Abstract
Sintered metallic friction materials are a smart choice for heavy-duty applications such as hydraulic or mechanical clutches of industrial machinery of large tonnage. In this research, the properties and friction behaviour of copper-based sintered clutches fabricated by two different processing routes are presented: on the one hand, conventional PM processing consisted of uniaxial pressing-sintering-sizing and on the other hand, an alternative route consisted of sintering the powder deposited by gravity and subsequent sizing. Different compositions based on bronze matrix, graphite as a solid lubricant and different friction modifiers or abrasives have been developed. The influence of the nature and particle size/morphology of the different raw materials on each processing route, especially on the sinterability and the friction behaviour of the clutches produced has been studied. For a preliminary evaluation of the tribological behaviour, pin-on-disc tests have been carried out at different speeds and loads on samples of 20 mm diameter. Additionally, the friction behaviour of the clutch plates was assessed using a specially designed dynamometer for testing at high speeds (up to 4000 rpm). Static and dynamic friction coefficients, and wear resistance were determined from these tests, depending on the type of material, surface geometry and lubricant, for different load and speed conditions.