DE1959690C3 - Process for the production of a coating layer on tools for cutting and non-cutting shaping - Google Patents

Description

The invention relates to a method for producing a coating layer on tools for the cutting and non-cutting shaping as protection against scouring or wear by depositing a Nitrides or carbonitrides of the metals of group IVa to VIa of the periodic table of elements a gas phase reaction.

When machining long and short chipping materials with the help of hard metal tools always a more or less strong scouring of the rake face, which increases the service life of the tools greatly diminishes. To avoid this, it is already known to use tungsten carbide-cobalt-hard metal cutting plates Sinter coating layers made of titanium carbide-cobalt-hard metal. As a result, on the one hand, the Maintaining the toughness of the base material and, on the other hand, the high crater strength of those containing titanium carbide Hard metals are exploited. The different expansion coefficients and sinter groups this coating layer and the base material have led to cracks, which is why they are known Composite carbides have not proven their worth.

It is also known to nitride hard metal tools on the surface in order to achieve a certain Increase in the wear resistance of such tools approximately equally against both scouring and can also be achieved against dulling (open surface wear). In addition, tools are made of steel and bronzes known with a coating of a hard nitride, boride and / or suicide des Titans are provided. Such tools are found because of the soft compared to the hard metal Substrate materials are only used where there are lower wear resistance requirements and

ίο where mainly the cutting material against sticking is to be protected with the material to be processed. Such tools are common today Machine processing, for example for turning with cutting speeds over 120 m / min, unsuitable

Recently, hard metal cutting inserts have become known that have a hard titanium corbid top layer of less than ΙΟμπι that from the Gas phase is precipitated. This enabled a certain improvement in terms of crater wear can be achieved.

It is an object of the present invention to provide a coating layer that still does has better resistance to scouring and wear than the previously known.

According to the invention, the nitride or carbonitride coating layer on tools is used to achieve this object made of hard metal. Unexpectedly, it has been shown that such hard material layers on Hard metal applied have a better crater behavior than the known TiC coating layers Carbide parts.

Rather, it cannot be inferred from the prior art that coatings made of metal nitrides or

J5 carbonitrides on tools made of hard metal have a particularly favorable influence on the crater behavior to have. Rather, it has been generally believed that coating layers made of metal carbides have the best properties in terms of wear and scour. However, this is true as stated was not to.

According to an advantageous embodiment of the invention, the coating layer made of titanium nitride or Consist of titanium carbonitride. In the case of a coating layer made of titanium carbonitride, 10 to 20% Titanium carbide may be present in the carbonitride mixed crystal. The thickness of the coating layer to be created on the hard metal parts can be 1 to 50 μπι.

According to a preferred method of manufacture

So the coating layer according to the invention, the deposition of the nitride or carbonitride on the surfaces of the hard metal parts by thermal decomposition of a halide of the metals of groups IVa to VIa of the periodic system of the elements with the simultaneous action of a pre-cleaned gas mixture of nitrogen, hydrogen and possibly gaseous hydrocarbons, for example methane, take place in a furnace in which the hard metal parts to be coated are heated ^{to 800 to 115O 0 C.}

The process is for the separation of titanium nitride from the gas phase (nitrogen-hydrogen mixture, loaded with titanium tetrachloride vapors) on objects made of metal or a metal alloy from the German patent specification 9 70 456 known per se. What is new, however, is the deposition of a metal nitride or carbonitrides from the gas phase onto the surfaces of hard metal parts.

The method provided according to the invention for producing a coating layer made of metal nitride or carbonitride on hard metal parts can, according to a preferred embodiment, be designed in this way That the hard metal parts are in a powder mixture of metal nitride during the coating in the furnace or carbonitride are embedded. This ensures that the top coat to be formed can be generated evenly on all surfaces of the parts. In addition, this results in the Possibility, according to a further preferred embodiment of the method according to the invention, the hard metal parts to move in the embedding powder mixture at the beginning of the coating, for example to turn. This achieves the effect of abrasive abrasion of the sintered skin on the hard metal parts, which can never be a hindrance to a coating.

The following are two examples of the manufacture of a titanium nitride and a titanium carbonitride coating indicated on hard metal parts.

example 1

A gas stream of sharply dried hydrogen and nitrogen is passed through with titanium tetrachloride vapor Passing the gases through a vessel (washing bottle) filled with liquid titanium tetrachloride and the pre-cleaned gas mixture combined via the hard metal plates into an oven in which the Tungsten carbide plates are heated to 800 to 1150 ° C. the Amounts of gas react on the surface of the glowing hard metal plates with a golden yellow image Titanium nitride layer. Surprisingly, it has been shown here that the adhesion of the TUannitride layer it is particularly good if the sintered skin is on all sides beforehand being abraded or abraded and when the nitriding time is about 30 to 60 minutes. this leads to a layer thickness of 10 to 50 μm.

Example 2

An aliquot of dry methane was used to produce a titanium carbonitride coating fed to the gas mixture of hydrogen, nitrogen and titanium tetrachloride. The aim is one Top layer containing 10 to 20% titanium carbide in the carbonitride mixed crystal contains. As the titanium carbide content increases, the color of the layer changes from golden yellow to red-yellow, a color similar to that of a

Composition 4 ΤΊΝ / 1 TiC is achieved.

The coating layers with gold-yellow titanium nitride or red-gold titanium carbonitride coating layers in the manner according to the invention provided hard metal plates have a long service life compared to uncoated ones

ίο plates, and another 50 to 100% higher Lifetime and crater resistance as hard metal plates coated with titanium carbide in a known manner. Technological The invention also has the advantage that at 100 to 300 ° C. lower coating temperatures can be used than when applying metal carbide top layers, so that the Tungsten carbide plates do not have any undesirable structural changes and excessive decarburization of the surface (Formation of a tj phase intermediate layer).

The application of other nitrides of the Obergangsrr.etaiie the IVa to Via metals and also from Cr2N is somewhat more difficult in terms of apparatus, because chlorides of the Metals mentioned are invariably solid at room temperature and they are therefore prior to passing through Nitrogen must be melted and superheated in order to be entrained in vapor form. However, it is also possible to dissolve certain amounts of the solid chlorides in the liquid titanium tetrachloride and so on Gas mixtures when passing nitrogen or

jo hydrogen to achieve the nitride mixed crystal as

Form top layers. With simultaneous presence

of methane form multi-component carbonitride layers

th.

As furnaces for carrying out nitriding

J5 horizontal, stationary, ceramic tube furnace or ceramic rotary kilns proven. In the case of the latter, it is particularly important to keep the goods in the to be embedded in a powder mixture as mentioned above, that a protection of the Pfouenkfeiten and corners In addition to a slightly abrasive effect (grinding off the sintered skin), Als is another type of furnace Furnace types such as those used for chrome plating of steel and those in the essentially consist of a retort.

Claims (5)

Patent claims: 1. Process for the production of a top coat on tools for cutting and non-cutting shaping as protection against scouring or wear by depositing a nitride or carbonitrides of the metals of group IVa to VIa of the periodic table of the elements a gas phase reaction, characterized in that that the top coat is applied to tools made of hard metal. 2. Process for the production of an overlay layer according to claim 1, characterized in that the nitride or carbonitride is deposited on the surface of the hard metal parts in a known manner by thermal decomposition of a Halides of the metals of group IVa to VIa of the periodic table of the elements with simultaneous Action of a pre-cleaned gas mixture of nitrogen, hydrogen and possibly gaseous hydrocarbon, for example methane, is carried out in a furnace in which the to coated hard metal parts to 800 to Il50 ° C are heated. 3. The method according to any one of claims 1 or 2, characterized in that the to be coated Surfaces of the hard metal parts before the coating by grinding, brushing or scrubbing of the Sinter skin are freed. 4. The method according to any one of claims 1 to 3, characterized in that the hard metal parts embedded in a powder mixture of metal nitride or carbonitride during coating in the furnace are. 5. The method according to claim 4, characterized in that the hard metal parts at the beginning of the Coating in the embedding powder mixture can be moved, for example rotated.