Enhancement of thermal contact conductance of coated junctions

The thermal contact conductance of coated, contacting aluminum 6061-T651 surfaces was studied experimentally. Four different coating materials, copper, silver, a phase mixture of copper-carbon, and a phase mixture of silver-carbon were evaluated using four different surface roughnesses for each coating material. All of the samples were tested at contact pressures of 125, 250, 375, and 500 kPa. The test results of thermal contact conductance are presented in terms of coating thickness, surface texture, and properties of the coating materials. Using the experimental data, dimensionless expressions were developed that relate the contact conductance of the phase mixture and pure coatings to the coating thickness, the surface roughness, the contact pressure, and the properties of the aluminum substrate. The effects of the surface roughness and of the phase mixture of the coatings on the thermal contact conductance were investigated. In addition, the load cycling effect on the thermal contact conductance was examined for bare aluminum 6061-T651 specimens. 15 refs.