EFFECTS OF METALLIC VAPOR-DEPOSITION PROCESS AND THE OVERALL COATING THICKNESS ON THERMAL CONTACT CONDUCTANCE

An investigation was conducted to determine the effects of the vapor d eposition process and the interstitial coating thickness on the overal l joint conductance of metallic interfaces. Eight aluminum 6061-T6 tes t specimens were coated with indium and tested while in contact with u ncoated aluminum 6061-T6 specimens. In the first test set, all specime ns were coated to a thickness of 3.51 mu m, but the vapor deposition p rocess was varied to produce both single and multiple-layered coated s pecimens. In the second test set, the coating thickness was varied fro m 0.026 mu m to 3.51 mu m. The results indicated that when creating mu ltiple layered coatings, oxidation and thermal cycling caused poor lay er adhesion, and resulted in significantly reduced dimensionless conta ct conductance enhancement factors than for single-layered coatings wi th an equivalent thickness. Additionally, the results demonstrated tha t the thermal contact conductance could be enhanced to much greater le vels than previously reported in the literature, and that the dimensio nless enhancement factor asymptotically approached a maximum enhanceme nt value. A theoretical maximum enhancement limit has been presented f or comparision with the experimental data.