Spark plasma sintered W, Ti6Al4V, Cu containing Nb-based alloys representing a new generation for high-temperature applications

Abstract

Novel spark plasma sintering (SPS) of W–Ti–Al–V–Cu containing Nb-based alloys, representing a new generation of refractory materials, are novel candidates for structural applications. Ni superalloys are currently used at temperatures close to their melting point. Therefore, a novel generation of refractory alloys is being applied at even higher temperatures. When compared to other refractory metals for applications in higher temperature environments, Nb-based alloys have shown great prominence owing to higher melting point. However, their applications have not yet been widely implemented. Indeed, there is a lack of research which might improve some restrictive aspects of Nb alloys, such as low temperature oxidation resistance as well as poor fracture toughness and ductility. To fill this gap, novel alloys with composition Nb-xW-15(Ti6Al4V)–1Cu (x = 5, 10 and 15 wt.%) were developed via SPS at 1400 and 1500 °C (with and without pre-compression). The alloys microstructure, density, hardness and oxidation resistance were characterized. X-ray diffraction and energy dispersive spectroscopy microanalysis confirmed the formation of Nb, Ti and W solid phases solution, as well as intermetallic, AlTi3, TiO2 and TiC compounds. The highest densification (97.5%) was obtained in the alloy with the highest content of 15 wt.% W sintered at 1500 °C and pre-compressed. Despite a lower hardness, it exhibited a parabolic oxidation kinetics from the beginning of the oxidation test. This behavior was attributed to the higher amount of Nb2O5, which increased the oxidation resistance of the alloy.

Keywords

• Niobium alloys
• Nb–W–Ti–Al–V–Cu
• Spark plasma sintering
• Oxidation resistance