Deposition of wear-resistant AlN-diamond composite coatings

We have prepared composite coatings of aluminum nitride (AIN) and diamond on silicon, copper and steel substrates and investigated their tribological properties. To control interfacial stresses, the coatings are prepared with a novel microstructure in which diamond forms a cellular network in a background matrix of AlN. This type of microstructure also imparts enhanced toughness and adhesion properties. Owing to matching of temperature variation in thermal expansion coefficients of AIN and diamond, thermal stresses within the compostie films are minimized while substrate-composite interfacial stresses are effectively accomodated in the background matrix of AIN, which is relatively softer than diamond. Selective abrasion and indentation measurements are carried out to investigate the utility of coatings for wear protection. The importance of AlN as a component material for forming high quality diamond composites is discussed.