Study on Surface Strength Increasing of Sliding Rolling Machine Element by Multiplex Surface Treatment

随着汽车等新型机械向轻量化、紧凑型发展，齿轮的表面强度设计问题日益严峻，迫切需要研究提高滑滚接触机械元件表面强度的方法。本课题拟在常规热处理表面硬化元件的基础上，通过喷丸、电镀、涂层等复合表面处理，提高滑滚接触机元件的表面强度。本课题旨在阐明复合表面处理机械元件的表面失效模式和表面强度的提高机理。作为上述意图的基础研究成果，主要总结如下：1。随着淬硬深度的增加、粉末粒径的减小和生坯密度的增大，离子氮化轧辊和齿轮的表面耐久性增加。从孔的图像处理和分形维数分析结果可以看出，孔分布对离子氮化烧结机械元件的表面耐久性影响很大。采用喷丸法对滚刀、电火花加工和刨齿齿轮进行表面改性。喷丸处理后，这些表面耐久性略有提高。对于复合表面处理的机械元件，化学镀镍磷和硫化改性后的表面硬化辊的表面耐久性得到了提高。在高比滑动工况下，镀镍磷化学镀镍磷合金的磨损负荷得到改善，而硫化镍磷合金的磨损负荷得到改善。

For the development of light weight and compact power transmission unit in recent machine such as motor car, the problem of surface strength design of gear becomes sever and it becomes a pressing need to investigate the improving method of the surface strength of sliding-rolling contact machine element. This research project was planned to increase the surface strength of sliding-rolling contact machine element by the multiplex surface treatment which is achieved by additional treatments of shot-peening, plating, coating and so forth on the conventional heat-treated surface-hardened element. This project intends also to clarify the surface failure model and the increasing mechanism of surface strength of the multiplex surface treated machine element. The results which were perfomed as a fundamental research for above mentioned intentions are summarised mainly as follows ;1. The surface durabilities of ion-nitrided roller and gear increased as the hardened depth increased, the particle diameter of powder decreased and the green density increased. It was understood from the results of image processing and fractal dimension analysis of pore that the surface durability of ion-nitrided sintered machine element was highly affected by the pore distribution.2. Hobbed, electrical discharge machined and shaved gear were surface-modified by shot-peening. These surface durabilities increased slightly by the shot-peening.3. Concerning the multiplex surface-treated machine element, the surface durabilities of case-hardened rollers modified by electroless Ni-P plating and sulfurizing were improved by their surface modifications. The scuffing load of sulfurized one was hardly improved, but that of electroless Ni-P plating one was improved at operating conditions of higher specific sliding.