Influence of interdiffusion with substrate on spreading of molten Au–18Ni braze alloy

Abstract

Arrest in the spreading of Au–18Ni braze alloy on a 12%Cr steel substrate has been investigated. Observations reported previously show that this alloy penetrates the oxide surface layer of the substrate at temperatures above its normal melting point to form a blister, but that spreading then ceases. It is shown here that the radius of the blister increases if the temperature of the substrate is increased until a stable radius is again achieved. Analyses show a correlation between the arrest in spreading and the composition of the spreading alloy, which suggests that interdiffusion of alloying elements between substrate and braze, leading to an elevation of melting point, is responsible for the behaviour.