The character of sintering under vacuum and its use in hot isostatic pressing in comparison with the air pre-sintering and slurry coating techniques for alumina-zirconia composites

摘要

The character of sintering under vacuum and its use in the hot isostatic pressing (HIP) ofAl{sub}2O{sub}3-ZrO{sub}2 composites were investigated. Densification by sintering undervacuum was more difficult than by sintering in air under the same sintering temperature. Sinteringunder vacuum also caused non-uniformity in structure, therefore bringing about damage or rupture bythe development of residual stresses during heterogeneous densification. However, pre-sinteringunder vacuum was proven to be favorable for pore elimination and densification if it was followeddirectly by HIPing, compared with pre-sintering, in air at the same bulk density; the reasons areanalyzed. The SiO{sub}2-B{sub}2O{sub}3 pyrex-coating technique was also employed to enablecomparison with pre-sintering techniques. The results show that slurry-coating processing can bringabout changes in the shapes and sizes of the final products. The defects in coatings were difficult toovercome completely, thus, the slurry-coating technique is considered to be unreliable for HIPtreatment.