Abstract
Thermal-spray (TS) technology was applied on Ni x Co 0.6 Fe 0.2 Cr y Si z AlTi 0.2 high-entropy alloys in this research. The results indicate that the hardness of high-entropy alloys undergoing a TS+ heat treatment (1100 °/10 h) is significantly increased to a near as casted state (1045 Hv) and provides excellent coarsening resistance performance resulting from the Cr 3 Si and several unidentified phases. This Ni x Co 0.6 Fe 0.2 Cr y Si z AlTi 0.2 alloy system does precipitate during casting, which is quite different compared to many applied alloys. The typical TEM images of the as casted Ni x Co 0.6 Fe 0.2 Cr y Si z AlTi 0.2 alloys with addition/removal of Mn, Si, and Ni element are also compared in this study. The results showed a significant amount of nano size particles (ranging from 5 to 10 nm), atoms segregation, twining structure and subgrain structure were distributed in the matrix. However, after the TS+ 1100 °C/10 h treatment, the main features found in the TEM are large amounts of nano size precipitates and dislocations. The mechanism of the dislocation formation and correlation of the hardness of the TS layer associated with the heat treatment are discussed. © 2010 Elsevier B.V. All rights reserved.