【作者】 邢海生；

【导师】 潘邻； 林峰；

【作者基本信息】 机械科学研究总院 ， 材料学， 2011， 硕士

【摘要】 奥氏体不锈钢有着出色的耐腐蚀性能,在化工、海洋、石油、仪表制造、食品生物、医学等行业中得到广泛的应用。它的使用量约占整个不锈钢产量的65%～70%。奥氏体不锈钢存在表面硬度低(250～300HV)、耐磨性和抗疲劳性能差。传统渗氮处理能有效提高奥氏体不锈钢的表面硬度,但同时出现Cr的偏析与CrN化合物生成,导致奥氏体不锈钢失去耐蚀属性。低温渗氮处理能够有效抑制CrN的析出,形成传统渗氮层相当硬度的S相,使奥氏体不锈钢的耐蚀性不降低。目前国内外针对奥氏体不锈钢低温渗氮处理工艺的研究主要靠离子法和气体法实现,液体法只有日本进行过研究。为开展奥氏体不锈钢低温液体渗氮工艺研究,本课题利用两种思路研制出可以在450℃以下使用的低温渗氮盐,均取得良好的效果。这两种盐CNO-浓度均超过了47%。使用自行研制出的低温渗氮盐,本文考察了液体渗氮温度对渗层的成分、组织、结构和性能的影响；430℃和440℃温度下液体渗氮时间对层深的影响；氢氟酸和电镀除钝预处理对层深的影响。比较了低温离子渗氮和液体渗氮的组织与结构的不同。对一些试验结果进行了更深入的探讨。在430℃对奥氏体不锈钢进行低温液体渗氮,相比传统液体渗氮,没有发生CrN的析出；渗层生长随着时间增长,8h后速度越来越慢；在3%NaCl溶液中,低温液体渗氮具有更高的维钝电流,但点蚀电位更高,抗点蚀能力增强；5%盐酸溶液浸泡试验表明低温液体渗氮试样耐蚀性与未处理试样相当,但是在6%FeCl3+0.05mol/LHCl溶液中耐蚀性要弱于未处理试样；环块磨损试验表明,低温液体渗氮试样和传统渗氮磨痕相似,摩擦系数低于未处理试样,磨损失重大大降低；低温液体渗氮层和低温离子渗氮层表面具有相似的结构,截面金相表明前者多了一层未知相,可能是碳原子固溶导致的。更多还原

【Abstract】 Austenitic stainless steels have excellent corrosion resistance, are widely used in the chemical, marine, petrochemical, instrumentation, manufacturing, food biotechnology, medicine and other industries. The use accounts for about 65-70% of stainless steels production.Common austenitic stainless steels have the properties of low surface hardness、poor wear resistance and fatigue resistance. Conventional nitriding treatment can effectively improve the surface hardness of austenitic stainless steel, but the generated segregation of Cr and CrN results in loss of corrosion properties of austenitic stainless steels. Low-temperature nitriding treatment can inhibit the precipitation of CrN to form S phase with fairly hardness of conventional nitrided layer, so that the corrosion resistance of austenitic stainless steels will not reduce. At home and abroad, low-temperature nitriding of austenitic stainless steels is being studied with the process of gas or plasma, however, the liquid method has only been studied in Japan.To carry out liquid nitriding austenitic stainless steels study, the paper with two kinds of ideas develops low temperature nitriding salts,which can be used below 450℃, and has achieved good results. CNO-concentrations of both salts are more than 47%.Using self-developed low-temperature nitriding salt, the paper examines some aspects as below:the liquid nitriding temperature on the diffusion layer compositions, morphologies, structure and properties; time on the impact of layer thickness at 430℃and 440℃temperature of liquid nitriding; hydrogen fluoride and plating methods for removing the passive film on the impact of layer thickness; comparison of low temperature plasma nitriding and liquid nitriding on different microstructures and phases; more discussions in-depth on some test results.Austenitic stainless steels at 430℃low temperature of liquid nitriding, have no precipitation of CrN; nitriding layer growth increases over time,but the speed gets slower after 12h; in 3% NaCl solution, liquid nitriding samples have higher passive current, but higher pitting potential, and get pitting corrosion resistance enhanced; 5% hydrochloric acid solution immersion tests show that samples liquid-nitrided at low temperature and untreated samples have fairly corrosion resistance, but corrosion resistance of the former in 6%FeCl3+0.05mol/LHCl solution is weaker than untreated sample; ring-block wear test shows that the low temperature samples liquid-nitrided and conventional nitrided samples have similar wear scars,and both coefficients of friction are lower than the untreated sample, thus may reduce the wear weight loss greatly; low-temperature liquid and low temperature plasma nitrided surfaces have a similar structure of layer, cross-section metallographies show that the former gets one more layer of unknown phase, which probably results from carbon solution.更多还原