This paper presents fretting wear and cold welding characteristics in a simulated space environment of three commonly used aluminium alloys (AA2219, AA7075 and AA6082) coated using the Keronite plasma electrolytic oxidation (PEO) process. The fretting wear and cold welding responses have been related to inherent microstructures of the coatings and their characteristics such as roughness, porosity, adhesion, composition and hardness. All coated specimens have been subjected to thermal cycling in vacuum, simulating extreme space condition temperatures that are often experienced by satellite mechanisms outside the spacecraft, due to the sun shine/shadow effect. Standard spacecraft fretting and cold welding tests have been conducted on the coated discs against an AISI 52100 steel pin before and after thermal cycling, and the resulting adhesion force as a function of cycles has been monitored. A high resolution 3D profilometer has been used in order to assess the volumetric wear loss or pile-up due to material transfer at contact surfaces and further supported by detailed examinations using high resolution scanning electron microscope (SEM) and energy dispersive spectral (EDS) analysis. The Keronite PEO coated aluminium alloys, before and after thermal cycling, showed no sign of cold-welding or any measurable adhesion value during the fretting tests with AISI 52100 steel. Detailed examination of the contact surfaces displayed only a minor coating destruction after the fretting. The results demonstrate that Keronite PEO coatings can be used for space applications like ''hold down points''.
Combating the fretting wear and cold welding of aluminium alloys on spacecraft hardware using the plasma electrolytic oxidation (PEO) process
Verhinderung von Reibverschleiß und Kaltpressschweißen an Aluminiumlegierungen für die Raumfahrt unter Anwendung des Verfahrens der plasmaelektrolytischen Oxidation (PEO)
2009
8 Seiten, 6 Bilder, 3 Tabellen, 9 Quellen
Conference paper
English
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