Chapter 24. High Strength TiB₂

Summary

It was described in the previous paper that fully dense TiB₂-20 wt% (2 mol% Y₂O₃-ZrO_-) sintered bodies were fabricated by glass encapsulation HIP (1600°C, 200 MPa, 2 h), and their 3-pt. bending strength was as high as 1200 MPa. In this material, grain growth occurred during sintering; the grain sizes of TiB₂ and ZrO₂in a sintered (HIP'd) body were 4–6 μ and 2–5 μ, respectively, while starting powder sizes of TiB₂ and ZrO₂ were 2 μm and 0.1 μm, respectively. To minimize this grain growth, 2.5–5 wt% SiC, whose size was 0.2 μm, was added. As a restult, the grain sizes of TiB₂ and ZrO₂ in a sintered body were 2–4 μm and 1–3 μm, respectively. The 3-pt. bending strength has increased to 1280 MPa. In addition to improving strength, adding SiC improved the sinterability of TiB₂-20 wt% (2 mol% Y₂O₃-ZrO₂); the sintered body whose density was 98.0% of full density was fabricated by vacuum sintering (1600%dGC, 4 h).