Effect of alloying on elastic properties of ZrN based transition metal nitride alloys
Introduction
Hard coatings based on transition metal nitrides are well established and routinely used for various industrial applications due to their outstanding properties like high hardness, wear and corrosion resistance [1]. Besides binary nitride materials, ternary and higher order material systems are exploited in search of advantageous combination of intrinsic and structure related material properties [1], [2]. In order to further improve the functional properties of these materials, the current research strategy is driven by the prospects of synthesizing new ternary or multinary systems, by means of alloying different metal or non-metal elements [3].
Among the ternary M1M2N (M = transition metal) systems, TiMN coatings have been the most widely investigated, whereas very few studies have been devoted to the ZrMN systems. It is known that ZrN has a lower coefficient of friction than TiN and other transition metal nitrides, and is relatively hard [4], [5]. However, its poor oxidation resistance hampers a broader range of applications. Therefore, alloying ZrN with transition metal was suggested in order to improve the oxidation resistance and possibly also the mechanical properties [6]. Recently, various ZrAlN and ZrTiN ternary coatings have received lots of attention due to their excellent properties [7], [8], [9], [10], [11], [12]. No experimental data is available at present for Zr1 − xMxN (M = Hf, V, Mo and W), and only few studies on Zr1 − xNbxN have been reported in the literature [13].
In this work, we report a comprehensive overview of structural and elastic properties of the binary transition metal nitrides and cubic AlN. Thus, we extend our calculation to study the effect of substitutional transition metal nitride element alloying on the elastic properties of ZrN at the atomic level. We therefore concentrate on the effects characteristic of a solid solution. It is our ambition to contribute towards relying on the phenomenological correlation between ductility and certain elastic properties of the solution phases. We use first-principle-based methods to investigate the structure, mechanical and electronic properties of Zr1 − xMxN, where M = Al, Ti, Hf, V, Nb, W and Mo ternary alloys to identify the candidate alloys for potentially hard coatings with enhanced ductility. The elastic properties are of particular interest as they determine the mechanical stability of the material and some important macroscopic properties. In addition, the density of sates and chemical bonding are used to provide insight into the bonding between nitrogen and transition metals.
Section snippets
Computational details
Total energy calculations have been performed using the density functional theory based on the generalized gradient approximation (GGA) of Perdew–Burke–Ernzerhof (PBE) [14], as implemented in the Vienna Ab initio Simulation Package (VASP) [15]. The electron and core interactions are included using the projector augmented wave (PAW) method [16]. The electronic wave functions were expanded with a basic set of plane waves with kinetic energies of up to 500 eV. Atomic positions were optimized until
Results and discussion
The optimized lattice constants a, formation energies Ef, and mass densities ρ of binary compounds are summarized in Table 1. Since there is a vast amount of existing data for the equilibrium lattice parameters in the literature, we refer to some experimental [23] and theoretical results [24], [25], [26], [27] for comparison. Our results are slightly larger than the experimental values, except for VN. It is well known that the generalized gradient approximation functional tends to underestimate
Conclusion
In summary, the present work has involved a computational study of the structural, elastic and electronic properties of ZrN based transition-metal nitride alloys. Trends in the atomic volume, elastic constants and formation energies of Zr1 − xMxN alloys were investigated for Ti, Hf, V, Nb, W, Mo and Al solute species x. Our results reveal that the ZrN TiN, HfN, VN, NbN and AlN compounds and Zr1 − xMxN alloys in B1 structural phase are thermodynamically and mechanically stable. Mixing Ti, Hf, V, Nb,
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