Abstract: The influence of gas nitriding process parameters on the size change of 1Cr11Ni2W2MoV martensitic stainless steel was studied,and the influence of solid solution cooling medium on the formation of passivation film and gas nitriding was discussed.The microstructure and phase of the nitrided layer were analyzed using optical microscopy,scanning electron microscopy,and X-ray diffraction.Its hardness was measured using microhardness,and the ability to form a passive film was evaluated using neutral salt spray experiments.The results showed that surface corrosion occurred during the 24 hour salt spray test of 1Cr11Ni2W2MoV stainless steel during solid solution oil quenching.When gas nitriding is carried out at 600℃for 12 hours,the nitriding layer is mainly composed of Fe_2-3N and Fe₄N phases,as well as a small amount of CrN phase.The hardness of the nitriding layer is above950HV0.1,and the thickness of the nitriding layer is≥260μm.When using solid solution water quenching,no surface rust phenomenon was found in the neutral salt spray test for 72 hours,and the depth of the infiltration layer was≤10μm,indicating that rapid solid solution cooling is beneficial for improving the ability of passive film formation on the surface of martensitic stainless steel.