Microcracks in heat treated martensite

Microcracks in heat treated martensite

Microcracks are easy to occur during the formation of martensite, which means that microcracks are difficult to form in the martensite structure of medium and high carbon steel and low carbon steel. This is because low-carbon martensite is parallel laths, which have less chance of collision with each other, and its plasticity is high. It can relax the stress through deformation and is not easy to produce microcracks. In high carbon martensite, due to the collision of martensite sheets with each other, the sheet martensite can not make corresponding deformation to eliminate the stress, resulting in the stress field at the collision, and microcracks will be formed when the stress is large enough. This congenital defect further increases the brittleness of high carbon martensite. Under the action of other stresses, the micro crack may develop into macro crack.