钢铁材料摩擦层结构演变与干摩擦自润滑行为研究进展

A Review on Microstructure Evolution in a Friction-induced Layer andthe Self-lubricating Behavior During Dry Sliding Friction of Steels

由于产生了大量的塑性变形、摩擦热、氧化和组织结构演变,摩擦层的形成不仅影响着材料的摩擦磨损特性,还可能在摩擦条件和材料微观结构匹配合理的情况下引发自润滑行为。研究摩擦层和自润滑行为的微观机制可为在不加入添加剂的基础上,获得新的固态润滑方法及对应润滑机制提供重要的理论依据。对磨材料的强度、硬度、层错能高低等特性差异将导致摩擦层结构演化形式、细化程度和深度均有所不同。特别是诸如低碳条状马氏体钢和珠光体钢等钢铁材料,因其具有马氏体束、块、条和珠光体中的铁素体、先共析相、渗碳体等亚结构特征,摩擦层内部结构的演变又与其他材料有所区别。干摩擦自润滑通常是因为表面氧化物和纳米级氧化颗粒的保护所致,但是材料不同或材料包含的微结构不同,能够形成的氧化物或氧化颗粒的类型和尺度亦有所不同。国内外学者展开了大量有关摩擦层和自润滑行为的研究,他们从摩擦层内部材料冷作硬化、晶粒细化和动态再结晶等方面分析了摩擦层高应变引起的材料组织结构演变,以及不同微观组织材料所表现出的摩擦层和摩擦磨损特性差异。此外,还对摩擦引起的纳米晶/结构对材料摩擦磨损特性产生的影响展开了大量研究。最后,研究人员试图利用摩擦接触导致的高应变速率和高应变梯度来获得超细化晶粒以制备表层纳米结构和调控材料的摩擦磨损特性。本文从塑性变形、结构演变规律和力学性能等方面综述了摩擦层的最新研究进展,讨论了影响摩擦层内部塑性变形程度的摩擦外载条件因素。另外,从摩擦层内部形成纳米结构、梯度结构和由表面氧化物颗粒形成的自润滑层等方面讨论了干摩擦过程中产生的自润滑现象及对应机制。最后,探讨了如何利用材料表层结构设计和预制自润滑层以获得优异的耐磨性能。

Due to the plastic deformation,frictional heat,oxidation and structural evolution,the friction-induced layers can not only affect friction and wear characteristics of materials,but also can induce the self-lubricating behavior under a specific condition.The researches on mechanisms of friction-induced layers and self-lubricating behavior can be used to provide an important theoretical basis for obtaining new solid lubrication methods and corresponding lubrication mechanisms without adding additives.Providing new ideas for surface wear resistance treatments and wear resistant evaluation of components.Different properties such as strength,hardness and stacking fault energy of materials will result in different micro structures evolution,refinement levels and depths of friction-induced layers.In particular,steels such as low-carbon martensitic steels and pearlitic steels with substructures such as ferrite,pro-eutectoid phase,cementite,etc.,which led to different structure evolution in the friction-induced layer from other materials.Many studies have shown that nano-oxide particles can naturally form and provide a protective layer during dry sliding wear.However,different materials and structures cause different structural evolutions under plastic deformation during dry sliding,which may result in different structures and sizes of the formed nano-oxide particles.Many researches on friction-induced layers and self-lubricating behaviors have been carried out,the structure evolution caused by high strain in friction-induced layers from the aspects of cold work hardening,grain refinement and dynamic recrystallization were analyzed.Also,friction and wear characteristics of materials with different microstructures and friction-induced layers were found out.In addition,many researchers focused on the effects of friction-induced nanocrystals/structures on the friction and wear characteristics of materials.And they attempted to obtain ultra-fine grains and nanostructures using the high strain rate and high strain gradient caused by frictional contact,which show good wear resistant characteristics.In this paper,the latest research literatures of friction-induced layers are reviewed considering plastic deformation,structural evolution and mechanical properties,and the frictional external loads conditions affecting the degree of plastic deformation in the friction-induce layer are discussed.In addition,self-lubricating phenomena and the corresponding mechanism during dry sliding friction are discussed from the aspects of forming nanostructures,gradient structures and self-lubricating layers.Furthermore,it is discussed how to optimize the surface structure of materials and prefabricated self-lubricating layers to obtain excellent wear resistance of steels.