M. Komac, D. Kolar, IJS, Ljubljana
S procesom zgoscevanja in utrjevanja silicijnitridne keramike v
visokotemperaturnem avtoklavu smo iskali zvezo med pogoji
izdelave, mikrostrukturo in mehanskimi lastnostmi. Silicijev
nitrid, ki vsebuje Al 2 O 3 , MgO in majhne kolicine kovinskega
silicija kot aditiva za sintranje, smo sintrali pri temperaturah
1650 stopinj C in 1770 stopinj C pod povisanim tlakom
dusika in vzorce zadrzevali
pri temperaturi 1400 stopinj C do 12 ur. Studirali smo morfologijo
kristalov alfa - Si 3 N 4 v gosto sintrani keramiki in njen vpliv na
velikost upogibne trdnosti. S kvantitativno analizo
mikrostrukture zlomnih povrsin smo pokazali, da imata v gosto
sintrani Si 3 N 4 keramiki velikost in porazdelitev velikosti
palicastih zrn alfa
- Si 3 N 4 najvecji vpliv na upogibno trdnost pri
sobni temperaturi. Po postopku sintranja v visokotemperaturnem
avtoklavu smo izdelali vzorce rezalnih no`ev in kroglic.
Kljucne besede: silicijev nitrid, mikrostruktura, trdnost
The relations between fabrication conditions, microstructure and
mechanical properties of silicon nitride (Si 3 N 4 ) have been
studied on the basis of densification and strengthening
processes. Si 3 N 4 with the adition of Al 2 O 3 , MgO and small
quantities of metalic silicon was sintered at temperatures 1650 degrees C
and 1700 degrees C under increased nitrogen pressure. The samples were
annealed after sintering up to 12 hours at 1400 degrees C. Morphology of
alpha - Si 3 N 4 in dense matrix and its influence on flexural stength
were studied. Quantitative microstructure analyses of fracture
surfaces confirmed that, at room temperature, mechanical
properties of the dense Si 3 N 4 ceramic were mostly influenced by
the grain size and the grain size distribution. In further
experiments it was shown that the applied sintering process could
be suitable for the preparation of cuting tools and balls in a
high temperature autoclave.
Key words: silicon nitride, microstructure, strength