Gall Resistance of Cast Graphitic Aluminum Alloys

Gall resistance of cast aluminum alloys containing dispersed graphite particles was investigated. Graphite particles were introduced by injecting nickel-coated graphite powders through an inert gas stream into molten aluminum alloys and then rapidly solidifying the melt in permanent mold castings. Incorporation of graphite particles permits aluminum alloys to withstand poor lubrication conditions (low bearing parameters) successfully without galling. Gall resistance increases with graphite content over the range studied.

Aluminum-silicon-nickel alloys containing more than about 1.8 weight per cent graphite in one or both mating members are able to run under conditions of boundary lubrication without galling. Dispersed graphite improves the gall resistance of aluminum alloys through a combination of several mechanisms; the principal one being the formation of a graphite-rich layer on the bearing surface of mated members.