Bainite

Definition - What does Bainite mean?

Bainite is a crystalline microstructure that can be found in steel. Bainite forms when steel is cooled slower than the rate required to form martensite but faster than the rate that would be required to form pearlite or another slower cooling rate crystalline microstructure. Bainite is typically considered hard and brittle.

Corrosionpedia explains Bainite

Bainite is named after Edgar Bain in honor of the work he accomplished in the realm of steel crystalline structures and temperature transformation phases.

Bainite is a combination of ferrite and cementite. The amount of cementite and ferrite formed depends on the carbon content of the steel and the rate at which it was cooled from the critical temperature. If the carbon content is lower, there will usually be less cementite present. Higher amounts of carbon in the steel allow for higher amounts of carbides mixed in with the ferrite.

Bainite can come in two forms. Upper bainite forms around 400°C to 550°C (752°F to 1022°F). The other form, lower bainite, forms around 250°C to 450°C (482°F to 842°F). While both are considered bainite, they have slightly different arrangements of ferrite, cementite and austenite. This also causes some differences in mechanical properties between the two.

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