Experimental Study of the Coating Found on Scuffed Cast-Iron Piston Rings During Operation in Nitrided-Steel Cylinders
AIRCRAFT ENGINE RESEARCH LAB CLEVELAND OH
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Cast-iron piston rings that were run in nitrided-steel cylinder barrels under scuffing conditions showed a coating material on the scuffed areas. Only a few of the 14 etching reagents that were tried attacked the coating chemically, indicating good corrosion resistance. The Vickers hardness number of the coating material was found to be 640. The coating formed to a maximum thickness of about 0.0001 inch on the running surface of the piston rings. Evidence was found that the steadite in the cast iron is associated with the formation of the coating. The coating also appears to contain voids or minute flakes of graphite. On the basis of results obtained from the use of Steads reagent, it was found that the surfaces of cast-iron piston rings that have been run under normal operating conditions show more steadite than new rings and that scuffed rings show more steadite than either new or normally operated unscuffed rings.
- Reciprocating and Rotating Engines