Mechanical characterization of electrochemically based W – Cu joints for low-temperature heat sink application

Abstract

Joining of the armor material tungsten to other alloys and especially to copper components which will act as heat sinks in divertor application is rather challenging due to the missing miscibility of tungsten and copper. This metallurgical behavior avoids the direct processing of W – Cu joints with sufficient mechanical stability. Introducing adapted interlayers can overcome these limitations if they exhibit extended miscibility with both partners to be joined.Electrochemical plating was chosen as deposition technology for such reactive interlayers and demonstrators were processed with a 10μm thick reactive Pd interlayer and joined by diffusion bonding. Their metallurgical behavior was characterized in dependence on processing temperature, reaction time and applied pressing load. The fabricated joints were mechanically qualified by shear testing. Cracking of the joints never appeared at the boundary of interlayer to W. The demonstrators revealed reasonable and applicable shear strength of around 100MPa. The observed shear strength values and formed microstructures in the joining zone will be displayed and discussed in dependence on the applied processing parameters. The developed bonding process by applying electrochemically plated interlayers has proven to be a reliable tool with industrial application potential.