# US 8,771,585 B2 · Method for manufacturing ceramic components

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- Number: US 8,771,585 B2
- Document ID: US8771585B2
- Status: Granted
- Kind: B2
- Application number: 13/060,099
- Filed: 2008-08-29
- Published: 2011-10-27
- Granted: 2014-07-08
- Earliest claimed: 2008-08-29
- Assignees: SKF GmbH
- Applicants: Zhijian Shen; Saeid Esmaeilzadeh; Katarina Flodstrom; Charlotte Vieillard
- Inventors: Zhijian Shen; Saeid Esmaeilzadeh; Katarina Flodstrom; Charlotte Vieillard
- Web page: https://patentgrep.com/patent/US8771585B2

## CPC

- C04B 35/593: obtained by pressure sintering
- C04B 35/5626: {based on tungsten carbides}
- C04B 35/597: based on silicon oxynitride, {e.g. SIALONS}
- C04B 35/62655: {Drying, e.g. freeze-drying, spray-drying, microwave or supercritical drying}
- C04B 2235/3225: Yttrium oxide or oxide-forming salts thereof
- C04B 2235/3869: Aluminium oxynitrides, e.g. AlON, sialon
- C04B 2235/3873: Silicon nitrides, e.g. silicon carbonitride, silicon oxynitride
- C04B 2235/5436: micrometer sized, i.e. from 1 to 100 micron
- C04B 2235/5445: submicron sized, i.e. from 0,1 to 1 micron
- C04B 2235/6562: Heating rate
- C04B 2235/6567: Treatment time
- C04B 2235/661: Multi-step sintering
- C04B 2235/767: Hexagonal symmetry, e.g. beta-Si3N4, beta-Sialon, alpha-SiC or hexa-ferrites
- C04B 2235/77: Density
- C04B 2235/78: Grain sizes and shapes, product microstructures, e.g. acicular grains, equiaxed grains, platelet-structures
- C04B 2235/785: Submicron sized grains, i.e. from 0,1 to 1 micron
- C04B 2235/788: Aspect ratio of the grains
- C04B 2235/80: Phases present in the sintered or melt-cast ceramic products other than the main phase
- C04B 2235/96: Properties of ceramic products, e.g. mechanical properties such as strength, toughness, wear resistance
- C04B: LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE {(roofing granules E04D7/005)}; CERAMICS (devitrified glass-ceramics C03C10/00); REFRACTORIES; TREATMENT OF NATURAL STONE

## Abstract

The invention concerns a method for manufacturing a ceramic material with pseudo-isotropic microstructure. The method for tailoring the microstructure for manufacturing of sintered ceramic components involves a spark plasma sintering (SPS) process. By performing the SPS process in at least two steps it is possible to separate densification from grain growth. An initial sintering step at a first temperature and a first pressure, followed by a controlled grain growth step at a higher temperature and lower pressure makes it possible to manufacture ceramic components with controlled microstructure and improved mechanical properties.

## Claims

### Claim 1

A method for manufacturing ceramic components comprising silicon nitride or sialon or mixtures thereof, with a tailored microstructure by a spark plasma sintering (SPS) procedure in an SPS unit, wherein a powder or pre-formed green body in the SPS unit is treated in a first densification step at a first temperature and a first pressure in order to densify the powder or green body, whereafter the temperature is increased and the pressure is decreased such that the material in the SPS unit is treated in a second grain growth step following the first step at a second temperature which is higher than the first temperature and a second pressure that is lower than the first pressure in order to promote anisotropic grain growth of whisker-like β-silicon nitride and/or β-sialon grains in the component, wherein a holding time of the first densification step is long enough to obtain a density of not less than 97 percent of the theoretical density.

### Claim 2 (depends on 1)

The method of claim 1, wherein the powder or pre-formed green body additionally comprises rare earth oxides, aluminium nitride, aluminium oxide and/or oxynitrides of silicon aluminium.

### Claim 3 (depends on 1)

The method of claim 1, wherein the powder or green body is treated in the first step at a first pressure, a uniaxial pressure between 20 and 150 MPa, a heating rate of 5 to 600 degrees Celsius per minute and a first temperature between 1400 and 1600 degrees Celsius and that the second temperature of the following grain growth step is between 1600 and 1800 degrees Celsius and the second pressure is below 10 MPa.

### Claim 4 (depends on 3)

The method of claim 3, wherein the holding time of the of the following grain growth step is between 1 and 60 minutes.

### Claim 5 (depends on 4)

The method of claim 4, wherein the holding time of the following grain growth step is between 3 and 20 minutes.

### Claim 6 (depends on 3)

The method of claim 3, wherein the uniaxial pressure is between 30 and 70 MPa.

### Claim 7 (depends on 3)

The method of claim 3, wherein the first temperature is between 1450 and 1600 degrees Celsius.

### Claim 8 (depends on 3)

The method of claim 3, wherein the second pressure is below 5 MPa.

### Claim 9 (depends on 1)

The method of claim 1, wherein a holding time of the first densification step is long enough to obtain a density of or not less than 99 percent of the theoretic density.

### Claim 10 (depends on 9)

The method of claim 9, wherein the holding time of the first densification step is between 1 and 60 minutes.

### Claim 11 (depends on 10)

The method of claim 10, wherein the holding time of the first densification step is between 3 and 20 minutes.

### Claim 12 (depends on 9)

The method of claim 9 wherein the second temperature of the following grain growth step is between 1650 and 1750 degrees Celsius.

### Claim 13 (depends on 1)

The method of claim 1, wherein the whisker-like grains have a width and a length, the length being at least about 1.76 times longer than the width.