CATHODIC SPUTTERING FOR PREPARATION OF LUBRICATION FILMS

In order to investigate their lubricating behaviour, thin films of MoS(x), CF(x) and CaF2 were prepared by cathodic sputtering: d.c. reactive magnetron sputtering of a molybdenum or MoS1.6 target in an Ar-H2S atmosphere for MoS(x) films; r.f. diode sputtering of a polytetrafluoroethylene target in an argon or Ar-C3F8 atmosphere for CF(x) films and of a CaF2 target in an argon atmosphere for CaF2 films. The properties of the films (morphology, structure, composition, hardness, density, friction coefficient and wear) were investigated in relation to the deposition parameters. Adherent and dense films were deposited on stainless steel substrates. The thickness ranged from 0.5 to 28-mu-m for MoS(x) films, from 0.5 to 4-mu-m for CF(x) films and from 0.2 to 4-mu-m for CaF2 films. The MoS(x) layers present a hexagonal structure with various preferred orientations, the CaF2 layers are cubic with a (111) preferred orientation, while the CF(x) coatings are amorphous. Numerous tribology tests were performed on MoS(x) films in dry air or nitrogen. Minimum friction coefficients of 0.025 (pin on disk) and 0.01 (collar axle) were found for MoS1.5-1.7 films exhibiting a (001) preferred orientation and a hardness of 5000 MPa. The best wear results were observed for MoS1.8 films exhibiting a hardness of 2000 MPa. Other experiments were carried out in liquid nitrogen. Finally, the film behaviour in humid air was analysed. Tribology test conditions for CF(x) and CaF2 are being optimized.