In-situ solid solution of Mo or Cr in WB2: Densification, microstructure, and properties

Abstract

Pure tungsten diboride (WB2) ceramic prepared by the boro/carbothermal reduction combined with spark plasma sintering (SPS) of WB2 can reach a relative density >90%. However, the final sintered density still needs further improvement to meet the application requirement. In this study, the WB2 ceramics doped with Mo or Cr (W0.95Mo0.05B2 and W0.95Cr0.05B2) were prepared and the effects of Mo or Cr doping on powder characters, sintering behavior, microstructure, mechanical and physical properties of WB2 were systematically investigated. The results showed that the average particle size of the WB2 powders was increased significantly after adding either dopant, and the relative density of WB2 ceramics was improved from ∼93% to ∼95% and 96% with Cr and Mo addition, respectively. However, the Vickers hardness of WB2 with either dopant was reduced. On the other hand, the W0.95Mo0.05B2 solid solution exhibited slight improvement on both of the thermal and electrical conductivity as compared with WB2. But, both of the thermal and electrical conductivity of W0.95Cr0.05B2 solid solution decreased significantly to about 50% of the values obtained for WB2. The decrease in thermal and electrical conductivity of W0.95Cr0.05B2 solid solution was mainly attributed to the formation of high concentration of atomic defects, i.e. dislocations.