Compositions: ceramic – Ceramic compositions – Refractory
Patent
1988-07-12
1989-12-05
Niebling, John F.
Compositions: ceramic
Ceramic compositions
Refractory
264 65, 423266, 423608, C04B 3548
Patent
active
048852660
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention concerns ceramic materials used in engineering applications. More particularly it concerns zirconia ceramics which are partially stabilised with magnesia and which have high strength and good thermal shock resistance.
BACKGROUND TO THE INVENTION
In the specification of U.S. Pat. No. 4,279,655, magnesia partially stabilised zirconia ceramic materials, which possess good thermal shock resistance and high strength and wear resistance, are described. As noted in that specification good thermal shock resistance and high physical strength had, for many years, been regarded as mutually exclusive properties of ceramic materials. However, by producing materials with a specified microstructure, this hitherto unforseen combination of physical properties was found to be achievable.
In some situations where ceramic materials may be used, it is not necessary for the ceramic material to possess both exceptional strength and good thermal shock resistance. For example, for low temperature applications, such as in wire drawing and in bioceramics (synthetic joints for humans and animals), the strength and wear resistance of the ceramic is more important than its thermal shock resistance, but for high temperature applications, such as extrusion dies for brass, copper and steel, thermal shock resistance and reasonable strength are the essential attributes of the materials.
Most uses of ceramic materials can be categorised by reference to the temperature range in which the material is to function. To illustrate this point, examples of applications of ceramic materials are provided in Table 1 below (which is not intended as an exhaustive listing of the applications of ceramic materials).
TABLE 1 ______________________________________
TEMPERATURE
OF USE APPLICATIONS
______________________________________
Low temperature Bio-prosthesis devices; dry
(Room temperature
bearings; wear resistant lining
to about 400.degree. C.)
and tiles; guides for wire bars
and threads; sizing tools for the
powder metallurgy industry;
scraper blades for the coal
industry and other mining indus-
tries; tappet (cam follower)
facings; valve guides, valves
and seals; nozzles for auto-
claves, (for example in paper
making); nozzles for slingers
and hydro-cyclones; dies for wire
drawing, cold tube drawing,
powder compaction and injec-
tion moulding of plastics;
pump (including slurry pump)
liners, spindles, seals and
pistons; abrasive and corrosive
chemical handling apparatus.
Intermediate tempera-
Engine components such as valve
tures (from about 400.degree. C.
guides and cylinder liners;
to about 700.degree. C.)
powder extrusion dies; dies
for hot extrusion of aluminium
metal; some induction heating
equipment components; non-
ferrous liquid metal pump parts.
High temperatures
Brass, copper and steel extru-
(from about 700.degree. C.
sion dies; engine components
to about 1000.degree. C.)
such as hot plates, piston tops
and valve seats; non-ferrous
liquid metal pump parts.
Very high temperatures
Dies for extrusion of steel,
(in excess of 1000.degree. C.)
zirconium, titanium and other
difficult metals.
______________________________________
It is an objective of the present invention to provide ceramic materials which have properties that make them particularly suitable for use in a required temperature range.
DISCLOSURE OF THE PRESENT INVENTION
The present inventors have found that to produce magnesia partially stabilised zirconia ceramics that have exceptional thermal shock resistance, a material that has a microstructure of the material described in the specifications of U.S. Pat. No. 4,279,655 may be used, but the amount of monoclinic zirconia within the grains of the ceramic material (that is, excluding monoclinic zirconia in the grain boundaries) has to be increased.
This discovery has enabled the present invention to develop a range of partially stabilised zirconia
REFERENCES:
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patent: 4513089 (1985-04-01), Kummer et al.
patent: 4525464 (1985-06-01), Claussen et al.
Duwez et al, "Stabilization of Zirconia with Calcia and Magnesia", J. Am. Chem. Soc. (5-1952), vol. 35, No. 5, pp. 107-113.
Drennan et al, "Effect of SrO Additions on the Grain Boundary Microstructure and Mechanical Properties of Magnesia-Partially-Stabilized Zirconia", J. Am. Ceramic Soc., V 69, 7, pp. 541-546, Jul. 1986.
Garvie Ronald C.
Hannink Richard H. J.
Hughan Robert R.
Murray Michael J.
Stringer Robert K.
Commonwealth Scientific and Industrial Research Organization
Marquis Steven P.
Niebling John F.
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