Development of Ferrium S53 High-Strength, Corrosion-Resistant Steel

摘要

S53 was developed under Strategic Environmental Research and Development Program (SERDP) funding as an alternative to the use of Cadmium (Cd)-plated high-strength landing gear steel. QuesTek Innovations LLC had developed the Materials by Design methodology in which alloys could be designed from first principles using a computational approach that avoided the need for the extensive trial-and-error formulation and testing that has been the mainstay of the alloy manufacturing industry since its inception. S53 was designed to be equivalent in mechanical properties to Cd-plated 300M ultrahigh strength steel used in landing gear, and equivalent in corrosion resistance to the lower strength 15-5PH stainless steel used in actuators. It also replaces 4340 and 4340M steels and other high-strength steels (such as 4330 and HP9-4- 30) used in landing gear and actuators. There is also a potential for using S53 in place of lower strength corrosion-resistant (CRES) steels such as 15-5PH, 17- 4PH, and PH13-8Mo, which are used in applications such as hydraulic actuators that require a combination of strength and corrosion resistance. The demonstration objectives were twofold: 1. To demonstrate and validate the Materials by Design methodology for developing new alloys. 2. To demonstrate and validate a CRES steel that would be mechanically equivalent to 300M ultrahigh strength landing gear steel, but with corrosion resistance equivalent to 15-5PH stainless steel used in modern aerospace actuators. These objectives were met, with two minor exceptions: (1) the tensile yield of S53 is slightly lower than 300M (213 ksi min versus 230 ksi min), although ultimate (to which landing gear are designed) was the same (280 ksi) and (2) under corrosion testing, S53 visually corrodes more rapidly than the target 15-5PH, although the pit growth rate is only a little higher (and it is pit depth that drives condemnation). Only service experience will show whether the difference is significant.