Evaluation of Protection Schemes for Ultrahigh-Strength Steel Alloys for Landing Gear Applications

Each year, the Air Force’s Ogden Air Logistics Center (OO-ALC) condemns nearly $300 million of steel landing gear components.  These components are victims of hydrogen embrittlement, corrosion, and stress cracking associated with alloys currently in use for landing gear.  The cost associated with the condemned hardware is accompanied by a significant environmental burden. Ogden-ALC produces more than 2000 lbs of toxic cadmium during landing gear overhauls. With military aircraft operating at unprecedented levels, the stress placed on landing gear in the field and on the system to support them, is creating an environment in which both cost and product availability are essential concerns.

This paper and presentation covers the various protection schemes associated with ultrahigh-strength alloys used in landing gear applications. The alloys evaluated in this study include 4340, 300M, AerMet® 100, Ferrium® M54^TM, and Ferrium S53®. Ferrium S53 is the only corrosion resistant alloy of the group that is being evaluated. Ferrium S53 was developed in collaboration with the United States Air Force to address the need for elimination of the use of Cadmium as a protection scheme. Evaluation of prime and paint, Zinc-Nickel, and Cadmium plating of S53 will be compared to that of Cadmium plating of the other landing gear alloys. The test data presented is based on salt fog testing per ASTM B117 with scribes of varying width across test panels. Additional data related to in-process test results of threshold stress corrosion cracking per ASTM G49 will be summarized in the presentation. In January 2008, SAE issued an Aerospace Materials Specification (AMS 5922) for Ferrium S53, corrosion resistant bars and forgings:  10cr-5.5ni-14co-2mo-1w (0.19-0.23c) vacuum induction melted, vacuum arc remelted, normalized, and annealed.  There are currently two commercial suppliers for S53.