Elsevier

Applied Surface Science

Volume 253, Issue 18, 15 July 2007, Pages 7535-7539
Applied Surface Science

Nanostructured TiN coating prepared by reactive plasma spraying in atmosphere

https://doi.org/10.1016/j.apsusc.2007.03.062Get rights and content

Abstract

In the present study, the nanostructured TiN coatings are obtained by means of reactive plasma spraying in the air. The XRD analysis shows the coating was mainly composed of TiN (max. 86.3%) and a small quantity of Ti3O. Their microstructures were observed by SEM and TEM. The TEM pictures show the TiN coatings were composed of the nanoscaled grains (range from 70 to 90 nm), and the Scherrer equation analysis on the average grain size corresponded with that result. The effects on the average grain size also were studied by changing the spraying power and the spraying distance.

Introduction

Titanium nitride (TiN) processes superior wear resistance, erosion resistance, heat resistance and a low friction coefficient [1], [2], [3], thus it has been widely applied in some fields as an engineering ceramic, such as for cutting tool coatings and semiconductor technology [3], [4].

At present, the TiN coatings are mainly obtained by physical vapour deposition (PVD) or chemical vapour deposition (CVD) [5], [6], [7], [8]; however, due to the low efficiency of deposition, the thicknesses of these coatings are very thin (<10 μm) [9]. The prior studies show [10], [11] that the performances of TiN coating depend on its thickness; for example, the thicker the TiN coating, the better the wear resistance and corrosion resistance. Moreover, if the thickness of the TiN coating is less than 12 μm, it would not be able to resist the osmosis of corrosives. Therefore, making the TiN coating thick is a good way to obtain better performance.

Using plasma spraying technology to get a thick TiN coating has been reported in the former references [1], [2], [12]. T. Bacci [2] has prepared a TiN coating with a thickness of 60 μm using reactive plasma spraying, and the spraying was performed in a pure nitrogen atmosphere chamber at 500 bar. However, the coating was mainly composed of the residual Ti and some TiN, Ti2N. Akira Kobayashi [1], using a gas tunnel-type plasma jet, prepared a TiN coating whose thickness was over 200 μm. In addition, Wenran Feng [12], [13] especially studied the microhardness and tribological properties of the reactive plasma-sprayed TiN coating; E. Galvanetto [14] investigated the formation of titanium nitrides during the reactive spraying of titanium by means of XRD and XPS.

However, all the previous studies on the plasma spraying of TiN were carried out in the nitrogen-containing spraying chamber or using a gas tunnel-type plasma jet; spraying that is carried out in the air has not been found in the former references. Furthermore, few studies were curious about the microstructure of the reactive plasma-sprayed TiN coating by TEM, and the grain size has not been analyzed before.

Section snippets

Fabrication of the TiN coatings

The experiments were carried out by a plasma spraying system, which consisted of a GDP–2 electric power of 50 kW and a BT-G3 gun manufactured by JiuJiang Device Company in China. Q235 steel (Fe–0.14–0.22 wt.% C) was used as the substrate material, which was machined into samples of 15 mm × 10 mm × 10 mm. In order to get a rough surface, the substrate's surface was sandblasted before the reactive plasma spraying. Commercially available pure titanium powder, produced by Beijing General Research Institute

The phase composition of the coating

Fig. 2 shows the X-ray diffraction pattern of coating sample 1; its spraying parameters are shown in Table 2. The phases detected in the coating are TiN (fcc) and Ti3O (hcp); no other phases were found. There are five sharp TiN peaks appearing in the spectrum, which indicate that TiN is the primary phase in this coating. Their crystal planes are (1 1 1), (2 0 0), (2 2 0), (3 1 1) and (2 2 2), and the (1 1 1), (2 0 0) planes are the preferred orientations among them. However, five weak Ti3O peaks are also

Conclusion

Nanostructured TiN coatings were formed by reactive plasma spraying, and the following results were obtained:

  • 1.

    The thickness of the reactive plasma-sprayed nanostructured TiN coating is more than 300 μm, and the coating is composed of TiN (main) and Ti3O.

  • 2.

    The TiN ratio decreases with an increase of input power in the plasma jet, and it can reach the maximum value of 86.3% when the input power is 26 kW.

  • 3.

    The average grain size ranges from about 70 to 90 nm when the spraying distance is 100 mm and the

Acknowledgements

This work is financed by the National Natural Science Foundation, P.R. China (Grant No. 50472033), and the author would like to thank them for their financial support.

References (18)

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