Synthesis and Tribological Behavior of Metal Diboride-Nitride Coatings: Optimizing the Hard and Compliant Response

University Of Illinois At Urbana-Champaign, Urbana IL

Investigators

Abstract

The research objective of this award is to develop mechanically hard and wear-resistant tribological coatings such that: (a) the coating process affords high conformality (i.e., uniform thickness everywhere within reentrant shapes); (b) the coating provides low friction, and low wear under normal operating conditions; and (c) the tribological performance is stable and predictable under extreme operating conditions, such as high load and high temperature. Specifically, low-temperature chemical vapor deposition is used to deposit coatings of the transition metal diborides HfB2, CrB2, and TiB2 using single-source, impurity-free precursors such as Hf(BH4)4. Alloying with nitrogen affords HfBxNy coatings that have a variable elastic compliance; alloying with Cr is used to enhance oxidation resistance; and multilayer coatings are synthesized to engineer the relationship between hardness and elastic response, which affects the tribological behavior. If successful, the results of this research will have a significant impact: it will enable the development of advanced devices that are free of lubricants and which have excellent lifetime under aggressive operating conditions. These include, but are not limited to, energy-efficient and oil-free compressors and microelectromechanical-based sensing and actuating devices. Graduate and undergraduate engineering students benefit through involvement in the research. Students spend summer time at Sandia National Laboratories, as well as have direct interaction with both Sandia and Emerson Climate Technologies. The results are broadly disseminated by presentations at domestic and international professional conferences, by publication in upper-tier peer-reviewed scientific journals, by seminars given at university and industrial laboratories, and by news stories that discuss the work as well as the critical role of the National Science Foundation.