38CrMoAl 钢 520 °C不同气氛离子渗氮层表征

In order to explore the influence of different atmospheres on the microstructures and properties of plasma nitrided layers, the nitrided treatments are carried out on 38CrMoAl steel at 520 °C for 4 h, 8 h and 12 h in different atmosphere (NH₃ or NH₃ + N₂). The modified layers are characterized by optical microscope (OM), microhardness tester, X-ray diffraction (XRD), scanning electron microscope (SEM), electrochemical workstation. After nitrided in NH₃, the average thickness of the modified layer is 249.4 μm, the average mass gain is 2.30 mg / cm², the hardness reaches the maximum (990.5 HV_0.05) after 4 h, the main phase is γ'-Fe₄N, the minor phase is ε-Fe_2-3N. After nitriding in NH₃ + N₂, the average thickness of the nitriding layer is 294.8 μm, the average mass gain is 2.39 mg / cm², the hardness reaches the maximum (1 000.2 HV_0.05) after 4h, the main phase is ε-Fe_2-3N, and the minor phase is γ'-Fe₄N. After nitriding in NH₃ + N₂ for 4, the corrosion rate of the nitrided layer is the smallest (108.05 μm / a), and the current density decreases to the lowest (0.919 × 10^-5 A / cm²) 9.19 μA / cm².