Microstructure and improved tribological performance of graphite/copper‑zinc composite coatings fabricated by low pressure cold spraying

Abstract

It is a challenge to obtain metal-solid lubricant composite coatings with good tribological performance by cold spraying due to the poor interfacial bonding between solid lubricants and metal matrix along with uncompacted microstructure of the resulted composite coatings. Here, we report the preparation of graphite reinforced copper based composite coatings with improved self-lubricating and anti-wear performance by low pressure cold spraying via the rational feedstock design in combination with metallic pretreatment of graphite. Zinc particles are blended with the copper particles and used as the feedstock to produce a fully dense copper‑zinc matrix and ZnO during sliding process, which produces the durable binding of lubricating graphite ingredients to the contact surfaces. The graphite lubricants are pretreated with electroless copper coatings to improve their compatibility with copper‑zinc matrix and their content in the cold-sprayed composite coatings. It is found that graphite/copper‑zinc composite coatings with low COF, good wear resistance and high load capability can be obtained by tuning the content of copper-coated graphite in the feedstock. The mechanism on reduction of friction and wear for graphite/copper‑zinc composite coatings is also discussed.