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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了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.
The microstructure, C concentration distribution, surface phase structure of carburized layer on the surface of 316L stainless steel were investigated by OM, EPMA, XRD and IXRD in the process of low temperature colossal carburization (LTCC) Residual stress.The mass transfer and diffusion model of LTCC was established based on the theory of thermodynamics.The C concentration and activity distribution of carburized layer were calculated by DICTRA software and compared with the experimental results.The results showed that after LTCC treatment 316L stainless steel surface will form a high hardness S phase and produce compressive residual stress.In addition, increasing the concentration of CO in the carburizing process can significantly increase the C concentration in the carburized layer on the stainless steel surface, thereby increasing the hardness and compressive residual stress. When the concentration of C is lower, the calculated concentration and activity distribution of C coincide well with the experimental results. When the concentration of C is higher, the calculation result is lower due to the decrease of trap array point and the residual compressive stress of larger compressive strength.