EP2547805A1

EP2547805A1 - Coating based on nial2o4 in spinel structure

Info

Publication number: EP2547805A1
Application number: EP11711494A
Authority: EP
Inventors: Juergen Ramm
Original assignee: Oerlikon Trading AG Truebbach
Current assignee: Oerlikon Surface Solutions AG Pfaeffikon
Priority date: 2010-03-18
Filing date: 2011-03-18
Publication date: 2013-01-23
Also published as: JP5771884B2; US9428826B2; WO2011113927A1; CN103189541A; US20130036942A1; EP2369031A1; CN103189541B; EP2369031B1; EP2369031A9; JP2013522058A

Abstract

The invention relates to a coating that comprises at least one compound of oxygen and/or nitrogen with at least two metal materials, said compound being present at least partly in the spinel structure. The invention also relates to a method for coating and to a coated substrate.

Description

Coating on N1AI ₂ O ₄ base in spinel structure

The invention relates to a coating according to the preamble of claim 1.

CVD oxide layers or layer systems which contain these CVD oxide layers are known which find very wide application in the field of machining of steel and cast iron (CVD = chemical vapor deposition). The oxide layer consists mainly of aluminum oxide before ^¬ in the corundum (alpha alumina or CX-Al ₂ O 3), which is deposited at temperatures around 1000 ° C on the tools. The high deposition temperature (= substrate or tool temperature) limits the choice of tool materials mainly to hard metals such as tungsten carbide or to composites made of ceramic materials in a metallic matrix (so-called cermets) or to high temperature stable ceramics such as SiC or SiN. In vie ^¬ len applications, especially in the Hartmetallwendeschneidplat ^¬ th, the -Αΐ ₂ θ3 is not directly on the tool abge ^¬ eliminated, but it is first a TiCN layer up ^¬ claimed that the harder than the -Αΐ ₂ θ3 is, but less resistant to oxidation. This thus structured layer system has against al ^¬ lem advantages if it can be worked layer systems with thick (ym> 15), which is the case especially in the continuous machining of gray cast iron. When interrupted

Cuts are the tensile stresses in the layer passing through the high deposition temperature and the temperature-based Fehlanpas ^¬ solution between layer materials and substrate occur disadvantageous. It comes to cracking in the layer system, sometimes even before the use of the tool.

The advantage of the CVD method to produce thick layers in a relatively simple and inexpensive way, does not come all ^¬ recently into play when it comes to work particularly tough materials. In this case, very sharp tool edges must be provided and the coating must not lead to a large increase in the tool edge radius, which is the case with the thick CVD layers and the uniform layer deposition.

A further disadvantage is that material abrasion may occur at the cutting edge of the tool which promotes uncontrolled edge wear. These deposits are believed to be related to the reactivity of the Ti in the layer. It has been observed that Ti-Al-N layers decompose at temperatures between 800 ° C and 900 ° C at the surface and it comes to a porous surface layer of low mechanical strength. The chemical or oxidative layer resistance of this material system is therefore no longer guaranteed at these temperatures. Experience has shown that such deposits can be drastically reduced if an oxidic layer closes the nitridic layer towards the surface of the layer. This with a CVD

To solve layer system is unsatisfactory for the following reasons: once, for the reasons already mentioned above, no thick layers are deposited, otherwise the sharp cutting edge geometry can not be met. Second, the CVD layers are usually composed of TiCN and -Αΐ ₂ θ3 and both materials are inferior in hardness and toughness of a good Al-Ti-N layer. That would presumably result in worse service lives with comparable layer thickness. Finally, the CVD layer system is under tensile stress, resulting in early layer failure, at least in interrupted cut applications.

For the fields of application of difficult to machine materials such as titanium and its alloys (for ^¬ game example with magnesium) and nickel-based alloys (known partially under the trade names Inconel®) are tools (for example, indexable inserts) with a small cutting edge radius, that is with a sharp-edged geometry current state of Technology. In order not to lose the edge sharpness even after the coating, therefore, thin layers are necessary, which are preferably made before ^¬ by PVD (PVD = physical vapor deposition). Of course, the directionality of the PVD coating is also advantageous here, which allows to coat chipboard and flank of an indexable insert by appropriate substrate holder at a different rate. For these applications, layers of Al-Ti-N are preferably used, with different metal proportions. This Al-Ti-N material produced by PVD has not only high toughness but also good oxidation resistance. Tools that have been coated with these ver ^¬ schleißmindernden layers are now considered best solution for tool coatings within the scope of difficult to machine materials.

However, the cutting parameters for such applications differ significantly from those used in mild steel and cast iron. Typical cutting speeds for the nickel-based alloys are 50 m / min and below, as opposed to several hundred meters per minute in steel or cast iron. The reason for this is the enormous mechanical and thermal load on the cutting edge, which is the case with applications for difficult-to-machine materials. Therefore is working on the improvement of tool materials, especially with regard to improving the thermal conductivity. An improvement of the tool coating in terms of thermal stability (oxidation resistance, che ^¬ mix stability and mechanical strength at high temperatures Tempe ^¬) would help defuse addition the described problems.

A disadvantage of the present state of the art is therefore low productivity in machining of hard machineable material, which is due to the low Zerspanungs ^¬ speed.

An interesting way of PVD - coating is the Zerstäu ^¬ ben targets (sputtering). In doing so, ions are accelerated to the target surface and knock small conglomerates out of the target. This possibility is described, for example, in WO 2008/148673. Here is a sputtering process

Presented (HIPIMS) gierungstarget in which one or more AlMe Le ^¬ atomized (sputtered) is where in accordance with one embodiment, the deposited layer two oxide phases or a mixed oxide of the type (Ali_ _x Me _x) ₂ 0 ₃ or spinel (Me) _x Al ₂ 0 ₃₊ x

(0> x ^ l). Unfortunately, this publication does not specify how and by what means between the two oxide phases and the mixed oxide can be selected or how the coating process must be performed to between the layer type (Ali_ _x Me _x ) 2O ₃ or spinel (Me) _X A1 ₂ specifically for For 0 _{3 + X} select ^¬. The example confirms the ability of producing an oxide of the type (Ali_ _x Me _x) 2 O _3, namely alpha-Al ₂ 0 _3, but it is left open, could be achieved as other structures. In particular, provides the expert the question of which level ^¬ took to be taken so that the knocked-out in the sputtering from the target conglomerates any Structure, for example, selectively settles as spinel (Me) _x Al20 ₃ + _x on the substrates to be coated.

The object of the invention is to provide a layer which essentially combines the high hardness and toughness of the Ti-Al-N (or Al-Ti-N) with greater thermal stability to chemical reactions or oxidation. In addition, a layer material is to be created, which has hervorra ^¬ ing mechanical properties, even at elevated temperatures.

The problem is solved with the features of claim 1.

Advantageous developments are characterized in the subclaims.

The coating, layer or layer system according to the invention is deposited on cutting tools in order to reduce the abrasive, chemical and oxidative wear of these cutting tools during the cutting process.

This oxide-containing layer is preferably or Schichtsys ^¬ system for tools used, which called for the cutting of ^so-¬ be used "difficult zerpanbaren materials," such as, for example, titanium alloys, high-nickel-containing steel alloys, and some types of stainless steels with special alloys that increase the hardness and chemical wear of the materials.

The layer or the layer system can also be used for catalytic purposes.

Advantageously, the solid materials constituting the layer have a similar oxide as well as nitride. Liehe crystal structure and crystallize preferably in cubic structure, the oxide preferably at least partially in cubic structure of the spinel.

An object of this invention is that the layer is so ausgest ^¬ taltet that in addition to the oxides with spinel structure also shares of other oxides can be introduced, which can be formed from the Feststoffanfeilen of the radioactive target used. These oxides should preferably have a finely crystalline or amorphous structure and thus serve to improve the mechanical layer properties, especially at elevated temperatures. For example, to be achieved, that they increase the breaking strength of the layer and reduce mechanical clamping ^¬ voltages that can entste ^¬ hen through the different expansion coefficients between the functional oxide layer and the support and adhesive layers and the substrate (tool).

According to the invention multilayer layers can be produced which are synthesized substantially in a crystal structure.

With the layer or the layer system according to the invention, in addition to the tools made of high-temperature resistant materials such as cemented carbides, composites (cermets), diamond, ceramics of SiC (silicon carbide), SiN (silicon nitride), c-BN (eubie boron nitride) Even less temperature-resistant materials made of HSS (high speed steel) or other steel alloys and aluminum components can be coated with advantage.

According to the invention, the object is achieved by layers which comprise at least one iAl ₂ 0 ₄ layer in spinel structure. Ge ^¬ Mäss a preferred embodiment includes a inventions dung contemporary layer N1AI ₂ O ₄ in spinel structure as well as aluminum oxide ^¬ in at least one of the phases from the group of X-ray amorphous, corundum, gamma phase, kappa phase or theta phase. In accordance with a further preferred embodiment, the layer according to the invention contains N1Al ₂ O ₄ in spinel structure and a NiO constituent, which is preferably present in X-ray amorphous phase.

In a further particularly preferred embodiment of the present invention can be at XRD measurements on the layer at least 2 reflexes, but preferably 3 reflexes mes ^¬ sen, which, with the given in Fig. 11 reference 01-077- 1877 of N1AI ₂ O ₄ in Substantially match and essentially not originate from the substrate. These are preferably the reflections of the [3 1 1] plane at 2Θ = 37.0 °, the [4 0 0] plane at 2Θ = 45.0 ° and the [5 1 1] plane at 2Θ = 59.6 °. In the most preferred embodiment of the present invention, the X-ray spectrum in the angular range of

20 ° <2Θ <90 °, in addition to the reflections of the substrate, essentially only reflections of the NiAl ₂ O ₄ reference 01-077-1877 of FIG. 11.

In a further preferred embodiment, a multilayer system is present, containing layers with N1AI ₂ O ₄ in spinel structure and in addition, metallic oxides and / or nitrides, being different in adjacent layers, the metallic components in percentage. Due to the multi-layer design, the toughness is increased. Thus, there is in Wesentli ^¬ chen no thickness limitation. In addition, the the

Layer system inherent energy can be increased, resulting in greater hardness. According to the invention the the N1AI ₂ O ₄ alternately contain multi-layer system containing in Spi ^¬ nellstruktur also one or more additional crystalline and amorphous Oxidpha ^¬ sen, preferably high-temperature phases. In a further embodiment of the present invention, gradient layers are realized which include N1AI ₂ O ₄ in Spi ^¬ nellstruktur constant lattice constant and varies the proportion of a present amorphous phase within the layer gradually and / or continuously.

The inventors have surprisingly found that the layers according to the invention can be produced in an economical manner by means of spark evaporation. During spark evaporation, so-called droplets are formed. The conglomerates are not oxidized fully or not fully durchnit ^¬ tured metallic constituents or intermetallic compounds, resulting from the target. The production of layers according to the invention is particularly economical if the filtering of such droplets can be dispensed with. A layer having such droplets, therefore, identified as produced by means of arc evaporation ^¬ layer ^¬ the. Thus, in one embodiment of the present invention, the N1Al ₂ O ₄ spinel-structured layers include the droplets typical of spark evaporation. In particular, layers produced by means of spark evaporation can be produced which comprise N1Al ₂ O ₄ in spinel structure or cubic structure, the droplets of which have a majority, preferably essentially all, a metal content of less than 50% by% nickel.

The invention is exemplified erläu tert ^¬ reference to a drawing it in which:

Fig. 1: a comparison of the XRD spectra of Probenl215 and

1217, which were prepared with varying oxygen flow, but almost identical reflexes zei ^¬ gen; FIG. 2 shows an SEM cross-section of sample 1216 showing the N1Al ₂ O ₄ layer with the approximately 150 nm thick chromium adhesion layer; FIG.

3 shows a comparison of the XRD spectra of the samples 1214 and

1216, which were prepared with varying oxygen flow and chrome adhesive layer and again show na ^¬ hezu identical reflexes, there is no indication that the chromium adhesion layer influences the spinel structure of the IAL ₂ 0 _4;

4 shows a comparison of the XRD spectra of the samples 1214 and

1216, which were prepared with varying oxygen flow and chrome adhesive layer and again show na ^¬ hezu identical reflexes, which represented better dealt with at ^¬ shows 2Θ scale that the chromium peak of the adhesive layer either on the toilet-reflex of the Sub ^¬ strates yet on which the iAl ₂ 0 ₄ is located;

5: an RBS spectrum of the sample 1217 with calculated

Layer composition ·

6: an RBS spectrum of the sample 1216 with calculated

Layer composition ·

7: an RBS spectrum of the sample 1215 with calculated

Layer composition ·

8: an RBS spectrum of the sample 1214 with calculated

Layer composition ·

9: a comparison of the XRD spectra of sample 1217 (Ni-Al ₂ O ₄ ) with the synthesized Ni-Al-N layer (Pro be 1231), the reflections of the oxide and nitride are approximately at the same 2Θ place;

10 shows a comparison of the XRD spectra of sample 1217 (Ni-Al ₂ O ₄ ) with the synthesized Ni-Al-N layer (sample 1231, which again shows the agreement of the oxide and nitride peaks in a better resolved 2Θ scale;

11 shows an SEM Querschnittsaufnehma of a layer system of an Al-Ti-N support layer and a fiction, modern ^¬ Ni-Al-0 functional layer;.

FIG. 12 shows an enlargement of a region of FIG. 11 between the layers; FIG.

Fig. 13: Reference data for NiAl ₂ O ₄ (Reference 01-077-1877); Fig. 14: Reference data for Cr (reference 01-089-4055); Fig. 15: Material characteristics sample 1214; Fig. 16: Material characteristics sample 1215; Fig. 17: Material characteristics sample 1216; Fig. 18: Material characteristics sample 1217;

Fig. 19: Examples of synthesized layer systems, the NiAl ₂ 0 ₄

Contain material as the adhesive layer comes ^¬ example, also Cr, CrN, AlCrNN, Ni-Al-N, Ni-CrN, TiN, ZrN or VN in question when backing comes ^¬ example, also TiCN in question. The invention is based on experiments that were made in a spark evaporation plant of the type Innova the company OC Oerlikon Balzers AG. As substrates for the coating indexable inserts made of hard metal (WC based) and composite ^¬ materials (cermets) were used. The spark sources were equipped with Ni-Al targets. In the case described pulverme targets ^¬ tallurgisch prepared were used. However, targets made in a different manner, containing the combination of Ni and Al in the target, can also be used for this process, for example melt metallurgically produced or plasma sprayed targets. In addition, work was also carried out with Tar ^¬ gets with other materials to produce the respective adhesive layer or support layer or to incorporate their Fest ^¬ materials in the transition to the functional layer or in the functional layer itself.

The principal method of spark evaporation for oxide production is known. In the present case, therefore, the basic principles of spark evaporation will only be discussed roughly.

During spark evaporation, a plasma is usually generated in a vacuum chamber in the form of a high-current low-voltage arc discharge on a material source, referred to below as the target. The material to be evaporated is placed in this process as a cathode to the negative pole of a voltage source. For example, by means of a Zündein ^¬ direction of the arc is ignited. The arc melts the cathode at one or more cathode spots where the current transition is concentrated. Essentially, electrons are pulled out of the cathode. In order to maintain the arc, it is therefore necessary to constantly provide for electron supply to the corresponding cathode surface. The arc, or meaning also called Are, moves on the cathode surface. It comes to a extremely fast heating of small target surface areas, which locally vaporizes material.

For a more detailed description, reference is made to the patent applications filed by the same applicant, such as, for example, WO 2006/099760, WO 2006/099759, WO 2008/009619, WO 2006/099758 or WO 2008/043606.

To prepare the oxide layer (functional layer) of the invention compound Ni-Al target were used, the nickel proportions between 10 at% and 80 at% having, preferably ^¬ between 20 at% and 60 at%.

As reactive gas for the functional layer either pure oxygen was used during the Fun ^¬ kenverdampfung or a mixture of oxygen and nitrogen, both with and without argon admixture. Nitrogen or a mixture of nitrogen and oxygen, again with optional addition of argon, was usually used in the transitions between the adhesion or support layer and the functional layer. The selection and addition of the gases depends on which chemical to ^¬ composition of the layer to be synthesized is sought: purity nitrogen for a nitride, pure oxygen for an oxide or a mixture of both gases for an oxy nitride. It is known to those skilled in the art of PVD coating that other reactive gases may be added to the spark evaporation, for example C ₂ H ₂ as an example of a carbonaceous gas, to carbides, or a mixture of C ₂ H ₂ and nitrogen, to carbonitrides produce. Of ^these possibilities, use is made primarily of the adhesive and / or supporting layer. The gas flows for the above-guiding ^¬ te coating system are controlled by gas flow controller. In addition, there is also the possibility of Regi ^¬ ment of gases on the Kammertotaldruckruck (pressure control), of which In some cases, the coating was also made use of. Typical chamber tails were between 0.3 Pa and 10 Pa, typical gas flows between 0 and 2000 sccm.

The spark currents were varied in large areas. For voting decision of the functional layer was worked with currents of between 60 A and 350 A, with both DC pulsed as Funkenströ ^¬ me were used. The range of preferred spark currents is between 80 A and 200 A.

Were coated in a substrate temperature range between 200 ° C to 600 ° C substrates were applied to substrate bias Zvi ^¬ rule -20 and -300 V. Preferably, bipolar pulsed substrate bias has been used, especially during coating with the oxide layers.

Prior to the actual coating step, the known in the art occurring in vacuum pretreatments of heating and etching steps were carried out to subject the already cleaned outside the vacuum substrates even a wide ^¬ ren pretreatment in vacuo.

After these pretreatment steps, the substrates are coated with the layers which take place before the actual functional layer deposition. Usually this is a layer which serves as an intermediate or adhesive layer (interface) for the later layer or the later layer package. Typical known materials for this adhesive layer are Al, Ti, Cr, Zr, Nb both in metallic form and as nitrides. In some cases, to improve adhesion for certain tools (substrates), these layers may contain Ni and / or Co according to an embodiment of the present invention. Combinations of these materials and their nitrides also lead to improved layer adhesion in many cases. When Examples are Ni-Cr, Ni-Al, Al-Ni-Cr, Zr and their nitrides may be mentioned, without this enumeration should be ver ^¬ limited.

Depending on the application, after the intermediate or adhesive layer, it may be useful to apply further layers before the actual functional layer deposition. These can serve, for example, to create an adapted transition to the functional layer. But you can also increase the Verschleißbe ^¬ resistance of the entire layer package, so even be of functional importance. Known to those skilled nitrides and carbonitrides of the elements Al, Ti, Cr, Zr and Nb and nitrides and carbo-nitride of two such Ele ^¬ elements (eg AlTiN or AlCrN) have been proved. It has proven to be particularly advantageous if these layers also contain Ni and / or Co.

For the coating of the adhesive layer and / or the support layer either elemental metallic targets are used, which consist of the above-mentioned metals or composite targets, which are made of mixtures of two or more elements, for example powder metallurgy or as an alloy or as an intermetallic compound or by plasma spraying.

Finally, the coating of the substrate coated with adhesive layer and backing layer takes place with the actual functional layer. The transition from the adhesive or support layer to the functional layer can be made fluent or abrupt. Smooth transitions, for example, achieved ^¬ to by the targets that were needed for the adhesive layer or the support layer, for a time be operated together with the targets of the functional layer both and thus will be a mixed layer in transition. Another Possibility to create a mixture or a graded transition exists by ramping the gas flows. If the adhesive or support layer, a nitride layer abge ^¬ excreted was the target of the functional layer can be operated at ^¬ fänglich in nitrogen which then graded or abrupt is replaced, for example, by oxygen, in order of a nitride in an oxynitride and then to pass into the pure oxide.

As a first preferred variant of the functional layer, a Ni-Al oxide layer is deposited. For the coating, Ni-Al mixed targets with a mixture of 30 at% nickel and 70 at% Al were used and the evaporation of the target material takes place in a pure oxygen atmosphere. The oxygen fluxes are selected from the range given above. The targets may in turn have been produced by powder metallurgy or as an alloy or as an intermetallic compound or by plasma spraying. In the present experiment we worked with powder metallurgy targets. It should be remembered here that nickel self ^¬ companies has magnetic. This can lead to unwanted guidance of the spark on the target. In practice, this has not been shown so far, because the addition of oxygen or nitrogen has a stabilizing effect on the spark discharge from ^¬ . In particularly critical cases, pulsed spark operation can further support this stabilization.

As a result of this synthesis, surprisingly, an oxide layer is obtained whose X-ray spectrum indicates a cubic structure and which, when compared with the data base, can be unambiguously assigned to the compound N1Al ₂ O ₄ . Surprisingly, this result is above all because no Bragg reflections of other oxides were found, neither reflections of any aluminum oxides nor of nickel oxides. It is known to those skilled in that the -Αΐ ₂ θ3 forms at about 1000 ° C, whereas the N1AI ₂ O _{4 formed} only at higher temperatures above 1300 ° C at reasonable rates. One would expect that the corundum phase of the Al ₂ O ₃ forms rather than the spinel phase of the iAl ₂ 0 ₄ .

A number of these Ni-Al oxide layers were prepared and analyzed. Figure 1 shows the XRD spectra of Ni-Al oxide films produced with different oxygen fluxes. A logarithmic representation of the intensity of the scattered X-rays was chosen to better distinguish between the substrate and the coated substrates. The XRD spectrum of the uncoated WC substrate (indexable ^insert ) can be seen as a line with pronounced noise. As a comparison, the XRD spectra of the coated substrates are represented by circular and triangular symbols. The sample points of sample 1215 were shown with open triangular symbols and the samples of sample 1217 with open circular symbols. The XRD database was compared to a N1AI ₂ O ₄ spectrum

(01-077-1877, Fig. 13) in bar form from above (black lines) additionally inserted in the figure, the bar lengths reflecting the relative intensities of the X-ray reflections of the reference sample with each other. All reflections of the X-ray spectrum of both coated substrates can be assigned. The reference data, the dominant in the measured spectrum (311) (400) and (511) reflections are easily zugeord ^¬ net. In addition to these dominant reflexes, one can still find the reflexes (331) and (422), as well as hints of

(531) and (442) with lower intensity. For the overlap with the substrate reflections, the (220), (440) and (444) reflections occur. The XRD analysis shows that a crystalline layer of Ni-Al ₂ O ₄ can be synthesized by reactive sputtering, the cubic (Fd-3m) or spiral has nellstruktur. This synthesis was carried out in the present example at 550 ° C substrate temperature. This substrate ^temperature is well below the formation temperature of this compound in thermal equilibrium.

The layers shown in Fig. 1 were synthesized with different reactive gas flows, but deposited without adhesive layer directly on the WC substrate. As discussed earlier, Figure 1 shows the overlap of some substrate reflections with the layer reflections. To now largely ruled out that the layer synthesized solely for spinel ^¬ the could, because there the Substra ^¬ tes comes to this "Nukleationshilfe", both coatings were in otherwise identical processes, but thick with an additional 150 nm chromium Adhesive layer produced. Sample 1214 was again with 300 sccm and sample 1216 is again of 800 sccm oxygen flow Herge ^¬. In Fig. 2, the SEM image of a Bruchquerschnit ^¬ tes is shown on the sample 1216 and you can see the thin ^{adhesive ¬} layer. The result of the XRD analysis on this

Layers is shown in FIG. For the chromium, a reference spectrum (01-089-4055, Fig. 14) was again selected from the XRD database, which has an Im-3m (cubic body-centered) structure. As expected, this spectrum explains the additional peaks in the spectrum derived from the chromium adhesion layer. The chrome peaks of the reference are shown as gray bars. At the low Ni-Al-0 Schichtdi ^¬ bridge of about 2 ym Cr is still easy to measure. The (211) peak of Cr shows no overlap with substrate peaks. The (110) peak can be separated well if the 29 scale is better resolved, as is done in FIG. 4. At this better resolution one sees a clear separation of the substrate peak from the (110) Cr peak and the (400) NiAl ₂ 0 ₄ peak. However, the (200) peak of the Cr again shows overlaps with the substrate peak. Since for all samples 1214 to 1217 the measured layer peaks of N1Al ₂ O _{4 at} practically the same 29 values as the comparison of Figures 1 and 3 shows, one can conclude that there is formation of NiA ^ C ^, whether with or without an adhesive layer prior to film deposition the Ni-Al-0 functional layer is used, so it does not need a nucleation layer.

Also, the chemical composition of the layers made at 300 sccm and 800 sccm oxygen fluxes was analyzed. The analysis was carried out by means of EDX and RBS measurements. Since no significant difference between the EDX and the RBS analysis could be found for the metallic compositions, only the RBS measurements are to be discussed here because they give quantitatively better information about the oxygen content and also qualitatively the depth profile of the metals in the vicinity describe the layer surface.

In Fig. 5, the RBS spectrum of sample 1217 is shown. The evaluation showed a composition of io. ₅ sAl ₁ . ₄₂ O ₂ .7. If this is normalized to nickel, NiiAl2 results. ₄ s0 ₄ .66 · At first glance, this seems to be a discrepancy to the XRD analysis, since the peaks of the spinel structure could be clearly assigned to the stoichiometric N1AI ₂ O ₄ . This situation can be explained by the fact that besides the Ni-Al ₂ O ₄ another oxidic material is formed. Of course, based on the target composition, the alumina is obvious. If one assumes that stoichiometric spinel forms and forms the difference, one obtains AI0.45O0.66 or otherwise normalizes AI2O2.94, which corresponds to the stoichiometric alumina within the error limits. As expected, the same composition is obtained for Sample 1216 (Figure 6), as these are also, except for Cr Adhesive layer was prepared in an identical deposition process for the Oxidfunk ^¬ tion layer.

However, another result is obtained for sample 1215 (Figure 7) and 1214 (Figure 8) made with lower oxygen flux. For both samples, there is a co ^¬ setting Nio. ₅ Al ₁ . ₅ O ₂ .7, which corresponds to a composition of NiAl30s.4 when normalized to Ni. This suggests a layer consisting of NiAl ₂ 0 ₄ with additional amounts of AIO ₁ .4 or, which is synonymous, Al ₂ O ₂ .8, so again an additional proportion of alumina in the layer.

These measurement results support the following conclusions. Once addition to the NiAl ₂ 0 ₄ spinel is implemented in addition in the target EXISTING ^¬ dene material in an oxide. The determining factor for Kris ^¬ tallstruktur but the spinel and the alumina is is X-ray amorphous, ie the crystallite size is too small to result in the X-ray diffraction to reflections. While no electron diffraction was performed on these layers, such analysis is expected to show fine crystalline Al ₂ O ₃ with crystallite sizes around 5 nm or smaller in a high temperature phase (alpha, theta, gamma, kappa).

The second surprising conclusion concerns the depen ^¬ dependence of the ratio of the metallic components in the syn ^¬ thetisierten layer. While an Al / Ni ratio of 3.0 was measured for the 300 sccm oxygen flow layers (samples 1214 and 1215) (near the near surface), an Al / Ni ratio is obtained for 800 sccm oxygen flow (samples 1216 and 1217) from 2.5. This means that the oxygen flux can be used to control the concentration of the target components Ni and Al in the layer (with the same target concentrations of the metallic constituents!). The possibility, that the target surface Funkenbe ^¬ drove several hours still not in the "balance" (ie that the top ^¬ surface of the target by powder metallurgy was not conditioned) was, one can exclude with the experience of other coating processes with reactive spark evaporation. This is also shown by the target surfaces recorded in the SEM with elastically backscattered electrons.

According to the experiments, the oxygen is mainly consumed for the N1AI ₂ O ₄ spinel structure and alumina is formed from the "remainder" of the available oxygen. By the oxygen flow further sccm to 1200 he was ^¬ höht, it came virtually to the target entspre ^¬ accordingly stoichiometric layer formation, which was in this case IAL ₂ 0 _4th It could not be accurately clarified why there is this influence of the ratio of Targetkompo ^¬ components on the oxygen flow with respect to the layer.

For targets with larger nickel contents (eg above 50 at%) it has been shown that, in addition to the formation of the N1AI ₂ O ₄ spinel, nickel oxide and not alumina are formed. In this case too, the influence of the Al / Ni ratio on the oxygen flow was again observed.

This is regarded as inventive as it allows for moving ^¬ cher target composition layers with different ratio of the metal components that are present in the target, particularly produce such mixed oxide by the oxygen flow is regulated.

The results discussed so far emphasize the importance of covering large areas of oxygen flux in the synthesis of N1AI ₂ O ₄ layers. The Therefore, methods of reactive spark evaporation offers tremendous advantages over reactive sputtering process which can be used in principle also to the layer synthesis, although not due to the process have the opportunity to oxygen flow quasi independent einzu of process stability make ^¬. The skilled worker knows that when working in the oxygen gas only narrow process window in the sputtering existie ^¬ reindeer, the target avoid poisoning. The operation of the radio sources in a pure oxygen and oxygen in large ^¬ rivers or oxygen partial pressures also affects the conditioning process to the target surfaces. This is of particular importance in mixed targets that are produced by powder metallurgy. After the ignition of the spark leads to a significant modification of the target surface, which suggests that convert the elementary components on the target surface in intermetallic compounds or mixed crystals ^¬. Depending on whether this process for the layer synthesis is desirable or not, is therefore ge ^¬ go in the first use of the targets with or without target shutter to avoid a layer structure on the substrate, or to obtain a copy of conditioning (possible nucleation) in the layer structure.

The temperature stability of the oxide layer with the NiA ^ C ^ Spi ^¬ nell structure was verified by these temperature cycles were exposed up to 1100 ° C and the stability of the Rönt ^¬ genspektren was observed under these conditions. There was no significant change in the spectra, which indicated a change in the crystal structure of the spinel. At temperatures above 1000 ° C, only diffusion processes of the WC cemented carbide inserts took place; for example, the diffusion of the co-binder could be observed by RBS analysis. The quality of the coupling of the Ni-Al-oxide layer at the sub ^¬ strat or to the adhesive or backing layer is decided by the ^¬ importance for the performance of the coated tool or component. One can experience has shown assume that material related layer transitions create a particularly good Ver ^¬ bund. However, it has also been shown that materials of similar crystal structure and lattice constants show more intimate adhesion than non-structural materials. In order to now the N1AI ₂ O to connect _four layer particularly well to the WC substrate was of the ^¬ half attempts to Ni-Al-N layer using the moving ^¬ chen targets which were needed for the N1AI ₂ O ₄ Oxidfunktions ^¬ layer , There were thus operated, the Ni-Al target in a nitrogen (either flow controlled or druckgere ^¬ loop). An X-ray spectrum was prepared from the layer thus prepared. 9 shows the result of the XRD measurement of this layer in comparison to the XRD measurement of the sample 1217. In addition, the X-ray spectrum of the WC substrate is indicated again and the bars again show the iAl ₂ 0 ₄ reference spectrum. No reference spectrum could be found in the database for the Ni-Al-N layer, indicating that this compound has not yet been synthesized or investigated. The comparison indicates that some peaks of the oxide and the nitride are in approximately the same positions, namely the (311), (400) and (511) peaks (Oxidrefe ^¬ ence). This is shown more clearly once again in FIG. 10 with a spread 2Θ axis. The measurement result is indicative of similar crystal structures, and suggests that the nitrogen can be replaced gradually by the oxygen and vice ^¬ versa without causing major changes in the crystal structure, which means that Ni-Al-N is present in similar cubic structure as the NiAl ₂ 0 ₄ . This measurement result and the material ^¬ similarity leave good coupling behavior between nitride and oxide expect. Accordingly, in the experiments no adhesion problems between the Ni-Al-N and the Ni-Al-0 Schicht and also the Scratch tests, which were carried out for the purpose of quantifying the adhesion, showed above-average adhesion.

But even with different materials an excellent adhesion of the Ni-Al oxide was observed for the previously deposited layer if the other material cubic Struk tur ^¬ had. Above all, this could be for the coupling

Tio. ₅ Alo.5N, Tio. ₄ alo. ₆ N and Tio. ₃₄ alo. ₆₆ N and it is believed that this also applies to wide ranges of other Ti / Al ratios, as long as the material predominantly cubic structure.

As an example, FIG. 11 shows the SEM cross-sectional image of a layer system consisting of an Al-Ti-N

Support layer and a Ni-Al-0 functional layer according to the invention consists. A higher magnification of the area Zvi ^¬ rule the layers (Fig. 12) demonstrates the transition between nitride and oxide, and shows that there are no abrupt changes in the morphology of the layers, indicating good adhesion. FIG. 11 also shows the typical in the Fun ^¬ kenverdampfung droplets in the submicron range, which occur mainly in the use of multi-component target. The germs of the droplets mainly contain the metal of the high-melting component of the multicomponent target. The picture also shows larger spatters that were generated before the start of the oxide coating and that can be greatly reduced by skillful litigation. Their number and size can be reduced in various ways (eg by using source apertures with targeting prior to coating with the source closed or masking the "oxide" targets during nitride coating). However, you can completely avoid these splashes do not evaporate if the substrates are exposed directly to the sources and do not use elaborate filters.

Further examples of cubic structure support layers are TiN, CrN, TiCN and AlCrN, which list is not intended to be limiting. Particularly advantageous are adaptations to materials which amount to a multiple or a part of the lattice constants of a = 8,049 given in FIG. 13 for the NiA1204. Can in this case the skilled person is aware that this lattice constant "fine-tuned" by varying the concentration of the layer-forming elements and that it is possible "mismatched" over a certain layer thickness (ie, with a small difference in lattice ^¬ constant of the superimposed layers ). The case built into the layer system stress can be controlled by a multi-layer design so teilwei ^¬ se that there is no delamination.

It is therefore advantageous for the performance of the layer that the process control allows an uncomplicated and secure production of layers in multi-layer structure. With the reactive spark evaporation one can produce multilayer structures in very different ways. The first method is to operate targets of different materials alternately or spatially offset in the plant. In addition, the reactive gas can still be varied, ie, at ^¬ play, the oxygen or nitrogen flow or its pressure. Especially beneficial are then materials which form kubi ^¬ cal structures, both in the different materials as well as the reaction products of the materials with the reactive gases.

Another interesting method of multilayer fabrication is to use targets that are made of the same me- consist of metallic components (here Ni-Al), but with respect to this different composition. Of course, these can also be operated alternately or simultaneously with different reactive gases. The result is multilayer coatings in the same material system, but with changing ratio of the target components (Ni / Al ratio) and corresponding reactive gas components in the layer. Or a multi-layer design, which in addition to the changing ratio of the target components is additionally generated and superimposed by different reactive gases.

Novel is the production of multi-layer structures by using the same targets, which are operated only with a variation of the oxygen flow and for the production of which in principle no substrate rotation requires, although this can take place naturally. As already discussed above, the oxygen flux also changes the Ni / Al ratio, which is the cause of the multilayer structure.

The layers produced by the above method were tested for their mechanical properties. Of course, it can not be entered on all attempts. By way of example, only the results of samples 1214 to 1217 are shown here again, their Marten hardness (HM) at maximum test force, their elastic indentation modulus (EIT / l-vs ^A 2), their plastic deformation fraction (nplast), their indentation hardness (HIT) at maximum Test load and their hardness value according to Vickers (HV) were measured. The results are shown in FIGS. 15 to 18. The layers show excellent Vickers hardnesses of about 3200 for the low oxygen flow samples of 300 sccm and about 3000 for the larger oxygen flux of 800 sccm. The elastic penetration module is higher in comparison to other PVD oxide layers and is even ty- for some nitrides based on Al-Ti. As a comparison also Hardness measurements were performed on a Korundstandardprobe that a Vickers hardness between H _v = 2500-2700 erga ^¬ ben. These hardness values are thus below those of the spinel ^layers according to the invention.

To demonstrate the possibilities with respect to coating materials, coating design and manufacturing method, various coating systems were prepared which are Darge ^¬ provides in Fig. 19. The possibilities of variation are great and not all possible layer system should be represented by FIG. Almost all adhesive layers can be combined with almost all support layer materials. However, it makes economic sense to design the entire layer system so that the number of targets of different materials is kept as small as possible, ie that all layers with a target material or at least adhesion and support layer with a Ma ^¬ material or support and functional layer with a Target material can coat ^¬ rial. The layer thicknesses were not indicated individually in FIG. 19, since they may be over large areas vari ^¬ ated. Typical thickness ranges for the various ^¬ which are layers:

Adhesive layer: 0.05 ym to 2 ym

- Support layer: 1 ym to 15 ym

- Functional layer: 1 ym to 15 ym

Also has not been described in detail that can be changed via the substrate bias of the stress in the film and that generates at higher substrate bias compressive stresses ^¬ the resulting still higher values for hardness measurement, but which can lead to adhesion problems with layer thicknesses above 10 ym , The high hardness of the layers and the fact that they form the high-temperature-stable spinel structure encouraged chip removal tests in difficult-to-machine materials such as austenitic stainless steels and nickel-based alloys, titanium and titanium alloys. As an example, a closer look at the machining of a nickel-based alloy (Ni-Cr-Mo) will be given. The outer longitudinal turning tests were carried out on well geschliffe ^¬ NEN inserts with smooth surfaces and was compared between uncoated, coated by default by the manufacturer (Al-Ti-N-based) and coated with the inventive film inserts. As an example, here on a supporting layer of Tio. ₃₄ Alo.66N with the N1AI ₂ O ₄ functional layer.

Coatings were prepared on 3 ym layer thickness (2 ym support layer 1 ym functional layer) compared to the free surface and the termination criterion for the life comparison of the coated inserts was chosen wear at 300 nm if it came to the failure of the tool press ^¬ ges not before. The indexable inserts were operated at cutting speeds of v _c = 30, 60 and 90 m / min with a feed of 0.2 mm / rev and a cutting depth of 2 mm. Coolant was used. The results showed the expected 25% improvement in the life of the manufacturer-coated version over the uncoated for 30 m / min. At 60 m / min, the cutting edge of the uncoated tool became unstable. The tool according to the invention with the layer facing ^¬ te about 50% greater life than the uncoated tool at 30 m / min and 20% longer life than the ^¬ be coated tool at 60 m / min. There was also at 90 m / min a significant difference in quality compared to the wear of the manufacturer coated tool, which is based on a stabilization of the cutting edge by the Close the inventive layer. In this area, the uncoated tool failed completely.

The application of this hard and high-temperature stable coating was also tested for other applications outside of the tool coating. ^¬ had a beneficial because with out that these oxide layers can be produced at low temperatures even, thus also normal steel and also temperature-sensitive steels can be provided with this hard and oxy dationsbeständigen layer. Thus, components and components were coated in the engine area, which are exposed to high wear at high temperatures, such as piston surfaces, piston rings and components in the turbocharger and other parts in the Abgasbe ^¬ rich. Also advantageous is the protection against hot gas corrosion in the turbine sector of aircraft construction.

Another application of this layer is expected for catalytic applications. Ni-Al 0 ceramics, for example, gel technology can be made with the sol, it is known that they have catalytic activity, eg greenhouse gas unschäd ^¬ Lich. Therefore, nickel is typically embedded in an alumina ^¬ matrix by nickel is applied to aluminum and heated in air. It is therefore advantageous for a Kataly ^¬ sator, the inventive N1AI ₂ O ₄ layer to be used with alumina, the ratio can be adjusted. This is possible for the first time on a coating method that can produce ^¬ without high-temperature step both materials and that in one process step.

Advantageous Effects of the Invention:

As shown, the invention allows the production of layers (by reactive spark evaporation), the cubic N1AI ₂ O ₄ in spinel structure (with submicron splashes).

In addition to the layer units of cubic N1AI ₂ O ₄ in spinel structure, the layer may have other proportions of aluminum oxide ^¬, which consist of at least one of the Hochtemperaturmodi ^¬ fications of the alumina and that of alumina of the alpha, gamma, theta, kappa structure.

The layer can also be synthesized in such a way that, in addition to the cubic N1Al ₂ O ₄ in spinel layer portion, it contains proportions of ku ^¬ bischem Ni-0 in different crystallite size. Before ^¬ preferably, the layer may consist essentially only of the cubic N1AI ₂ O ₄ in spinel component.

The layer is characterized by high temperature stable egg ^¬ properties, which means that it has the typically high for the spinel curing, the loose less quickly than the size of the nitrides is the case. The cubic N1Al ₂ O ₄ Spi ^¬ nell structure of the layer according to the invention is maintained even at temperatures above 1000 ° C.

The cubic N1AI ₂ O ₄ layer ensures especially in combination ^¬ nation cubic underlayers stable layer transitions, especially with TiN, Ti-Al-N and TiCN, ZrN, Zr-Al-N, ZrCN, which contributes to excellent adhesion.

In addition to the Ni-Al-0 layer according to the invention, a further novel Ni-Al-N layer system was synthesized for the first time using reactive spark plating, which has a cubic structure with the spinel of very similar lattice constants according to the measured XRD spectrum. This fact allows both the "material-matched" and "lattice-constant matched" bonding of the Ni-Al-N and Ni-Al-0 layers to each other. Particularly advantageously, the layer composite Zvi ^¬ rule of the Ni-Al-0 layer with material other layers designed, if this also cubic structure having having lattice constants which are an integral part or an integral multiple of the lattice constant of the Ni-Al-0 spinel essentially such as Al-Ti-N.

The inventive layer of Ni-Al-0 has a high hardness, which is higher than Hv 2300, Hv preferably about 2500, more preferably about Hv before ^¬ 2700th The mechanical strength of the Ni-Al-0 spinel layer can be further improved by the incorporation of Aluminiumoxi ^¬ the high-temperature structures or Ni-0, in particular with respect to toughness.

In this case, the second oxide introduced into the layer in addition to the NiAl ₂ O ₄ preferably has very different crystallite sizes, preferably smaller than those of the spinel and more preferably X-ray-amorphous structure.

As a particularly chemically stable, a layer of NiAl ₂ 0 ₄ and NiO has been found, both oxides are present in a cubic structure.

As shown, the transition from nitride to oxide can be driven in the same target material.

It is the production of multilayer films of a target material by changing the oxygen flow or

which surprisingly leads to a change in the Ni / Al ratio in the multilayer structure. The process according to the invention allows the production of a Ni-Al-containing multi-layer layer in a continuous cubic structure by varying the nitrogen-oxygen flux.

The inventive method allows the production of N1AI ₂ O ₄ layers, in particular in spinel structure, wherein the content of alumina and nickel oxide can be controlled via the oxygen flow.

target

The process according to the invention, starting from a plasma-sprayed single-phase Ni-Al target, leads to a target whose surface has a plurality of intermetallic compounds or mixed crystals of the following type: Al ₃ N ₁ , Al ₃ N _{1 2} , AlNi, Al ₃ N ₁ ₅ , AlN ₃ , It is important to assume the condition of the condition of the target. In particular, it is possible to condition the target behind a shutter by means of Various ^¬ ner oxygen fluxes. This, for example, to avoid Schichtinhomogenitäten.

The invention can be used with advantage inter alia in the following applications:

- Included as wear protective coating on cutting tools, insbeson ^¬ wider particularly advantageous to toilet and cermet, ceramics, Di ^¬ amant and substrates, Cr, such as HSS and also for applications in hard machinable material.

- Between the substrate and functional layer, a cubic CrN layer can be provided as a support layer. As high-temperature corrosion protection, the layers according to the invention can be used in internal combustion engines and exhaust gas systems or in turbine blades.

Finally, it should again be pointed out that the layers ^{according to the} invention are harder than corundum and at least in the multilayer version more elastic than ordinary PVD oxides, that lattice matching is possible and, for example, the embedding of a cubic N 1 Al ₂ O ₄ structure in high-temperature aluminum oxide structures is performed can.

A coating has been presented which comprises at least one compound of oxygen and / or nitrogen with at least two metallic materials, characterized in that the compound is present at least partially in spinel structure.

The coating may have an intrinsic compressive stress of the compound having components between 0.2 GPa and 5 GPa. In this way, the stability of the Beschich ^¬ tion is increased.

Preferably, one of at least two metallic mate rials ^¬ nickel and / or aluminum. In the case of nickel and aluminum, the XRD spectrum may show the 311, 400 reflections, and preferably also the 511 reflex.

The compound may be N1Al ₂ O ₃ and other components of the coating may be in X-ray amorphous phase. Optionally, the X-ray amorphous phase present in other components of aluminum oxide and / or nickel oxide umfas ^¬ sen, wherein optionally the alumina preferably is in the corundum and / or gamma phase. Such a coating may comprise a plurality of superposed layers and the layers may have substantially identical metallic chemical elements but with different metallic proportions. In particular, the layers may even have substantially identical chemical elements.

The coating may include the droplets that are typical for spark evaporation.

It may be a cubic support layer comprises, preferably from the group Al-Ti-N, Ti-C-N, Ti-N, Cr-N or mixtures thereof.

A process has been disclosed for coating substrates by means of spark evaporation, which is characterized in that the target used is an alloy target which has between 10 at.% And 80 at.%, Preferably between 20 at.% And 60 at.% Nickel and which as reactive gas Oxygen and / or nitrogen is used. The alloy target may comprise aluminum.

By means of oxygen flux, preferably between 300 and 800 sccm sccm, the Al / Ni ratio can be varied currency ^¬ rend of the coating according to the invention.

There have been disclosed coated substrates, in particular tools or components, which are characterized in that the surface of the substrate on which the coating comes to rest comprises a steel, in particular Cr-containing steel, such as HSS. The coated substrate may be an indexable insert.

Claims

claims

1. coating, which comprises at least one compound of oxygen and / or nitrogen with at least two metallic materials, characterized in that the Ver ^¬ bond is present at least partially in spinel structure.

2. Coating according to claim 1, characterized in that the intrinsic compressive stress of the compound having constituents of the coating is between 0.2 GPa and 5 GPa.

3. Coating according to claim 1, characterized in that the at least two metallic materials nickel umfas ^¬ sen.

4. Coating according to one of claims 1 and 2, characterized in that the at least two metallic Materia ^¬ materials include aluminum.

5. Coating according to claim 3, characterized in that the XRD spectrum shows the 311, 400 and preferably also the 511 reflex.

6. The coating according to claim 3, characterized in that the connection N1AI ₂ O ₄ and further constituents are present in the coating Be ^¬ X-ray amorphous phase.

7. The coating according to claim 6, characterized in that the X-ray amorphous phase present in other components of aluminum oxide and / or nickel oxide, wherein ge optionally the alumina preferably is present in ^¬ Korundstruk ^¬ structure and / or gamma phase.

8. The coating according to any one of the preceding claims, characterized in that the coating consists of a multi ^¬ number is formed by superposed layers, but the layers have identical metallic chemical Ele ^¬ elements with different metallic components.

9. Coating according to claim 6, characterized in that the layers have identical chemical elements.

10. Coating according to one of the preceding claims, characterized in that the coating has the typical droplets for spark evaporation.

11. Coating according to one of the preceding claims, characterized in that it comprises a cubic support layer, preferably from the group Al-Ti-N, Ti-C-N, Ti-N, Cr-N or mixtures thereof.

12. A method for coating substrates by means of spark evaporation, characterized in that a Le ^¬ targeting target is used as target, which between 10 at% and 80 at%, preferably between 20 at% and 60 at% nickel know and that as reactive gas oxygen and / or stick ^¬ substance is used.

13. A method for coating substrates by spark evaporation, characterized in that an alloy target, which contains aluminum as a component, is used for producing a coating according to claim 9.

14. A method for coating substrates by spark evaporation, characterized in that by means of the Sauer ^¬ material flow, preferably between 300 sccm and 800 sccm, the Al / Ni ratio during the formation of a coating according to any one of claims 9 or 10 is varied.

15. A coated substrate, in particular tools or compo nents ^¬, characterized in that the surface of the substrate on which the coating comes to lie, is a steel and the coating is designed according to one of claims 1 to 11.

16. Coated substrate, in particular tools or compo ^¬ nents according to claim 15, characterized in that the steel contains Cr.

17. A coated substrate, in particular tools or compo nents ^¬ according to claim 15 or 16, characterized in that the steel is a high-speed steel.

18 coated substrate, in particular tools or compo ^¬ nents, characterized in that it is a cutting ^¬ cutting plate, wherein a coating according to claim ^¬ 11 is provided.