Thermal contact conductance of molybdenum-sulphide-coated joints at low temperature

TLDR: In this paper, the effectiveness of MoS2 coating on aluminum and stainless steel contacts at different interface temperatures and loads is determined, and experiments are carried out over a range of low temperatures.

Abstract: J OINTS used for cryogenic structural supports and satellite deployment mechanisms are often exposed to very low temperatures. These joints, unlike those for ground applications, do not usemetal-to-metal contact. A conducting or insulating interstitial medium is introduced at the interface for controlling the contact conductance. When gold and silver plating and the use of thermal grease is adopted for enhancing the contact conductance, a reduction in contact conductance is achieved by providing a nonmetallic coating at the interfaces. Molybdenum sulphide (MoS2) is widely used as the nonmetallic coating in cryogenic structural joints, because it not only reduces the joint conductance but also provides dry lubrication at the joint. A precise knowledge of the contact conductance of the coated joint is essential, especially at the low temperatures at which it is used for estimating the parasitic heat-conduction loads through the cryogenic structural supports. A variety of nonmetallic coatings such as manganese dioxide, silicon elastomer, carbon black, and polyethylene have been evaluated over a range of interface temperatures and pressures [1,2]. The temperatures considered in the preceding studies are essentially above the ambient. A general model for computing the conductance in multilayered contacts was developed by Muzychka et al. [3] for a flux tube having two applied coatings. The need remains to determine contact conductance of nonmetallic coating [4] such as MoS2 at low temperatures. In this paper, the effectiveness of MoS2 coating on aluminumand stainless steel contacts at different interface temperatures and loads is determined. Experiments are carried out over a range of low temperatures.