Strengthening Mechanism of Nanosized Magnesium Silicate Hydroxide on the Tribological Properties of Phosphate-Bonded Solid Coatings

Abstract

Natural serpentine and nanosized magnesium silicate hydroxide (MSH) were separately incorporated to improve the tribological properties of phosphate-bonded solid coatings. The differences in tribological properties between natural serpentine and MSH at different temperatures were elaborately explored. It was suggested that MSH can more apparently improve the antiwear performance of phosphate coatings than natural serpentine. The specific reasons were attributed to the big specific surface area and weak thermal stability of MSH. Under the combined effort of frictional force and friction temperature, the structural water in MSH can be easily dehydrated and can generate numerous dangling bonds on the outside surface. Simultaneously, structural distortion of MSH also inevitably occurred, which resulted in lots of oxygen functional groups of MSH being released at the frictional interface during the friction process. Besides, MSH has a strong cation replacement ability, and therefore, it can easily adsorb and undergo tribochemical reactions with the metal-based worn surface. In consequence, a composite protective tribo-film was in situ formed on the worn surface and direct abrasion on the worn surface was greatly alleviated during the friction process. The results offered an approach for designing and preparing antiwear phosphate composite solid coatings for the tribological applications of metal-based friction pairs at different friction temperatures.