| TiN coatings were deposited on M2 high speed steel by the plasma enhanced chemical vapor deposition(PECVD) process using a gas mixture of TiCl₄, NH₃, H₂ and Ar with various NH₃/TiCl₄ flow rate ratios(Q(NH₃)/Q(TiCl₄)), and the effect of the flow rate ratio on the color, structure and property of TiN coatings has been investigated. Structural and compositional analyses were conducted by X-ray diffraction method(XRD), transmission electron microscopy(TEM), Rutherford backscattering spectroscopy(RBS), as well as Auger electron spectroscopy(AES). At low flow rate ratios, bright gold coatings with high hardness and low resistivity could be formed. At higher ratios, on the other hand, coatings of brown color were formed. They showed porous microstructures with considerably decreased microhardness. Results from structural and compositional analyses showed that a large amount of oxygen had been substitutionally incorporated in the brown color TiN during the deposition process to form titanium oxynitride. It has been found, however, that the color change of TiN coatings is closely related with the surface roughness of the coating rather than with the presence of oxygen in the coating. |
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