Abstract: Effect of vacuum gas quenching pressure on hardness of four martensitic stainless steels (2Cr13,9Cr18,1Cr17Ni2 and 0Cr17Ni4Cu4Nb) was studied. The results show that the core hardness of the 2Cr13 steel bars with diameter of 30,50 and 80 mm under the gas quenching pressure of 1.5, 3 and 5 bar is greater than 45 HRC, respectively, and the surface hardness for the three steels is greater than 49.5 HRC. When gas quenching pressure is increased, the hardness of 2Cr13 steel increases. The core hardness of the 2Cr13 steel bars with diameter of 30 mm is the same as the surface hardness. The core hardness of the 2Cr13 steel bars with diameter of 50 and 80 mm is lower than the surface hardness. The steel bars of 9Cr18, 1Cr17Ni2, 0Cr17Ni4Cu4Nb with diameters of 30,50 and 80 mm are all hardened under the gas quenching pressure of 1.5, 3 and 5 bar, and the core hardness is the same as the surface hardness.

Key words: vacuum gas quenching, martensitic stainless steel, hardness