Three-body abrasive wear of composite coatings in dry and wet environments

A con!parison of three-body abrasive wear behaviour of aluminium composite coatings in both wet and dry environments is presented. Composite coatings reinforced with discontinuous ceramic particles of either Al2O3, SiC or TiC were studied. These metal matrix composite (MMC) coatings were formed on AA5083 aluminium alloy using a plasma transferred are (PTA) surfacing technique. The aim of the present work was (1) to investigate the environmental influence on wear behaviour, and (2) to study the effectiveness of each reinforcement phase towards coating wear resistance. Low stress abrasive studies were conducted using a sand/rubber wheel abrasion tester. For similar wear conditions. the environment significantly influenced wear behaviour. The wet environment promoted a higher wear rate compared to the dry conditions. The establishment of steady-state abrasive wear conditions was related to the formation of a tribolayer. This layer formed at the wearing surface (1-3 mu m in thickness) and was composed of plastically deformed matrix material, silica fragments and in the case of MMC coatings, fractured particles of the reinforcement phase. The formation of a tribolayer has previously been identified under dry sliding wear conditions, but not in relation to abrasive wear. The wear performance of MMC coating was influenced by the type, size and volume fraction (V-i) of the reinforcement phase and the wear environment. (C) 1998 Elsevier Science S.A.