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High temp / low wear coatings for oil-free pistons

2003

We are developing a heat engine for a cogeneration unit. To reduce service intervals we wish to eliminate oil from all high temperature sliding surfaces. We have a small 316SS piston which runs at about 400 degrees C. It currently uses phosphor bronze rings running on an electroless nickel bore and is lubricated by oil. We would like to find a coating we could use on the piston, rings, or bore or all of these that will allow us to eliminate the oil. The piston side loads are low - only the ring tension. The materials of the piston, bore and rings can be changed if necessary.

This will be a high volume product and so the process must be affordable. Any suggestions?

Paul van de Loo
- Adelaide, SA, Australia

At 400C not even teflon composites will hold too long. I would consider a nickel composite with Moly dissulfide (a very common solid lubricant), Ti nitride or a similar intermetallic compound for the bore over a hard enough tool steel substrate. The rings can remain phosphor bronze. G. Marrufo-Mexico

Guillermo Marrufo
Monterrey, NL, Mexico
2003