High‐entropy (Ti 0.2 V 0.2 Nb 0.2 Mo 0.2 W 0.2 )Si 2 with excellent high‐temperature wear resistance

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Abstract
The oxidation products (MoO 3 and V 2 O 5 ) have low melting points and tend to sublimate at high temperatures despite that MoSi 2 and VSi 2 may possess good self‐lubricating properties. To cope with this challenge, a high‐entropy transition metal disilicide was designed in this work in which transition metal elements that could form high melting point oxides were deliberately added. The high‐entropy (Ti 0.2 V 0.2 Nb 0.2 Mo 0.2 W 0.2 )Si 2 (HE‐MSi 2 ) with hexagonal structure was successfully prepared by SPS using Ti, V, Nb, Mo, W, and Si powders as the initial materials in this work. The HE‐MSi 2 presents a high hardness (11.8 ± 0.4 GPa) and elastic modulus (387.2 ± 46.8 GPa). In particular, its hardness is higher than that of the corresponding disilicides. Noteworthy, HE‐MSi 2 demonstrated superior wear resistance when compared to Mo‐Si‐based ceramics (such as MoSi 2 , Mo 5 Si 3 , and Mo 5 SiB 2 ), high‐entropy carbides (such as (MoTaWVTi)C, (HfMoNbTaTi)C, and (TiVNbMoW) 4.375 , and traditional single‐phase ceramics (including Sialon, Si 3 N 4 , Al 2 O 3 , SiC, and ZrO 2 ). Meanwhile, at a high temperature of 600°C, the friction coefficient and wear rate were reduced to 0.64 ± 0.05 and (1.88 ± 0.15)×10 6 mm 3 /N·m, respectively. The preferential oxidation of different elements of the HE‐MSi 2 was validated through systematical characterization of composition evolution, which was dominantly impacted by high temperature and friction induction.
Funding Information
  • National Key Research and Development Program of China (2022YFB3809000)
  • West Light Foundation, Chinese Academy of Sciences (2021)

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