Innovative Approaches for the Development of Ultra-High Strength Intrinsically Corrosion Resistant Steel

The materials used in Navy aircraft are subjected to the harsh corrosive maritime operational environment which can cause costly maintenance problems and failures. Current alloys such as AerMet 100 have excellent strength and toughness but are not corrosion resistant. This SBIR has the goal of developing ultra high strength stainless steels with mechanical properties equal to those of AerMet 100 and the corrosion resistance of PH 13-8 (H1025). The Phase I SBIR designed and modeled alloys along with demonstrating the feasibility of producing and testing laboratory scale quantities of the alloys. Two martensitic stainless steel type alloys containing 12 % Cr, 4-6% Ni were designed and produced using strengthening mechanisms of (1) secondary hardening and NiAl precipitates or (2) secondary hardening enhanced by Si additions. Testing results showed that the alloys with secondary hardening and NiAl precipitates had low toughness. Si additions had positive effects on secondary hardening, but Si should be used with Co additions instead of Ni to get improved strength and toughness. The proposed Phase II program involves producing/evaluating secondary hardening steels containing 12 % Cr, 10 %Co with Si or Al and producing/evaluating generic and actual landing gear component parts made from the new alloys.