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为解决17CrNiMo6机车牵引齿轮在热处理工艺中出现的晶界氧化超标问题,通过相关的热力学计算,阐述了晶界氧化(IGO)的产生机理;采用BBH型前室预抽真空多用炉、金相和硬度检验对该齿轮进行了热处理工艺实验,并对产生晶界氧化的部位取样进行显微电镜光学扫描和能谱分析。能谱分析结果表明:晶界氧化产生的黑色网状物的主要成分是Cr和O,减少Cr氧化物的生成量可以降低晶界氧化的程度。分析Fe、Cr和氧化性气氛的平衡曲线,找出了影响Cr氧化物生成的渗碳工艺参数(加热期的均温速度,强渗期和扩散期的温度、碳势、保温时间),优化工艺使齿轮的晶界氧化程度很好地达到了技术要求。
In order to solve the problem of excessive grain boundary oxidation of 17CrNiMo6 locomotive traction gears in the heat treatment process, the generation mechanism of grain boundary oxidation (IGO) was expounded through the related thermodynamic calculation. The BBH pre-evacuated multi-purpose furnace, Hardness test of the gear heat treatment process experiments, and the site of grain boundary oxidation occurred microscopic scanning electron microscopy and energy spectrum analysis. The results of energy spectrum analysis show that the main components of the black network formed by the grain boundary oxidation are Cr and O. Reducing the formation of Cr oxide can reduce the extent of grain boundary oxidation. The equilibrium curves of Fe, Cr and oxidizing atmosphere were analyzed to find out the parameters of carburizing process (the average temperature during heating, the temperature, carbon potential and holding time during strong infiltration and diffusion) Technology to gear the grain boundary oxidation well meet the technical requirements.