Structural Characterization of Titanium Nitride Coatings on AISI M2 Steel

摘要

In this work, some surface properties of AISI M2 steel were improved by a thermo-reactive deposition process. Gas nitriding was realized on AISI M2 steel at 550℃ for 2 h in an ammoniac atmosphere and then, titanizing treatment performed on pre-nitrided steel in the powder mixture consisting of ferro-titanium, ammonium chloride and alumina at 1000℃ for 1-4 h. Structural characterization of titanium nitride layer formed on the surface of AISI M2 steel was carried out by using optical microscopy, scanning electron microscopy, electron microprobe and X-ray diffraction (XRD) analysis. The hardness measurements of titanium nitride layer were conducted under 10 g loads by using Vickers microhardness indenter. Structural analysis studies showed that titanium nitride layers formed on the AISI M2 steel samples were smooth, compact and homogeneous. XRD analysis show that the coating layer formed on the steel samples includes TiN, Fe_6Mo_7N_2, C_(0.7)N_(0.3)Ti, C_(0.3)N_(0.7)Ti and V_2N phases. The hardness of titanium nitride layers formed on the steel samples is between 2040±186 and 2418±291 HV_(0.01). The thickness of titanium nitride layer formed on the steel samples ranged from 3.86±0.43 μm to 6.13±0.47 μm, depending on treatment time.