GRAPHALLOY Bushings and Bearings

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Friday, December 21, 2007

What is GRAPHALLOY and when should I use it?

GRAPHALLOY(r) is a solid, uniform combination of graphite and metal. Molten metal is impregnated into a graphite substrate under high temperature and pressure. Used as a bushing or wear surface, GRAPHALLOY survives dusty atmospheres, high temperature, submersion and corrosive environments. GRAPHALLOY does not swell, shrink, or cold flow.

Graphalloy is self-lubricating and used in difficult applications when a rolling element bearing would fail. It deposits a graphite layer on the inner race which is not normally removed by high temperatures or submersion in a fluid. It is not normally a competitive replacement for a ball bearing where there are no environmental complications.

Hard carbons for bearings and bushings

Q. Hard carbon materials are available; will they perform better GRAPHALLOY(r) for bushings?

A. Carbon materials can be made over a wide range of hardnesses - from soft brush materials to nearly ceramic hard mechanical seal face materials. Hard carbons can be much harder than usual shaft materials. These hard carbons can score shafts to the point where the shaft is actually cut.

Bushings, especially those internal in pumps, are intended to be wear parts, absorbing the shocks, rubbing and abrasion of normal use without damaging the shafting. GRAPHALLOY is chosen for pumps to provide non-galling, self-lubricating bearings.

GRAPHALLOY with a moderate hardness is used in most pump applications to ensure that expensive shaft materials will be protected.