Method of making reaction bonded/hot pressed Si.sub.3 N.sub.4 fo

Details Method of making reaction bonded/hot pressed Si.sub.3 N.sub.4 fo Method of making reaction bonded/hot pressed Si.sub.3 N.sub.4 fo

1984-09-20

1989-07-18

Derrington, James

Abrasive tool making process, material, or composition

With inorganic material

Metal or metal oxide

264 65, 264332, 264325, 501 97, C04B 3558

Patent

active

048489840

ABSTRACT:
A method of making a reaction bonded/hot pressed silicon nitride comprising object is disclosed. Second phase crystallites are formed prior to hot pressing. A mixture of silicon, SiO.sub.2, and 0.4-2.3 molar percent (by weight of the silicon) of oxygen carrying agents, i.e., Y.sub.2 O.sub.3 and Al.sub.2 O.sub.3, is performed and reaction nitrided to form discs or billets having at least 60% alpha Si.sub.3 N.sub.4 and a high proportion of second phase crystallites which displace substantially all silicate glass except for a controlled small quantity. The reactive amounts of Y.sub.2 O.sub.3, Al.sub.2 O.sub.3 and SiO.sub.2 are controlled to assure formation of substantially Y.sub.1 SiO.sub.2 N as the second phase crystallite. Al.sub.2 O.sub.3 is controlled in an amount of 0.4-4% by weight to ensure that the small proportion of glass serves to protect the oxynitrides against linear oxidation kinetics. The hot pressed material has no visual mottle porosity associated therewith.

REFERENCES:
patent: 3839540 (1974-10-01), Arrol et al.
patent: 4351787 (1982-09-01), Martinengo et al.
patent: 4401617 (1983-08-01), Ezis et al.
patent: 4440707 (1984-04-01), Shimamori et al.

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