Abstract
α-SiC and β-SiC starting powders mixed with 1 wt% B and 1 wt% C as densification aids, were pressed and normally sintered at 2000-2200°C. These sintered compacts and commercial sintered compacts (Kyo-sera, SC201) were HIP'ed without capsule using in 100 MPa Ar gas and N2 gas at 1700°C.
Weight change, density and flexural strength were investigated, and the results obtained were summarized as follows:
(1)The amount of weight gain during N2-HIP treatment which was remarkably large in case of low temperature sintered compacts (about 15%), was caused by the reaction between high pressure N2 gas and SiC.
(2)The density of all specimens increased by HIP treatments, and the density of N2-HIP'ed compacts was increased with the weight gain.
(3) The flexural strength of sintered a-SiC and commercial SiC compacts increased by HIP treatments, and the higher strength was obtained in case of N2-HIP treatment. It was considered that the flaw size in SiC compacts was apparently decreased by the rod like Si3N4 crystal which was formed y the reaction between N2 gas and SiC.
