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通过在盐浴渗氮中施加7.5 V的直流电场,在不同外热温度(545~575℃),不同保温时间(60~120 min)下对35钢进行盐浴渗氮,研究了直流电场对35钢盐浴渗氮动力学的影响。利用光学显微镜、X射线衍射仪对渗层的显微组织、厚度及物相进行了测试和分析。结果表明:直流电场对活性氮原子在基体内部的扩散有显著促进作用,提高渗氮速度,降低盐浴渗氮温度或缩短保温时间;直流电场盐浴渗氮的扩散系数都比常规盐浴渗氮提高约2倍,扩散激活能从常规盐浴渗氮的220 k J/mol降低到181 k J/mol,从而达到增加渗层厚度的显著效果。有无直流电场条件下盐浴渗氮,35钢渗层主要物相均为ε-Fe3N及少量γ’-Fe4N。
Salt-bath nitriding of 35 steel was carried out at different external heating temperatures (545 ~ 575 ℃) and different holding time (60 ~ 120 min) by applying a direct current electric field of 7.5 V to the salt bath nitriding. Effect of 35 Steel Salt Bath on Nitriding Kinetics. The microstructure, thickness and phase of the layer were tested and analyzed by optical microscope and X-ray diffractometer. The results show that the DC electric field can significantly promote the diffusion of active nitrogen atoms inside the matrix, increase the nitriding rate, decrease the nitriding temperature or shorten the holding time. The diffusion coefficients of direct-field salt bath nitriding are higher than conventional salt bath infiltration Nitrogen increased about 2 times, and diffusion activation energy decreased from 220 kJ / mol to 181 kJ / mol for conventional salt bath nitriding, so as to achieve a significant effect of increasing the thickness of the diffusion layer. With or without DC field salt bath nitriding, 35 steel layer of the main phase are ε-Fe3N and a small amount of γ’-Fe4N.