Abstract
The increase in strength of gold-nickel brazed joints, with increasing joint gap is explained by considering the mode of failure of the joints. Failure occurs in an apparently semi-brittle manner by crack initiation and propagation. Crack propagation is considered to be the controlling factor in joints brazed at 970°C. On raising the brazing temperature to 1000°C the controlling factor changes to one of crack initiation. This is the result of changes in the braze alloy microstructure due to pick up of small amounts of alloying elements from the steel. The effects of alloying between braze material and steel, on the joint microstructure, are considered and a corner of the gold-nickel-silicon ternary is calculated, silicon having been found to have a large effect on the joint microstructure.