授 摘 要 超级奥氏体不锈钢是 20 世纪 60 年代发展起来的含有高铬、镍、钼和超低碳的特种不锈钢。与传统的奥氏体不锈钢相比，超级奥氏体不锈钢具有优异的耐点蚀和耐缝隙腐蚀性能。由于超级奥氏体不锈钢在氯化物及很多还原性酸介质中优越的耐蚀性而被广泛应用于造纸漂白、海水脱盐、烟气脱硫和化工废气处理等一些较恶劣腐蚀环境中。然而，当超级奥氏体不锈钢在高温下长时间保温，会有很多析出相出现，包括碳化物、氮化物和金属间相等，最常见的第二相是 M23C6型碳化物及金属间相 ，
2、chi 及 Laves 相。还有一些第二相如：M6C，R 及 Cr2N比较少见。这些析出相对材料的力学性能、腐蚀性能和组织稳定性有着重大的负面作用，对于还未大量在高温环境中应用的超级奥氏体不锈钢来说，研究其析出行为和对性能的影响比工程应用显得更为重要，避免超级奥氏体不锈钢在热加工、热处理及焊接等高温加工过程有害的第二相出现，为其今后的实际应用提供理论基础。 本课题采用金相显微镜、扫描电镜、能谱分析、透射电镜和动电位极化曲线法等，对 254SMo 和 904L 两种超级奥氏体不锈钢材料的高温析出相的析出规律进行了研究；掌握了不同热处理工艺对超级奥氏体不锈钢力学性能的影响，明确了热处理制度、合金成
3、分、第二相析出和点蚀性能之间的关系。获得的主要结论如下：904L 的析出敏感温度为 900，254SMo 的析出敏感温度为 950。904L 的析出相主要集中在晶界，而 254SMo 晶界和晶内均有析出，Mo 含量较高的 254SMo更容易产生析出相。 经过 SEM 和 TEM 分析得出 904L 中的析出相以链状连续分布于晶界，主要为 相。254SMo 析出相的类型比较复杂，其晶界和晶内均有析出，在晶界主要表现为块状和长条状，晶内主要为粒状，经分析，晶界块状为 相，晶界条状和晶内粒状为 chi 相。 析出相的出现对超级奥氏体不锈钢力学性能有一定的影响，明显降低了高温下超级奥氏体不锈钢的塑性。
4、随着时效温度逐渐接近钢西安建筑科技大学硕士论文 的析出敏感温度以及时效时间的延长，两种超级奥氏体不锈钢的耐腐蚀性能明显下降。 关键词：关键词：超级奥氏体不锈钢；析出相；组织；力学性能；耐腐蚀性能西安建筑科技大学硕士论文 Effect of ageing on microstructures and mechanical properties of superaustenitic stainless steels Specialty: Materials Processing Engineering Name: Liu Xiaohua Instructor: Prof. Zou Dening A
5、BSTRACT The super austenitic stainless steel (SASS) is developed in the 1960s with a high content of chromium, nickel, molybdenum and special extra-low carbon stainless steel. Compared to the conventional austenitic stainless steel, super austenitic stainless steel has excellent resistance to pittin
6、g and crevice corrosion resistance. Because of the superior corrosion resistance in chloride and many reducing acid medium, the super austenitic stainless steel is more suitable for some harsh industrial working conditions, such as paper bleaching, seawater desalination, flue gas desulfurization, an
7、d some of the more severe corrosion environments, such as chemical waste gas treatment. However, austenitic stainless steels are easily embrittled by inappropriate heat treatment or prolonged exposure at elevated temperatures as a result of the formation of second phases such as carbides, nitrides,
8、and intermetallic phases. Among the various second phases, the most commonly observed precipitates are M23C6 carbide, intermetallic sigma, chi, and Laves phases, although other minor phases such as M6C carbide, R phase, phase and Cr2N. These precipitation has a significant negative effect to the mec
9、hanical properties, corrosion resistance and organizational stability of material, for not a lot in the application of super austenitic stainless steel in high temperature environment, the study of its precipitation behavior and the performance impact of the super austenitic stainless steel is more
10、important than the engineering application, in order to avoid the emergence of the second phase which harmful to the super austenitic stainless steel during hot working, heat treatment and welding high temperature operation of super austenitic stainless steel, which provides the theoretical foundati
11、on and its practical application in the future. 西安建筑科技大学硕士论文 In view of this, this article by optical microscopy, scanning electron microscope and transmission electron microscope and X-ray diffraction inspecting technology, the solid solution process after the two super austenitic stainless steel a
12、t different temperature of aging, and study the high temperature separation behavior and composition in super austenitic stainless steel high temperature separation phase influence. The results show that: 904L SASS are inclined to precipitate at the temperature of 900 , and 254SMo is sensitive to th
13、e temperature of 950 , precipitates of 904L are mainly distributed in the grain boundary, while precipitates of 254SMo are distributed in grain boundary and inter grain, under the same heat treatment condition, we found that 254SMo with more content of molybdenum is easier to precipitate than 904L.
14、The SEM and TEM analysis indicate that the precipitates of the 904L SASS continuous distributed in grain boundary as a chain, mainly for the sigma phase. While the precipitates of 254SMo SASS is complicated, they mainly distributed in grain boundary with the shape of block and long strips, inside th
15、e grain with the shape of granular, TEM analysis show that the precipitates of grain boundary is phase, grain boundary strips and the granular phase inter grain are chi phase. Precipitates play a significant effect on the mechanics properties of super austenitic stainless steel, which obviously redu
16、ces the ductility of super austenitic stainless steel at high temperature. When the aging temperature approach to sensitive temperature and prolong the aging time, the corrosion resistance of the super austenitic stainless steel decreased obviously. Keywords: super austenitic stainless steel; precipitated phase; microstructure; mechanical properties; corrosion resistance西安建筑科技大学硕士论文 I 目 录 1 绪论绪论.
