Influence of carbon on bond strength betvveen nickel and Ni–W alloys

Abstract

lloys with compositions of Ni–90W, Ni–80W, and Ni–50W (all wt-%) have been fabricated using liquid phase sintering followed by thermomechanical processing. These Ni–W alloys and high purity W were diffusion bonded with both high purity and commercial purity Ni using hot isostatic pressing. The fracture strengths of the bonds were measured using a lap shear test. The microstructure developed in the bond zone was examined using scanning electron microscopy, X-ray diffraction, electron probe microanalysis, and transmission electron microscopy. The influence of carbon on the bond strength of the joints formed between W or Ni–W alloys and Ni was investigated. Three types of Ni–W carbide, Ni₆W₆C, Ni₂W₄C, and NiW₃C, were found close to the joints formed between the Ni–W alloys and commercial purity Ni. The effect of the formation of Ni–W carbides on the bond strength and fracture mode is discussed, together with the possibility of increasing the bond strength between commercial purity Ni and high purity W through the applications of gradient interlayer.

MST/1248