Development and characterization of spark plasma sintered novel Ni, Cu, WC containing Nb-Based alloys for high-temperature applications

Abstract

Niobium (Nb)-based alloys have not yet been considered to replace nickel (Ni)-based alloys as engineering component in high temperature applications. In spite of its elevate melting temperature, Nb is known for very limited oxidation resistance as well as lower fracture toughness and ductility. These disadvantages combined with relatively high cost, have not favor the high temperature engineering applications of Nb-based alloys. Therefore, for the first time, the present work developed spark plasma sintered novel Nb-based alloys with additions of Ni, Cu and WC, that allowed them to compete with conventional, Ni-based alloys. Alloys with composition Nb-xNi-2Cu–2WC (x = 5, 10 and 15 wt.%) were fabricated by sintering at 1000, 1100 and 1200 °C. The novel alloys microstructure, porosity, hardness and oxidation resistance were characterized and evaluated. X-ray diffraction analysis revealed the formation of Nb2C, δ Ni3Nb intermetallic. Nb alloy with 10 wt.% Ni spark plasma sintering at 1200 °C displayed superior properties of 97% densification, 1205 Vickers hardness, coherent granular Nb2O5 oxides, and 1.84 × 10−7 g2cm4.s−1 oxidation parabolic rate, as compared to other common Nb alloys and some conventional Ni-based alloys for high temperature applications.

Keywords

• Niobium alloys
• Nb-Ni-Cu-WC
• Spark plasma sintering
• Oxidation resistance