Influence of triboinduced films on failures and frictional behaviour of gears with particular focus on running-in processes - experimental and analytical investigations

通过润滑剂添加剂与齿轮齿面的相互作用形成摩擦诱导膜（tribofilms）可以对齿轮的失效机制和摩擦行为产生显著影响。虽然在研究计划的第一部分中，开发了一种实用的优化磨合方法，以提高正齿轮的承载能力，但尚未详细考虑磨合和运行期间摩擦膜形成的复杂机制。然而，由于所有结果都显示出对所研究的润滑剂添加剂的明显依赖性，因此在研究计划的第二部分中，系统地研究了摩擦膜的形成和演变与齿轮的承载能力和摩擦行为之间的联系。这需要详细了解摩擦学系统的局部应力和允许应力：一方面，通过适当的表面分析技术研究摩擦膜和近表面区域的物理和化学成分，另一方面，通过研究合作伙伴IMK马格德堡对润滑接触进行详细的数值模拟来确定局部应力。因此，技术表面上摩擦膜的局部形成可以与润滑接触中的局部应力相关联。基于所进行的调查，模型和概念的发展，以澄清，摩擦膜导致高或低的摩擦和高或低的承载能力，在齿轮应用。关于齿轮承载能力的研究，重点是点蚀和胶合的失效模式。还研究了摩擦膜是否可以同时对所有研究区域（擦伤、点蚀、摩擦行为）产生积极影响。由于摩擦膜仅通过使用润滑剂而有效，无需精心设计修改和额外努力，因此研究计划第二部分的结果对资源保护做出了重要贡献。研究计划的结果为添加剂和润滑剂制造商以及最终用户选择合适的润滑剂添加剂和优化齿轮传动应用的现有润滑剂添加剂配方提供了一种方法。

The formation of triboinduced films (tribofilms) by interaction of lubricant additives with gear flank surfaces can have significant influence on the failure mechanisms and frictional behaviour of gears. While in part I of the research programme a practical and optimized running-in method for increasing the load carrying capacity of spur gears has been developed, the complex mechanisms of tribofilm formation during running-in and operation have not been considered in detail. However, since all results have shown a clear dependency on the investigated lubricant additives, in part II of the research programme the connection between formation and evolution of tribofilms with load carrying capacity and frictional behaviour of gears is investigated systematically. This requires detailed knowledge about local stresses and permissible stresses of the tribological system: On the one hand, the physical and chemical composition of the tribofilm and of the near surface region is investigated by suitable surface analysis techniques and on the other hand the local stresses are determined by means of detailed numerical simulations of the lubricated contact at the research partner IMK Magdeburg. Hence, the local formation of tribofilms on technical surfaces can be connected to the local stresses in the lubricated contact. Based on the conducted investigations, models and concepts are developed in order to clarify, which tribofilms cause high or low friction and high or low load carrying capacities in gear applications. With respect to the investigations on the load carrying capacity of gears, the focus is on the failure modes pitting and scuffing. It is also investigated, if tribofilms can have positive effects on all investigation areas (scuffing, pitting, frictional behaviour) at the same time. As tribofilms are effective solely by the use of lubricant without elaborate design modifications and additional efforts, the results of part II of the research programme make an important contribution to resource conservation. The findings of the research programme provide an approach for selecting appropriate lubricant additives and for optimising existing lubricant additive formulations for gear drive applications for the additive and lubricant manufacturers as well as for end users.