STM-279 Assesment of the Cold Welding between Separable Contact due to Impact and Fretting under Vacuum
A common failure mode seen during the testing and operation of spacecraft is termed ‘cold welding’. European laboratories refer to this as ‘adhesion’, ‘sticking’ or ‘stiction’. This publication is intended to provide the space community with the most recent understanding of the phenomenon of ‘cold welding’ in relation to spacecraft mechanisms with separable contact surfaces. It presents some basic theory and describes a test method and the required equipment.
Cold welding between two contacting surfaces can occur under conditions of impact or fretting. These surfaces may be bare metals, or inorganically or organically coated metals and their alloys. Standard procedures for quantifying the propensity of material surface pairs to cold weld to each other are proposed. Of particular interest will be the contact data of different materials, which are presented in numerical form and as tables summarising contacts between materials that can be either recommended or considered unsuitable for use under vacuum. The data have been compiled in a database that can be accessed online.