Nanostructured multielement (TiHfZrNbVTa)N coatings before and after implantation of N+ ions (1018cm−2): Their structure and mechanical properties

Abstract

a b s t r a c tMultielement high entropy alloy (HEA) nitride (TiHfZrNbVTa)N coatings were deposited by vacuum arc and their structural and mechanical stability after implantation of high doses of N + ions, 10 18 cm À2 , were investigated. The crystal structure and phase composition were characterized by X-ray diffraction (XRD) and Transmission Electron Microscopy, while depth-resolved nanoindentation tests were used to determine the evolution of hardness and elastic modulus along the implantation depth. XRD patterns show that coatings exhibit a main phase with fcc structure, which preferred orientation varies from (1 1 1) to (2 0 0), depending on the deposition conditions. First-principles calculations reveal that the presence of Nb atoms could favor the formation of solid solution with fcc structure in multielement HEA nitride. TEM results showed that amorphous and nanostructured phases were formed in the implanted coating sub-surface layer ($100 nm depth). Concentration of nitrogen reached 90 at% in the near-surface layer after implantation, and decreased at higher depth. Nanohardness of the as-deposited coatings varied from 27 to 38 GPa depending on the deposition conditions. Ion implantation led to a significant decrease of the nanohardness to 12 GPa in the implanted region, while it reaches 24 GPa at larger depths. However, the H/E ratio is P0.1 in the sub-surface layer due to N + implantation, which is expected to have beneficial effect on the wear properties.

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“…One such a method is ion implantation, in particular Si implantation found popularity in integrated circuit processing to create p-type junctions near to the surface. − Threshold voltage control and good precision of implantation depth serve as beneficial accommodation to the required dopant distribution and concentration. Recently, ion implantation was introduced to heterostructure design enabling the creation of new phases and structures in the nanometer-thick layers. − …”

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