Improved wear resistance of P/M tool steel alloy with different vanadium contents after ion nitriding

Tool steels produced by powder metallurgy (P/M) processes are technologically well established and are used in various applications. However, the need to improve their surface properties arises when P/M parts are subjected to severe wear. The objective of this work is to study the influence of vanadium on the ion nitriding process and the abrasive wear of ion-nitrided P/M materials. Two P/M alloys; CPM-3V and CPM-15V, which contain different V contents, were ion-nitrided at 550 °C for 1 and 5 h. The nitrided layers were characterized by microhardness, pin-on-disc wear testing, optical microscopy (OM), scanning electron microscopy (SEM) with energy-dispersive X-ray spectrometry (EDS) and X-ray diffraction (XRD) systems. The hardness of the layers increased considerably after ion nitriding, due to the formation of VN. In the abrasive wear test, it was verified that the hardness increase resulted in a smaller mass loss when the compound layer composition is primarily VN and γI-Fe4N.