Research on ion nitriding process was conducted with respect to subway coupling made of 31CrMoV9 structural alloy steel and with modulus of 4 mm.The surface hardness and the depth of the nitrided layer and microstructure were analyzed and the bending fatigue property test was conducted by means of optical microscope,microhardness tester and fatigue bending machine.The results show that when NH3 flow unchanged,the uniformity of the nitrided layer depth from tooth crest to tooth root and the bending fatigue strength increase,and the thickness of the surface compound layer is more uniform with the increase of Ar flow.The nitriding process which meets the drawing's technical requirements is ultimately determined as follows:nitriding at 540 ℃ for 36 h and flow ratio of NH3 to Ar is 10 to 7 to get 280 Pa furnace pressure.Finally,through the actual production verification,the nitriding process has good operability.
NETL
NSTL
万方数据
