Densifying (Hf _0.2 Zr _0.2 Ta _0.2 Nb _0.2 Ti _0.2 )C high‐entropy ceramics by two‐step pressureless sintering

Abstract

Abstract A pressureless two‐step sintering method was used to densify high‐entropy carbide (Ti 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2 )C, with high density and good mechanical performance. The material was heated up to 2200°C and subsequently soaked at 1900°C for 2–8 h with the incorporation of 2–4 wt.% phenolic resin. With increasing resin content, the large‐sized pores disappeared, and the average grain size decreased. However, with increased holding time from 2 to 8 h, the average grain and pore size did not change significantly, the density increased up to 96.2%, and evident grain growth of graphite was observed. The mechanical properties of (Ti 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2 )C with 4 wt.% phenolic resin addition and 8 h soaking at 1900°C were measured as follows: flexural strength 361±28 MPa, Vickers hardness 16.0±0.3 GPa, and elastic modulus 426±2 GPa.