Relationship Between Hardness and Abrasive Wear for some Aluminium Alloys

摘要

Abrasive wear of engineering and transport machine components caused by abrasive particles action is a major industrial problem. It is estimated that abrasive wear represents about 50% of the total wear encountered in industrial situations. Therefore it is necessary to develop experimentation to study the wear phenomena in order to optimize and improve the life of machine parts, and therefore save energy and resources. Classically it is considered that abrasive wear is inversely proportional to hardness (Archard law), but in fact several studies showed that the correlation between hardness and abrasive wear coefficient is far from being obvious. A study of an industrial case is proposed to show different morphologies of wear damage. Microscopic observations of aluminium alloy indicate plastic deformation of surface layers, work hardening and recrystallization. When large damage areas are present, subsurface observations show delamination phenomena and grains disorientation. In order to study the correlation between abrasive wear and hardness a modified pin-on-disc tribometer has been developed. This test makes possible to rub an aluminium plate against an abrasive disc in presence of water. The normal load (then the contact pressure) and the sliding speed are controlled. Wear measurements is made by weighing specimens. The effect of abrasive particle size and normal load on two-body abrasive wear have been investigated. A better correlation between abrasive wear and hardness has been found for coarse grains, while for low grain sizes this correlation is not verified. This difference can be explained by the evolution of various wear mechanisms and abrasive grains size. The abrasive wear presents also a linear variation according to the normal load for different size of abrasive grains. Results confirm that hardness is not the unique factor governing abrasive wear resistance.