Effect of SiC and MgO addition on mechanical and ablation characteristics of spark plasma sintered ZrB2-based composites

The effects of SiC (20-30 vol. %) and MgO (1-3 vol. %) on sinterability, phase evolution, microstructures, mechanical and ablation characteristics of spark plasma sintered ZrB2-based composites were investigated in the present study. The analytically estimated residual stresses decreased with SiC and MgO addition. The highest relative density of 98.29 +/- 0.36% and microhardness of 16.13 +/- 2.91 GPa were observed for the composite containing 2 vol. % MgO owing to uniform dispersion of SiC and MgO in the ZrB2 matrix. The highest fracture toughness and critical energy release rate of 6.15 +/- 0.41 MPa.m(0.5) and 88.53 +/- 11.73 J/m(2) were observed for the composite containing 3 vol. % MgO due to the invigoration of toughening mechanisms (SiC particle pull-out, crack deflection and bridging). The ablation resistance was enhanced with MgO addition and the highest ablation resistance was observed for the composite containing 2 vol. % MgO. The composites retained maximum hardness and fracture toughness of 14.17 +/- 3.03 GPa and 5.91 +/- 0.4 MPa.m(0.5) after ablation test, which were 87.85% and 96.09% of maximum hardness and fracture toughness before ablation test. [GRAPHICS] .

Automated summary

The effects of SiC and MgO on various properties of spark plasma sintered ZrB2-based composites were investigated. The results show that the addition of SiC and MgO can reduce residual stresses, improve relative density and microhardness. In addition, the addition of MgO also enhances fracture toughness, critical energy release rate, and ablation resistance. Finally, the composites retain high hardness and fracture toughness after ablation testing.