Tribological properties of polymer-sheet-adhered metal hybrid gear

A preliminary study was made on the tribology of nylon 66/poly(phenylene ether) polymer sheets adhered to steel gear teeth against a counter steel gear with reference to friction, surface morphology, noise reduction and torque in comparison with a pair of steel gears lubricated with molybdenum grease. Tribological experiments were performed in a gear-testing machine at a rotating speed of 1000 rpm under high torques of the driving and driven gears, recording torque of each gear and noise-frequency profiles. It was found that periodical torque changes in a range of 17–5 N m at 1000 and 3000 cycles (revolutions) turned to 13–8 N m at 5000 cycles, indicating a change to stable cycle and torque conduction, probably due to a plastic surface deformation of the adhered polymer sheet for a smooth contact of pairing teeth. A harsh noise emission in the frequency range of 3–5 kHz was reduced circa 5 dBA as compared with a pair of steel/steel gear. It was found, however, that noise abruptly increased when only one of the adhered polymer sheets was spontaneously removed from the gear surface, probably because of its low adhesive strength against a shear during gear cycle.