Interaction between the microstructure and the properties of plasma nitrided austenitic stainless steels

等离子氮化奥氏体不锈钢显微组织与性能之间的相互作用

基本信息

批准号：
321139694
负责人：
Professor Dr. Günter Bräuer
金额：
--
依托单位：
Institut für Oberflächentechnik
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2016
资助国家：
德国
起止时间：
2015-12-31 至 2018-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/321139694?language=en
关键词：
Interaction between microstructure properties plasma

项目摘要

The research project focuses on a comprehensive study of the interactions between the plasma nitriding process, the material microstructure and the resulting properties, especially concerning the corrosion behavior, of austenitic stainless steels. The preliminary results show that the wear resistance is dominated by the thickness of the S-phase. It was found, that with increasing degree of deformation due to cold rolling or shot peening prior to nitriding, the thickness of the S- phase increases with otherwise identical nitriding conditions .There were significant influences of the materials microstructure and the surface condition on the corrosion properties. In particular, the increase in defect density due to plastic deformation reduces the corrosion resistance of plasma nitrided steels in the salt spray test. Contrary to the prevailing phenomenological assumption, that a reduction of the treatment temperature improves the corrosion behavior, is was found that a low temperature process (370 °C, 960 min) causes significantly worse corrosion behavior in salt spray test than a high temperature process (420 ° C, 360 min). With both parameter sets good matching thicknesses of the S phase were obtained. The reason for this behavior is seen in the formation of precipitates, resulting in a chromium depletion of the matrix. In order to formulate a mechanism based description of the precipitation mechanism in dependence of initial microstructure and treatment parameters, systematic TEM investigations will be carried out. Furthermore, potentiodynamic polarization tests in H2SO4 reveal, that all material states (nitrided and unnitrided ) were resistant to corrosion. Potentiodynamic polarization tests of nitrided sampels in NaCl, on the other hand, are in good accordance with the salt-spray test results in terms of the corrosion behavior. However, all unnitrided samples showed systematically a higher corrosion current than the nitrided samples.Based on the results and the derived hypotheses, the focus of the proposal is to gain a fundamental understanding by means of microstructural and microanalytical studies concerning the microstructural changes and their kinetics as function of microstructure and nitriding parameters. Based on this, another focus is the identification of standardized analysis methods which allow for a correlation between the microstructure and the resulting corrosion properties. The overall objective of the project is to formulate a conceptual model, which describes the relationship between microstructure, chemical composition and the nitriding process on the resulting corrosion and wear behavior.

该研究项目的重点是全面研究奥氏体不锈钢的等离子渗氮工艺、材料微观结构和所得性能之间的相互作用，特别是腐蚀行为。初步结果表明，耐磨性由厚度决定。研究发现，在渗氮前进行冷轧或喷丸处理时，随着变形程度的增加，在其他相同的渗氮条件下，S 相的厚度也会增加。材料的影响很大。特别是，由于塑性变形而导致的缺陷密度的增加降低了等离子渗氮钢在盐雾试验中的耐腐蚀性，这与普遍的现象学假设相反，即处理温度的降低。改善了腐蚀行为，发现低温工艺（370℃，960分钟）在盐雾试验中导致的腐蚀行为明显比高温工艺（420℃，360分钟）差。通过这两个参数集，获得了良好匹配的 S 相厚度。这种行为的原因在于沉淀物的形成，导致基体的铬消耗，以便制定基于沉淀机制的描述。通过对初始微观结构和处理参数的分析，将进行系统的 TEM 研究。此外，H2SO4 中的动电位极化测试表明，所有材料状态（氮化和未氮化）都具有耐腐蚀能力。另一方面，就腐蚀行为而言，氮化样品在 NaCl 中的测试与盐雾测试结果非常一致，但所有未氮化样品均表现出比氮化样品更高的腐蚀电流。以及衍生的假设，该提案的重点是通过微观结构和微观分析研究获得关于微观结构变化及其动力学作为微观结构和氮化参数的函数的基本理解。另一个重点是确定标准化分析方法，该方法允许微观结构与由此产生的腐蚀特性之间的相关性。该项目的总体目标是制定一个概念模型，描述微观结构、化学成分和氮化之间的关系。过程对由此产生的腐蚀和磨损行为的影响。