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

随着汽车等现代机械向轻量化、紧凑化方向发展，齿轮的表面强度设计问题日益突出，迫切需要研究提高滑动-滚动接触机械零件表面强度的方法。本研究计划在常规热处理表面硬化件的基础上进行喷丸、电镀、涂层等复合表面处理，以提高滑动-滚动接触机械零件的表面强度。本项目还旨在阐明复合表面处理机械零件的表面失效模式和表面强度的提高机理。主要研究结果如下：1.离子渗氮轧辊和齿轮的表面耐用度随着硬化层深度的增加而增加，粉末的颗粒直径减小，坯料密度增加。从气孔图像处理和分维分析的结果可以看出，离子氮化烧结机零件的表面耐久性受气孔分布的影响很大。对滚齿、电火花加工和剃齿齿轮进行喷丸表面处理。喷丸处理后，这些表面耐久性能略有提高。对于复合表面处理机械零件，采用化学镀Ni-P和硫化处理后的表面硬化辊，通过表面改性提高了表面耐久性。在高比滑移率下，渗硫层的胶合负荷几乎没有提高，而化学镀镍-磷层的胶合负荷有所改善。

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.