Metallurgical Failure Analysis, Mark Douglas Bell, PE, Consulting Metallurgical Engineer, San Diego, California, USA Bell Metallurgy
Metallurgical Failure Analysis
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Mark Douglas Bell, PE
Consulting Metallurgical Engineer

Hydrogen Embrittlement

High strength steels that have been plated, welded or exposed to nascent hydrogen at elevated temperatures will be embrittled by hydrogen. The single hydrogen atoms are small and will diffuse with energy from the heat of welding. They tend to concentrate at the tip of a crack or point of high stress. The concentration of hydrogen atoms will cause to metal to loose ductility and there by become embrittled.

Avoid using high strength steels unless necessary. Post weld heat treat to drive out the hydrogen after welding is common. High strength fasteners that have been plated are required to be baked for hours or even days to drive out the hydrogen.

A visual examination can properly identify the cause, with some materials it is necessary to use metallurgical microscopes and analytical equipment to make a good identification of the corrosion type. Corrosion testing to duplicate and thereby verify the type of corrosion is justified on some projects.

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