Elsevier

Ceramics International

Volume 44, Issue 5, 1 April 2018, Pages 4853-4858
Ceramics International

Wear behaviors of TiN/TiCN/DLC composite coatings in different environments

https://doi.org/10.1016/j.ceramint.2017.12.074Get rights and content

Abstract

Diamond like carbon (DLC) coatings have high wear resistance and low coefficient of friction and its features are being tried to be further developed. We deposited TiN/TiCN/DLC composite coatings on inconel substrates with closed field unbalanced magnetron sputtering system to improve the features of the conventional DLC coatings. Structural, chemical and bond types of the coating were obtained with the XRD, SEM, EDS and XPS analyses. Wear behaviors of the coatings were determined in atmosphere, distillated water and commercial oil conditions under low (2 N) and high (10 N) constant load values with using pin-on-disc tribo-test system. The wear results demonstrated that using the TiN/TiCN layers with the DLC coatings increased the load carrying capacity, decreased the CoF, and wear rates at the high load values.

Introduction

Carbon is the building block of most materials in nature. Carbon has many allotropic structures and has been used for years as a protective coating on machine surfaces where the friction-wear occurs when the diamond-like carbon (DLC) is produced in the laboratory environment. DLC coatings generally have high hardness, low wear rates and low friction of coefficient values hence DLC coatings are much worked and most commonly used protective coatings [1], [2], [3], [4]. On the other hand, the high hardness of the DLC coatings generally comes from the high residual stress in the lattice structure. This residual stress can cause the coatings to break up with the occurring of cohesive and adhesive cracks during the service life especially at high load values and hence this caused an increase in the wear rate and the friction of coefficient. Many studies have been made up to now and new studies are still being carried out to eliminate these disadvantages of DLC coatings and to further enhance its properties. Most likely, the most commonly used methods to obtain better properties are metal doped and using intermetallic interlayers in DLC coatings. Some studies have shown that using TiN or CrN interlayer between substrate and DLC coating provide good bonds and form very good adhesion [5], [6]. Added to this, improving mechanical and tribological properties of the DLC coatings, using the TiCN interlayer has given good results [7], [8]. In this context, it can be said that the co-use of TiN and TiCN interlayers will give better properties to the conventional DLC coatings.

In this study, we deposited TiN/TiCN/DLC composite coatings with closed field unbalanced magnetron sputtering system. The wear behaviors of the coatings were investigated in atmosphere, distillated water and commercial oil environment and results were evaluated with the literature comparatively.

Section snippets

Experimental

The TiN/TiCN/DLC coatings were deposited on inconel 600 (chemical composition is given in Table 1) substrates using the closed field unbalanced magnetron sputtering system. Four high purity titanium targets were used and they were placed to facing each other at 90° angles. Argon, nitrogen and C2H2 gases were used for plasma formation, nitrile phases and carbon source respectively. The details of the deposition parameters are given in Table 2. After the inconel and silicon substrates were placed

Structural properties

The cross-section SEM image of the TiN/TiCN/DLC coating deposited on silicon substrate is given in Fig. 1. When the SEM image is evaluated, the layers of the coating clearly seen in the SEM image. The thickness of the layers is about 250 nm, 750 nm and 500 nm for TiN, TiCN and DLC respectively. The total thickness of the coating is about 1.5 µm that it is an adequate value for protective coatings. It is seen that TiN and TiCN layers have very dense vertical columnar structure that showing very good

Conclusion

TiN/TiCN/DLC composite coatings were deposited on inconel substrates with closed field unbalanced magnetron-sputtering system and wear behaviors of the coatings were determined. The obtained results are listed below.

  • According to the XRD results the deposited coatings have crystalline TiN, TiCN and DLC phases in the structure.

  • The microhardness of the coating is 39.8 GPa and the total thickness of the coating is 1.5 µm.

  • The wear tests showed that the lowest wear rate and the lowest CoF value were

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