This paper describes the tests that were carried out to assess the tribological properties of a representative selection of the alloys and hardfacings being considered for the Diesel Exhaust Valve Materials Project. The accelerated wear tests were carried out in a rotating sliding test rig that was able to simulate the high valve seating pressure of a diesel engine and maintain it constant throughout the test period. A standard test with a Hertzian stress of 800 bat at a temperature of 650 deg C was carried out on all the alloys and hardfacings as an initial sorting test. These tests showed that ability to form a good glaze of compacted oxides on the wear surfaces was the dominating factor in reducing wear. A multivariable model of the results was developed in which the alloying elements were grouped with regard to their function. This highlighted the importance of the scale-forming elements, particularly chromium, but also showed the influence of the substrate hardening and strengthening additions in helping to reduce deformation and cracking of the scale. Hot hardness measurements on some of the materials confirmed the role of the hardening elements as having an important secondary function in reducing wear. Further wear tests at low temperatures and at higher stresses than in the standard test showed regions in which the good wear properties of some materials were significantly reduced. This appears to be due to the changing relative influences of oxidation in forming a glaze, and of high stress and substrate deformation in promoting the breakdown of the glaze.

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  • Features: References;
  • Pagination: 8p.

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Filing Info

  • Accession Number: 00659766
  • Record Type: Publication
  • Source Agency: Maritime Technical Information Facility
  • Files: TRIS
  • Created Date: Jul 21 1994 12:00AM