Article ID: J2020049
In order to investigate the effect of the screen hole state of the active screen plasma nitriding (ASPN) process using Ti screen, low carbon steel S15C was treated by ASPN treatment and DC plasma nitriding treatment (S-DCPN) using the Ti screen with the hole diameter of ϕ5 mm, 10 mm, and 20 mm and the open area ratio of 0％, 15％, 35％, and 55％. Plasma nitriding was performed at 873 K for 180 min at a gas pressure of 300 Pa under an atmosphere of 75％ N2 + 25％ H2. After the nitriding treatment, X-ray diffraction (XRD), surface microstructure observation, cross-section microstructure observation, wear test, Vickers hardness test, glow discharge optical emission spectrometry (GD-OES), and corrosion test were performed. As a result, the wear resistance of the ASPN-treated samples was improved under the condition that the deposit particles were small and the deposit layer was thick. In the cross-sectional microstructure of the S-DCPN-treated samples, a compound layer composed of iron nitrides and a diffusion layer in which γ’-Fe4N was precipitated by nitrogen diffusion were confirmed. The surface compound layer of iron nitrides was not formed when a screen with a hole size of 20 mm and open area ratio of 55％ was used. The results of SEM-EDX also confirmed the diffusion of titanium by S-DCPN treatment using a Ti screen.
