弹簧用51CrV4钢渗氮层微观组织与摩擦性能分析

为提高弹簧用51CrV4钢表面的耐磨性能,对其进行不同时间和温度下的渗氮处理,实验测试其微观组织,硬度以及摩擦性能。研究结果表明:渗氮层形成了未被腐蚀的明亮化合物层,扩散层由于受到浸蚀作用而转变为黑色。基底只有一种α-Fe组织。渗氮处理后形成了γ-Fe4N相、CrN相等多个物相组织。随着渗氮时间的增加和渗氮温度的增加,渗氮层厚度表现出单调增加的变化规律。渗氮后试样硬度达到950 HV以上,相对于原始试样硬度发生了明显上升。经过450℃与20 h处理后获得最小磨损率和摩擦系数,此时试样形成了较为光滑的磨痕形貌,磨损程度很小,当硬度提高后可以获得更高的耐磨能力。当温度继续上升以及时间延长后,渗氮物发生了粗化的现象,引起表面硬度减小,最终降低了耐磨性。

Microstructures and Tribological Properties of Ion-Nitrided 51CrV4 Steel Surface

The surfaces of 51 CrV4 steel,a spring material,were modified by ion nitriding.The influence of the nitriding temperature and time on the microstructures and tribological behavior of the nitrided layer was investigated with X-ray diffraction,scanning electron microscopy and conventional mechanical probes.The results show that the nitriding temperature and time had a major impact.For instance,as the nitriding temperature and time increased, the thickness of the bright,compact nitrided layer,comprising γ-Fe4N and CrN phases,increased;and nitrided for 20 h,the friction coefficient and wear-rate changed in a decrease-increase mode(V-shape curve) with an increase of the temperature.Nitrided at 450℃ for 20 h,the modified layer,with strong corrosion resistance and hardness up to 950 HV,had the smallest friction coefficient and the lowest wear-rate;however,a higher temperature and a longer time negatively affected the tribological properties because of the surface coarsening.