Effects of graphite on wear and corrosion behaviour of SiCp-reinforced copper matrix composites formed by hot pressing

The wear and corrosion properties of SiCp/graphite reinforced copper metal matrix composites (MMCs) fabricated by hot pressing have been evaluated. Electron microscopic studies were conducted to clarify the micromechanisms of wear and corrosion. The experimental resultsindicate that the hardness and wear loss increase with increasing SiCp content but decrease with increasing graphite content. In particular, the wear loss decreases with increasing graphite up to a content of 5 vol.-% then remains approximately constant as the graphite content isfurther increased to 7·5 vol.-%. The material porosity of the composites increased with the content of foreign particles (SiCp and/or graphite). The composites were immersed in an aqueous solution of 3.5 wt.-%NaCl at pH 6·7 for potentiodynamic and corrosion ratemeasurements. Pure copper exhibited the best corrosion resistance. The Cu/SiCp composite showed lower resistance, and the Cu/SiCp/graphite composite had the lowest resistance to corrosion. The poor corrosive properties of the composites were the result of galvanic andcrevice corrosion, which were influenced by residual stress/strain and differences in electrochemical potential between the additions (SiCp and/or graphite) and the copper matrix. Furthermore, the weight loss due to corrosion increased with increasing SiCp and graphitecontent.