45钢奥氏体氮碳共渗的组织结构及摩擦学性能

Microstructure and Tribological Behavior of Austenite Nitrocarburized Steel

利用液体法研究了对45钢铁素体及奥氏体作氮碳共渗处理的工艺；为便于比较，同时对45钢进行了淬火十低温国火处理。通过金相观察、显微硬度测试和X射线衍射分析，测定了两种氮碳共渗工艺处理后渗层的显微硬度分布及相结构，利用动摩擦系数测定仪及高速环-块磨损试验机测试了几种工艺处理后的试样摩擦系数及耐磨性能，并使用轮廓仪测定了试样表面的粗糙度。结果表明：奥氏体氮碳共渗后试样表面的化合物层由两层组成，表层为Fe3N，次表层为富含氮、碳的马氏体及奥氏体；而经铁素体氮碳共渗处理的试样，其表面的化合物层只有一层（由Fe3N及少量的FeZ－3N和Fe4N组成）；奥氏体氮碳共渗处理可获得更厚的化合物层。氮成共渗可明显降低材料的摩擦系数，改善材料的耐磨性能；在干摩擦、润滑及较低的试验载荷（＜800N）条件下，奥氏体氮成共渗的耐磨性能明显优于铁素林氮碳共渗处理，而当试验载荷较大（1000N）时，铁素体及奥氏体氮碳共渗处理的耐磨性趋于一致。

This paper deals with the ferrite and austenite nitrocarburizing technologies. For comparison, the quenching and tempering treatment was conducted. By means of metallographic examination, microhardness test and X-ray diffraction analysis, the phase construction and hardness profile of case hardened layers on 45 steel treated by nitrocarburizing were investigated. The surface roughness, friction coefficient and wear resistance of 45 steel treated by several processes were also investialed. The experimental results showad that a superior sub-surface hardness, a better hardness profile and a thicker compound layer were obtained by use of austenite nitrocarburizing, although the surface hardness were somewhat lower, two distince layers were clearly visible on the cross-sections of austenite nitrocarburized specimensconsisted predominately of E-compound (outer layer) and carbon/nitrogen martensite with a high percentage of austenite (inner layer), while the phase construction of ferritic nitrocarburized specimens was composed of E-compound and a small amount of Fe4N and Fe2~3N. The e phase formed on steel after nitrocarburizing had significant effect on reducing friction and improving wear resistance. Austenite nitrocarburizing improved wear resistance even further compared with ferrite nitrocarburining.