Assessment of Tribological Coatings for Foil Bearing Applications

A critical component in oil-free gas foil bearings is the tribological coating system that must be used on the journal/runner and the foil pads to ensure reliable operation during transient periods and start-stop cycles. The objective of this investigation was to evaluate the performance characteristics of potential coatings for use in foil bearing applications. Tribological tests were performed using a single foil thrust bearing pad in contact with a rotating flat disk at room temperature. The coatings consisted of a tungsten disulfide-based solid lubricant (Korolon™900), hydrogenated diamond-like carbon film (H-DLC), and thin dense chrome plating deposited by the Electrolyzing™process. The results demonstrated an excellent performance for the foil pads coated with the tungsten disulfide-based solid lubricant tested against either chrome-plated or H-DLC-coated disks. The very low friction that was expected for H-DLC, however, was not observed and the tungsten disulfide-based coating dominated the tribological behavior. It is concluded that the best coating system for foil bearing applications consists of placing the soft solid lubricant coating on the foil pad and the hard, wear-resistant coating on the disk. Other combinations provide high coefficients of friction and liftoff speeds and result in high levels of wear. This phenomenon is explained using the quasi-hydrodynamic theory of powder lubrication.

[1]  James F. Walton,et al.  Oil-Free Turbocharger Demonstration Paves Way to Gas Turbine Engine Applications , 2000 .

[2]  A. Grill,et al.  Friction control of diamond-like carbon coatings , 1997 .

[3]  H. Heshmat,et al.  On the Cognitive Approach Toward Classification of Dry Triboparticulates , 1994 .

[4]  I. R. McColl,et al.  A multilayer approach to high adhesion diamond-like carbon coatings on titanium , 1997 .

[5]  James F. Walton,et al.  Application of Foil Bearings to Turbomachinery Including Vertical Operation , 1999 .

[6]  A. Erdemir.  Design criteria for superlubricity in carbon films and related microstructures , 2004 .

[7]  Christopher DellaCorte,et al.  Composition optimization of self-lubricating chromium-carbide-based composite coatings for use to 760 C , 1987 .

[8]  C. Dellacorte,et al.  The Effect of Compositional Tailoring on the Thermal Expansion and Tribological Properties of PS300: A Solid Lubricant Composite Coating , 1997 .

[9]  T. Blanchet,et al.  Thrust-washer tribological evaluation of PS304 coatings against Rene 41 , 2005 .

[10]  H. Heshmat,et al.  The quasi-hydrodynamic mechanism of powder lubrication. Part II: Lubricant film pressure profile , 1992 .

[11]  Ali Erdemir,et al.  Tribology of diamond-like carbon films: recent progress and future prospects , 2006 .

[12]  H. Heshmat.  The Quasi-Hydrodynamic Mechanism of Powder Lubrication—Part III: On Theory and Rheology of Triboparticulates , 1995 .

[13]  H. Heshmat,et al.  The quasi-hydrodynamic mechanism of powder lubrication. I: Lubricant flow visualization , 1992 .

[14]  T. Blanchet,et al.  High-temperature evaluation of solid lubricant coatings in a foil thrust bearing , 2008 .

[15]  R. G. Kaur,et al.  Powder lubricated bearing operation to PV of half a million , 2002 .

[16]  E. E. Swanson,et al.  The Role of High Performance Foil Bearings in an Advanced, Oil-Free, Integral Permanent Magnet Motor Driven, High-Speed Turbo-Compressor Operating Above the First Bending Critical Speed , 2002 .

[17]  Hooshang Heshmat,et al.  On a common tribological mechanism between interacting surfaces , 1989 .

[19]  Christopher DellaCorte,et al.  Evaluation of Advanced Solid Lubricant Coatings for Foil Air Bearings Operating at 25° and 500°C , 1999 .

[20]  Hooshang Heshmat,et al.  Evaluation of DLC Coatings for High-Temperature Foil Bearing Applications , 2009 .

[21]  Kevin C. Radil,et al.  The Effect of Journal Roughness and Foil Coatings on the Performance of Heavily Loaded Foil Air Bearings , 2002 .

[22]  Christopher DellaCorte.  The Evaluation of a Modified Chrome Oxide Based High Temperature Solid Lubricant Coating for Foil Gas Bearings , 2000 .

[23]  James F. Walton,et al.  Coatings for High Temperature Foil Bearings , 2007 .

[24]  S. Jahanmir,et al.  Low-Friction Wear Resistant Coatings for High-Temperature Foil Bearings , 2005 .

[25]  Hooshang Heshmat,et al.  Thermal Features of Compliant Foil Bearings—Theory and Experiments , 2001 .

[26]  C. Dellacorte,et al.  Test Evolution and Oil-Free Engine Experience of a High Temperature Foil Air Bearing Coating , 2006 .

[27]  James F. Walton,et al.  On the Frictional Damping Characterization of Compliant Bump Foils , 2003 .

[28]  James F. Walton,et al.  ADVANCEMENTS IN THE STRUCTURAL STIFFNESS AND DAMPING OF A LARGE COMPLIANT FOIL JOURNAL BEARING: AN EXPERIMENTAL STUDY , 2007 .

[29]  James F. Walton,et al.  THE APPLICATION OF FOIL SEALS TO A GAS TURBINE ENGINE , 1999 .

[30]  James F. Walton,et al.  The Role of High Performance Foil Bearings in Advanced, Oil-Free, High-Speed Motor Driven Compressors , 2003 .

[31]  A. Erdemir.  Friction and wear of diamond and diamond-like carbon films , 2002 .

[32]  Christopher DellaCorte,et al.  A Systems Approach to the Solid Lubrication of Foil Air Bearings for Oil-Free Turbomachinery , 2004 .

[33]  Christopher Dellacorte,et al.  Tribological composition optimization of chromium-carbide-based solid lubricant coatings for foil gas bearings at temperatures to 650 °C , 1988 .