EP0149449A1 - Hard metal body, in particular a cutting tool - Google Patents

Abstract

1. A hard-metal body, in particular a hard-metal cutting tool, with a coating on the basis of carbides and/or nitrides of elements of Sub-Groups IV to VI of the Periodic System and at least one further coating on the basis of aluminium oxide and/or zirconium oxide, characterized in that the substrate of the base body has directly applied ot it a first coating formed by one or more layers with at least one layer having from 0.1 to 2.5 atom % aluminium and form 0.1 to 8.0 atom % oxygen - of oxycarbide, oxycarbonitride or oxynitride of a least one of the elements Ti, Zr, Hf, V, Nb, Ta and Cr, over which a second oxidic coating of one or more layers of aluminium oxide and/or zirconium oxide is applied.

Description

The invention relates to a hard metal body, in particular a hard metal cutting tool, with a coating based on carbides and / or nitrides of elements from IV. To VI. Subgroup of the periodic table and at least one other coating based on aluminum oxide and / or zirconium oxide.

Such tools are used above all in the machining of materials, in particular metal, for example turning, cutting and milling tools, milling heads, drills, saws and the like. They can also be used for non-cutting deformation, such as dies, nozzles, press rams, dies or the like. A large number of coated hard metal bodies with a base body and mostly multi-layer coatings are known, but there is always the endeavor to achieve high cutting speeds with as little wear as possible and also to have a tool available which can also withstand high necnanic stresses, such as those with an interrupted one Occur cut, withstands. All efforts are aimed at still increasing the service life of the tools and the ease of machining. For example, it is known from US Pat. No. 4,018,631 to produce a cutting body with a multiple coating, in which a carbide, nitride or carbonitride coating is applied to a sintered carbide substrate, then elements such as tungsten and cobalt from the base body the coating is allowed to diffuse in, then the coating is oxidized and an oxidic layer is applied to the pretreated coating. The disadvantage of such bodies is that the oxide formed in the process described layer tends to volume expansion. According to EP-PS 32 887, such phenomena should be reduced if Serge is worn to ensure that oxygen introduction is avoided at least in certain areas of the base body coating by first providing the body with a carbide nitride or carbon nitride layer diffusion from the substrate into the layer or vice versa, followed by a wear-resistant coating with oxide. Before this oxide layer is applied, the intermediate coating can be co-oxidized from the outside to improve the adhesion, but only in a layer thickness that does not reach the substrate.

It has now been found that the problems which arise as a result of the different physical and usage properties and intended use of the individual bearings of coatings of hard material bodies with highly wear-resistant oxioic outer coatings can be largely eliminated if the coating on the base body or substrate is underneath Compliance with certain quantity limits is doped with an element that is present in the outer coating or is related to it.

The invention relates to a hard metal body, in particular a hard metal cutting tool, of the type mentioned at the outset, which is characterized in that a first, oxygen-containing, carbidic and / or nitridic coating with at least one 0, directly on the substrate of the main body containing Ta 1 - 2.5 atomic% aluminum layer made of oxycarbide, oxycarbonitride or oxynitride, in particular oxycarbonitride, at least one of the elements Ti, Zr, Hf, V, Nb, Ta and Cr, preferably of titanium or zirconium is brought over which a second, oxidic coating with at least one layer, optionally containing boride-containing deposits, with an oxide of aluminum and / or zirconium is arranged, and the body is optionally heat-treated and / or compacted. The above-mentioned inclusions have at least substantial proportions of metal boride.

It has been found that the incorporation of aluminum in the small amounts mentioned into the first coating then brings about the effect of practically stepless transition of the properties of the individual layers of the coating into one another, so that the respectively specific favorable properties of carbide and / or nitride layers work synergistically with the excellent wear properties can be combined with oxidic (external) coatings. Not only the transitions between the two main types of coating, but also those from the substrate to the coatings are characterized by flexibility and high adhesion. It has been found that the presence of oxygen is not a problem even in the layer immediately adjacent to the substrate. With the new carbide bodies, high cutting speeds and high machining economy can be achieved with improved tool life.

If the oxycarbide, carbonitride or nitride - particularly preferred is oxycarbonitride - of the first coating has an aluminum content of 0.5 to 2 atom%, particularly secure adhesion of the two coatings is ensured, it being noted that zirconium oxide also having a second coating of aluminum alone is able to bring about the favorable effect.

Long service lives despite economically high cutting speeds can be achieved if the first coating has two or more layers with oxycarbide, oxycarbonitride or oxynitride, preferably oxycarbonitride, at least one of the above-mentioned elements, the aluminum content of the individual layers increasing from a layer directly adjacent to the substrate, optionally aluminum-free, increasing towards the outside.

Further improvements can be achieved in this direction if the aluminum content of the layers of the first coating does not increase substantially linearly from the area immediately adjacent to the substrate. The increase in the aluminum content can be gradual or practically continuous.

It has proven to be advantageous in practice if the oxygen content of the oxycarbide, oxycarbonitride or oxinitric layer (s) of the first coating in each case 0.1 to 8 atom%, preferably 1 to 5 atom%, is. At these contents in particular, it has been shown that oxygen in the coating applied to the substrate in no way has an adverse effect.

Similar to the presence of aluminum, the content of which can advantageously be kept increasing towards the outside, it is also technically advantageous with regard to the transition to the oxide coating if the first coating comprises two or more layers with an oxycarbide or oxycarbonitride or oxynitride, preferably oxycarbonitride, has at least one of the above-mentioned elements, the oxygen content of the individual layers increasing from the layer immediately adjacent to the substrate and increasing towards the outside, wherein even better operating behavior can be achieved if the Oxygen content in the first coating of the un _- indirectly adjacent to the substrate layer outwardly, preferably substantially linear ascending is. Very thin individual layers can also be present, so that the increase is practically continuous.

For a high level of stabilization of the oxidic coating, it is advantageous if it or at least some of its layers has zirconium of 1 to 20% by weight, preferably 2 to 15% by weight.

if, as provided in accordance with a further variant, the second coating has two or men oxidic bars, the zirconium content of the individual layers increasing from the outside, directly adjacent to the first coating and possibly free of zirconium, can be increased among others the abrasion on open surfaces subject to wear and thus estimate the remaining tool life, whereby an essentially linear - gradual or continuous - increase in the zirconium content is particularly beneficial in this regard. With such an estimation option, unintentional downtimes can be largely avoided.

It has been shown that the doping of the first coating or of its layers with aluminum itself has a stabilizing effect, so that the presence of zirconium is not urgent per se, the oxidic layer of the second coating immediately adjacent to the first coating can therefore also have a zirconium-free layer with aluminum oxide.

A further substantial increase in wear resistance can be achieved if the boride-containing deposits provided in the second coating, if appropriate, are those with aluminum and / or zirconium boride.

Especially by heat treatment, e.g. by means of a hot presser which is advantageously to be provided, a particularly ionic yet improved bond to individual layers of the coatings can be achieved. A body according to the invention is therefore particularly preferred if the substrate and layer (s) of the first and second coating each have diffusion zones with one another.

Another object of the invention is a process for the production of hard metal miners, in particular cutting tool bodies, as described so far, which is carried out in a manner known per se with regard to the application of the individual layers, an embodiment being preferred in accordance with the invention in which substrate body, preferably containing tantalum, is present after a gas phase separation process (CVD process) in the presence of a powder and aluminum, in the gas phase containing or delivering quantities which may change during the coating process, a first coating with at least one layer with oxycarbide, oxycarbonitride or oxynitride, in particular oxycarbonitride , at least one of the metals mentioned in detail above is applied, and then in the presence of an aluminum and / or zirconium and optionally boron, in a gas phase containing quantities which may change during the coating process, with a second coating at least one layer, optionally containing boride-containing deposits, is deposited with aluminum and / or zirconium oxide, whereupon the coated body obtained, if appropriate a post-compression process, preferably an isostatic pressing, in particular at pressures from 500 to 2500 bar, and / or a heat or heat treatment, preferably thermal diffusion treatment, in particular at temperatures of 900-1600 ° C., preferably from 1100 to 150 ° C. .

In order to achieve the desired, essentially linear, increase in the oxygen and / or aluminum content within the first coating, it is advantageous if, when separating its individual layers, the oxygen and / or the aluminum content of the gas phase during the coating process in a linear stepwise or continuous manner - is increased.

Finally, it can further advantageously be provided that when depositing a second coating with at least two oxide layers, the zirconium content of the gas phase is increased, preferably essentially linearly, during the coating process.

The invention is explained below on the basis of examples with results from test trials with the new cutting bodies.

Example 1:

Cuts made of hard metal (85% WC, 9.5% TiC - TaC, 5.5 Co) are czw. Vacuum heated to a temperature of 100 ° C, then treated with a gas mixture containing 5% TiCl ₄ , 8C% H ₂ , 5% N ₂ , 5% CH ₄ and 5% CO for 60 minutes. Then the gas mixture AlC _l 3 is mixed in amounts of 0.5% (test series la) and 1% (test series 1b with small amounts of CO (2% in each case) based on AlCl ₃ .

For comparison purposes, the addition of AlCl _{3 was} omitted. (Test series 1C) The total pressure in the furnace is 150 mbar during the treatments. After a treatment time of 210 minutes, a completely dense oxicarbonitride layer of about 3 µm thick was formed, each with an average of 0.5 atomic percent Al in the bodies of experimental series 1a and 1.4 atom in those of experimental series 1b % A1 was endowed.

Example 2: Test series 2a

Cuts made of hard metal (91% WC, 2.5% TiC + TaC, 6.5% Co) are heated in an oven under protective gas or vacuum to a temperature of 1000 ° C and then for 40 minutes with a gas mixture with 8% TiCl _4, 2% _ZrCl4, 70% hydrogen, 15% N ₂ and 5% CO ₂ initially (experiment A) treated. Thereafter, the TiCl _{4 is} replaced by AlCl ₃ for 5 min at intervals of 10 min and the CO ₂ content is continuously increased from 5 to 15% with a corresponding reduction in the H ₂ content. The total pressure in the furnace during this treatment is 650 mbar. After 90 minutes, an approximately 2.5 µm thick oxynitride Layer in which the Al content averaged 0.9 atomic% and the oxygen content from the substrate rose to the outside from 0.5 to 3.5 atomic%.

Test series 2b

The procedure is the same as in test series 2a, but 7.5 and 7.5% CH _{4 were} used instead of 15% N2 in the gas mixture. An approximately 2.5 μm thick oxycarbonitride layer with essentially similar aluminum contents and oxygen contents, as indicated for experiment la, is deposited on the substrate.

Test series 2c

In this series of experiments, AlCl ₃ was not added, but the treatment conditions according to series of experiments 2a and 2b were maintained. The coated material obtained contained no aluminum in its hard material layer.

Regarding the samples doped with aluminum according to 2a and 2b, it should be noted that in the layer directly adjacent to the substrate, into which aluminum can diffuse from the subsequent treatment, aluminum was analytically at the detection limit.

Example 3: Test series 3a

Cuts made of hard metal (79% WC, 10% TiC + TaC, 11% Co) are heated in an oven under protective gas or vacuum to a temperature of 1020 ° C, and then for 90 minutes with a gas mixture with 5% TiCl ₄ , 70% H ₂ and 25% CH ₄ treated. The working pressure in the furnace is 200 mbar. The temperature is then increased to 1050 ° C. and at a working pressure of 150 mbar, the temperature is 120 minutes 5% AlCl ₃ and 5% CO ₂ were alternately added to the gas mixture with a corresponding reduction in the hydrogen content in each case for 5 minutes.

After a total duration of 150 min, a coating has formed in test series 3a which has an Al content of 1.5 atom% Al and 6 atom% oxygen enriched against the outer surface, while Al and the oxygen content are close to the substrate are each less than 0.1 atomic%.

Test series 3b

No aluminum was detected, however the other conditions according to test series 3a were met.

Example 4: Test series 4a

Cutting bodies according to the preceding examples and test series are treated in a gas mixture with 10% AlCl ₃ , 80% H ₂ , 5% CO ₂ and 5% ZrCl ₄ for 120 min at a temperature of 1020 ° C, during which period at regular intervals of 8 min the proportion of CO _{2 is} reduced in each case for 2 minutes and replaced by BCl ₃ . Oxidic coatings are formed on the cutting bodies, which have embedded borides of aluminum or zirconium.

Test series 4b

If the procedure is otherwise the same, BCl _{3 is} not doped when coating samples from the test series la, 2a. The properties of the bodies obtained are summarized in a table at the end of the examples.

Example 5: Test series 5a

Cutting bodies according to the preceding examples and test series are treated in a gas mixture with initially 10% AlCl ₃ , 70% hydrogen, 12% CO ₂ , 5% ZrCl ₄ and 3% HC1 at 1030 ° C. and a working pressure of 200 mbar in such a way that the AlCl3 content is continuously reduced to 60% of the initial value over a period of 150 min and at the same time the ZrCl content is increased accordingly, so that the total AlCl ₃ + ZrCl remains constant. An approximately 2 μm thick layer with an outer zone rich in ZrO _{2 is} obtained.

test series 5b

The other conditions according to test series 5a are met, but the ZrCl ₄ was missing in the gas phase. The AlCl ₃ content was 12% and the H ₂ content was 73%. An approximately 1.5 to 2 μm thick, uniform aluminum oxide coating is also obtained.

The results of tests on cutting bodies produced according to this example are summarized in the table.

When testing the cutting bodies, the flexural strength and the turning tests on gray cast iron 235 HB with 1000 N / mm ² strength at test times of 15 min with cutting speed of 130 m min ^-1 , chip cross section axs = 2.0 x 0.25 mm ² , the wear mark width in mm, as well as on steel 34 Cr Ni Mo 6 at cutting speeds of 140 m min ^-1 , chip cross-section axs = 2.0 x 0.25 mm ² , the tool life in min was determined as the average of 5 test inserts.

The results clearly show the positive influence of the presence of Al in the first coating and that of oxygen. Improvements in wear properties are achieved by incorporating zirconium into the oxidic coatings applied to the base coating doped with Al according to the invention, and likewise by incorporating boride deposits.

The flexibility of the layers and their adhesion that can be achieved by installing Al in the base layer is particularly positive.

Claims (16)

1. hard metal body, in particular hard metal cutting tool, with coating on the base; Carbides and / or nitrides of elements from IV. To VI. Subgroup of the periodic table and at least one further coating based on aluminum oxide and / or zirconium oxide, characterized in that a first, oxygen-containing, carbidic and / or nitride coating with at least one 0.1. Directly on the substrate of the base body, preferably containing Ta - 2.5 atomic% aluminum layer made of oxycarbide, oxycarbonitride or oxynitride, in particular oxycarbonitride, at least one cerium element Ti, Zr, Hf, V, Nb, Ta and Cr, preferably of titanium or zirconium, is applied, over which a second, oxidic coating with at least one layer, optionally containing boron-containing deposits, is arranged with oxide of aluminum and / or zirconium, and the body, optionally compacted and / or heat-treated. 2. Hard metal body according to Claim 1, characterized in that the oxycarbide, oxycarbonitride or oxynitride, in particular oxycarbonitride, of the first coating has an aluminum content of 0.5 to 2 atom%. 3. Hard metal body according to claim 1 or 2, characterized in that the first coating has two or more layers with oxycarbide, oxycarbonitride or oxynitride, preferably oxycarbonitride, at least one of the elements mentioned in claim 1, the aluminum content of the individual layers of one layer that directly adjoins the substrate, possibly aluminum-free, rises outwards. _4th Hard metal body according to one of claims 1 to 3, characterized in that the aluminum content of the layers of the first coating increases substantially linearly outwards from the layer directly adjacent to the substrate. 5. Hard metal body according to one of claims 1 to 4, characterized in that the oxygen content of the OxiKarbid-, Oxikarbonitrid- upper oxynitride layer (s) of the first coating each 0.1 to 8 atom%, preferably 1 to 5 atom -%. 6. carbide body nacr one of claims 1 to 5, characterized in that cie the first coating has two or more layers with an oxycarbide or oxycarbonitride or oxynitride, preferably oxycarbonitride, at least one of the elements mentioned in claim 1, wherein the oxygen content of the individual Layers rising from the layer immediately adjacent to the substrate towards the outside. 7. hard metal body according to one of claims 1 to 6, characterized in that the oxygen content of the layers of the first coating from the layer immediately adjacent to the substrate away to the outside increases substantially linearly. 8. Tungsten carbide body according to one of claims 1 to 7, characterized in that the layer (s) of the second coating 1 to 20 wt .-%, preferably 2 to 15 wt .-% zirconium contains (contain). 9. hard metal body according to one of claims 1 to 8, characterized in that the second coating two or has more oxidic layers, the zirconium content of the individual layers increasing towards the outside from a layer which immediately adjoins the first coating and is possibly free of zirconium. 10. Tungsten carbide body according to one of claims 1 to 9, characterized in that in the second coating the zirconium genalt from the oxide layer immediately adjacent to the first coating is substantially linearly increasing towards the outside. 11. Hard metal body according to one of claims 1 to 10, characterized in that the oxide layer of the second coating immediately adjacent to the first coating is a zirconium-free aluminum oxide layer. 12. Hard metal body according to one of claims 1 to 11, characterized in that the boride-containing inclusions present in at least one layer of the second coating are formed by aluminum and / or zirconium boride (s). 13. Hard metal body according to one of claims 1 to 12, characterized in that the substrate and layer or layers of the first and second coating have diffusion zones. 14. A method for producing a hard metal body according to one of claims 1 to 13, characterized in that on a substrate body, preferably containing tantalum, by a gas phase deposition process (CVD process) in the presence of an oxygen and aluminum, optionally in during the Coating process changing amounts, containing or delivering, at least one of the in the metal phase mentioned in claim a first coating with at least one layer with oxycarbide, oxycarbonitride or oxinitric, in particular oxycarbonitride, at least one of the metals mentioned in claim 1 is applied, and then in the presence of an aluminum and / or zirconium, and optionally boron, in if necessary, during the coating process changing amounts containing gas phase, a second coating with at least one layer, optionally containing boride-containing deposits, is deposited with aluminum and / or zirconium oxide, whereupon the coated body obtained is optionally subjected to a post-compression process, preferably an isostatic pressing, in particular for printing from 500 to 2500 bar, and / or a heat or heat treatment, preferably thermal diffusion treatment, in particular at temperatures of 900-1600 ° C., preferably 1100-1500 ° C. 15. The method according to claim 14, characterized in that when depositing a first coating with at least two layers, the oxygen and / or the aluminum content of the gas phase during the coating process, preferably substantially linear, is increased. 16. The method according to any one of claims 1 to 2, characterized in that when depositing a second coating with at least two oxide layers, the zirconium content of the gas phase during the coating process, preferably substantially linear, increased