Scuffing behavior of 390 aluminum against steel under starved lubrication conditions

The scuffing characteristics of 390-T6 aluminum–silicon alloy sliding against 52100 steel are examined under starved lubrication conditions. The evaluation is based on a shoe-on-disc geometry which simulates the plate/shoe contacts in an automotive air conditioning swashplate compressor. Four shoe geometries (flat shoe, crowned shoe, crowned shoe with a dimple at the center and crowned shoe with a groove) are tested against 390-T6 aluminum discs. All tests are conducted in a high-pressure tribometer (HPT) under R134a (tetrafluoroethane) environment with a base polyalkylene glycol (PAG) lubricant. The effects of degree of lubricant starvation, sliding velocity, geometry of contact, surface topography, and a tin coating on scuffing are evaluated. It is hypothesized that scuffing of 390-T6 Al alloy under starved lubrication conditions is due to macroscopic adhesions leading to plastic shearing of the bulk material.