Nanocomposite Coatings for Severe Applications

This chapter summarizes key recent developments in the production and use of nanostructured and composite coatings and their tribological properties. Structurally, these coatings are unique and may consist of two or more phases in a nanolayered or evenly distributed nanocomposite fashion. At present, several physical and chemical vapor deposition (PVD and CVD) techniques are available for the deposition of nanocomposite coatings on all kinds of substrates. With the cathodic arc and high-power impulse magnetron sputtering (HIPIMS) methods, formation of multiphase and hence multifunctional coatings has become much easier. Unlike conventional coatings, nanostructured and composite coatings provide far superior friction and wear properties even under very harsh tribological conditions, including high contact loads and elevated temperatures in oxidizing environments. Some of the nanocomposite coatings are superhard and able to extend the wear life of metal-cutting and metal-forming tools significantly. The selection of grain-boundary phases and their thickness seems to control the hardness, toughness, and other mechanical properties of these films. Nanostructured and nanocomposite coatings hold great promise for applications involving severe operating conditions. In particular, these coatings can be ideal for transportation, aerospace, and manufacturing applications. Because of their superior mechanical properties and high chemical and structural stability, nanocomposite coatings can significantly lower friction and wear losses under rolling, rotating, sliding, cutting, grinding, chopping, drilling, milling, and forming operations that exist in numerous industrial sectors. They can also provide significant energy, environmental, and economic benefits in such operations.