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

Natural serpentine and nanosized magnesium silicate hydroxide(MSH)were separately incorporated to improve the tribological propertiesof phosphate-bonded solid coatings. The differences in tribologicalproperties between natural serpentine and MSH at different temperatureswere elaborately explored. It was suggested that MSH can more apparentlyimprove the antiwear performance of phosphate coatings than naturalserpentine. The specific reasons were attributed to the big specificsurface area and weak thermal stability of MSH. Under the combinedeffort of frictional force and friction temperature, the structuralwater in MSH can be easily dehydrated and can generate numerous danglingbonds on the outside surface. Simultaneously, structural distortionof MSH also inevitably occurred, which resulted in lots of oxygenfunctional groups of MSH being released at the frictional interfaceduring the friction process. Besides, MSH has a strong cation replacementability, and therefore, it can easily adsorb and undergo tribochemicalreactions with the metal-based worn surface. In consequence, a compositeprotective tribo-film was in situ formed on the worn surface and directabrasion on the worn surface was greatly alleviated during the frictionprocess. The results offered an approach for designing and preparingantiwear phosphate composite solid coatings for the tribological applicationsof metal-based friction pairs at different friction temperatures.

Automated summary

Natural serpentine and nanosized magnesium silicate hydroxide (MSH) were added to phosphate-bonded solid coatings to improve their tribological properties. The study revealed that MSH can significantly enhance the antiwear performance of phosphate coatings compared to natural serpentine due to its larger specific surface area and weaker thermal stability. The structural water in MSH can easily dehydrate and generate dangling bonds on the surface under the combined effect of frictional force and friction temperature. Additionally, MSH has a strong cation replacement ability and can undergo tribochemical reactions with the metal-based worn surface, leading to the formation of a composite protective tribo-film that alleviates direct abrasion.