Effect of vacuum gas quenching heat treatment on hardness of powder metallurgy high speed steel S390

The vacuum gas quenching heat treatment of powder metallurgy high speed steel S390 was carried out. The feasibility of vacuum gas quenching heat treatment and its effect on the hardness of S390 steel under certain cooling pressure and cooling rate were discussed. The results show that the effective thickness of powder metallurgy high speed steel S390 was 20 mm. Under the condition of cooling pressure of 0.8 MPa and cooling rate of 3 ℃/s, S390 steel could be vacuum quenched, and the steel would not crack. Under the same conditions, the hardness of S390 steel after four times tempering was 1.2 HRC less than that after salt bath heat treatment, and its red hardness was 3.1～3.7 HRC less than that after salt bath heat treatment.