Development of lead-free PTFE based sliding bearing materials.

摘要

A group of novel polytetrafluoroethylene (PTFE) based composite materials are developed for sliding bearing applications. The reinforcements include the newly developed T-401 Tribaloy alloy, which possesses better ductility than conventional Tribaloy alloys, spherical bronze particles, milled graphite and chopped carbon fibers. The specimens are fabricated with the compression moulding technique under different preforming and sintering cycles. The mechanical and tribological properties, and also the corrosion resistance to acid of the new composites are investigated with immersion density, durometer hardness, tensile, pin on disk and immersion corrosion tests, respectively. It is demonstrated that the wear resistance of all developed PTFE composites is much higher than that of pure PTFE, while the composites maintain the extremely low coefficient of friction of PTFE. Among the developed composites, the mixture of 40% PTFE + 15% T-401 + 45% bronze has the best combination of properties. Capable of working properly in different lubrication regimes and being much softer than lead-containing bearing materials, the composite has superior compatibility, conformability and embeddability to existing sliding bearing materials. This new material exhibits a yield strength of about 15 MPa, which is 50% higher than the best reported yield strength of existing PTFE composites, and the load capacity of this composite is comparable to that of lead-base babbitts. As a potential new generation of sliding bearing materials, the developed composite with cost-effective and corrosion-resistant features maintains the excellent antifriction property of PTFE, while its wear resistance is improved by one order of magnitude.