Effects of Heat Treatment on the Hardness and Self-Lubrication of Ni-P / WS₂ Composite Coating

Abstract

Adding particles to the Ni - P coating for forming a composite coating could further improve the mechanical properties, corrosion resistance and lubricating properties of the coating. Hence, Ni - P/WS2 composite coatings were prepared by chemical coprecipitation on the surface of Q235 steel, and the coatings were post - treated by heating. Subsequently, the influence mechanism of WS2 content in plating solution and heat treatment after precipitation on the hardness and self - lubrocating performance of Ni - P/WS2 composite coating was studied by electron microprobe (EPMA), X - ray diffractometer (XRD), scanning electron microscope (SEM) and hardness tester. Results showed that the content of P in the plating solution was stable, which was not affected by the concentration of WS2 particles in plating solution, and it was beneficial to precipitation of a proper amount of body centered cubic Ni3P hardening phase in the subsequent heat treatment, causing that the surface hardness of the composite coating was effectively improved. Moreover, WS2 particles in the coating played a lubricating role on the surface of the coating, which could effectively reduce the friction coefficient of the coating surface, and the heat treatment enabled the precipitation of body centered cubic Ni3P phase in the coating. Thus, the surface support for WS2 particles was enhanced, which was conducive to increase the self - lubrication of the coating surface and effectively reduce the friction coefficient.

Keywords

• ni - p/ws₂|chemical coprecipitation|heat treatment|composite coating|friction coefficient