Mechano-chemical factors in MoS2-film lubrication

The friction properties and the well reproducible endurance limits of MoS2-lubricant films, prepared from the dry powder, were studied on rigs. Special consideration was given to: (i) automation of the rubbing-in process, (ii) the control of temperature and atmosphere, (iii) photographic recording of the friction surface. The influence of physical factors was found to be similar to that known already for resin coated MoS2 films. Life expectancy is dramatically shortened by certain chemical factors: (a) instantaneously scoring pairs of metals as substrates, and (b) mechano-chemical reaction with water vapour and with oxygen. In a neutral atmosphere the life of the lubricant film becomes very long. In a film of metallic lustre and under conditions of dynamic loading, blisters, ultimately of microscopic dimensions, are rapidly formed. Blistering can be enhanced by physical means, e.g. addition of amorphous carbon, or by oxidation. Prolonged oxidation leads to embrittlement and finally descaling of the MoS2 film from the substrate