摩擦化学的主要研究领域及其发展趋势

本文从摩擦过程中表面产生的化学效应、干摩擦及油润滑状态下的摩擦化学三个方面评述了摩擦化学的研究内容和进展；介绍了摩擦化学在材料制备中的应用及摩擦化学的研究方法；对摩擦化学研究中存在的问题及其发展趋势进行了讨论。

MoS_2摩擦表面氧化与电子转移

MOS_2是优良的固体润滑材料,在摩擦过程中受到压应力、剪应力和摩擦热等环境因素的影响而导致表面氧化失效.用XPS技术对摩擦表面化合物的解析普遍认为是由Mo^(4+)和Mo^(6+)组成的混合物,并认识别MOS_2的失效造成硫原子的流失,继而Mo^(4+)更容易氧化成Mo^(6+).但是,Mo^(4+)转变成Mo^(6+)的反应历程迄今仍未澄清.我们采用电子自旋共振谱(ESR)和X-射线光电子谱(XPS)技术,研究Mo^(4+)向Mo^(6+)的反应历程时存在有Mo^(5+)的过渡态,Mo^(5+)进一步与氧作用生成稳定的Mo^(6+),并以MoO_3形式存在,因此,摩擦表面存在着Mo原子的多种化学状态.MOS_2摩擦表面化合物的形成,是Mo4d轨道上的电子转移过程.

Cooperative effect of surface alloying and laser texturing on tribological performance of lubricated surfaces

The cooperative effect of laser surface texturing(LST) and double glow plasma surface alloying on tribological performance of lubricated sliding contacts was investigated.A Nd:YAG laser was used to generate microdimples on steel surfaces. Dimples with the diameter of 150μm and the depth of 30-35μm distributed circumferentially on the disc surface.The alloying element Cr was sputtered to the laser texturing steel surface by double glow plasma technique.A deep diffusion layer with a thickness of 30μm and a high hardness of HV900 was formed in this alloy.Tribological experiments of three types of samples(smooth,texturing and texturing+alloying) were conducted with a ring-on-disc tribometer to simulate the face seal.It is found that,in comparison with smooth steel surfaces,the laser texturing samples significantly reduce the friction coefficient.Moreover,the lower wear rate of the sample treated with the two surface techniques is observed.

Analysis of the coated and textured ring/liner conjunction based on a thermal mixed lubrication model

For the ring/liner conjunction, well‐designed surface texturing has been regarded as a potential means to improve its tribological performance, as well as the application of coating. However, so far most researchers focused on the one of these aspects. In this study, the combined effect of coating and texturing on the performance of ring/liner conjunction is numerically investigated. A thermal mixed lubrication model is presented. The effects of the coating's thermal and mechanical properties on the tribological performance are studied under the cold and warm engine operating conditions. Along with the increasing coating thickness, the effects of the coating's thermal properties on friction loss are found to be significant, as well as the effects of the coating's mechanical properties. It is also found that a soft coating with a lower thermal inertia has a greater ability to reduce the friction loss of the textured conjunction.

Investigation into the tribological behaviors of press hardening steels on the tailored conditions

There has been a growing demand for safety parts with tailored properties in automobile industry.However,the understanding of tribological behavior of press hardening steels(PHS)on the tailored conditions is highly inadequate.The present work aims at creating new knowledge about the tribological characteristics of PHS on the tailored conditions and bridging this existing gap.The paper proposes an improved hot drawing tribo-simulator to simulate the realistic experimental conditions industry.Investigations were carried out on the condition of different initial heating temperatures,tool temperatures,austenitizing temperatures,cooling rates and microstructures.The presented results show that the whole frictional process is divided into three stages for both coated and uncoated steels.The frictional factor changes a lot and the peak value of frictional factor occurs for serious adhesive wear.The frictional factor rises as the tool temperature and austenitizing temperature rise.The surface morphology of tools indicates that the coating adhering to tool gets thicker as the tool temperature increases.With the increase of cooling rate,the frictional factor declines firstly and then rises to some extent.Flat dies with different temperatures are used to form specimens with different microstructures,which also affects the frictional factor and wear.