Effect of Screen Open Hole on Nitriding Behavior, Corrosion Resistance and Wear Resistance of Plasma Nitrided Low Carbon Steel Using Ti Screen

Abstract

In order to investigate the e ff ect 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 ϕ 5mm, 10mm, and 20mm and the open area ratio of 0 ％ , 15 ％ , 35 ％ , and 55 ％ . Plasma nitriding was performed at 873K for 180min at a gas pressure of 300Pa under an atmosphere of 75 ％ N 2 + 25 ％ H 2 . After the nitriding treatment, X – ray di ff raction ( 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 di ff usion layer in which γ ’ – Fe 4 N was precipitated by nitrogen di ff usion were con fi rmed. The surface compound layer of iron nitrides was not formed when a screen with a hole size of 20mm and open area ratio of 55 ％ was used. The results of SEM – EDX also con fi rmed the di ff usion of titanium by S – DCPN treatment using a Ti screen. ［ doi:10.2320 / jinstmet.J2020049 ］ ( Received October 14, 2020; Accepted November 18, 2020; Published January 22, 2021 )