Explore the compositional space of multicomponent nitride hard coatings through combinatorial approach

抄録

Introduction

Hard protective coatings have been widely used in diverse applications to improve the performance and durability of workpiece. Among all hard coating materials, multicomponent transition metal nitrides have drawn much of the attention due to their superior mechanical strength[1], chemical inertness[2], oxidation resistance[3] and thermal stability[4], which are all desirable material properties for anti-wear applications. However, these properties strongly depend on the chemical composition of the coatings. Owing to the chemical complexity of multicomponent nitride, the search for extraordinary coating materials is a rather time-consuming task. Thus, Accelerating the progress of investigating the compositional space of multicomponent nitride is crucial.

Results

In this study, an experimental combinatorial approach is adopted to efficiently explore the compositional space of multicomponent nitrides as illustrated in Fig.1. Two materials systems, HfNbTiVZrN and AlCrSiTiN, are fabricated through reactively co-sputtering technique. From the elemental quantification results, both HfNbTiVZrN and AlCrSiTiN exhibit wide composition spread for the metallic and metalloid elements.

For HfNbTiVZrN, the crystal structure is identified to be single phase rock-salt structure regardless of the chemical composition with the crystallite size from 4.4 to 30.9 nm. The hardness of HfNbTiVZrN exhibits a strong dependence on the composition and crystallite size with values ranges from 22.4 GPa to 39.3 GPa, showing significantly better mechanical properties than the constituent binary and ternary nitrides. Among all the compositions, Hf_3.5Nb_2.6Ti_22.9V_4.9Zr_17.7N exhibits the optimum hardness of 39.3 GPa. Scanning transmission electron microscope analysis indicates that the metallic elements are randomly distributed in the cation sub-lattice. The solid solution of atoms with different sizes could effectively hinder the movement of the dislocations, strengthening the mechanical properties.

For AlCrSiTiN, the incorporation of metalloid element (i.e. silicon) would induce the spinodal decomposition, leading to the formation of nanocomposite structure (nano-crystalline metal nitride/amorphous silicon nitride). These nanocomposite coatings would have the benefits of grain size refinement, precipitation hardening, grain boundary reinforcement, and nanostructure toughening. The hardness and fracture toughness of AlCrSiTiN are thus found to be strongly correlated to the silicon contents of the coatings, showing the optimum values at silicon contents around 8 at. %. In order to evaluate the performance of AlCrSiTiN at high temperature, oxidation test and high temperature tribological test are performed at 700℃. The results suggest that coatings with high toughness would have favorable high temperature wear resistance. On the other hand, the type of oxidation products would also influence the tribological behaviors at high temperature. It appears that avoiding adhesive wear behaviors (i.e. strong bonding between the formed oxide and testing counterpart) is beneficial for high temperature wear resistance.

References

[1] S.-Y. Hsu, Y.-T. Lai, S.-Y. Chang, S.-Y. Tsai, J.-G. Duh, Surface and Coatings Technology, 442 (2022) 128564.

[2] Y. Zhao, S. Chen, Y. Chen, S. Wu, W. Xie, W. Yan, S. Wang, B. Liao, S. Zhang, Vacuum, 195 (2022) 110685.

[3] W. Shen, M. Tsai, K. Tsai, C. Juan, C. Tsai, J. Yeh, Y. Chang, Journal of the Electrochemical Society, 160 (2013) C531.

[4] P.-K. Huang, J.-W. Yeh, Scripta Materialia, 62 (2010) 105-108.