The corrosion resistance of 75 candidate valve materials to attack by a model vanadic ash that simulates deposits formed on diesel exhaust valves was examined. Tests of 500h duration at 650 deg C resulted in a short list of alloys offering superior corrosion resistance to NIMONIC 80A at this temperature. The alloys were then evaluated at other temperatures in the range 500-700 deg C, from which 14 material combinations were selected for engine tests. Five alloys, two hardfacings and seven coating/alloy systems were selected. All of the more promising materials were nickel- or iron- based and contained chromium levels greater than 25% by weight. From this study, a corrosion model has been developed that allows the prediction of alloy performance in vanadic ashes over the temperature range 535-700 deg C. Agreement between the model and laboratory data is excellent. It is demonstrated that the model can predict alloy performance trends within diesel engines operating on residual fuel oils, although the corrosion rates within the engine are thought to reflect the higher contaminant fluxes seen in service.

Media Info

  • Features: References;
  • Pagination: 14p.

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Filing Info

  • Accession Number: 00659765
  • Record Type: Publication
  • Source Agency: Maritime Technical Information Facility
  • Files: TRIS
  • Created Date: Jul 21 1994 12:00AM