灰铸铁表面原位合成TiC复合强化层的摩擦磨损性能

Friction and wear performance of in-situ synthesized TiC composite strengthened coating on gray cast iron

通过等离子束表面合金化工艺用Ti-Fe合金粉末在灰铸铁表面制备了原位合成Ti C复合强化层。结果表明,合金化层厚度为350~400μm,与基体之间实现良好的冶金结合,合金化后试样表层硬度最高可达969 HV0.2,合金化区显微组织为残留奥氏体、针状马氏体和共晶莱氏体。XRD及SEM分析观察发现,在合金化区存在原位复合Ti C颗粒。通过销-盘型高温摩擦磨损试验对合金化试样和未经合金化处理的灰铸铁试样的室温及高温（473 K、673 K）下的摩擦磨损行为及机理进行了对比研究,磨损试验结果表明,合金化处理后,试样的耐磨性能相对于灰铸铁基体得到了明显改善,磨损率普遍下降3个数量级。根据扫描电镜（SEM）观察、能谱（EDS）检测和显微硬度测试分析结果可知,基体表层组织转变和Ti C颗粒是Ti C复合强化层耐磨性能提高的主要原因。

An in-situ synthesized TiC composite strengthened coating was prepared on gray cast iron via plasma transferred arc （PTA） surface alloying of Ti-Fe alloy powder. The results show that the alloyed layer has a thickness of about 350-400 μm, which has a well metallurgical bond with matrix. Microhardness test shows the surface hardness of alloyed samples reaches 969 HV0.2 maximum. The microstructure of alloyed zone is composed of residual austenite, acicular martensite and eutectic ledeburite, In-situ composite TiC particles is found in the zone with the help of XRD and SEM. The pin-on-disc high-temperature wear tests were carried out in order to compare the wear behavior and mechanism at room temperature and higher temperature （473 K and 673 K） between the alloyed sample and gray cast iron sample without alloying treatment respectively. The wear test results show that after PTA alloying treatment, the wear resistance of alloyed samplesis improved significantly compared to that of the gray cast iron, and the wear rate generally drops by 3 orders of magnitude. The improvement of the wear resistance of the TiC composite strengthened coating can be attributed to the transformation of surface microstructure and the presence of TiC carbides according to the analysis results of the composite coatings by SEM observation, EDS detection and microhardness test.