Study on Friction and Wear Characteristics of Advanced Al Alloy Matrix Composites

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Unidirectional sliding friction and wear tests of an Al-Si alloy impregnated graphite composite (Al-Gr) pin in contact with a bearing steel disk were conducted at a constant contact load as a variable of relative humidity (RH) in air and argon gas, and in ion-exchanged water, aimed at investigating friction and wear characteristics of the composite expected as an advanced sliding material. The influence of oxygen and water vapor in the atmosphere were mainly investigated. The composite has a minimum in friction and wear in the middle RH range, since compacted films consisting of Al alloy wear debris and graphite powders are zonally formed on the disk sliding surface, preventing adhesion due to metal-to-metal contact.Friction and wear characteristics of an alumina short fiber-reinforced Al-Si alloy matrix composite (AFRMMC) in contact with Al alloy (JIS AC8A or A2017) were elucidated in lubricating oil. Friction coefficient (μ) rapidly increases at a certain load for the AFRMMC against A2017 in machine oil and engine base oil. However, the load level where μ rapidly increases for the AFRMMC against AC8A does not appear, although the frictional mode transits to the boundary lubrication.Fretting characteristics of the Al-Gr and AFRMMC in contact with bearing steel were also investigated from test results in air as a variable of relative slip amplitude. The Al-Gr exhibited good tribological performance during fretting over the whole range of relative slip amplitude tested.