Composite body, production process and use

Details Composite body, production process and use Composite body, production process and use

1999-03-23

2001-05-01

Turner, Archene (Department: 1775)

Stock material or miscellaneous articles

Structurally defined web or sheet

Including components having same physical characteristic in...

C427S255290, C428S336000, C428S697000, C428S698000, C428S699000, C428S701000, C428S702000

Reexamination Certificate

active

06224968

ABSTRACT:

CROSS REFERENCE TO RELATED APPLICATIONS
The present application is a national stage of PCT/DE/96/02519, filed Dec. 30, 1996, based upon German national application 196 41 468.7 and 296 17 507.2 of Oct. 9, 1996 under the International Convention.
1. Field of the Invention
The invention relates to a composite which is comprised of a substrate body with a coating of one or more layers of carbides, nitrides, carbonitrides of Ti, Zr, Hf, V, Nb and/or Ta and/or of Al
2
O
3
or ZrO
2
.
The invention also relates to a process for producing a coating from a carbonitride of the aforementioned metals by CVD or plasma activated CVD on a base body or on a coated base body of a hard metal, cermet, steel or a ceramic.
2. Background of the Invention
The first coatings of the type with which the invention is concern which have become known according to the state of the art, are comprised of titanium carbide with a thickness of up to 8 &mgr;m with which an improved wear resistance effect against free-surface wear can be obtained. Further there are double or multiple coatings of titanium carbide and titanium nitride, especially with an outer layer of titanium nitride, which belong to the state of the art and with which a reduced corrosion can be achieved with cutting inserts used for chip removal. For further improvement of such cutting inserts, multilayer coatings with the layer sequence TiC, Ti(C,N)—TiN have been proposed. In addition, it has been found that the natural brittleness of ceramics like Al
2
O
3
can be minimized when Al
2
O
3
in thin layer form is deposited thereon and also Tin, Ti(C,N) and an outer layer of Al
2
O
3
can comprise multilayer coatings for such use. While the patent literature, for example in the framework of a special coating process as in EP 0 229 282 B1, generally speaks of carbides, nitrides and/or carbonitrides of the elements titanium, zirconium, hafnium, vanadium, niobium and/or tantalum, the described examples are limited to titanium compounds as the coating material, in part, in combination with aluminum oxide. Correspondingly the same can be said for ZrO
2
in combination with or as a replacement for oxide-containing coatings. First in DE 36 20 901 A1 or EP 0 250 865 A1 (with the same contents) a cutting insert is described whose edge is coated with titanium carbide, titanium carbonitride and/or titanium nitride and whose outer cover layer is comprised of a thin zirconium nitride coating. The zirconium nitride which has poorer wear characteristics than the aforementioned titanium compounds, is intended to hinder oxidation of the basic layers underlying this layer by atmospheric oxygen so the good wear characteristics of the titanium carbide-titanium carbonitride-and/or titanium nitride coatings are fully retained. In practice, zirconium compounds are not normally used as coating materials.
However, in U.S. Pat. 3,854,991 (or CH-A-585 273) a coated sintered hard metal product is described in which the coating is comprised of HfCN and/or ZrCN and has X-ray diffraction lattice constants which in the case of HfCN and a mixture of HfCN and ZrCN lie between 4.570 and 4.630 angstrom and in the case of ZrCN lie between 4.6 and 4.62 angstrom. In the case of ZrCN, the C/N ratio is clearly less than 1. To produce this hafnium or zirconium carbonitride, a hafnium and/or zirconium halogenide is conducted together with hydrogen, nitrogen and a hydrocarbon at a temperature of 1000 to 1300° C. across a substrate.
OBJECT OF THE INVENTION
It is the object of the present invention to provide a substrate body having a multilayer coating whose wear characteristics for chip removal machining or under otherwise abrasive loading is improved and has of an increased life.
SUMMARY OF THE INVENTION
This object is achieved with composite body in which claim
1
which is characterized in that is composed of a carbonitride of Zr, Hf, V, Nb, Ta or Cr and that this layer is deposited either directly upon an Al
2
O
3
or ZrO
2
layer or upon a thin intermediate layer of a maximum thickness of 0.5 &mgr;m of TiN directly on an Al
2
O
3
or ZrO
2
layer. The aforementioned carbonitride layer preferably has a thickness of at least 2 &mgr;m to a maximum of 6 &mgr;m and/or the Al
2
O
3
or ZrO
2
layer has a thickness of 2 &mgr;m, preferably 3 &mgr;m or more. The respective thicknesses are provided on the cutting corners of composite bodies which are formed as cutting inserts. It is also possible to form the outer layer of the aforementioned carbonitride, especially ZrCN or HfCN, and also to apply one or more outer layers on this carbonitride layer whereby the layer thickness or the total thickness of the one or more outer layers does not exceed 2 &mgr;m and preferably does not exceed 1 &mgr;m. In other words in the framework of the present invention one can obtain equally good solutions when the aforementioned carbonitride layer has coated thereon even extremely thin further layers. Preferably when such composite bodies are used as cutting inserts for turning, the following layer thicknesses are used: TiN: 0.5 to 2 &mgr;m; TiCN: 9 to 13 &mgr;m; Al
2
O
3
: 2 to 4.5 &mgr;m and ZrCN: 2 to 4 &mgr;m. For corresponding cutting inserts used for milling preferably the following layer thicknesses are chosen: TiN: 0.5 to 2 &mgr;m; TiCN: 9 to 13 &mgr;m; Al
2
O
3
and ZrCN: 4 to 6 &mgr;m, whereby one of the layers Al
2
O
3
and ZrCN is at least 1 &mgr;thick.
The substrate body can, according to a further feature of the invention be composed of hard metal, a steel, a cermet or a ceramic, especially a material based on Si
3
N
4
. Preferred hard metal substrate bodies are comprised of 5.5 to 8.5 mass % Co, preferably 5.5 to 6.5 mass % Co as a binder, the balance WC. Alternatively, the substrate body can comprise 1 to 3 mass % TiC, 2 to 5 mass % TaC, 1 to 3 mass % NbC and 5.5 to 8.5 mass % Co, the balance WC.
For producing the carbonitride layer from Zr, Hf, V, Nb, Ta or Cr, according to a first alternative, a plasma-activated CVD is used in which the reactive gas atmosphere at the set reaction chamber, apart from hydrogen, argon and a chloride of the named metal, also contains ionized and/or nonionized carbon-nitrogen donors with triple bonding, whereby the bond spacing between the carbon and nitrogen at room temperatures lies between 0.114 and 0.118 nm. Especially, the ionized and nonionized C-N donors are generated by ionization and thermal dissociation of gasses of the cyanide group (CN-triple bonding) by means of a plasma activation at temperatures between 400° C. and 700° C. and a pressure of 100 to 1000 Pa. Suitable substances, which can liberate cyanide radicals (—CN) at the reaction temperature, are organic compounds like hydrogencyanide, cyanamide, cyanogen, cyanoacetylene and acetonitrile. In the deposition, the substrate body can be connected as the cathode for the plasma activation and a pulsed direct current can be applied, such as the process described for example in DE 38 41 731 C1.
Alternatively it is also possible to apply the named hard material coating from carbonitride by means of CVD, whereby the gas phase, at a reaction temperature between 700° C. and 1100° C. and preferably at pressures between 5 kPA and 100 kPa, contains, in addition to H
2
and/or Ar and chlorides of the above-mentioned metals, also carbon donors and nitrogen donors which have a C—N molecular group. This is preferably a cyanide group with a triple bond between the carbon and nitrogen, whose spacing at room temperature amounts to between 0.114 and 0.118 nm. Such compounds are hydrogen cyanide, cyanamide, cyanogen, cyanacetylene or acetonitrile. Alternatively or in part, such gaseous compounds can also be used which have CN molecular groups with a single bond between the carbon and the nitrogen. Molecules with single CN bonds include methylamine and ethylenediamine. The present invention includes within its framework appropriate substances containing the cyanide group; compounds of this kind are in principle known in the state of the art and are for example described in DE 25 05 009 A1. Other gaseous media can be gate

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