Preparation of high-entropy carbides by different sintering techniques

Johannes Pötschke,Manisha Dahal,Björn Matthey,Alexander Michaelis,Anne Vornberger,Mathias Herrmann

doi:10.1007/s10853-021-06004-y

Abstract

Dense (Hf, Ta, Nb, Ti, V)C- and (Ta, Nb, Ti, V, W)C-based high-entropy carbides (HEC) were produced by three different sintering techniques: gas pressure sintering/sinter–HIP at 1900 °C and 100 bar Ar, vacuum sintering at 2250 °C and 0.001 bar as well as SPS/FAST at 2000 °C and 60 MPa pressure. The relative density varied from 97.9 to 100%, with SPS producing 100% dense samples with both compositions. Grain size measurements showed that the substitution of Hf with W leads to an increase in the mean grain size of 5–10 times the size of the (Hf, Ta, Nb, Ti, V,)C samples. Vacuum-sintered samples showed uniform grain size distribution regardless of composition. EDS mapping revealed the formation of a solid solution with no intermetallic phases or element clustering. X-ray diffraction analysis showed the structure of mostly single-phase cubic high-entropy carbides. Hardness measurements revealed that (Hf, Ta, Nb, Ti, V)C samples possess higher hardness values than (Ta, Nb, Ti, V, W)C samples.

Highlights

Carbides of group IV, V, and VI of transition metals (TiC, ZrC, NbC, HfC, TaC, VC, Cr3C2, Mo2C, and WC) are refractory carbides that combine high melting temperatures, high hardness, and high elastic modulus [1, 2]
Different relative densities were obtained for each high-entropy carbides (HEC) material produced by the different sintering methods, as can be seen from Table 3
The relative density of the HEC samples varied from 97.9 to 100%, with samples sintered from SPS yielding 100%, and vacuum sintering yielding 99.5% regardless of compositions

Summary

Introduction

Carbides of group IV, V, and VI of transition metals (TiC, ZrC, NbC, HfC, TaC, VC, Cr3C2, Mo2C, and WC) are refractory carbides that combine high melting temperatures, high hardness, and high elastic modulus [1, 2]. These refractory carbides are used as single carbides or in form of hard phases for tool steel or hardmetals ( known as cemented carbides or cermets). There is a need for more stable materials to withstand an even broader range of extreme environments For such physical, chemical, and mechanical properties, a high entropy concept is added in this field of refractory carbides. These novel carbides are called high-entropy carbides (HEC) [5,6,7,8,9,10,11,12,13,14,15,16,17,18]

Methods

Results

Conclusion