Ferrium S53 was developed for use as a structural stainless steel for aircraft landing gear. S53 has a corrosion resistance equivalent to 15-5PH H900, strength equivalent to or better than 300M (AMS 6257A) and SAE 4340 (see Mechanical Properties), optimum microstructure features for maximum fatigue resistance, and a surface hardenability equal to or greater than 67 HRC for wear and fatigue. Please see updated designation and information on this alloy in Alloy Digest SA-589, December 2008. This datasheet provides information on composition, physical properties, hardness, and tensile properties as well as fracture toughness. It also includes information on corrosion resistance as well as forming, heat treating, and machining. Filing Code: SS-942. Producer or source: QuesTek Innovations, LLC. Originally published October 2005, revised June 2008, updated December 2008.