Effect of Graphite Particle Size on the Wear of Graphite-dispersed Bronze Castings

Abstract

The effect of graphite particle size on the wear of graphite-dispersed bronze castings has been investigated. Sound ingots having uniform dispersion of graphite particles were obtained by adding copper-coated graphite particles to the melts containing about 1 at%Ti. Casting of ingots was carried out by pressure crystallization casting under a high pressure of about 62 MPa. Cu-5Sn-5Zn-4Pb-0.8Ti and Cu-5Sn-5Zn-4Pb-0.8Ti-0.5P alloys containing 6% graphite (about 20 vol%) have been used for the investigation of wear resistance. The graphite particle size varied from 8 to 100 mesh.
The results obtained are summerized as follows: (1) It is found that the wear resistance tends to increase as the graphite size is coarser. It is considered that the tendency depends on the following phenomenon. The graphite tends to be covered easily by a plastic flow layer as the graphite is finer, and consequently lubrication by graphite does not continue. (2) When phosphorus is added to the alloys, the graphite size dependence against sliding wear is decreased and wear resistance is increased. (3) The alloys containing pulverized graphite powder have high wear resistance as compared with granulated graphite powder.