Stock material or miscellaneous articles – All metal or with adjacent metals – Composite; i.e. – plural – adjacent – spatially distinct metal...
Patent
1996-06-03
1999-02-16
Zimmerman, John J.
Stock material or miscellaneous articles
All metal or with adjacent metals
Composite; i.e., plural, adjacent, spatially distinct metal...
428332, 428698, 428699, 428701, 428655, 428657, 407119, 51309, 501 87, B32B 1510, B24D 324, C04B 3501
Patent
active
058718508
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This application is a PCT 371 international application, having application Ser. No. PCT/JP95/02016, filed 2 Oct., 1995.
The present invention relates to a coated hard metal material prepared by coating cemented carbide or cermet with a hard material, and more particularly, it relates to a coated hard metal material which is employed for a cutting tool. The present invention provides a cutting tool material which is excellent in wear resistance and chipping resistance, and can withstand a high-speed or high-efficiency cutting condition, in particular.
BACKGROUND INFORMATION
It is known that a cutting edge temperature of a cutting tool during cutting exceeds about 800.degree. C. at the maximum even under an ordinary cutting condition with a cutting rate of about 100 to 300 m/min. Further, in recent years, manufacturers who use machining operations, such as especially a car manufacturer, have increased the demand for development of a tool which can be used for cutting under a condition of a higher speed or a higher feed rate than the conventional one, such as a high speed of at least 300 m/min., for example, in order to improve productivity per unit time, in consideration of the, speed of NC machine tools, to reduce the production cost, and to achieve shorter working hours.
However, the cutting edge temperature of the cutting tool exceeds 1000.degree. C. in such a cutting condition, and this is an extremely severe condition for the tool material. If the cutting edge temperature is increased, the cutting edge is plastically deformed by heat, to cause regression of the cutting edge position. At a temperature exceeding 1000.degree. C., further, the base material such as cemented carbide forming the tool is oxidized and wear abruptly progresses.
In order to avoid such damage of the tool caused by cutting, tools are used that have been prepared by forming various types of hard coating layers on surfaces of hard metals by chemical vapor deposition or physical vapor deposition. Historically, a tool coated with a Ti compound first appeared, and improvement of the cutting speed was attained since the same is superior in stability under a high temperature as compared to cemented carbide. Thereafter a tool prepared by further coating a Ti compound with an Al.sub.2 O.sub.3 layer of 1 to 2 .mu.m thickness was developed to make it possible to further improve the cutting speed, and hence this forms the mainstream of the current coated cutting tool.
Al.sub.2 O.sub.3 has a small standard formation free energy, and is chemically more stable than the Ti compound. Thus, it is said that an Al.sub.2 O.sub.3 film brings a great effect for suppression of crater wear in a cutting face portion that is heated to the highest temperature in the cutting edge, and is suitable for high-speed cutting. Further it is said that propagation of cutting heat is suppressed and a hard metal material of the tool base can be kept at a low temperature since heat conductivity of Al.sub.2 O.sub.3 is small. In order to develop a tool which is capable of higher speed cutting, therefore, it is expected that the Al.sub.2 O.sub.3 layer may be further thickened.
When the Al.sub.2 O.sub.3 layer is thickened, however, hardness is reduced since bulking of crystal grains forming the coating layers progresses, and a reduction of wear resistance on the flank comes into question. It has been recognized that, if such a tool is used in practice, the dimensions of the workpiece being cut are changed by regression of the cutting edge position since the progress of wear is quick, and the life of the tool is extremely short.
On the other hand, a method of preventing bulking of crystal grains by dividing an Al.sub.2 O.sub.3 layer into plural layers is proposed in Japanese Patent Publication No. 5-49750. According to this method, the grain size of Al.sub.2 O.sub.3 can certainly be reduced and wear resistance can be improved. On the other hand, boundaries between Al.sub.2 O.sub.3 and other materials are increased, and hence separation at the interf
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Ikegaya Akihiko
Kitagawa Nobuyuki
Moriguchi Hideki
Uchino Katsuya
Fasse W. F.
Fasse W. G.
LaVilla Michael
Sumitomo Electric Industries Ltd.
Zimmerman John J.
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