Heat treatment procedures
The specimens were coated with an anti-oxidation paste to reduce oxidation and decarburization during heat treatment. Annealing of specimens was carried out in an electric furnace at 1223K for 18ks. Annealed specimens were austenitized at 1273K and 1373K for 3.6ks, and hardened by fan air cooling (FAC). The hardened specimens were tempered between 623873K for 12ks and cooled in still air