GB2211184A

GB2211184A - A tool for machining a carbon material

Info

Publication number: GB2211184A
Application number: GB8824115A
Authority: GB
Inventors: Kyoichi Ichinoseki; Takashi Miyatani; Hiraku Yamazaki; Katsumi Hoshina
Original assignee: Toshiba Ceramics Co Ltd
Current assignee: Coorstek KK
Priority date: 1987-10-15
Filing date: 1988-10-14
Publication date: 1989-06-28
Anticipated expiration: 2008-10-14
Also published as: GB2211184B; GB8824115D0; DE3834742A1; JPH01103205A

Description

A TOOL FOR MACHINING A CARBON MATERIAL AND PROCESS OF PRODUCING IT The

present invention relates to a tool for machining carbon material and a process of producing the tool.

Various tools made of cemented carbide have been used for machining carbon materials. However, conventional carbide tools are easily worn by carbon so that they have only a short life.

An object of the present invention is to provide a tool for machining carbon material, which tool has a long life.

Another object of the present invention is to provide a process of producing the tool.

According to the present invention, the tool for machining carbon material is made of a ceramicscomposite material comprising 50 to 95 vol. % of alumina (A1203) matrix having a particle diameter of 0.1 to 2 microns and 5 to 50 vol.t of silicon carbide whisker (SiC whisker) having a diameter of 0.5 to 2.5 microns and a length of 10 to 80 microns. The alumina matrix and silicon carbide whisker are uniformly dispersed in and mixed with each other.

-10 to 50% of the alumina matrix may be TiB2 or ZrB2 having a particle diameter of 0.5 to 10 microns.

The ceramics-composite material has a density higher than 98% of the theoretical density.

A tool according t o the present invention can be produced in the following manner.

A prescribed amount of alumina having a particle diameter of 0.1 to 2 microns is mixed with a sintering auxiliary such as MgO and a volatile medium such as water and acetone. The mixture is pulverized and mixed by a wet process. The pulverized mixture is further mixed with a prescribed amount of silicon carbide whisker which has previously been disintegrated into small particles of 0.5 to 2.5 microns in diameter and 10 to 80 microns in length by a pot mill or the like. The mixture is mixed by a wet process. It is preferable that the alumina matrix and the silicon carbide whisker are uniformly dispersed in each other, with the formation of silicon carbide whisker aggregate minimized. The obtained slu-rry is freed of the volatile medium or water used for wet mixing. The dried powder composed of alumina and silicon carbide whisker is granulated. The granules are sintered into a ceramic s-compos i te material of proper size by using a hot press or the like. The hot press is operated with a proper pressure so that the resulting ceramics-composite material has a density higher than 98% of the theoretical density. The thus obtained ceramicscomposite material is finished by a diamond tool into a proper shape which is suitable for machining carbon material.

The tool of the present invention should dontain a proper amount of silicon carbide whisker. With a content less than 5 volA# the ceramicscomposite material lacks sufficient fracture toughness and the tool is liable to chip. With a content in excess of 50 volAr the ceramics- composite material has a low density and is porous, and the tool is also liable to chip. The ceramics-composite material has a preferred fracture toughness when it contains 5 to 50 volA of silicon carbide whisker.

Examples of the tool are an end mill, a cutting chip and a blade for counterboring a susceptor which supports wafers in semiconductor processing. Examples of silicon carbide whisker are SCW of Tateho Chemical Industries Co. Ltd.,, SC-7 of Arco Chemical Co. and TWL of Tokai Carbon Co.

Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:- Fig. 1A is a front elevational view of an end mill according to the present invention.

Fig.' IB is a bottom plan view of the end mill of Fig. 1A.

Pig 2A is a top plan view of a f irst embodiment of a cutting tip according to the present invention.

Fig. 2B is side elevational view of the cutting tip of Fig. 2A.

Fig. 3A is a top plan view of a second embodiment of a cutting tip according to the present invention.

Fig. 3B is a side elevational view of the -cutting tip of Fig. 3A.

Fig. 4A is a front elevational view of a blade for counterboring a susceptor according to the present invention.

Fig. 4B is a side elevational view of the blade of Fig. 4A.

Figures 1A, 1B, 2Ai 2Bi 3A0 3B, 4A and 4B show tools which can be produced according to the present invention for working on carbon materials. In each case,, the tool is conventional in shape but is made from a material and by a process which ensures long life and high quality.

Examples of the manufacture of counterboring tools as shown in Fig. IA and Fig. 1B are set forth below. It will be understood that the examples set forth below are also applicable for the manufacture of the tools shown in the other dravingst the only_ difference being in the shape of the final tool.

Example 1

75.4g of alumina matrix was added to 0.5 wt.% of MgO for making a mixture. The mixture was added to 450 ml of acetone and pulverized and then mixed.

- To the pulverized mixture was added 3.29 of silicon carbide whisker which had previously been disintegrated by a pot mill. The silicon carbide whisker was NSW of Tateho Chemical Industries Co.i Ltd. The resulting mixture was composed of alumina and silicon carbide whisker in the ratio of 95:5 by molume. Thust there was obtained 439g of a slurry in which silicon carbide whisker was uniformly dispersed. The slurry was freed of acetone by evaporation. The dried powder was granulated. The granule (31g) composed of alumina and silicon carbide whisker was subjected to hot pressing at 1,800C for 0.5 hours under a pressure of 49 MPa. Thus# there was obtained a ceramics-composite material. The cer am ics- composite material was fabricated by a diamond tool into a tool for machining a carbon material which was in the shape of a blade for counterboring a susceptor, as shown in Pigs. 1A and 1B. The tool was evaluated for hardness# bending strength, toughness, and abrasion resistance, in comparison with a conventional cemented carbide tool for machining a carbon material. The results are shown in Table 1.

Example 2

The same procedure as in Example 1 was repeated except that the ratio of alumina and silicon carbide whisker was changed to 75:25 by volume. The tool was evaluated in the same manner as in Example 1 in comparison with a conventional tool. The results are shown in Table 1.

6 Exam21e 3 The same procedure as in Example 1 was repeated except that the ratio of alumina and silicon carbide whisker was changed to 50:50 by volume. The tool was evaluated in the same manner as in Example 1 -in comparison with a conventional tool. The results are shown in Table 1.

COMPARATIVE EXAMPLES The same procedure as in Example 1 was repeated except that the ratio of alumina and silicon carbide whisker was changed to 100:0 and 40:60 by volume. In addition. a tool of silicon nitride ceramics was also prepared. These three kinds of tools were evaluated in the same manner as in Example 1 in comparison with a conventional tool. The results are shown in Table 1.

c Table 1

Bending Fracture Example Hardness strength toughness Relative No. composition of specimen (HV) (kg/mm2) MParn- life Prior art Cemented carbide 1300 130 30 1 Example

1 A1203+5v01%SiCM 1700 60 3.5 1.5 Example

2 A1203+25voMiC(W) 1900 25 5 2.5 Example

3 A1203+5OvoMiC(W) 2200 65 6 1.5 Compar ative Example

1 A1203 1650 55 3 Comparative Example 2 A1203+6OVOMiC(W) 2200 40 3.5 0.5 Compar ative Example

3 Si3N4 1650 90 7 1 Remarks: (1) SiC(W) represents silicon carbide whisker.

(2) The relative life is based on the life of a conventional cemented carbide tool which is regarded as 1.

It is noted from the above-mentioned results that the tool made of alumina alone suffered from edge nicks on account of low fracture toughness. The tool made of a ceramics-composite material containing alumina and more than 60 vol. of silicon carbide whisker is inferior to the tool made of a ceramics- -composite material according to the present invention containing alumina and 5 to 50 vol.% of silicon carbide whisker, in regard to abrasion resistance# edge resistance to chipping and life, because the former has a lower density than the latter. Also, the tool of the present invention is superior in abrasion resistance to a cemented carbide tool for machining a carbon material.

Having described specific embodiments of the present invention, it is believed obvious that modifications and variations are possible in the light of the above teachings.

T 1.

9

Claims

CLAIMS:

1. A tool. for machining a carbon material, which is made of a uniformly dispersed and mixed material comprising:

a) 50 to 95 vol. of alumina matrix -having a particle diameter of 0.1 to 2 microns, and b) 5 to 50 vol.% of silicon carbide whisker having a diameter of 0.5 to 2. 5 microns and length of 10 to 80 microns.

2. A tool as cl in claim It wherein the material has a density higher than 98% of the theoretical density.

3. A tool as claimed in claim l# in which the alumina matrix comprising 50 to 90 vol.% of alumina having a particle diameter of 0.1 to 2 microns and 10 to 50 vol.% of TiB2 or ZrB2 having a particle diameter of 0.5 to 10 microns.

4. A tool as claimed in claim 1, wherein the material contains M90 as a sintering auxiliary.

5. A tool as claimed in claim 1, wherein the material contains water and acetone as a volatile medium.

6. A tool as claimed in claim lt wherein the tool is an end mill.

7. A tool -as claimed in. claim 1, wherein the tool is a cutting chip.

8. A tool as claimed in claim l# wherein the tool is a blade for counterboring a susceptor which supports wafers in semiconductor processing.

9. A process for producing a tool, for machining a carbon material, comprising the steps of mixing 50 to 95 volA of alumina (A1203) matrix having a particle diameter of 0.1 to 2 microns with a sintering auxiliary and volatile medium; pulverizing and mixing the mixture by a wet process; mixing the pulverized mixture with 5 to 50 volA of silicon carbide whisker (SiC whisker) having a diameter of 0.5 to 2.5 microns and length of 10 to 80 microns by a wet process to be slurry; freeing the slurry of the volatile medium; granulating the volatile freed powder; sintering the granules into a ceramicscomposite material of proper size and of a density higher than 98% of the theoretical density; and machining the ceramics-coaposite material into a proper shape which is suitable for machining a carbon material.

10. A process as claimed in claim 9. wherein the sintering is a hot press.

11. A process as claimed in claim 9, in which the alumina matrix comprising 50 to 90 volA of alumina having a particle diameter of 0.1 to 2 microns and 10 to 50 volA of TiB2 or UB2 having a particle diameter of 0.5 to 10 microns.

12. A process as claimed in claim 9, wherein the sintering auxiliary is MgO.

13. A process as claimed in claim 9, wherein the volatile medium is water and acetone.

14. A process as claimed in claim 9, wherein the alumina matrix and silicon carbide whiskerare uniformly dispersed in each other, with the formation of silicon carbide whisker aggregate minimized.

15. A tool for machining a carbon material substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.

16. A process for producing a tool, for machining a carbon material substantially as hereinbefore described with reference to the accompanying drawings.

r Published 1989 at The Patent Office, State House, 86171 High Rolborn, London WC1R4TP. Further copies maybe obtained from The Patent Omce. Sales Branch, St Mary Cray, Orpington, Kent BR5 3RD. Printed by Multiplex techniques ltd, St Mary Cray, Kent, Con. 1187