Ternary Transition Metal Diborides: A New Generation of Protective Coating Materials?

Abstract

Future high-performance components used in aviation and energy production require customized protective coating materials to fulfil specific criteria on efficiency as well as durability. Next to the well-established nitride-based coatings are boron containing systems an upcoming and highly promising class. Here, ternary transition metal diborides are relatively unexplored compared to their binary counterparts such as hard and inelastic TiB2. Typically, these boride-based coatings are limited by their brittle behaviour as well as volatile oxide scale formation. Within this study, we want to address these specific challenges on various ternary model systems within group IV to VI transition metal diborides (e.g. M1-xMxB2-z prototypes). The phase formation of the two competing hexagonal structure types (α AlB2 vs. ω-W2B5-x) has been investigated for different non-reactive PVD based deposition routes. In addition, different alloying concepts for enhancing the ductile character as well as oxidation resistance of these superhard ternary diborides will be discussed in detail.