Causes and Prevention of Structural Materials Failures in Naval Environments

摘要

An analysis is made of most corrosion related naval aircraft structural materials failure problems. The phenomena of stress corrosion cracking, hydrogen or environmental cracking, corrosion fatigue and exfoliation corrosion are discussed. Methods of determining hydrogen embrittling effects and hydrogen concentration are described and related to sustained load tolerances of cadmium plated high strength steels. An electro-mechanical test is described to illustrate the hydrogen-induced elastic deformation effect in steels. This test procedure has been also used to calculate the hydrogen diffusion coefficient as well as the hydrogen concentration. A technique which can monitor corrosivity of the naval environment aboard ship has been reported. Metallurgical methods of mitigating corrosion such as heat treatment and alloy development are described. Mechanistic aspects of corrosion-assisted mechanical failures (cracking) are analyzed and a multidisciplinary approach to solve the problem is described. It is demonstrated that modifications of the crack-tip chemistry can effectively lead to inhibition of corrosion fatigue and stress corrosion cracking in high strength alloys. (Author)