Experimental Investigation of Friction Coefficient and Wear Rate of Brass and Bronze under Lubrication Conditions

The present study is conducted in order to compare the frictional and wear behaviour under mixed lubrication of two pins: bronze (CuSn9P) and brass (CuZn39Pb2), sliding on a steel disc (XC42). The selection of this type of brass and bronze was made because they are not large differences in microhardness, however, have a completely different microstructure. All tests were carried out by using a pin-on-disc tribometer, with a plane contact mode and a pure sliding velocity. The results indicate that friction coefficient and the wear coefficient of brass are significantly higher in comparison to bronze for the two studied roughness (Ra = 2 and 0.15 μm). We also note that for the brass the friction is slightly affected by the roughness of the discs, and the running time is reduced. Regarding bronze, the friction passes from 0.17 for the rough disc (Ra = 2 μm) to 0.02 for the smooth disc (Ra = 0.15 μm) with a time of running about 2000 s; the low value of friction corresponds to the transition to a hydrodynamic regime. The analysis of the microstructure of brass shows a high shear of the surface layers, with a severe plastic deformation, which is not the case for the bronze that is not affected by observable deformations.