Nanocomposite tribological coatings for aerospace applications

• Published in: Surface & coatings technology Vol. 116-119; pp. 36 - 45
• Main Authors: Voevodin, A.A., O'Neill, J.P., Zabinski, J.S.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.09.1999
• Subjects: Aerospace tribology; Carbide; Diamond-like carbon; Dichalcogenide; Nanocomposite coating; Carbide; Dichalcogenide; Nanocomposite coating; Diamond-like carbon; Aerospace tribology
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/S0257-8972(99)00228-5

Challenges in aerospace tribology and composite coatings for aerospace applications are briefly reviewed. Attention is given to nanocomposite coatings made of carbide, diamond-like carbon (DLC) and transition-metal dichalcogenide phases. The preparation of such coatings within the W–C–S material system using a hybrid of magnetron sputtering and pulsed laser deposition is described. Coatings consist of 1–2 nm WC and 5–10 nm WS2 grains embedded in an amorphous DLC matrix. These WC/DLC/WS2 nanocomposites demonstrate low friction and wear in tests performed in high vacuum, dry nitrogen and humid air. Coatings are found to adapt to the test conditions, which results in: (1) crystallization and reorientation of initially nanocrystalline and randomly oriented WS2 grains; (2) graphitization of the initially amorphous DLC matrix; (3) reversible regulation of the composition of the transfer film between WS2 and graphite with environmental cycling from dry to humid; and (4) possible DLC/WS2 synergistic effects, providing friction reduction in oxidizing environments. These adaptive mechanisms achieve low friction coefficients of 0.02–0.05 and an endurance above two million cycles in space simulation tests. This also provides stable coating performance and recovery of low friction in tests simulating ambient/space environmental cycling. Correlations among WC/DLC/WS2 chemistry, structure, hardness, friction and wear are discussed. The tremendous potential of such composites for aerospace tribology is demonstrated.