| Budget Amount *help |
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2005: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 2004: ¥3,100,000 (Direct Cost: ¥3,100,000)
|
|---|
| Research Abstract |
Dense W-B-C ceramics were prepared by a reactive resistance-heated hot-pressing of B_4C-W-WC powders which induced the solid-state reaction B_4C + 5W + 80WC→4WB+81WC to find the most suitable range of sintering temperature. Dense ceramics were obtained above 1650 ℃ Sintered bodies obtained at 1650 ℃. had fine WC grains and hence high hardness. Above 1700 ℃, grain-coarsening of WC occurred and hardness greatly decreased. Since the narrow range of sintering temperature make it more difficult to control their quality. Therefore, it is necessary to widen the sintering temperature range by adding a grain-growth inhibitor. Thus, the effect of VC, which are widely know as the most effective grain-growth inhibitor for WC in WC-Co, was examined on mechanical properties. Fully dense ceramics were obtained above 1750 ℃ for a powder containing VC-doped WC. Dense ceramics obtained at 1800 ℃ had almost the same grain size of WC as the starting powder, showing a good grain-growth inhibitor. Below 1700 ℃, WB, W_2B and W_2C were formed as reaction products, and, above 1750 ℃, WB was not produced. VC did not dissolve in WC grains, and precipitated at WC/WC grain boundaries and around WB and W_2B grains. The bulk density increased with sintering temperature and approached 15.5 g cm^<-3> above 1750 ℃. Young's modulus increased gradually with sintering temperature and became constant above 1750 ℃. Its maximum value was 689 GPa. Poissons' ratio was constant in the sintering temperature range. Vicker's hardness was above 25 GPa in the sintering temperature range because the grain growth of WC was effectively impeded. The fracture toughness had a maximum value of 5.3 MPa m^<1/2>, being a little lower than that without VC.
|
