Stock material or miscellaneous articles – Structurally defined web or sheet – Including components having same physical characteristic in...
Reexamination Certificate
1999-08-05
2001-07-31
Turner, Archene (Department: 1775)
Stock material or miscellaneous articles
Structurally defined web or sheet
Including components having same physical characteristic in...
C051S307000, C051S309000, C204S298010, C204S298020, C427S249300, C427S255120, C427S255290, C427S255360, C427S299000, C427S314000, C427S331000, C427S372200, C427S378000, C427S402000, C427S419100, C428S141000, C428S323000, C428S325000, C428S408000, C428S469000, C428S472000
Reexamination Certificate
active
06268045
ABSTRACT:
The present invention relates to a component coated with a hard material, in particular diamond, for example a tool, to a process for its production and to a device for carrying out the process.
Heavy-duty tools for chip-forming or chipless machining of components to be processed consist of a cemented carbide or cement substrate material and a low-wear hard material layer which is applied to the substrate material.
These substrate materials consist of carbides which may be mixed with for example nitrides or the like and are embedded in a metallic matrix (for example cobalt and/or nikkel and/or iron), for example WC with 0.2 to 20% by weight of Co.
Fine crystalline substances, such as diamond, are used as the material for the layers applied to the substrate material in the case of particularly effective tools. However, it has proved difficult to apply diamond layers of this type with good adhesion to the substrate materials.
A great deal of effort has been made to improve the adhesion of a diamond layer of this type, with a wide variety of solutions having been examined for their effectiveness in improving adhesion.
Thus, EP 0 384 011 A1 and WO 95/15258 propose two quite contrasting solutions.
EP 0 384 011 A1 describes a diamond coating process, with which the existing grain structure of the substrate material is refined by a heat treatment at the surface, in order to promote nucleation for diamond coating at the grain boundaries of the substrate, and thereby to achieve better adhesion of the applied diamond layer.
The starting point is substrates whose grain size is in the region of 1 to 4 &mgr;m. After a heat treatment, a surface layer of the substrate material is produced, which is distinguished by a grain size of about 0.3 &mgr;m, and can thus be termed fine-grained. In order to improve the adhesion, it is proposed to reduce this grain size of the surface layer yet further, since it was assumed that a further reduction in the grain size would lead to an increase in the nucleation. However, the adhesion of the diamond layer in tools produced in this way has not proved satisfactory.
In WO 95/15258, it is proposed to make a mechanical bond between the diamond layer and the substrate surface layer, and to do this, in contradiction to the teaching of the abovementioned EP 0 384 01 A1, by increasing the grain size of the surface layer using a heat treatment.
For this purpose, the starting point is substrate materials which already have a relatively large grain size of 1 to 6 &mgr;m. Satisfactory adhesion of the diamond layer is only achieved for a grain size of the substrate surface layer measuring at least 15 &mgr;m.
However, the disadvantage arises that the large grain size, of more than 15 &mgr;m, for the surface layer of the substrate material permits only a poor quality for the surface of the diamond layer, since the deep structure of the surface layer of the substrate has repercussions on the properties of the applied diamond layer, in particular its surface roughness, and leads to coarsening and forming of burs at for example cutting edges. It must furthermore be taken into account that, in particular when metals are being cut, use is made of substrate materials whose grain sizes are less than 1 &mgr;m. They are distinguished in that the toughness of the substrates increases with decreasing grain size. In particular, grain sizes of as little as 10 to 500 nm can already be produced, and have outstanding material properties for use as cutting tools. Starting substrate materials of this type cannot, according to WO 95/15258, be provided with a diamond coating which adheres satisfactorily.
A further disadvantage results from the process temperature during the heat treatment of the substrates which leads to said grain sizes. The process temperature is in the region of 1500° C.
This high temperature is close to the sintering temperature of customary substrate materials, and therefore has the disadvantage that the tools do not meet the shape and dimensional tolerances for which they were made.
With regard to carrying out a complete process, for example for diamond coating, it has to date been customary to carry out the pretreatment of the substrate and its coating in two different reactors, so that a plurality of devices were needed. As, for example, also in WO 95/15258, the pretreatment required that one of the reactors be configured as a furnace for higher temperatures, or for a wet chemical pretreatment, for example in order to remove the binder from the substrates. It has not to date been possible to carry out all the pretreatment and coating steps for a substrate in one device without conversion.
On the basis of this prior art, the object of the invention is to provide a component, for example a tool, which is provided with a firmly adhering hard material layer, in particular a diamond layer, and which allows the hard material layer to have a high surface quality. The further objects of the invention are to specify a process for producing a component of this type, and to develop a device for carrying out the process.
The invention relates to a component, for example a tool, having an inner cemented carbide or cement substrate material and an outer hard material layer, the grain size of the inner substrate material being less than 1 &mgr;m, the surface layer of the substrate material having a grain size of less than 10 &mgr;m and a surface roughness R
z
of less than about 0.7 &mgr;m, and the surface roughness R
z
of the hard material layer being less than about 5 &mgr;m, preferably up to 0.3 &mgr;m.
A tool of this type is distinguished in that, for example when metals are being cut, it is possible to employ the customarily used substrate materials with correspondingly small grain size. By providing a surface layer of the substrate material with a grain size of less than 10 &mgr;m, for example up to 1 &mgr;m, this surface layer is provided with a structure that permits mechanical bonding to a hard material layer, for example a diamond layer, in which the grain size of the surface layer generally is higher than the grain size of the inner substrate material.
Besides diamond as the hard material, it is also possible to use materials such as cubic boron nitride, Al
2
O
3
, or other hard materials, such as compounds containing metals of the forth to sixth subgroup of the periodic system, which need mechanical bonding to the surface layer in order to adhere to a substrate.
Besides the bonding of the hard material layer to the surface layer of the substrate, on account of the grain size chosen for the surface layer it is possible for the hard material layer to have a surface roughness with such small values as to permit high-quality processing with tools produced in this way.
The surface layer of the substrate material preferably has a thickness of 1 to 50 &mgr;m, more preferably of 5 to 10 &mgr;m. For values above 10 &mgr;m, a multi-layer structure with a certain grain size can be produced.
In the case of diamond, and also with other coating materials, the hard material layer preferably has a thickness of up to 50 &mgr;m, more preferred up to 20 &mgr;m and most preferred up to 15 &mgr;m. This value depends on the respective application of the component or tool. This thickness relates to the distance of the outer surface of the hard material layer from the surface of the substrate, and does not therefore take into account the proportion of the hard material layer which extends into the substrate.
A suitable process for producing such a tool coated with a hard material comprises the steps of:
a) introducing a fine-grained cemented carbide substrate or carbide-containing cement substrate into a vacuum system with a heating device and at least one gas feed connection;
b) removing carbon from the carbides of the surface layer of the substrate at a substrate temperature in the region of about 900° C. to about 1400° C. and in an oxygen-containing atmosphere; c) introducing carbon into the surface layer of the substrate at a substrate temperature in the region of about 900° C. to about
Frank Martin
Lemmer Oliver
Leyendecker Antonius
Banner & Witcoff , Ltd.
Cemecon-Ceramic Metal Coatings-Dr.-Ing. Antonius Leyendecker Gmb
Turner Archene
LandOfFree
Hard material coating of a cemented carbide or carbide... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Hard material coating of a cemented carbide or carbide..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Hard material coating of a cemented carbide or carbide... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2567028