Definition - What does Cementite mean?
Cementite consists of iron and carbon compounds combined chemically, having the chemical symbol Fe3C. It is composed of 93% iron and 7% carbon. This compound is brittle, hard and falls under the ceramic classification.
Cementite plays a vital role in metallurgy. When immersed in a solution of 1%–3% sodium chloride, its corrosion resistance increases significantly.
Cementite is also known as iron carbide.
Corrosionpedia explains Cementite
Cementite forms directly through the melt in white cast-iron cases. In the case of carbon steels, it can be formed by either the cooling of austenite or tempering of martensite. As mentioned, cementite consists of 7% carbon; thus in the iron-carbon phase system, the alloy is not cast iron or steel since all its available iron content is in the cementite.
In some cases, cementite combines with ferrite, a byproduct of austenite, in order to build bainite and pearlite or lamellar structures.
Since cementite tends to be unstable thermodynamically, it is eventually converted to graphite and ferrite.
Its role in metallurgy is widely appreciated by industries worldwide due to the fact that immersion in sodium chloride solution greatly enhances the corrosion protection properties of this substrate.