Three-body abrasive wear testing of soft materials

This paper investigates some of the problems associated with determining the 'three-body' (rolling particle) abrasion resistance of soft materials such as polymers and soft metals. The ball-cratering micro-scale abrasion apparatus, initially developed for testing hard coatings, has been used to study the behaviour of soft materials: polymethylmethacrylate (PMMA): commercially pure aluminium, tool steel and, as a reference hard material, glass-bonded alumina. The importance of the initial entrainment of abrasive particles and its effect on the outcome of the test is discussed with reference to the hardness and roughness of the spherical counter-body. The morphology and evolution of the wear scar have been carefully studied. Problems associated with the measurement of the scar and subsequent calculation of the wear rate are identified, and solutions to these are suggested. The effects of normal load on particle entrainment and wear rate for soft materials are also described. Recommendations are made for the optimum test conditions for micro-scale abrasion testing of soft materials. (C) 1999 Elsevier Science S.A. All rights reserved.