Analysis of diamond-like carbon and Ti/MoS2 coatings on Ti-6Al-4V substrates for applicability to turbine engine applications

Ti-6Al-4V substrates have been coated by diamond-like carbon (DLC) films, w ith no surface pretreatment, and have been coated by Ti/MoS2 films, with a simple surface pre-cleaning. The DLC films were deposited by planar coil r. f. inductively-coupled plasma-enhanced chemical vapor deposition (r.f. ICPE CVD); the Ti/MoS2 films were deposited by magnetron sputtering. Both the DL C and Ti/MoS2 films were characterized by pull tests, hardness tests, scann ing electron microscopy (SEM), and wear tests (pin-on-disk and block-on-rin g) to compare their adhesion, hardness, surface topology, and wear properti es to plasma-sprayed Cu-Ni-In coating currently used for turbine engine app lications. The DLC films were easily characterized by their optical propert ies because they were highly transparent. We used variable-angle spectrosco pic ellipsometry (VASE) to characterize thickness and to unequivocally extr act real and complex index of refraction, providing a rapid assessment of f ilm quality. Thicker coatings yielded the largest hardness values. The DLC coatings did not require abrasive pretreatment or the formation of bond-lay ers to ensure good adhesion to the substrate. Simple surface pre-cleaning w as also adequate to form well-adhered Ti/MoS2 on Ti-6Al-4V. The results sho w that the DLC and Ti/MoS2 coatings are both much better fretting- and wear -resistant coatings than plasma-sprayed Cu-Ni-In. Both show excellent adhes ion to the substrates, less surface roughness, harder surfaces, and more we ar resistance than the Cu-Ni-In films. (C) 2000 Published by Elsevier Scien ce S.A. All rights reserved.