Thermal Constriction Resistance of Phase-Mixed Metallic Coatings

A phase-mixed coating using plasma-enhanced deposition onto a cold surface can offer excellent characteristics of adhesion of coatings to a wide range of base materials, and very close control of coating thickness. These physical characteristics are of great importance to the control of surface contact situations and in particular to the thermal constriction resistance of contact joints, with many applications in thermal control systems. Analytical expressions were developed for the thermal constriction resistance of cylindrical contact spots in such coatings. The thermal constriction parameter was presented in the dimensionless form as a function of the contact geometry, coating thickness, and thermal conductivity ratio of the two different coating materials. Finally, the results of analytical thermal constriction resistance were compared with experimental investigation using copper-carbon and silver-carbon phase-mixed coating materials. Conclusions on selecting phase-mixed coating materials were based solely on the thermal point of view