Microstructure of Carburized 12KhN3A Steel after Electromechanical Surface Quenching and Hardness Distribution over the Depth

To confirm the effectiveness of electromechanical surface quenching, the microstructure, chemical composition, and hardness of 12KhN3A steel samples before and after surface quenching are investigated. After electromechanical surface quenching to a depth of 1 mm, a fine-grain gradient structure (hardness up to 740 HV) is formed, consisting of needles of martensite, austenite, and carbides. Below this layer, there is a troostite–martensite structure (hardness up to 631 HV). At the boundary of the quenching zone, the hardness is as much as 328 HV. Within the ferrite–pearlite structure, it decreases to 179 HV.