DD255446A3 - HARD COAT WITH HIGH WEAR RESISTANCE AND DECORATIVE BLACK OWN COLOR - Google Patents

Abstract

Hard material layer with high wear resistance and decorative black inherent color find special use for decorative purposes and also in cutting and forming tools. The invention has for its object to develop using plasma-assisted coating process, a layer system which has intermediate layers and a cover layer as a black hard material layer, in which the outer pressure and shear forces are taken without disturbing the layer. According to the invention, a layer system is proposed to solve the problem, in which a layer of an element of the IV a, V a group of the PSE is deposited, then a nitride layer of the same element and subsequently a carbide layer of this element. As a cover layer immediately after a hard carbon layer is built up, which has a decorative black appearance. If TiC contents are left in the final carbon layer, an anthracite color is achieved.

Description

Field of application of the invention

The invention relates to a hard material layer with high wear resistance and decorative black intrinsic color. Such layers find particular use for decorative purposes. As examples have become known watch cases and bracelets, controls of consumer goods and bumpers on motor vehicles. Depending on the usable hardness, the insert may also be used to reduce wear and corrosion, e.g. done with cutting and forming tools.

Characteristic of the known technical solutions

Among other known solutions, e.g. Galvanic methods have been enforcing in recent time, in particular physical deposition methods, such as sputtering or ion plating. EP 0130754 describes a decorative carbon layer and a method. Thereafter, by sputtering a carbon target, a disordered carbon layer is deposited whose intrinsic color is black. In addition, a protective layer, for. B. polymethane, apply. However, these layers are known to have insufficient adhesive strength, hardness and corrosion resistance. Furthermore, in the case of metallic substrates, undesirable edge carburization may occur during the layer deposition. The application of such layers for functional purposes is largely excluded.

To improve the adhesion of the coating material is, for. For example, in JP 57-200557, it has become known that suitable intermediate layers are applied between the cover layer and the substrate. In the example, it is a titanium intermediate layer and a titanium carbide topcoat. The TiC cover layer has an anthracite gray inherent color. A pure black can not be realized.

EP 0087836 proposes a sliding layer applied by chemical or physical deposition methods which consists of a mixture of carbon and a metal, in which case no carbide is expressly formed. The metal used is also used as an adhesion-promoting intermediate layer. These layers have in particular good sliding properties compared to steel. The hardness of the layer is relatively low compared to a hard material layer. For own color no information is given.

The solutions given give specific partial solutions, without that "the black hard material layer", which dissolves both decorative and functional tasks was found.

Object of the invention

The invention aims to provide a decorative black and wear-resistant hard material layer, in particular for substrate materials which require low deposition temperatures.

Explanation of the essence of the invention

The invention has for its object to develop using plasma-assisted coating process, a layer system which has intermediate layers and a cover layer as a black hard material layer, in which the external pressure and shear forces are absorbed without disturbing the layer.

According to the invention, a layer system is proposed for solving the problem, in which a per se known adhesion-promoting layer of an element of the IVa, Va group of the PSE is deposited on the cleaned substrate, then a nitride layer of the same element and subsequently a carbide layer of the element. This combination has the function of an adhesion-promoting intermediate layer and the structure of the actual "hard material" layer. As a cover layer, a carbon layer is built up immediately thereafter. The carbon layer may also have embedded crystallites of carbides, the intermediate layer-forming element.

According to the object and the object of the invention, a layer deposition is carried out continuously with the method of plasma-assisted layer deposition. As a result, the deposition temperatures can be kept low (less than 500 ^° C.) and it is only under the action of ions that it is possible to produce a "hard" carbon matrix.

For explanation, the layer system will be described in detail below. With the first component of the intermediate layers, the application of a layer of an element of the IVa, Va group of the PSE (titanium, zirconium, hafnium, vanadium, niobium or tantalum) a good adhesion to the most metallic substrates is prepared and at the same time in a known manner Diffusion barrier, for possibly diffusing out of the substrate material or even from the layers to be built in diffusing constituents to create. In the first place, titanium has proved to be successful, since titanium also makes it easy to form nitrides and carbides, which follow in the further layer structure.

The thickness of this metal element layer is between 50 and 500 nm and is determined primarily by the element itself and by the material of the substrate.

Immediately after the formation of the element layer, i. without that the possibility of foreign layer formation, z. As oxide formation is given, the structure of the first hard material layer of the nitride of the first component of the intermediate layer forming element takes place. This layer has the task of compensating for stresses that can arise within the layer system due to different thermal expansion coefficients. This makes it possible to build up a relatively thick carbide layer, known for its hardness and thermal stability, again from the first interlayer-forming element, without the adhesion problems of the interlayer occurring, which could be eliminated only by the application of relatively high substrate temperatures. Depending on the intermediate layer-forming element and the layer thickness required for the particular mode of use of the layer system, these are at 100 to 1500 nm for the nitride and 200 to 3000 nm for the carbide layer.

The high hardness of the carbide layer guarantees a high abrasion resistance of the composite stabilized by the nitride layer. Compared with a carbide layer applied directly to the substrate or the adhesion-promoting diffusion barrier, the adhesion is substantially increased and it is possible to increase the layer thickness without fear of flaking under mechanical stress.

After the formation of this interlayer system - diffusion barrier and adhesion - stress compensation - hard material layer - a carbon layer is deposited in direct process control as a cover layer. Important is the effect of ions that cause the deposition of a hard carbon, often in such cases of "diamond-like carbon" or "iC layers" spoken.

A further development of the layer, which depends essentially on the intended use of the layer and the element used, involves the formation of a carbon layer with a gradually increasing carbon content, without the formation of carbide crystallites within the carbon matrix being dispensed with.

The layer according to the invention or the layer system has a decorative black inherent color. With TiC portions still embedded in the final carbon layer, and depending on the element forming the intermediate layer, color gradations between deep black and anthracite can be realized without losing the mechanical properties of the layer system.

The real advantage of the proposed solution is that the decorative black inherent color is combined with the high wear resistance of the hard material layer.

The application of the PVD method (physical vapor deposition) has proved to be particularly favorable, since in this case the particular advantage of the relatively low deposition temperature is effective and no damage to the substrate material occur.

When using the layer system for high wear loads, z. As in cutting and forming tools, the top layer still has the particular beneficial effect that the carbon has very good sliding properties. The hard carbon layer realizes a significant reduction in the coefficients of friction on the "supporting" base of the nitride-carbide hard-material layer, which absorbs the significant mechanical pressure loads Single layers, still the further advantage that after wear of the hard carbon layer with carbide crystallites nor the carbide layer and later the nitride layer acts as a hard material layer.

embodiment

The invention will be explained in more detail below with reference to three exemplary embodiments.

Example 1:

A wrist watch case made of stainless steel, e.g. X 10 Cr Ni 18.10, should be provided with an abrasion-resistant, decorative black layer. By means of an arc discharge evaporator, the following layer system is deposited in a PVD process:

Ti 89 nm TiN _x lOOOnm TiC _x 300 nm iC-TiCv 2000 nm

During the entire process, the evaporation of the titanium was not interrupted and only the reaction components nitrogen and carbon varied by changing the gas flow. Foreign layers, in particular oxygen-containing, are avoided due to the process. The cover layer has a proportion of TiC _x in the iC matrix of about 10% by weight and causes a dark anthracite-colored inherent color. The layer is resistant to abrasion, resistant to

Synthetic sweat and does not tend to chipping even under conditions such as impact or impact. The hardness is HV 0.02 = 3800kpmrrT ² . The coefficient of friction with respect to steel μ = 0.023.

Example 2:

Similarly to Example 1, a deep black coating is to be carried out on a similar wrist watch case instead of an anthracite-colored coating. For this purpose, a layer according to Example 1 is constructed in an equivalent manner. The hydrocarbon layer with a TiC _x content of 10 wt .-% is thereby deposited with a arc current of 200 A and a burning voltage of 36V. The reactive gas pressure for C ₂ H ₂ is at 3 ... 6 = 10 " ² Pa and the substrate voltage at

By changing the magnetic field leading to the arc, the arc length is then increased and the burning voltage increases to a value of 48V, with the arc current regulated. At the same time, the cathode of the evaporator and substrates are interconnected in the same DC voltage and it forms an RF plasma oscillation.

By lowering the arc current to about 100A, a layer deposits on the substrates, which initially has about 8 atomic% titanium carbide within the carbon matrix and after a deposition time of 15 minutes is essentially a pure carbon layer.

This carbon layer has a deep black inherent color. It has a thickness of Ο, δμ, ιη, is electrically insulating and chemically resistant, especially against artificial sweat. Their gloss corresponds to the surface condition of the nickel layer serving as a base.

Example 3:

The high stress of twist drills in printed circuit board production from fiber-reinforced laminates leads to a short service life of the same, which could be met only unsatisfactorily by the use of carbide. In particular, high frictional forces between the drill and the circuit board material result in the formation of rough and dirty bore contours, as the plastic material is applied to the drill. Previous attempts to protect such drills with an applied directly on the hard metal base body iC layer against wear, fail because of unresolved adhesion problems. In order to eliminate these shortcomings, the following layer system was set up:

Ti 50 nm TiN _x lOOOnm TiC _x 'iOOOnm iC-TiCv 500 η m

The hardness of the layer deposited in this way was HV ₅₀ 4500 kpmm ² . The coefficient of friction was found to be 0.020 versus steel. In order to prevent the chipping of the iC TiC _x from the TiC _x layer, a gradual increase in the iC content was used, so that a C gradient forms within a layer thickness of 300 nm. The outermost 200 nm thick layer then has a homogeneous mixing ratio with 25 wt% TiC _x and 75 wt% iC. The service life of the twist drills has been significantly increased.

Claims (5)

1. hard material layer with high wear resistance and decorative black inherent color, consisting of a layer system, characterized in that successively a first layer of an element of the IVa, Va group of the PSE, thereon a nitride layer of the element, subsequently a carbide layer of the same element and finally a carbon layer is built up. 2. hard material layer according to item 1, characterized in that the transition from one sublayer to the other at least partially gradual. 3. hard material layer according to item 1, characterized in that the final carbon layer contains a carbide content of 3 to 30 wt .-% of the total layer substance. 4. hard material layer according to item 1, characterized in that the layer thicknesses for the element of IVa, Va group 5 to 100nm, the nitride layer 100 to 1 500nm, the carbide 200 to 3000nm and the carbon layer 100 to 2000nm amount. 5. hard material layer according to item 1, characterized in that is used as the element of the IVa, Va group titanium.