17 - High-entropy alloys for high-temperature structural/tribological applications

Abstract

The chapter proposes the concept of advocating the exploration of high-entropy alloys (HEAs) as advanced structural/tribological materials capable of surpassing the operational temperature range of conventional nickel-based superalloys. First, the exceptional phase stability of refractory HEAs (RHEAs) at ultrahigh temperatures is explained, highlighting its significance in achieving desired mechanical properties at high temperatures. Subsequently, the outstanding high-temperature mechanical properties and thermal deformation capability of RHEAs were emphasized, elucidating the primary strengthening mechanism and deformation mechanism. Moreover, extensive examination of the high-temperature friction behavior of these alloys allows for the identification of three key mechanisms that enhance their wear resistance, while also providing insights into their potential application in the field of high-temperature lubrication. The mechanism of rapid oxidation in refractory alloys is discussed, and based on this, an analysis is conducted on how the current antioxidant strategy inhibits pest oxidation and scale peeling of refractory elements. The high-temperature fatigue and creep behavior of RHEAs in recent years have been comprehensively summarized. The existing research limitations and prospective directions for future research and development were deliberated upon.