What are thermal processing atmospheres?
Fabricated metal products are often processed at various stages in fabrication at high temperatures to change their properties to match the needs of the intended application. Examples of high-temperature processing include annealing, sintering, and brazing. Because high temperature intensifies the oxidation caused by atmospheric oxygen that can lead to oxidation damage of the metal product, the metal must be protected from atmospheric oxygen (and from oxygen that might be liberated from surface oxides at temperature). Atmospheres containing hydrogen are the oldest and most frequently employed technique for protecting metal parts at high temperatures. Hydrogen reacts with molecular oxygen and makes it non-reactive with the metal, thereby protecting the metal. Certain parts are processed in a vacuum atmosphere, often because they are incompatible with hydrogen.