Tribological properties of sprayed alumina coatings sealed by electro-deposition of Cu

An electrolytic deposition procedure has been used to completely seal the open porosity of plasma sprayed alumina with Cu. Scanning electron microscopy (SEM) showed that the open porosity was sealed, leaving only closed pores in the coating. Both sealed and unsealed materials have been evaluated and compared using standard tribological testing, including scratch testing, abrasion, particle erosion and wear in dry sliding contact. As a result of the sealing procedure the wear rate was found to decrease markedly in erosion and abrasion while the wear rate increased in dry and lubricated sliding. The dominant mechanisms responsible for the wear are discussed, as well as the advantages and limitations of electro-deposition as an alternative sealing procedure for sprayed coatings. It is concluded that electro-deposition is a promising sealing technique for selected tribological applications.