Calcium sulfate as a high temperature solid lubricant

Both composite coatings and layered structures of CaF2 and WS2 were grown via pulsed laser deposition (PLD) on steel substrates and TiN coated steel substrates. Films were found to be lubricious at temperatures up to 500 degrees C. XPS analysis of specimens indicated that the CaF2 and WS, materials interacted to form CaSO4, among other compounds. CaSO4 was then evaluated as a solid lubricant coating and found to have an excellent coefficient of friction of similar to 0.15 at 500 degrees C. Comparison of CaSO4 films with CaF2 films showed CaSO4 films performed better than CaF2 coatings both alone and in layered structures with WS2 or Ag. (C) 1998 Elsevier Science S.A. All rights reserved.