High-temperature compressive behaviour and failure mechanism of high entropy carbides modified by Cr addition

The effect of Cr addition on the compressive and failure behaviour of high entropy carbides (HECs) at temperatures of 1400-1600 degrees C and stresses of 200-300 MPa was investigated by comparing two groups of ceramics: (Zr,Nb,Hf,Ta)C (HEC4) and HEC4 with Cr addition (HEC5-Cr), and 8-metal carbides (Ti,Zr,Hf,V,Nb,Ta,Mo,X)C with W or Cr addition for X. The HEC-Cr systems showed significantly lower compressive strain than Cr-free HECs under identical conditions. HEC4 showed a strain of about 1.4 % at 1500 degrees C under 200 MPa for 6 h, while HEC5-Cr demonstrated only 0.05 % strain. To the best of our knowledge, HEC5-Cr exhibited the lowest steady creep rate among carbides reported under similar conditions. Creep is almost negligible in HEC-Cr ceramics, mostly because the grain boundary sliding and cracking were restricted by the strong Cr-rich grain boundaries. The Cr addition changed the failure behaviour of HECs: the Cr-free HEC samples shattered into numerous pieces due to severe grain boundary deformation, the HEC-Cr samples typically fractured into two parts with transgranular failure. The strategic addition of Cr to HECs enhances compressive performance and modifies fracture behaviour, indicating their potential as superior materials for high-stress, high-temperature applications.