Comparison of W–Cu composite coatings fabricated by atmospheric and vacuum plasma spray processes

• W/Cu composite coatings were fabricated by air plasma spray (APS) and vacuum plasma spray (VPS) processes.
• Microstructure, some physical properties and thermal characters are compared.
• Both thermal conductivity and CTE of VPS-W/Cu coating are much higher than those of APS-W/Cu coatings.
• Reasons for the differences in thermal properties of W/Cu coatings are discussed.

Tungsten (W) coatings with different copper (Cu) contents (15 vol.% and 25 vol.%) were fabricated by atmospheric plasma spray (APS) and vacuum plasma spray (VPS) technologies, respectively. Phase composition and microstructure of the composite coatings were characterized. Physical properties, including porosity, oxygen content, microhardness and density of the coatings were examined. Thermal properties, including coefficient of thermal expansion (CTE) and thermal conductivity of the coatings were characterized. The results showed that the oxide content and porosity in the VPS-W/Cu coatings were apparently lower than those of the APS-W/Cu coatings. The CTE and thermal conductivity of the W–Cu composite coatings increased with the addition of Cu. The VPS-W/Cu coatings had apparently higher CTE and thermal conductivity compared with the APS-W/Cu coatings containing similar Cu content. The effects of the Cu incorporation in the composite coatings and the fabrication process on the coatings' properties were discussed.