An Evaluation of Galling-Resistant Materials for the A-10 GAU/8/A Gun Mounts

Abstract

Abstract : Laboratory procedures were developed to duplicate the fretting and galling that occurs in the 17-4PH stainless steel spindle and 4340 steel pillow block of the A-10 GAU-8/A gatling gun. The procedures were then used to evaluate galling-resistant materials, coatings, and lubricants for incorporation into replacement gun mounts. The program involved duplicating the reciprocal lateral sliding motion of the mount spindle in its mating pillow block and applying an impact load in synchonization with the sliding. A short-term solution was found which improved baseline material wear life by a factor of two; it involved applying either AFSL-41 or MIL-L-46010 dry film lubricant and MIL-G-81827 high pressure grease to mating parts. Two long-term solutions were identified which extended specimen life by over an order of magnitude. In one case, the 17-4PH spindle material was replaced by H11 steel. The other case involved plating baseline materials with 0.0015 inch-thick electroless nickel. Both long-term solutions also incorporated the dry film and grease. Unsatisfactory results were achieved with hard chrome, improperly applied dry film, and polyimide and polyamide resins. Originator-supplied keywords included: Fretting, Galling, Dry Film Lubricant, AFSL-41, MIL-L-46010A, Electroless Nickel, Stainless Steel, 17-4 PH, 4340 Steel, Tool Steel, H11 Steel, Chrome, Torlon, Polyamide, Vespel, Polyimide, GAU-8/A, High-Pressure.