Wear-protective coatings are used in computer disk drives, cutting tools and other tribological applications. Each application has different property objectives for the protective coating. Therefore, one must tailor-design such coatings for individual applications. This paper presents two examples to illustrate the science and technology involved in the development of these wearprotective coatings. The first example is the development of TiN/SiNx multilayer coatings for high temperature and rolling contact fatigue applications. Using dual-cathode reactive sputtering, we were able to obtain TiN/SiNx multilayer coatings with an equiaxed grain structure (rather than the usual columnar structure), which is crucial in improving rolling contact fatigue lives. More important, by optimizing the individual layer thickness in this system, we provide strong evidence that the multilayer structure is preserved up to 1000°C. This suggests that these coatings may be useful for high-temperature applications. The second example is the development of ultrathin protective overcoats for hard disks with extremely high storage density. The objective is to develop 2 nm thick overcoats, which must provide both wear and corrosion protection. In this case, this requires the coating to be atomically smooth and pinhole-free and at the same time to be compatible with the lubricant used in this application. It is shown that nitrogenated carbon (CNx), when deposited under optimal pulsed dc conditions, can satisfy all these requirements down to 1- 2 nm.
