Investigation of wear properties of graphite added self-lubricated bronze bearings

In this study, the effects of graphite addition on wear and friction performance of self lubricated bronze bearings produced by P/M technology were investigated. The content of graphite in the prealloyed CuSn10 bronze powder with a mean diameter of 60 µm was varied from 1 to 3 in steps of 1 wt pct, and blended for 20 minutes in the Turbula to homogenize the powder mixture. The powder mixtures were compacted in a die under pressures from 100 MPa to 250 MPa with 50 MPa intervals. Sintering was carried out in a nitrogen controlled atmosphere at 800°C for 20 minutes. Density and porosity of the sintered bearing materials were calculated by applying Archimedes? Principle. Porosity distribution at various pressures after sintering was recorded using optical microscope. Then, sintered samples were impregnated with SAE 30 engine oil under 0.2 atm and 80°C for an hour, and retention capabilities were calculated. Later, bronze bearing materials without graphite were produced with the same technique to compare wear performance with graphite added self-lubricated bronze bearing materials. Using pin-on-disc test apparatus produced by means of thesis, self-lubricated bearing materials were tested at 1 m/s sliding velocity, 15 N load, and 2000 m distance in laboratory conditions. Wear rates and friction coefficients were calculated.The results indicated that the friction and wear performance of self-lubricated bronze bearing materials were dependent on amount of graphite addition, compacting pressure and oil content. When the pressing pressure was increased, the density of the bearing materials increased, but percentage of porosity and percentage of oil content decreased. Results of friction and wear tests showed that with adding graphite and increasing pressing pressure there was a decrease in wear rate and the friction coefficient became more stable.