Tribological behaviour of diamond coatings sliding against Al alloys

Abstract

A low wear rate, combined with exceptional physical properties, makes diamond an ideal candidate for the machining of non-ferrous materials. It is particularly interesting for tooling aluminium and its alloys as it offers these soft materials clean cutting and lets the shavings slide on the tool surface. It results from studies dealing with the friction of diamond against aluminium, that the tribological behaviour of this pair is greatly influenced by the presence of oxides, more particularly Al 2O 3, on the counterface surface. It was therefore necessary to better understand the role of these oxides during the cutting process, the way they modify the nature of the contact, and their effects on transferred layer formation. The tribological behaviour of diamond coatings prepared by the combustion flame process, sliding against aluminium alloys under different environments (vacuum, oxygen and water vapour), at two applied normal loads is presented here; the modifications of both the coatings (formation of amorphous carbon) and the counterfaces (depth of the friction track), as well as the transferred layers (chemical composition, aspect) are specifically studied. The surface changes are revealed by scanning electron microscopy observations. Raman spectroscopy and energy dispersive spectroscopy analyses were realised to highlight the observed phenomena.