A promising high temperature self-lubricating Cu-based superalloy with coherent cuboidal L12-γʹ phases

Abstract

High temperature self-lubricating materials including composites or coatings exhibit remarkable tribological property but typically suffer from poor ductility. Therefore, striking a fine balance between these two properties is a great challenge. In this work, series of high-temperature self-lubricating Cu100-x(Ni3Al1)(x/4) superalloys were obtained, and it possesses both good tensile strength at room temperature or high temperature and appreciable elongation value (its elongation can reach up to 3%). Compared with other high temperature self-lubricating materials, it has already made great progress in the aspect of mechanical property. The results showed that the source for remarkable high temperature tribological properties derives from the synergistic effect of naturally formed oxide scale and high temperature bearing capacity. In the naturally formed oxide scale, the CuO layer provides excellent lubrication action due to those unique advantages, such as easy to shear, formation of twinning and brittle-ductile transition at high temperature. Additionally, the existence of substantial coherent interfaces hinders the crack initiation. The dense and continuous γ-Al2O3 protective layer can hinder the diffusion of the oxygen anions and metal cations, which is beneficial to inhibit the further oxidation of the alloy. The work provides a novel strategy for the design and preparation of high temperature self-lubricating materials.