Diffusion Welding of High Temperature Alloy A286 and Hastelloy X

Abstract

The diffusion-welding characteristics of γ' precipitation-hardened nickel-iron alloy A286 and solid-solution-strengthened nickel-base alloy Hastelloy X have been studied by microscopy, electron probe microanalysis, tensile tests, and stress-rupture tests.
In diffusion welding of A286 without any interlayer metals some titanium compounds were formed at the weld interface, which caused very poor joint properties. However, the formation of these compounds were fairly prevented by welding with a nickel foil interlayer at above the solvus temperature of γ' and η precipitates.
The diffusion heat treatment to promote the joint homogenization remarkably improved the joint properties, and diffusion welds of A286 and Hastelloy X with nickel foil interlayers were made which exhibited 80-100 % joint efficiency in 815°C stress-rupture tests.
An alloy interlayer having similar compositions to those of the base metal sometimes reduced the weldability.