Computational Design of High-Strength, High-Toughness Stainless Steels for Carrier-Based Aircraft Components

A novel computational materials design approach is being applied to create a nanostructured high-strength, high-toughness stainless steel that meets the stringent mechanical properties for carrier-based aircraft components. Currently, the Navy uses AerMet100 for critical aerospace components. However, this alloy is non-stainless and highly susceptible to both corrosion and hydrogen embrittlement, which can lead to stress corrosion cracking. As a result, a number of aircraft components, such as landinggear, require a costly cadmium coating process to protect against corrosion. Cadmium, a known carcinogen, represents significant environmental risks in both primary manufacture and at DoD overhaul and repair facilities. During Phase I, threefirst-generation alloys were computationally designed, and prototype heats were ordered. The material properties will be characterized during the Phase I Option program. Under this proposed Phase II SBIR, two more generations of prototypes will bedesigned, produced and characterized. The lessons learned from these prototype alloys will be applied to produce and characterize a large-scale heat of the most promising alloy design. A new high-strength, high-toughness stainless alloy will benefit theenvironment and have dual-use application for the commercial aerospace market and other commercial markets such as marine equipment. The primary anticipated benefit of developing a unique structural stainless alloy for carrier-based aircraft componentswould be environmental. AerMet 100, the steel currently used for carrier-based aircraft components, is nonstainless and requires a costly cadmium coating process to protect against corrosion. Cadmium is a known carcinogen and represents significantenvironmental risks in both primary manufacture and at DoD overhaul and repair facilities. Eliminating this coating process has a tremendous potential for reducing long-term maintenance costs and eliminating environmentally hazardous processes.Furthermore, many of the major items that are cadmium plated, such as landing gear, are damage tolerant and sensitive to hydrogen embrittlement during maintenance and stress corrosion cracking during use. This sensitivity makes stress corrosion crackingthe primary failure mechanism for landing gear - a failure that often causes significant collateral damage to the aircraft, even though the failure usually takes place while it is parked. The Boeing Company has also provided a letter of support for thisproposed Phase II SBIR as the development of a high-strength, high-toughness stainless equivalent to AerMet 100 would have significant commercial aerospace potential.