Impact Properties of Diffusion Bonded Joints

Study on Diffusion Bonding in Steels (Report 2)

Abstract

Charpy impact tests have been carried out on diffusion bonded joints in 2.25Cr-1Mo steel and 13Cr steel, and the effects of surface roughness and annealing treatment (postheat treatment) on charpy impact properties of the joints have been investigated. Impact properties of the joints confined the bonding deformation have been also assessed. The results obtained here are summarized as follows;
1) Decreasing the surface roughness resulted in improvement of the impact properties. Surface roughness appears to be an important factor in diffusion bonding since smooth surfaces brought together will have a larger bonding area than rougher surfaces.
2) Subsequent to diffusion bonding, the annealing treatment could improve the impact properties of the joints in both 2.25Cr-iMo steel and 13Cr steel.
3) The joints that were bonded after the laying surfaces were subjected to high temperature oxidation showed very low impact properties. Oxide films on the faying surfaces prevent diffusion bonding although the oxide films are broken up by the plastic flow at the points of contact along the interface and metal to metal occurs partially.
4) As the degree of the bonding deformation was increased, the impact properties improved because of promoting the diffusion of atone across the interface followed by increasing the metal to metal contact area.
5) In the diffusion bonding with confining the bonding deformation, the impact properties increased with the product of pressure and pressing time. The result suggests that to achieve high impact property, it is necessary to choose an optimum bonding pressure in the diffusion bonding with a given deformation.