microstructure

What Is Cementite? Fe₃C — the Phase That Gives Steel Its Hardness

Cementite (Fe₃C) is the compound of iron and carbon and one of the hardest phases in steel: ~800 HV. On its own it is glass-brittle — but combined correctly with ferrite it becomes the true source of steel's strength. From pearlite to bearing steel, all the forms of cementite.