Effect of solid solution and boron vancancy on the microstructural evolution and high temperature strength of W-doped ZrB2 ceramics

Abstract W-doped ZrB2 ceramics were hot-pressed at 1800–2100 °C by using W additive. The effects of W doping on the densification, microstructure, and high temperature strength of ZrB2 ceramics were investigated. The reaction between ZrB2 and W resulted in the formation of WB, ZrB and boron vacancies in ZrB2-x. The solid solution formed by dissolving WB in ZrB2-x has core-shell structure, inhibited the grain growth and densification of ZrB2 ceramics. (W,Zr)B converted to liquid promoted densification at 2100 °C, and dissolved the oxygen from the surface of ZrB2 powders. The ZrB2 ceramics with 3–10 vol% W exhibited fine microstructures and high grain boundary strength. The cleaning boundary produced by WB significantly improved the flexural strength of ZrB2 ceramics at 25–1600 °C. (Zr,W)B precipitated from vacancy-rich (Zr,W)B2-x solid solution under tensile stress at 1600 °C.