# US 2021/0276923 A1 · Composite ceramic bodies and applications thereof

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- Number: US 2021/0276923 A1
- Document ID: US20210276923A1
- Status: Published application
- Kind: A1
- Application number: 16/703,205
- Filed: 2019-12-04
- Published: 2021-09-09
- Earliest claimed: 2019-12-04
- Applicants: Kennametal Inc.
- Inventors: Jason GOLDSMITH
- Web page: https://patentgrep.com/patent/US20210276923A1

## CPC

- C04B 35/597: based on silicon oxynitride, {e.g. SIALONS}
- C04B 35/6455: {Hot isostatic pressing}
- C04B 2235/3206: Magnesium oxides or oxide-forming salts thereof
- C04B 2235/3225: Yttrium oxide or oxide-forming salts thereof
- C04B 2235/3873: Silicon nitrides, e.g. silicon carbonitride, silicon oxynitride
- C04B 2235/3878: Alpha silicon nitrides
- C04B 2235/3882: Beta silicon nitrides
- C04B 2235/75: Products with a concentration gradient
- C04B 2235/767: Hexagonal symmetry, e.g. beta-Si3N4, beta-Sialon, alpha-SiC or hexa-ferrites
- C04B 2235/80: Phases present in the sintered or melt-cast ceramic products other than the main phase
- C04B 2235/85: Intergranular or grain boundary phases
- C04B 2235/96: Properties of ceramic products, e.g. mechanical properties such as strength, toughness, wear resistance
- C04B 2235/963: Surface properties, e.g. surface roughness
- 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

In one aspect, ceramic bodies are described herein exhibiting composite architecture. Briefly, a composite ceramic body comprises a bulk region including a mixture of alpha-SiAlON and beta-SiAlON, and a surface region covering the bulk region, the surface region having a residual stress of −500 MPa to 500 MPa and a thickness of at least 5 μm.

## Claims

### Claim 1

A composite ceramic body comprising:
a bulk region comprising a mixture of alpha-SiAlON and beta-SiAlON; and
a surface region covering the bulk region, the surface region comprising a mixture of alpha-SiAlON and beta-SiAlON and having a residual stress of −100 MPa to 300 MPa and a thickness of at least 5 μm, wherein the composite ceramic body is in the as-sintered state.

### Claim 2 (depends on 1)

The composite ceramic body of claim 1, wherein alpha-SiAlON is present in the surface region in an amount greater than 95 weight percent of the surface region.

### Claim 3 (depends on 1)

The composite ceramic body of claim 1, wherein alpha-SiAlON is present in the surface region in an amount greater than 98 weight percent of the surface region.

### Claim 4 (depends on 1)

The composite ceramic body of claim 1, wherein the bulk region comprises beta-SiAlON in an amount greater than 70 weight percent.

### Claim 5 (depends on 1)

The composite ceramic body of claim 1, wherein the surface region comprises mixed metal oxide.

### Claim 6 (depends on 1)

The composite ceramic body of claim 1, wherein the bulk region comprises less than 20 weight percent alpha-SiAlON.

### Claim 7 (depends on 1)

The composite ceramic body of claim 1, wherein the bulk region further comprises an additive phase comprising metal oxides, metal oxynitrides, metal borides or mixtures thereof.

### Claim 8 (depends on 7)

The composite ceramic body of claim 7, wherein the metal oxides, metal oxynitrides, and metal borides comprise one or more metallic elements selected from the group consisting of aluminum, silicon and metallic elements of Groups IIIB-VIB of the Periodic Table.

### Claim 9 (depends on 8)

The composite ceramic body of claim 8, wherein the metal oxides comprise one or more Lanthanide series elements.

### Claim 10 (depends on 7)

The composite ceramic body of claim 7, wherein the additive phase comprises Y2Si3N4O3.

### Claim 11 (depends on 7)

The composite ceramic body of claim 7, wherein the additive phase is located at SiAlON grain boundaries.

### Claim 12 (depends on 7)

The composite ceramic body of claim 7, wherein the additive phase forms one or more solid solutions with alpha-SiAlON, beta-SiAlON, or silicon nitride.

### Claim 13 (depends on 7)

The composite ceramic body of claim 7, wherein the one or more additive phase is present in an total amount of 0.1 to 15 weight percent.

### Claim 14 (depends on 7)

The composite ceramic body of claim 7, wherein the additive phase is present in an amount of 2-5 weight percent.

### Claim 15 (depends on 1)

The composite ceramic body of claim 1, wherein the surface region has a Vickers hardness of at least 15.5 GPa.

### Claim 16 (depends on 1)

The composite ceramic body of claim 1, wherein the bulk region has a fracture toughness of at least 4.5 MPa·m0.5.

### Claim 17 (depends on 1)

The composite ceramic body of claim 1 having a surface roughness of less than 600 nm.

### Claim 18 (depends on 1)

The composite ceramic body of claim 1 having a surface roughness of 300-600 nm.