Mécanismes d'usure de revêtements de nitrure de titane et d'aluminium en microtribologie

Wear behaviour of protective Ti1-xAlxN (0 ≤ x ≤ 1) thin films PVD deposited is studied according to micro and nano-structure of the layers. Film structure is the cause of their functional properties. Growth directions of the nanostructured films are determined by X-ray diffraction. Damage modes were investigated through microtribology tests at room temperature against an alumina ball to prevent wear from the counterpart, at low loads and low sliding velocities to avoid the growth of an oxide layer. To understand wear mechanisms caused by the friction of the ball, several tests were carried out: toughness determined by scratch tests, wear scar observation by Scanning Electron Microscopy and measurement of the wear volume by holographic interferometric profilometry. When wear debris get trapped in the wear scar, their amount, linked to crack initiation resistance of films, and their nature, ductile or brittle, have a great influence on the final damage. Al-rich films, texturing predominantly along the [002]h direction of the hexagonal lattice, show a brittle behaviour. Ti-rich films, whose main growth direction is [200]c of the cubic lattice, are ductile and show a better resistance to wear. For these films, the presence of domains growing along the [111]c direction seems to have a major influence on toughness. Indeed, the amount of wear debris is linked to the proportion of domains crystallizing along this direction. Mots clefs : Materiaux nanostructures, Taux d’usure, Tenacite, Microstructure, Diffraction des rayons X, Holographie. 21 Congres Francais de Mecanique Bordeaux, 26 au 30 aout 2013