Wear Behavior of Copper–Graphite Composites Processed by Field-Assisted Hot Pressing

Qian Liu,Antonio Galisteo,José Torralba,Roberto Guzmán De Villoria,Miguel Castillo-Rodríguez

doi:10.3390/jcs3010029

Abstract

Copper–graphite composites with 0–4 wt % graphite were fabricated by field-assisted hot pressing with the aim of studying the effect of graphite content on microhardness and tribological properties. Experimental results reveal that hardness decreases with the graphite content. Wear testing was carried out using a ball-on-disc tribometer with a normal load of 8 N at a constant sliding velocity of 0.16 m/s. The friction coefficient of composites decreases significantly from 0.92 to 0.29 with the increase in graphite content, resulting in a friction coefficient for the 4 wt % graphite composite that is 68.5% lower than pure copper. The wear rate first increases when the graphite content is 1 wt %; it then decreases as the graphite content is further increased until a certain critical threshold concentration of graphite, which seems to be around 3 wt %. Plastic deformation in conjunction with some oxidative wear is the wear mechanism observed in pure copper, while abrasive wear is the main wear mechanism in copper–graphite composites.

Highlights

Copper–graphite composites possess the positive properties of both components, i.e., the high thermal and electrical conductivity of copper with the low thermal expansion coefficient and good lubricating properties of graphite
Copper–graphite composites are usually prepared by a powder metallurgy process that provides a uniform material at low production costs, but the process gives rise to a weak copper–graphite interface
These high values are in agreement with those typically achieved by field-assisted hot pressing [13,14]

Summary

Introduction

Copper–graphite composites possess the positive properties of both components, i.e., the high thermal and electrical conductivity of copper with the low thermal expansion coefficient and good lubricating properties of graphite. Studies have shown that copper–graphite composites with finer particle sizes and better distribution exhibit higher load withstanding capacity and lower friction coefficient and wear rate due to a thick graphite layer that forms at the contact surface [5,6,7]. Copper–graphite composites are usually prepared by a powder metallurgy process that provides a uniform material at low production costs, but the process gives rise to a weak copper–graphite interface. This drawback can be overcome by coating the graphite particles with copper before consolidation

Methods

Results

Conclusion