Effects of PEEK's surface roughness on seizure behaviors of PEEK/steel pairs under oil-lubricated sliding contacts

Abstract

Effects of surface roughness of polyether ether ketone (PEEK) on the seizure behaviors of PEEK/steel pairs are studied using a block-on-ring wear tester under oil-lubricated conditions. The blocks are made of unfilled PEEK and a PEEK composite filled with carbon fibers of 30 mass%. The block's surface roughness varies between 0.03 to 4.77 μm Ra. The ring is made of forged steel (SF540A) and its surface roughness is 0.12 μm Ra. The sliding velocity and load are 19 m/s and 883 N respectively. During the test, the ring temperature is measured with an alumel-chromel thermo-couple with a diameter of 0.5 mm, located 1 mm below the frictional surface. Results indicate that the seizure behaviors are strongly dependent on the PEEK material's surface roughness. Seizure occurs in both materials when the surface roughness exceeds a certain value. The critical surface roughness in the PEEK composite is significantly higher than in PEEK. Thus it is concluded that the PEEK composite has an excellent seizure-resistant property at high sliding velocity. Wear scars are observed using a scanning electron microscope. The seizure mechanisms are discussed from the viewpoints of the SEM observation results and the ring temperature.

Keywords

• peek
• peek composite
• surface roughness
• seizure
• sliding friction and wear
• oil lubrication