Al2O3 coated cutting tool

Details Al2O3 coated cutting tool Al2O3 coated cutting tool

2000-05-18

2002-05-07

Turner, Archene (Department: 1774)

Plastic article or earthenware shaping or treating: apparatus

Diverse distinct type shaping means

Shaping orifice and either a downstream preform reshaping...

C051S307000, C051S309000, C428S336000, C428S698000, C428S472000, C428S701000, C428S702000

Reexamination Certificate

active

06382951

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a cutting tool for metal machining, comprising at least one body containing PCBN, (polycrystalline cubic boron nitride), with or without cemented carbide backing, and a hard and wear resistant refractory coating on the surface of said body. The coating is adherently bonded to the body and covers all functional parts thereof. The coating is composed of one or more layers of refractory compounds of which at least one layer consists of fine-crystalline &ggr;-Al
2
O
3
, deposited by Plasma Activated CVD-methods (PACVD).
BACKGROUND OF THE INVENTION
Cutting tools having cutting edges formed of a superhard abrasive such as a cubic boron nitride (CBN) based material are manufactured by powder metallurgical techniques and are mainly used for the machining of cast iron and hardened steel. Several types of CBN cutting tools are known, the majority of which consisting of a CBN tip that has been brazed onto a cemented carbide insert. Others have the CBN sintered directly to a cemented carbide backing of sufficient thickness to produce an insert while yet others consist of solid CBN-containing body without any cemented carbide backing.
Subjecting a sintered CBN body to temperatures over 1,000° C. may result in undesirable structural changes in the material. Furthermore, in the case of a brazed insert the braze joint will be destroyed.
Swedish patent application 9704387-1 discloses a method for depositing refractory alumina (Al
2
O
3
) thin layers on cutting tools made of cemented carbide, cermet, ceramics or high speed steel. The invented method is a Plasma Activated Chemical Vapor Deposition (PACVD) process in which the plasma is produced by applying a bipolar pulsed DC voltage across two electrodes to which the tool substrates to be coated are fixtured and electrically connected.
WO 98/28464 discloses that by applying a coating including a MTCVD-TiCN and a CVD-Al
2
O
3
layer to such a CBN tool material, substantial advantages in tool life can be achieved when machining hardened ball bearing steel.
U.S. Pat. No. 5,503,913 discloses improving the wear properties of tools with a cutting edge of cubic boron nitride or polycrystalline cubic boron nitride to coat the superhard body with a 0.5-6 &mgr;m thick coating of one or more oxides of the metals Zr, Y, Mg, Ti or Al. The coating is deposited from the gas phase at temperatures up to 800° C., preferably using a pulse plasma CVD-process.
SUMMARY OF THE PRESENT INVENTION
According to the present invention, the disadvantages associated with the prior art are overcome.
According to one aspect of the present invention there is provided a cutting tool comprising a substrate and a coating; said substrate comprising a body containing at least 35 vol-% cubic boron nitride; and said coating comprising at least one layer of alumina, said alumina layer consisting essentially of &ggr;-Al
2
O
3
with a grain size between 5 and 200 nm.
According to a further aspect, the present invention provides a method of making a cutting tool comprising a substrate and a coating by a plasma activated chemical vapor deposition technique, wherein the technique comprises: pulsing a DC voltage between two electrodes to which substrate bodies to be coated are fixtured and electrically connected, such that the electrodes alternately act as an anode and a cathode; providing an atmosphere comprising AlCl
3
, H
2
and Ar together with at least one oxygen donor chosen from O
2
, CO
2
, CO, and N
2
O; providing a pulse frequency of 5-100kHz; providing a pulse amplitude of 300-1000 volts, and providing a substrate temperature of 500-900° C.


REFERENCES:
patent: 5503913 (1996-04-01), König et al.
patent: 5516588 (1996-05-01), van den Berg et al.
patent: 5674564 (1997-10-01), Ljungberg et al.
patent: 5693417 (1997-12-01), Goedicke et al.
patent: 5700551 (1997-12-01), Kukino et al.
patent: 5879823 (1999-03-01), Prizzi et al.
patent: 6090476 (2000-07-01), Thysell et al.
patent: 6210726 (2001-04-01), Schiller et al.
patent: 0 744 473 (1996-11-01), None
patent: WO 98/28464 (1998-07-01), None
patent: WO 99/27155 (1999-06-01), None
O. Zywitzki et al., “Effect of the substrate temperature on the structure and properties of A12O3layers reactively deposited by pulsed magnetron sputtering,”Surface and Coatings Technology, 82 (1996), pp. 169-175.
“Deposition of hard crystalline Al2O3coatings by bipolar pulsed d.c. PACVD,” Ch. Täschner et al.; Elsevier 1998.

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