Tribological behavior of Cu-Cr-SiCp in situ composite

In situ composites based on copper chromium alloys have important application in resistance welding electrodes and improvement of their mechanical and wear properties may offer better materials for similar applications. In the present investigation, mechanical and tribological properties of Cu-Cr-SiCp composites have been investigated and compared with as-received wrought copper and cast copper. The cast in situ Cu-4%Cr-4%SiC composite has a matrix of solid solution of chromium in copper, containing grayish phases of carbides such as Cr-C, Cr23C6, Cr3C7, and Cr-Si-C, as determined by X-ray diffraction analysis and optical microscopy. The cumulative volume loss of the cast composite as determined by pin-on-disk tests for dry sliding wear against hardened steel counterface, is observed to decrease to about 65% and 72%, respectively, as compared to those observed in as-received copper and cast copper at 40 N loads. The surface profile of the samples after wear test, show a significantly lower R-t and R-z in all the three materials at 20 N load. Bearing ratio curve shows that Mrl, the extent of surface which will wear out faster, has a higher value for the composites compared to that in as-received copper although the composites wear out much less because of reinforcement. Mr2, oil retaining property from the bearing ratio curves, has a fairly steady value of about 10% in cast composite after dry sliding under increasing load. (C) 2008 Elsevier B.V. All rights reserved.