Development of Corrosion-Hydrogen Cracking Resistant Aircraft Alloys from Mechanistic Understanding

High strength steel components for Navy aircraft are subjected to the harsh corrosive maritime environment. Specifically, Hydrogen Environment Assisted Cracking (HEAC) is a dominant problem associated with corrosion. This STTR project is aimed at establishing the experimental characterization and modeling method as well as fundamental understanding necessary to develop corrosion resistant high strength steels. The Phase II STTR work will expand and validate the predictive tool methodology established in Phase I to the environmental and mechanical loading conditions characteristic of selected JSF components for program risk reduction. The predictive tool for HEAC will be delivered to NAVAIR for use on Navy aircraft and ASTM standardization advocated. Phase II work will combine processing alternatives and alloy modifications based upon the feasibility shown in Phase I to enhance the HEAC resistance of AerMet 100 steel and to develop low cost, high strength steels with good HEAC resistance. Specifically, the role of chilling on the HEAC resistance of AerMet 100 will be established and a secondary hardening steel that is lower in cost than AerMet 100 but with equal or better HEAC resistance will be developed.