title: Temperature-dependent wear mechanisms for magnetron-sputtered AlTiTaN hard coatings.
abstract: AlTiTaN coatings have been demonstrated to have high thermal stability at temperatures up to 900 °C. It has been speculated that the high oxidation resistance promotes an improved wear resistance, specifically for dry machining applications. This work reports on the influence of temperature up to 900 °C on the wear mechanisms of AlTiTaN hard coatings. DC magnetron-sputtered coatings were obtained from an Al(46)Ti(42)Ta(12) target, keeping the substrate bias at -100 V and the substrate temperature at 265 °C. The coatings exhibited a single-phase face-centered cubic AlTiTaN structure. The dry sliding tests revealed predominant abrasion and tribo-oxidation as wear mechanisms, depending on the wear debris formed. At room temperature, abrasion leading to surface polishing was observed. At 700 and 800 °C, slow tribo-oxidation and an amorphous oxide formed reduced the wear rate of the coating compared to room temperature. Further, an increase in temperature to 900 °C increased the wear rate significantly due to fast tribo-oxidation accompanied by grooving. The friction coefficient was found to decrease with temperature increasing from 700 to 900 °C due to the formation of oxide scales, which reduce adhesion of asperity contacts. A relationship between the oxidation and wear mechanisms was established using X-ray diffraction, Raman spectroscopy, scanning electron microscopy, surface profilometry, confocal microscopy, and dynamic secondary ion mass spectrometry.
authors.affiliation: SAM Department, CRP-Gabriel Lippmann , 41, Rue du Brill, L-4422 Belvaux, Luxembourg.
authors.forename: Vishal
authors.initials: V
authors.lastname: Khetan
authors.forename: Nathalie
authors.initials: N
authors.lastname: Valle
authors.forename: David
authors.initials: D
authors.lastname: Duday
authors.forename: Claude
authors.initials: C
authors.lastname: Michotte
authors.forename: Christian
authors.initials: C
authors.lastname: Mitterer
authors.forename: Marie-Paule
authors.initials: MP
authors.lastname: Delplancke-Ogletree
authors.forename: Patrick
authors.initials: P
authors.lastname: Choquet
keywords: TiAlN; friction; hard coating; oxidation; wear mechanism