Antiwear lubrication coating for bearing surfaces for hydrodynamic fluid bearings

Abstract

A very thin lubricating coating on one or both of the facing surfaces defining the gap of the hydrodynamic bearing. The lubricant film would need to be very thin, in the range of about 10 Å to 1000 Å, so that the film is thin enough that it does not materially affect the performance of the hydrodynamic bearing gap which is about typically 1-10 &mgr;m. The thin film could be a perfluoropolyether (PFPE) or a mixture of PFPE or a phosphazine derivative. To improve the adhesion and lubricating performance, functional PFPE can be used. For pure metallic surface like steel, phosphate esters can also be used because of its affinity with the metallic surface, e.g., ferrous. For example, the film could be PFPE, or a mixture of PFPE and a phosphazine derivative. The lubricant should be chosen to be thermally stable, and non-reactive with the typical ambient environment. The lubricants also have to have very low vapor pressure so that it lasts for the life of the bearing, as it will be applied only once during the manufacturing process. As an alternative, particularly if one of the surfaces of the bearing gap is ferrous, a phosphate esther could be used. Particularly with this type of coating, the material could be quenched in the phosphate esther, providing the desired thin surface coating. A thin film of phosphate esters without quenching can also be a effective wear protective coating. The thin lubricant film can be applied to both metallic surface as well as on the surface with hard coating. The use of coating allows for the usage of free machining or soft material which itself is vulnerable to wear degradation; the use of thin film safeguards the hard coating from wear failure.