Details

Autor(en) / Beteiligte

• Homma, K
• Tatsuno, T
• Okada, H

Titel

Effects of Sintering Aids on Properties of Normally Sintered and HIP'ed Si sub 3 N sub 4

Ist Teil von

• Journal of the Japan Society of Powder and Powder Metallurgy, 1987-02, Vol.34 (2), p.73-77

Erscheinungsjahr

1987

Quelle

EZB Electronic Journals Library

Beschreibungen/Notizen

• Si sub 3 N sub 4 powders mixed with 6 wt.% Y sub 2 O sub 3 --2-6 wt.% Al sub 2 O sub 3 and 6 wt.% Y sub 2 O sub 3 --1-5 wt.% MgO as sintering aids, were pressed and normally sintered at 1600 deg C. The sintered compacts were HIP'ed without using a capsule in 100 MPa nitrogen gas at 1700 deg C. Density, weight change, alpha to beta phase transformation and flexural strength were studied, and the results obtained were summarized as follows: (1) The amount of weight loss during sintering was relatively small in case of Y sub 2 O sub 3 --Al sub 2 O sub 3 series, so that the sinterability was better than in Y sub 2 O sub 3 --MgO series. (2) In case of both the series, the amount of alpha to beta transformation in sintered compacts was decreased compared with the compacts which contained 6 wt.% Y sub 2 O sub 3 only, and the tendency in Y sub 2 O sub 3 --Al sub 2 O sub 3 series was more remarkable than in Y sub 2 O sub 3 --MgO series. (3) The mean strength of Y sub 2 O sub 3 --Al sub 2 O sub 3 series was improved from 340 to 700 MPa by HIP treatment. It was found that the improvement of strength depended on not only density, but also alpha to beta transformation and fibrous structure formation in Si sub 3 N sub 4 during HIP treatment. 12 ref.--AA