THERMAL CONTACT CONDUCTANCE OF A PHASE-MIXED COATING LAYER BY TRANSITIONAL BUFFERING INTERFACE

The thermal contact conductances of metallic joints having phase-mixed coating layers applied by a novel transitional buffering interface te chnique was investigated. This study is restricted to relatively low c ontact pressure and to microhardness (P/H) ratios, 10(-4) < P/H < 6 x 10(-4), where very little data exist. These results are extremely usef ul for some applications such as electrical contacts in spacecraft. Th e purposes of this work were 1) to conduct an experimental study to ex amine four different coating materials, two pure materials, and two ph ase-mixed materials; and 2) to develop a theoretical model for a phase -mixed coating layer to predict the thermal contact conductance under the first-load cycle. The theoretical model included both the thermal and mechanical (microhardness) aspects of the contact problem. An exte nsive experimental program was carried out employing four different co ating materials, as well as a broad range of surface roughness and mic rohardness. In order to obtain more robust coatings than conventional methods with better endurance, an adhesion test was conducted to inves tigate the adhesive strength of transitional buffering interface (TBI) coating layers.