High manganese steel is generally harder than manganese steel. This is due to the higher carbon content and the presence of additional alloying elements in high manganese steel, which enhance its hardness and wear resistance. According to the American Iron and Steel Institute (AISI), manganese steel typically has a hardness of around 200-300 HB (Brinell hardness), whereas high manganese steel can achieve hardness values of 400-600 HB. The increased hardness of high manganese steel is a result of the formation of a harder and more wear-resistant carbide layer on its surface during the work hardening process. This layer is formed due to the high carbon content and the presence of manganese, which promotes the precipitation of carbides.