Large enhancement of thermal conductance at ambient and cryogenic temperatures by laser remelting of plasma-sprayed Al2O3 coatings on Cu

Highlight• Plasma spraying and subsequent laser remelting to improve alumina coatings on copper. • Optimization of the laser processing to minimize the size and impact of microcracks. • Optimized alumina coatings on copper as heat sinks with electrical insulations. • Large enhancement of cryogenic thermal conductance of these Cu/alumina/Cu joints. Joints of high thermal contact conductance and electrical insulation have been obtained by coating copper supports with thin alumina (Al₂O₃) layers (of 140–150 μm thickness). This has been achieved by a combination of plasma spraying process and the subsequent coating remelting by a near-Infrared (n-IR) laser. With a proper optimization of the laser processing conditions, it is possible to transform the metastable γ-Al₂O₃ phase of the as-sprayed coatings to stable α-Al₂O₃, and to achieve denser alumina coatings. This results in a large enhancement of the thermal conductance of the joints, enabling their application as heat sinks at cryogenic and ambient temperatures. The process proposed in this work is scalable for the formation of alumina coatings on large metallic pieces of complex geometries.