Dry sliding wear behaviour at ambient and elevated temperatures of plasma transferred arc deposited aluminium composite coatings

Abstract

Plasma transferred arc (PTA) surfacing is a surface engineering process in which a coating is deposited on the substrate by the injection of metal powders and/or ceramic particles into the weld pool created by the formation of a plasma plume. The present work involved the tribological evaluation of metal matrix composite (MMC) coatings deposited onto an aluminium alloy using the PTA technique. Coatings were fabricated by the deposition of an Al–Ni powder containing either Al2O3 or SiC particles. Dry sliding wear behaviour of the coatings was evaluated at ambient and elevated temperatures. Under sliding conditions of low applied stress and ambient temperature, reinforcement properties such as interfacial structure and fracture toughness have a significant influence on wear resistance. The SiC particles, which exhibit high interfacial bonding and toughness, support the matrix by acting as load bearing elements, thereby delaying the transition in wear mechanism as applied stress increases. As applied stresses exceed the fracture strength of the SiC and Al2O3 particles, these particles suffer fragmentation and/or debonding and no longer support the matrix. At higher stresses and elevated temperature, matrix properties such as flow stress and the tribolayer formation play more important roles in determining wear resistance.