Lubrication and repair of metal surface by nano-fluid

The nanoparticles with both lubrication and surface repair properties have been tried to be used in metal working fluid and has been widely concerned by researchers all over the world. Different from the traditional working fluid, the nano-processing fluid prepared by uniformly dispersing nanoparticles into aqueous or oily base fluid not only has the functions of lubrication and cooling, friction reduction and abrasion resistance, but also its surface repair function deserves more attention and has a higher application prospect in improving the surface quality of metal processing. Nano-fluid has so many superiorities in metal processing, but the dispersion stability, lubrication mechanism and surface repair function are still hot issues in the field of nano-lubrication. The work aims to introduce the research and development of the lubrication mechanisms and micro-mechanism of nanoparticles after the surface repair properties for the past few years. From the selection and dispersion of nanoparticles, two main methods to improve the dispersion stability of nanoparticles were discussed, including surfactant addition and surface modification of nanoparticles. Four widely recognized lubrication mechanisms of nanoparticles including rolling mechanism, tribo-film mechanism, self-repairing mechanism and mechanical polishing effect were mainly discussed. The theoretical model, applicable conditions and cooperative relationship of these four lubrication mechanisms were also summarized according to previous researches. Furthermore, the repair action of nanoparticles on metal surface was present based on the lubrication mechanisms. The physisorption film, chemical reaction film and tribo-healing film were also distinguished and compared to analyze the micro-mechanism of surface repair. © 2019, Chongqing Wujiu Periodicals Press. All rights reserved.