Densification studies of refractory materials using Hot Isostatic Pressing (HIP) and tantalum containment.

摘要

Powders of crystalline rohmbohedral boron were HIP processed to near full density at 1500-1800(degree)C and 206.8 MPa. At 1700(degree)C, the densification of boron was independent of particle size in the range of <37 (mu)m to 10 mm. At 1500(degree)C, only the <37-(mu)m powder reached near full density. Silicon and calcium impurities were found to segregate in the grain boundaries during densification. Results indicate that plastic yielding was to dominate densification mechanism. Boron nitride powder with 0.97% oxygen content was pressed to a density of 2.21 g/cm(sup 3) at 18000(degree)C and 206.8 MPa. The density of high-purity hot-pressed graphite was increased by 15% to 2.10 g/cm(sup 3) at 2200(degree)C and 206.8 MPa. These results show that refractory metal containers used in hot isostatic pressing significantly expand the availability of high-density-high purity materials. 3 refs., 7 figs., 2 tabs.