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US 5,094,986 AGranted
Wear resistant ceramic with a high alpha-content silicon nitride phase
AssigneeHercules Incorporated
InventorsRoger L. K. Matsumoto, Allan B. Rosenthal
Life of this patent
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Abstract
Disclosed is a wear resistant sintered ceramic product comprising (a) 40-98 weight percent silicon nitride having a high alpha-phase content, (b) 2-60 weight percent of a silicide of iron, cobalt or nickel and (c) up to 20 weight percent of at least one oxide, nitride, or silicate of an element of IUPAC groups 2, 3, 4, 13 or the lanthanide series. A method for making such a product is also disclosed.
Claims13
In a sintered ceramic product consisting essentially of
- (a) from about 40 to about 98 percent silicon nitride,
- (b) from about 2 to about 60 percent of silicides of at least one metal selected from the group consisting of iron, nickel and cobalt, and
- (c) up to about 20 percent of at least one oxide, nitride or silicate of an element selected from IUPAC group 2, 3, 4, 13 or the lanthanide series, all percentages being by weight based on the total weight of the product,
- the improvement comprising an alpha-to-beta ratio of silicon nitride in the sintered ceramic product that falls within area A of FIG. 1 and a content of high metal-content silicides in the sintered ceramic product that is at least 50% by weight of the silicides present.
1 more element
In a process for preparing a sintered ceramic product comprising
- (1) intimately mixing a powder mixture consisting essentially of
- (a) from about 50 to about 98 percent silicon nitride,
- (b) from about 1 to about 50 percent of at least one metal selected from the group consisting of iron, nickel and cobalt, or an oxide or alloy thereof, and
- (c) from 0.02 to about 20 percent of at least one oxide, nitride or silicate of an element selected from IUPAC group 2, 3, 4, 13 or the lanthanide series, all percentages being by weight based on the total weight of the powder mixture,
- (2) reacting the components of the powder mixture by heating to a temperature of 1300.degree.-1700.degree. C. in a non-oxidizing atmosphere until component 1(b) is completely converted to its corresponding silicides, and
- (3) maintaining the powder mixture at a temperature of 1300.degree.-1700.degree. C. in the non-oxidizing atmosphere until the composition formed in (2) densifies,
- the improvement comprising reacting the components of the powder mixture until the alpha-to-beta ratio of silicon nitride in the sintered ceramic product falls within area A of FIG. 1 and at least 50% by weight of the silicides in the sintered ceramic product are high metal-content silicides.
4 more elements
Dependencies are inferred from the claim text.