Friction and wear behavior of a centrifugally cast lead-free copper alloy containing graphite particles

Abstract

The tribological properties of a centrifugally cast lead-free copper alloy (C90300), containing an average of 13 vol pct graphite particles (5 m), have been studied. Friction tests were carried out at three different loads of 44, 88, and 176 N using a pin-on-disk testing method for the base copper alloy and the copper-graphite composite against a 1045 steel disk counterface. The friction coefficient, temperature rise, and weight loss of the pin and disk were measured. To understand the wear mechanism, the wear debris and the surfaces of the pin and the disk were analyzed before and after the tests, using scanning electron microscope (SEM) and energy-dispersive X-ray (EDX) analysis. The friction coefficient of the copper-graphite pins was lower than that of the base-alloy pins for all applied loads, which was attributed to the presence of the graphite in the matrix. It was also observed that the presence of graphite in the matrix reduces the transfer of iron from the counterface to the pins, but enhances the transfer of materials from the pins to the counterface. The temperature rise in the counterface running against the base-alloy pins was larger than the temperature rise in the counterface running against the copper-graphite pins, both tested under similar conditions. In addition, the effect of element transfer on the friction coefficient, variations in the weight of the pins and the counterface, as well as the surface roughness, are attributed to the formation of a graphitic tribolayer on the surface of the copper-graphite pins. An isostrain model predicting the friction coefficient of the composites is proposed, which agrees well with the measurements in the present article as well as with measurements made by other investigators. [10]

Effect of Carbon on Tensile Properties and Wear Behavior of P/M FeAl Alloy

“…6(b)), and thus decreasing the metal-to-hard Al 2 O 3 ball contact and the wear rate. Similar results were reported in copper-graphite composite 17,18) and aluminium-graphite composites. 19) In those works, the reduced friction due to the presence of graphite in the matrix was also reported.…”

Influences of graphite reinforcement on the tribological properties of self-lubricating aluminum matrix composites for green tribology, sustainability, and energy efficiency—a review

“…Graphite particles act as solid lubricant at the contact interface, which enhance the tribological properties of these composites compared to unreinforced aluminum alloys or aluminum alloys reinforced by non-carbonous ceramic particles [32,82,83]. In general, solid lubricants to fabricate self-lubricating composites are solid carbon (carbon fibers [84][85][86], graphite particles [87][88][89][90][91], CNTs, graphene), molybdenum disulfide, and hexagonal boron nitride [2, 16,81]. Low friction coefficient and low wear rate are the key properties of self-lubricating materials as well as their high seizure resistance.…”

“…The poor mechanical properties of Al/Gr composite can be solved by adding another ceramic particle, such as Al 2 O 3 or SiC, as a secondary reinforcement and fabricating a hybrid metal matrix composite (HMMCs) [70,125,126]. In self-lubricating HMMCs, the hard particle increases the mechanical properties of the composite, while the soft particles act as a lubricant and decrease wear rate and friction coefficient [88] by generating a solid lubrication film between contact surfaces as validated by fractography studies [127]. Additionally, the protective solid graphite film prevents pull off of the hard particles from the hybrid composite surface, which results in less surface Fig.…”

Wear and frictional mechanisms of copper-based bearing alloys

“…For environmental and legal reasons, efforts are being made to remove lead from bearing alloys. Numbers of materials are already proposed as alternative to leaded alloys, in particular metallic composites containing self-lubricant particles like graphite, MoS 2 or PTFE [1][2][3][4]. Increasing the wear performances of alternative materials to leaded bronze requires a scientific understanding of the relevant mechanisms, and in particular of the relationship between materials microstructure and tribological behavior.…”