# Microstructure and Mechanical Properties of Tungsten Zircaloy-4 Diffusion Welding Interface

## TL;DR

This study examines how to bond tungsten with a corrosion-resistant zirconium alloy using high-temperature welding, and finds that the bond strength and hardness depend on the welding temperature.

## Contribution

The paper introduces a new method for creating a strong, corrosion-resistant bond between tungsten and Zircaloy-4 using diffusion welding and identifies the resulting microstructure and mechanical properties.

## Key findings

- A diffusion layer of ZrW2 forms at the interface, increasing in thickness with higher welding temperatures.
- The ZrW2 layer has a hardness of about 17.96 GPa, significantly higher than the base materials.
- Bonding strength peaks at 83.9 MPa when welding at 1000 °C but decreases at higher temperatures.

## Abstract

The tungsten target block is widely used as a target material in spallation neutron sources. However, due to the poor corrosion resistance of tungsten, a corrosion-resistant metal layer needs to be coated on the surface. In this study, Zircaloy-4 coating on tungsten was prepared by hot isostatic pressure diffusion welding in the temperature range of 900 °C to 1400 °C. The microstructure and mechanical properties of the zirconium–tungsten interface were studied. The results show that a clear intermediate diffusion layer was formed at the interfaces, and no obvious defects were found. As the HIP temperature increased from 900 °C to 1400 °C, the thickness of the diffusion layer gradually increased from 0.28 μm to 10.74 μm. Composition and phase structure analysis of the intermediate diffusion layer showed that the main phase of the diffusion layer is ZrW2. The nanoindentation hardness results near the interface showed that the hardness of the ZrW2 diffusion layer was significantly higher than that of W and the zirconium alloy, reaching around 17.96 GPa. As the HIP temperature increased, the bonding strength between Zry-4 and W matrix first increased and then decreased, with the highest bonding strength of 83.9 MPa when the HIP temperature was 1000 °C.