Non Martensitic Structure of Spiral Bevel Gears

When we use Spiral Bevel Gears, we may hear the term 'non martensitic structure'. What is it? In fact, the non martensitic structure of spiral Bevel Gears is another name for the black structure on the surface of carburized or carbon nitrogen co carburized gears. Generally speaking, after quenching the spiral bevel gears, fine needle like high carbon martensite may sometimes appear on the surface of the parts. However, due to various reasons, mixed structures such as bainite and troostite may form on the surface of the gears, so we are accustomed to calling it non martensitic structure. So it is more obvious in untreated or slightly corroded carburized or carbonitriding metallographic samples, but this actually has no impact on our use.