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316L奥氏体不锈钢低温超饱和渗碳实验及热动力学模拟研究
发布人：上海艾荔艾金属材料有限公司www.shailiai.com
更新时间：2015-09-30
采用 OM、EPMA、XRD 和 IXRD 等手段，研究了低温超饱和渗碳（low temperature colossal carburization，LTCC）工艺中 CO气体浓度对 316L 不锈钢表面渗碳层的微观组织、C 浓度分布、表面相结构以及残余应力的影响。
奥氏体不锈钢低温超饱和渗碳实验及热动力学模拟研究EXPERIMENTAL RESEARCH AND THERMODYNAMIC SIMULATION OF LOW TEMPERATURE COLOSSAL CARBURIZATION OF AUSTENITIC STAINLESS STEEL
采用 OM、EPMA、XRD 和 IXRD 等手段，研究了低温超饱和渗碳（low temperature colossal carburization，LTCC）工艺中 CO气体浓度对 316L 不锈钢表面渗碳层的微观组织、C 浓度分布、表面相结构以及残余应力的影响。基于热动力学理论建立 LTCC 传质和扩散模型，利用 DICTRA软件计算了渗碳层的 C 浓度和活度分布，并与实验结果进行比较。结果表明，经 LTCC工艺处理后的 316L 不锈钢表面会形成高硬度的 S 相，并产生压缩残余应力。另外，增加渗碳工艺中 CO 浓度可以显著提高不锈钢表面渗碳层中的 C 浓度，进而提高其硬度和压缩残余应力。在 C 浓度较低时，计算的 C 浓度和活度分布与实验结果吻合很好，当 C 浓度较高时，由于陷阱阵点的减少以及较大压缩残余应力的作用导致计算结果偏低。
Because of excellent corrosion resistance, good toughness and machinability, austenitic stainless steels are widely used in many industries. In order to improve the corrosion resistance, the carbon content of austenitic stainless steel is ultra-low results in low surface hardness, poor wear and fatigue resistance properties which limit its application. Low temperature colossal carburization (LTCC) is a kind of novel surface strengthening technology of austenitic stainless steel which can significantly increase the surface hardness, while keeping the original excellent corrosion resistance because of the absence of the carbides. The wear, fatigue and corrosion resistance of austenitic stainless steel of low temperature carburized layer have been investigated in recent years. However, the researches of key technical parameters, especially the carburizing atmosphere and the alloying element, have been rarely reported for intellectual property protection. In this work, OM, EPMA, XRD and IXRD are used to investigate the effect of CO concentration on the microstructure, carbon concentration distribution, phase constitution and residual stress of the carburized layer on 316L austenitic stainless steel surface. Based on thermodynamic theory, the model of carbon transfer and diffusion was also built by software DICTRA to calculate the distribution of carbon concentration and activity of low temperature carburized layer. The results reveal that S phase is detected on 316L austenitic stainless steel surface treated by LTCC, and the compressive residual stress is formed at the same time. The increment of CO concentration can significantly increase the carbon concentration of carburized layer, which improve the hardness and compressive residual stress. The simulated carbon concentration and activity distributions were in accordance with the experimental results when the carbon concentration is lower, but when the carbon concentration is higher, the simulated carbon concentration is lower than experimental results due to the decrease of trapping sites and high compressive residual stress.