Tribological Behavior of Cathode Plasma Electrolytic Deposited Al2Y4O9 Coating on Aluminum Alloy

Abstract

Ceramic coatings are widely used as protective barriers on the surfaces of various metals and alloys.Herein, a novel surface ceramic treatment, i.e., cathode plasma electrolytic deposition (CPED), is proposed for the surface of an Aluminum (Al) alloy. The coating, prepared in an Y(NO 3 ) 3 aqueous solution on the surface of the Al alloy, consists of Al 2 Y 4 O 9 as the major phase component, Y 2 O 3 as a minor phase component, and amorphous Al 2 O 3 in the grain boundaries. As the applied voltage and deposition time increased, the crystallization of the coatings was enhanced. When deposited at 130 V for 10 min, the contact angle of the ceramic coating reached 141.0 ± 2.6°, indicating an enhanced self-cleaning effect.The ceramic coating also exhibited excellent self-lubricating and anti-wear effects. The friction coe cient of the CPED-treated sample vs. ZrO 2 ball or bearing steel ball decreased from 0.55-0.65 to 0.26-0.31 when the load was 3 N and the reciprocating velocity was 10 mm/s. Correspondingly, the wear rate of the CPED-treated sample vs. the ZrO 2 ball or bearing steel ball was signi cantly reduced. Results indicated that CPED is effective for the formation of self-cleaning and anti-wear ceramic coatings on Al alloys.