Effect of Working Pressure on Microstructure and Properties of Plasma Nitrided Layer of H13 Steel

H13 mould steel was plasma nitriding treated at different working pressures in a self-made LD-650 type DC plasma chemical vapor deposition furnace.The effect of the working pressure on microstructure and properties of the nitrided layers was studied.The results show that the working pressure significantly influenced the thickness of the nitrided layer.As the increase of working pressure,the thickness of the nitrided compound layer increased firstly and then decreased.A nitrided layer with maximum thickness of 9 μm was obtained at the working pressure of 1 066 Pa.The influence of the working pressure on the surface hardness of H13 steel was slight.The volume fraction of ε and γ′ phases in the layer increased with the working pressure increase,and reached to the maximum values at the working pressure of 1 066 Pa,which were 37.1% and 35.7% respectively.The nitrided layer had a good performance at the pressure under the test condition.