Self-assembly of TaC@Ta core–shell-like nanocomposite film via solid-state dewetting: Toward superior wear and corrosion resistance

• Published in: Acta materialia 2018-11, Vol.160, p.72-84
• Main Authors: Ren, Ping, Wen, Mao, Zhang, Kan, Du, Suxuan, Zhang, Yidan, Chen, Jianhong, Zheng, Weitao
• Format: Article
• Language: English
• Subjects: Corrosion; Phase transformation; Solid-state dewetting; Superhard nanocomposite; Tribology
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/j.actamat.2018.08.055

The improvement of comprehensive properties including hardness, toughness, wear, and corrosion resistance in the transition-metal carbides/nitrides (TMC(N)) films, especially avoiding the trade-off between the hardness and toughness, is strongly required for various applications. Herein, we provide a new strategy, by activating solid-state dewetting during layered deposition, to accomplish the self-assembly of ordered TaC@Ta core–shell-like nanocomposite film consisting of TaC nanocrystallines encapsulated with thin pseudocrystal Ta tissues (∼1.5 nm). The novel core−shell-like structure can simultaneously achieve superhardness (∼45.1 GPa) mainly dominated by the Orowan strengthening mechanism and high toughness attributed to the indenter-induced phase transformation from the pseudocrystal to body-centered cubic α-Ta, together with drastically enhanced wear and corrosion resistance. Furthermore, thin pseudocrystal Ta encapsulated layer (∼1.5 nm) in the TaC@Ta core–shell-like structure helps for promoting the formation of lubricious TaOx Magnéli phase during sliding, thereby further dropping the coefficient of friction relative to TaC monolayer. Apparently, solid-state dewetting may provide a new route to construct ordered TMC(N)@TM core–shell-like nanocomposite structure capable of combining superhardness, high toughness, low friction, and superior wear and corrosion resistance. [Display omitted]