Antiwear lubrication coating for bearing surfaces for hydrodynamic fluid bearings

Abstract

A very thin lubricant coating is applied to one or both of the facing surfaces defining the gap of a hydrodynamic bearing to prevent wear of these surfaces. The lubricant film is necessarily 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 lubricant 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 ester could be used. Particularly with this type of coating, the surface of the hydrodynamic bearing could be quenched in the phosphate ester to provide the desired thin lubricant coating thereon. 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 surfaces as well as surfaces with hard coatings. The use of a hard coating allows for the usage of free machining or soft material which itself is vulnerable to wear degradation; the use of a thin lubricant film safeguards the hard coating from wear failure.