Friction and wear properties of piston ring materials for the Stirling engine.

Abstract

The results of friction and wear tests for choosing piston ring and cylinder liner materials for the Stirling engine are described. Polyimide composites and a PEEK composite for piston rings, and several surface hardened metals and ceramics for cylinder liners were tested in a helium atmosphere from room temperature to 200°C. The polyimide composite had the lowest wear rates for the counter surface roughness Rmax=0.5∼1μm and the counter materials hardly affected these values. The PEEK composite seemed to decrease its wear rate when the counter surface roughness decreased. The coefficients of friction were lowest for the cylinder liner material surface roughness Rmax=0.5∼1μm and they seemed to be affected by these materials. The polyimide composite which contained PTFE and graphite was chosen for the piston ring material and a Cr2O3 coating was chosen for cylinder liner surface hardening.