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Environment Conscious Gas Nitriding of Austenitic Stainless Steels

奥氏体不锈钢的环境意识气体渗氮

基本信息

批准号：
10650710
负责人：
SUEYOSHI Hidekazu
金额：
$ 0.64万
依托单位：
Kagoshima University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 1999
项目状态：
已结题

项目摘要

Three types of austenitic stainless steels, SUS304, SUS316 and SUS310, were preheated in air at various temperatures. Depthwise changes in the surface film composition were analyzed by X-ray photoelectron spectroscopy. Gas nitriding was conducted in a controlled-atmosphere furnace by changing the nitriding temperature and time. Nitriding behavior were examined in connection with the kinetics of the nitriding reaction.The nitriding reaction occurs locally at an early stage of the nitriding treatment. The whole surface becomes covered with a nitrided layer by coalescence of nitrided regions. Thereafter, nitrided layer with a uniform thickness is formed by the growth in a depth direction. Diffusion of nitrogen through the nitrided layer is the rate-determining process in the growth of the nitrided layer. Nucleation of the nitriding reaction is greatly accelerated by atmospheric preheating. The nitrided layer with a uniform thickness and sufficiently high hardness for practical use is obtained when appropriate preheating in air is applied to produce a surface film consisting mainly of iron oxides at the surface and containing a low concentration of CrィイD22ィエD2OィイD23ィエD2 and a high concentration of FeO in the interior. A hardness of the nitrided layer decreases with increasing nitriding temperature.It is confirmed from the present results that gas nitriding of austenitic stainless steels is possible without any chemical pretreatment.

将三种奥氏体不锈钢SUS304、SUS316和SUS310在空气中以不同的温度进行预热。利用x射线光电子能谱分析了表面膜成分的深度变化。通过改变渗氮温度和渗氮时间，在可控气氛炉中进行气体渗氮。结合氮化反应动力学考察了渗氮行为。渗氮反应在渗氮处理初期局部发生。由渗氮区合并而成的渗氮层覆盖了整个表面。然后沿深度方向生长，形成厚度均匀的氮化层。氮在氮化层中的扩散是氮化层生长的速率决定过程。大气预热大大加速了氮化反应的成核。充分均匀的渗氮层厚度和硬度高,实际使用时获得适当的预热空气中应用于表面产生一个电影为主的铁氧化物表面,含有低浓度的CrィイD22摊位ィエD2Oィイc15ィエD2和高浓度FeO说的内部。渗氮层的硬度随渗氮温度的升高而降低。结果表明，奥氏体不锈钢无需任何化学预处理即可进行气体氮化。