不同表面技术对挺柱组织及耐磨性的影响

目的 为解决挺住可靠性不足的问题，研究不同表面技术对提高可靠性的效果。方法 采用软氮化、感应淬火和复合技术三种表面处理方法制备挺柱。利用显微硬度计、金相显微镜等对三种挺柱的组织、硬度进行了分析。利用SRV摩擦磨损试验机测试不同挺柱在干摩擦、富油、贫油条件下的摩擦系数，并通过体视显微镜和轮廓仪对磨损后的形貌和深度进行了分析。最后在发动机台架上进行1000 h负载循环耐久试验，验证挺柱可靠性。结果 氮化挺柱表层组织由0.006 mm厚的白亮层和0.2 mm厚的扩散层构成，硬化层薄，硬度过渡不平缓，且白亮层中含有大量疏松缺陷。感应淬火挺柱表层为2 mm厚的普通马氏体，硬化层深且硬度过渡平缓。复合强化挺柱表层由0.04 mm厚的含氮马氏体层和2 mm厚的普通马氏体组成，硬度过渡平缓且硬化层深。氮化与复合强化挺柱干摩擦和富油摩擦系数随磨损时间基本保持不变，干摩擦系数分别为0.56、0.54，富油摩擦系数均为0.174，表明两种挺柱都具有优良的抗粘着磨损与磨粒磨损性能。感应淬火挺柱干摩擦系数随磨损时间急剧增加，最大达0.95，此时因粘着抱死导致试验过早终止，富油摩擦系数稳定在0.164，表明其具有优良的抗磨粒磨损性能，但抗粘着磨损性能极差。此外，复合技术挺柱在台架耐久中的表现远优于氮化挺柱，表面未出现异常磨损及剥落，而氮化件表面剥落严重。结论 复合技术可有效提升挺柱可靠性。

Effect of Different Surface Treatment on Tappet Microstructure and Wear Resistance

The work aims to improve wear resistance. The tappet was treated by three kinds of surface treatment including nitriding, inducting hardening and compound technology. The microstructure and hardness of three tappets were analyzed by microhardness tester and metalloscope. The friction coefficient of tappets under three lubrication conditions, including dry friction, sufficient lubrication and insufficient lubrication was studied by SRV friction wear testing machine. Wear morphology and depth were analyzed by stereoscopic microscope and surface profile measuring instrument. Reliability of different tappets was studied by 1000 hours load cycle endurance test at engine bench. Nitriding tappet surface microstructure consisted of 0.006 mm thick compound layer and 0.2 mm thick diffusion layer. Its hardness layer was thin and the transition was not smooth. There were a lot of porosity defects in white layer. Inducting hardening tappet surface microstructure consisted of 2 mm thick general martensite layer. Its hardness layer was deep and the transition was smooth. Compound technology tappet surface microstructure consisted of 0.04 mm thick nitric martensite layer and 2 mm thick general martensite layer. Its hardness layer was deep and the transition was smooth. The friction coefficient of nitriding and compound technology tappets were constant under dry friction and sufficient lubrication. The friction coefficient was 0.54 and 0.56 under dry friction. The friction coefficient were 0.174 under sufficient lubrication. Both tappets had excellent adhesive and abrasive wear resistance performance. The friction coefficient of inducting hardening tappet sharply increased under dry friction and was up to 0.95. By the time, the test was terminated due to adhesion clamping. Its friction coefficient was constant at 0.164 under sufficient lubricatio. This indicated that inducting hardening tappet had better abrasive wear resistance performance, but it had poor, adhesive wear performance. In addition, the reliability of compound technology tappet was higher than that of nitriding tappet. The surface of compound technology tppet was free from abnormal wear and peeling, while the surface of nitriding tappet had worse peeling. Compound technology can effectively improve the reliability of tappet.