US 5,449,647 AGrant

Silicon Carbide Whisker Reinforced Cutting Tool Material

Issue Date:1995-09-12

•15 Claims

Abstract

There is now provided an oxide based ceramic cutting insert for chipforming machining of heat resistant alloys comprising a ceramic oxide based matrix and 5-50% by volume of homogeneously dispersed whiskers of silicon carbide. The whiskers have an average length of 4-7 .mu.m, with substantially all of the whiskers having a length less than 10 .mu.m.

Metadata

Assignee

Sandvik AB

Inventor

Gunnar Brandt

Application Information

Application Number:US 2461358

Filing Date:1994-05-19

Priority Date:1994-01-21

Art Unit:118

Classifications

IPC:

C04B 35117C04B 35577

Field of Search:

5015189;95;127;128309

Patent Drawings

This patent does not have any drawings.

Description

Background of the Invention

The present invention relates to ceramic cutting tool materials particularly useful for machining of heat resistant alloys and particularly to such cutting tool materials in which monocrystalline silicon carbide whiskers are uniformly distributed in an alumina matrix.

U.S. Pat. No. 4,543,345 (Wei) discloses a material comprising a matrix selected from the group consisting of alumina, mullite and B.sub.4 C having homogeneously dispersed therein 5-60 vol % of silicon carbide whiskers said silicon carbide whiskers having a micro-crystalline structure and a size range of about 0.6 .mu.m in diameter and a length of 10-80 .mu.m with an average aspect ratio (length/diameter) of 75. Similar values are found in U.S. Pat. No. 4,961,757 (Rhodes). The latter patent discloses that these materials are useful for metal cutting.

It is generally understood that a high aspect ratio promotes the toughening mechanisms crack bridging and pull-out. See Baeck and Kim, "The Effect of Whisker Length on the Mechanical Properties of Alumina-SiC-Whisker Composites", J Of Mat Sci 24 (1989), p. 1589-1593; and Wadsworth and Stevens, "The Influence of Whisker Dimensions on the Mechanical Properties of Cordierete/SiC Whisker Composites", J of The European Cer Soc 9 (1992), p. 153-163.

Objects and Summary of the Invention

It is an object of this invention to avoid or alleviate the problems of the prior

It is further an object of this invention to provide ceramic cutting tool materials particularly useful for machining of heat resistant alloys and particularly to such cutting tool materials in which monocrystalline silicon carbide whiskers are uniformly distributed in an alumina matrix.

In one aspect of the invention there is provided an oxide based ceramic cutting insert for chipforming machining of heat resistant alloys comprising an alumina based matrix and 5-50% by volume of homogeneously dispersed whiskers of silicon carbide wherein substantially all of the whiskers have a length less than 10 .mu.m.

In another aspect of the invention there is provided a method of producing an oxide based ceramic cutting insert for chipforming machining of heat resistant alloys comprising an alumina based matrix and 5-50% by volume of homogeneously dispersed whiskers of silicon carbide by forming a mixture comprising alumina, sintering additives and grain growth inhibitors and 5-50% by volume of silicon carbide whiskers, wherein substantially all of the silicon carbide whiskers in said mixture have a length less than 10 .mu.m.

In another aspect of the invention there is provided a method of cutting metal wherein a curing tool is brought into contact with a metal workpiece and the cutting tool and metal workpiece move relative to each other whereby metal is removed by the cutting tool from the metal workpiece, the improvement comprising using an oxide based ceramic cutting insert comprising an alumina based matrix and 5-50% by volume of homogeneously dispersed whiskers of silicon carbide wherein substantially all of the whiskers have a length less than 10 .mu.m.

Detailed Description of the Preferred Embodiments of the Invention

It has now surprisingly been found that substantially smaller aspect ratios in the order of 10 give advantageous behavior when using the composite material as cutting tools for machining heat resistant alloys.

The ceramic cutting tool material according to the present invention comprises an alumina based matrix with 10-50%, preferably 15-45% by volume of homogeneously dispersed whiskers based upon silicon carbide. The average alumina grain size is less than 5 .mu.m and typically in the order of 2 .mu.m.

The diameter of the whiskers is less than 1 .mu.m, preferably 0.4-0.7 .mu.m and their average length is preferably 4-7 .mu.m (average aspect ratio about 10) with a standard deviation of 2-5 .mu.m, preferably about 4 .mu.m. Alternatively, substantially all of the whiskers have a length less than 10 .mu.m. By "substantially all" is meant that at least 95 %, preferably at least 98%, most preferably at least 99%, of the whiskers have a length less than 10 .mu.m.

Alternatively, the alumina matrix further contains up to 20 vol % ZrO.sub.2. This addition of zirconia may add further toughening to the material as described in U.S. Pat. No. 4,657,877.

According to the present invention, the ceramic composites are prepared by mixing alumina powder and conventional sintering additives and grain growth inhibitors with monocrystalline SiC whiskers with any suitable mixing technique.

After drying, the mixture is hot pressed or hot isostatically pressed to a density at least 99% of theoretical density.

The aspect ratio of the whiskers is not very much affected by the mixing technique and the hot pressing operation although it is expected that at least the longer whiskers will be broken. The desired aspect ratio of the whiskers can be adjusted by premilling of the whiskers prior to mixing with alumina. The aspect ratio of commercial SiC whiskers are normally much higher than 10. However, such premilling can be used to break the whiskers and thus reduce the aspect ratio. Premilling conditions can be adjusted in accordance with known techniques to produce suitable whiskers.

The invention is additionally illustrated in connection with the following Examples which are to be considered as illustrative of the present invention. It should be understood, however, that the invention is not limited to the specific details of the Examples.

Example 1

Alumina-30 vol % SiC whisker composites with different length of the whiskers were produced by the following procedure. The raw materials used are listed in Table 1.

The whisker lengths of the raw material and after the different milling steps were measured after dispersion of the whiskers at a low concentration in an ammonia solution and subsequently drying on a specimen holder. SEM micrographs were then analyzed manually in a Quantimet 570 picture analyzer from Cambridge Instruments.

The composition was kept constant for all variants at 25 weight % SiC.sub.W and 0.1 weight % MgO and Y.sub.2 O.sub.3 respectively. All compositions were hot pressed at 1825.degree. C. for 100 min at 25 MPa to discs of diameter 80 mm.

Table 2 shows the premilling times that were used for the evaluation of varying aspect ratio on cutting performance and corresponding whisker lengths.

The sintered materials were characterized with respect to density, hardness, fracture toughness and fracture strength. Hardness and toughness were measured using a Vicker's indentation with a 10 kg load. All measurements were performed on the plane perpendicular to the hot pressing direction. Fracture toughness was calculated according to the formula ##EQU1## where p=the force in N and

c=the crack length after the indentation.

The fracture strength was measured in a three point bending test. Mean fracture stress was calculated from 9 specimens 13.3.times.3.5.times.2.0 mm, span 9 mm, load rate 50 N/s. The measured values can be found in Table 3.

Example 2

The materials were tested in metal cutting operations. For this purpose inserts with ISO designation RNGN 120400 T01020 were produced from the hot pressed discs.

Two kinds of turning tests were performed; one DOC(Depth of cut) notch resistance test and one toughness test.

The DOC notch resistance test was conducted by wet turning on a cylindrical Inconel 718 bar, using the following data:

Feed rate=0.15 mm/rev

Cutting speed=250 m/min

Depth of cut=1.5 mm

The toughness test was performed dry using a steel (SS 2242) plate workpiece. The shape in combination with an increasing feed rate results in fracture. The time until fracture is a measure of the toughness of the cutting tool material. The turning data was:

Feed rate=0.1 mm/rev, increased 0.1 mm/rev every minute

Cutting speed=90 m/min

Depth of cut=1.5 mm

Results from the cutting tests can be found in table 4.

From the tests it can be concluded that variant B is slightly more wear resistant and shows a better toughness behavior than variant A with unmilled whiskers. Too much milling reduces both wear resistance and toughness behavior.

The principles, preferred embodiments and modes of operation of the present invention have been described in the foregoing specification. The invention which is intended to be protected herein, however, is not to be construed as limited to the particular forms disclosed, since these are to be regarded as illustrative rather than restrictive. Variations and changes may be made by those skilled in the art without departing from the spirit of the invention.

Claims

What is claimed is:

1. An oxide based ceramic cutting insert for chipforming machining of heat resistant alloys comprising an alumina based matrix and 5-50% by volume of homogeneously dispersed whiskers of silicon carbide wherein at least 95% of the whiskers have a length less than 10 .mu.m.

2. The oxide based ceramic cutting insert of claim 1 wherein the average length of the whiskers is about 4-7 .mu.m.

3. The oxide based ceramic cutting insert of claim 1 wherein the matrix further contains up 20 vol % ZrO.sub.2.

4. The oxide based ceramic cutting insert of claim 1 wherein said whiskers have a diameter less than 1 .mu.m.

5. The oxide based ceramic cutting insert of claim 4 wherein said whiskers have a diameter of 0.4-0.7 .mu.m.

6. The oxide based ceramic cutting insert of claim 1 wherein said whiskers have an average aspect ratio of about 10.

7. The oxide based ceramic cutting insert of claim 1 wherein at least 98% of the whiskers have a length less than 10 .mu.m.

8. The oxide based ceramic cutting insert of claim 7 wherein in at least 99% of all the whiskers have a length less than 10 .mu.m.

9. A method of producing an oxide based ceramic cutting insert for chipforming machining of heat resistant alloys comprising an alumina base matrix and 5-50% by volume of homogeneously dispersed whiskers of silicon carbide, the method comprising forming a mixture comprising alumina, sintering additives and grain growth inhibitors and 5-50% by volume of silicon carbide whiskers, wherein at least about 95% of the silicon carbide whiskers in said mixture have a length less than 10 .mu.m and sintering the mixture.

10. The method of claim 9 wherein the average length of the whiskers is about 4-7 .mu.m.

11. A method of cutting metal, the method comprising contacting a metal workpiece with a cutting tool and moving the cutting tool and metal workpiece relative to each other so that metal is removed from the metal workpiece by the cutting tool, the cutting tool comprising an oxide based ceramic cutting insert comprising an alumina based matrix and 5-50% by volume of homogeneously dispersed whiskers of silicon carbide wherein at least about 95% of the whiskers have a length less than 10 .mu.m.

12. The method of claim 11 wherein said composite contains 15-45% by volume of said whiskers.

13. The method of claim 11 wherein the average length of the whiskers is about 4-7 .mu.m.

14. The method of claim 9, wherein at least 99% of the whiskers have a length less than 10 .mu.m.

15. The method of claim 11, wherein at least 99% of the whiskers have a length less than 10 .mu.m.

Patent Citations (119)

Patent	Date	Inventor
US492767	1893-02-01	Acheson
US560291	1896-05-01	Acheson
US718892	1903-01-01	Acheson
US722792	1903-03-01	Acheson
US722793	1903-03-01	Acheson
US723631	1903-03-01	Acheson
US1028303	1912-06-01	Tone
US2294056	1940-04-01	Thompson
US2979414	1961-04-01	Rijshkewitch et al.
US3335049	1967-08-01	Pultz
US3386840	1968-01-01	Gruber
US3407090	1968-10-01	Hertl
US3459842	1969-08-01	Wakefield
US3507632	1970-04-01	Swoboda et al.
US3541672	1970-11-01	Hulse
US3575789	1971-04-01	Siefert et al.
US3813340	1974-08-01	Knippenberg et al.
US3833389	1974-09-01	Korreya et al.
US3933984	1976-01-01	Kimura et al.
US3972161	1976-08-01	Zoiss
US4044934	1977-01-01	Prochazka
US4060412	1977-11-01	Divecha
US4063908	1977-11-01	Ogawa et al.
US4097293	1978-06-01	Komega et al.
US4158687	1979-06-01	Yajima et al.
US4218253	1980-08-01	Dworak et al.
US4240835	1980-12-01	Laskow et al.
US4259112	1981-03-01	Dolowy, Jr. et al.
US4280973	1981-07-01	Moskowitz et al.
US4284612	1981-08-01	Horne, Jr. et al.
US4314852	1982-02-01	Brennan et al.
US4320203	1982-03-01	Brandt et al.
US4323323	1982-04-01	Lumby et al.
US4324843	1982-04-01	Brennan et al.
US4332909	1982-06-01	Nishida et al.
US4343909	1982-08-01	Adams et al.
US4366254	1982-12-01	Rich et al.
US4388255	1983-06-01	Simpson
US4394231	1983-07-01	Nicolas
US4410635	1983-10-01	Brennan et al.
US4412854	1983-11-01	Layden
US4453343	1984-06-01	Grimes, Sr.
US4463058	1984-07-01	Hood et al.
US4464192	1984-08-01	Layden et al.
US4485179	1984-11-01	Brennan et al.
US4500504	1985-02-01	Yamamoto
US4507224	1985-03-01	Toibana et al.
US4526875	1985-07-01	Yamamoto et al.
US4543345	1985-09-01	Wei
US4554201	1985-11-01	Andreev et al.
US4585500	1986-04-01	Minjolle et al.
US4657877	1987-04-01	Becher et al.
US4666467	1987-05-01	Matsamoto et al.
US4673658	1987-06-01	Gadkaree et al.
US4710940	1987-12-01	Sipes, Jr.
US4739507	1988-04-01	Byer et al.
US4745091	1988-05-01	Landingham
US4746635	1988-05-01	Inoue et al.
US4749667	1988-06-01	Jun et al.
US4789277	1988-12-01	Rhodes et al.
US4849381	1989-07-01	Brandt et al.
US4889835	1989-12-01	Niihara et al.
US4916092	1990-04-01	Tiegs et al.
US4961757	1990-10-01	Rhodes et al.
US4994416	1991-02-01	Tiegs et al.
US5017528	1991-05-01	Tiegs et al.
US5059564	1991-10-01	Mehrotra et al.
US5123935	1992-06-01	Kanamoru et al.
US5177037	1993-01-01	Schuldies
US5246894	1993-09-01	Okuda et al.
US5250477	1993-10-01	Baldoni, II et al.
US5346517	1994-09-01	Collin
BEX767030	1971-11-01
EPX67584	1982-12-01
EPX85744	1983-08-01
EPX194811	1986-09-01
EPX202504	1986-11-01
EPX208910	1987-01-01
EPX351134	1990-01-01
EPX579587	1994-01-01
JPX47803	1972-01-01
JPX48-027891	1973-04-01
JPX48-30803	1973-04-01
JPX49-40121	1974-10-01
JPX52-47803	1977-04-01
JPX53-27517	1978-08-01
JPX56-92180	1981-07-01
JPX57-146237	1982-09-01
JPX58-91073	1983-05-01
JPX58-48621	1983-10-01
JPX59-30778	1984-02-01
JPX59-54680	1984-03-01
JPX59-102861	1984-06-01
JPX59-102862	1984-06-01
JPX59-137366	1984-08-01
JPX60-05079	1985-01-01
JPX62-36991	1987-02-01
JPX8963969	1989-03-01
SEX7100577	1975-02-01
CHX586166	1977-03-01
GBX954285	1964-04-01
GBX2157282	1985-10-01
SUX346281	1972-08-01
SUX353930	1972-11-01
SUX380615	1973-07-01
SUX381645	1973-08-01
SUX446489	1975-04-01
SUX478823	1975-10-01
SUX477977	1975-11-01
SUX481578	1975-11-01
SUX483378	1975-12-01
SUX484204	1975-12-01
SUX530017	1976-11-01
SUX530018	1976-11-01
SUX533577	1976-11-01
SUX629197	1978-09-01
SUX657003	1979-04-01
WOXWO86/05480	1986-09-01
WOXWO92/21635	1992-12-01

Non-Patent Literature (56)

"Toughening Behavior in SiC-Whisker-Reinforced Alumina", Becher et al., Metals and Ceramics Div., Oak Ridge National Laboratory, Oak Ridge, TN 37831 Dec. 1984.
"Development of SiC-Whisker-Reinforced Ceramics", Wei et al., Oak Ridge National Lab., Oak Ridge, TN 37830, Ceramic Bulletin, vol. 64, No. 2 (1985) no month.
"Alumina Ceramic Tools, Mitsuhiko Furukawa", Nippon Tungsten Co., Ltd., Fukuoka, Japan, Ceramic Bulletin, vol. 62, No. 12 (1983) pp. 1384-1387 no month.
"Summary of Japan's Innovative Industrial Materials", G. Fisher, Ceramic Bulletin, vol. 64, No. 1 (1985) pp. 34-37 no month.
1986 IR100 Competition Winners, Research & Development, Oct. 1986.
"Final Report on Development of Improved Cutting Tool Materials", Oct. 1965, AFML-TR-65-306, Whitney et al.
"New and Improved Cutting Tool Materials", Mar. 1969, AFML-TR-69-50, Whitney et al.
"Metals and Ceramics Division Progress Report", Published Sep. 1984, Oak Ridge National Laboratory.
"Preliminary Reports, Memoranda and Technical Notes of the Materials Research Council Summer Conference, Department of Materials and Metallurgical Engineering", Jul. 1984, La Jolla, Calif.
"Metals and Ceramics Div. Progress Report", Published Jan. 1986, Oak Ridge National Laboratory.
"Impact Strength of Alumina Composites", Barta, et al., Ceramic Bulletin, vol. 51, No. 5, (1972), pp. 464-470 no month.
"Fibre Reinforced Ceramics", D. C. Phillips, Materials Development Division, A.E.R.E. Harwell, England, Feb. 1981.
"High-Strength Silicon Carbide-Fibre-Reinforced Glass Matrix Composites", by K. M. Prewo et al. J. of Mat. Science, 15, pp. 463-468 (1980).
"Silicon Carbide Yarn Reinforced Glass Matrix Composites", Prewo et al., J. of Matrix Science, 17, pp. 1201-1206--1982 no month.
"Silicon Nitride Ceramic Composites with High Toughness", Lindley et al., Nature Sol 229, pp. 192-193, Jan. 15, 1971.
"Silicon Carbide Whisker-Reinforced Aluminum Composite" Am. Ceram. Soc. Meeting, Columbus, Ohio Nov. 2, 1983) Wei et al.
"Silicon Carbide Fiber Reinforced Glass-Ceramic Matrix Composites Exhibiting High Strength and Toughness", Prewo, et al. J. Material Sci., 17 (1982) 2371-2383 no month.
"Fabrication of Silicon Carbide Whisker-Silicon Nitride Composite Materials and their Physical Properties" Tamari et al., Osaka Kogyo Gijutsu Kiho, 33(2), 129-134, 1962 no month.
"Studies on the Application of Hot-Pressed Silicon Nitride Ceramics as Cutting Tools", Miao Ho-Cho et al., Ceramurgia International, vol. 6, No. 1, 1980 no month.
Chemical Engineers Handbook, 5th Ed., 1973, 21-30 to 21-36, Perry no month.
"Handbook of Fillers and Reinforcement for Plastics", Katz, et al. (1978) 446-464 no month.
"Short Fiber Reinforcement: Where the Action is", J. V. Milewski, Plastics Compounding, Nov./Dec. 1979, 17-37.
"Growth Phenomena in Silicon Carbide", Philips Research Reports v. 18, pp. 161-274 (1963), Knippenberg no month.
"Temperature Measurement in Commercial Silcon Carbide Furnaces", Trans Electrochem., Soc., v. 61, pp. 217-232 (1932) Ridgeway no month.
"A Comprehensive Treatise On Inorganic and Theoretical Chemistry", v. V, pp. 875-887 (1940), Mellor no month.
"Carbide of Silicon--Its Purpose and Use in Steel", The Iron Age, v. 63, No. 5, (1899), Tone.
"Interfaces in Alumina-SiC Whisker Composites", Ceramic Microstructures '86: Role of Interfaces, Materials Science Research Series No. 21, Plenum Press, New York (1987), Tiegs et al. no month.
"The Formation and Dissociation of Silicon Carbide", Trans, Elect. Soc., v. 68, pp. 87-109 (1935), Ruff no month.
"Deposition of Carbon on Vitreous Silica", J. Chem. Cos., pp. 1362-1366 (1948), Iley et al. no month.
"Abrasives" Chapter 9 Silicon Carbide, pp. 68-75, 166-167, Springer-Verlag, New York (1971), Coss, Jr. no month.
"Microstructures of Ceramics--Structure and Properties of Grinding Tools", pp. 118-127, 130-131, 144-149, 195-199, Akademiai Kiado, Budapest (1980), Moser, (English translation by I. Finaly), no month.
"Ceramic Composites Emerging as Advanced Structural Materials", Ron Daganl, C&EN, Washington, Feb. 1, 1988.
"SiC Whiskers, For fibrous Composite Engineering Materials", University of Wisconsin, Oct. 7-8, 1965, Shaffer no month.
"Tool and Manufacturing Engineers Handbook", Third Edition, 1976 pp. 1-25 to 1-33 and 5-17, Dallas no month.
"Whisker Technology", Army Materials and Mechanics Research Center, 1970, pp. 443-468, Levitt. no month.
"Handbook of Structural Ceramics", Skorsky Aircraft Division United Technologies Corporation, 1991, pp. 7.40 to 7.47, Schwartz no month.
"Silicon Nitride Whisker and Silicon Carbide Whisker of" Tateho Chemical Industries Co., Ltd. Tateho Chemical Industries Co., Ltd. (1984) no month.
"Silicon Carbide Whiskers, Recent Advances in Engineering Science", V, 5 pt. 1 (1970), pp. 1-17, Shaffer no month.
"Alumina as a Ceramic Material", The American Ceramic Society, (1970) pp. 131-133, Gitzen no month.
"Ceramics in Machning Process", (1966) pp. 209-301, King et al. no month.
"Rolle of ZrO.sub.2 and TiC on Performance of Alumina Based Ceramic Cutting Tools", Trans. Ind. Ceramica Society, 49 (3), pp. 60-66 (1990), Basu et al. no month.
"Toolling & Production", vol. 50, No. 12, Mar. 6, 1985.
"Evaluation of Ceramic Inserts for Machining Glass 30 Gray Cast Iron", Metcut Report No. 2312-38101-1 for Arco Metal Company, Greer, South Carolina 29651, Nov. 20, 1984.
"A Competitive Assessment of the U.S. Advanced Ceramics Industry" Prepared by Industry Analysis Division, Office of Industry Assessment Trade Information and Analysis Assistant Secretary for Trade Development, Mar. 1984.
"GaAs diode-pumped Nd:YAG laser", J. Appl. Phys., vol. 43, No. 11, Nov. 1972 pp. 4603-4505, L. J. Rosenkrantz.
"Room-temperature cw operation of an efficient miniaturized Nd:YAG laser end-pumped by a superluminescent diode", Appl. Phys. Lett., vol. 29, No. 11, 1 (Dec. 1976), pp. 720-722, K. Washio et al.
"Efficient frequency-stable laser-diode-pumped Nd:YAG laser", Optics Letters, vol. 10, No. 2 (Feb. 1985) pp. 62-64, Zhou et al.
"Intracavity second-harmonic generation in a ND pentaphosphate laser", Appl. Phys. Lett., vol. 29, (1976) pp. 176-179, S. R. Chinn no month.
"Efficient Frequency-Doubled Single-Frequency Nd:YAG Laser", IEEE Journal of Quantum Electronics, vol. QE-10, No. 2, (Feb. 1974), pp. 253-262, Wm. Culshaw et al.
"High external efficiency (36% 5 micron mesa isolated GaAs quantum well laser by organometallic vapor phase epitaxy", Appl. Phys., Lett. 46, No. 2, 15 (Jan. 1985) pp. 121-123.
"Low-current-density LED-pumped Nd:YAG laser using a solid cylindrical reflector", J. Appl. Phys., vol. 45, No. 3, (Mar. 1974) pp. 1357-1371, G. I. Farmer et al.
"Efficient LiNdP4012 lasers pumped with a laser diode", Applied Optics, vol. 18, No. 23 (Dec. 1, 1979) pp. 3882-3883.
"Efficient and damage-resistant tunable cw dye laser", J. Appl. Phys., vol. 44, No. 6, (Jun. 1973) pp. 2775-2780, Jacobs et al.
"Highly efficient neodymium: yttrium aluminum garnet laser end jumped by a semiconductor laser array", Apply. Phys. Lett. 47(2), (Jul. 15, 1985) pp. 74-77, Sipes.
"The Influence of Whisker Dimensions on the Mechanical Properties of Cordierite/SiC Whisker Composites", Journal of the Eruopean Ceramic Society 9 (1992) pp. 153-163, Wadsworth et al. no month.
"The effect of whisker length on the mechanical properties of alumina-sic whisker composites", Journal of Materials Science 24 (1989) pp. 1589-1593, Baek et al. no month.

Abstract

Description