DE3434616A1 - Surface layers comprising titanium-boron-nitride compounds, and process for producing them - Google Patents

Abstract

Surface layers for sintered hard metal bodies, especially blanking dies, are proposed which comprise titanium boron oxynitride of the general formula TiBxOyNz where x = 0.30 to 0.75; y = 0.05 to 0.25 and x + y + z = 0.98 to 1.3. The production process for surface layers of this type is based on chemical vapour phase deposition and is characterised by secondary treatment of the sintered hard metal bodies, which have been pretreated in a TiCl4-N2-H2 gas mixture, in a gas atmosphere comprising TiCl4, BCl3, N2 and H2 which is admixed with from 0.005 to 0.04% by volume of H2O.

Description

Surface layers made from TStan-boron-nitride compounds

and manufacturing method The invention relates to surface layers made of titanium-boron-nitride compounds for cemented carbide bodies, in particular cutting inserts from sintered carbides of metals from IV. to VI. Subgroup of the PSE with single metal of the iron group and a manufacturing process for such surface layers according to the principle of chemical vapor deposition in one made of TIC14 BCl3, N2 and H2 existing reaction atmosphere.

Increasing the wear resistance of hard metal base bodies through surface layers of hard materials is published in a large number of publications described and implemented in products. Surface layers are known pure hard materials such as carbides, borides, nitrides and silicides of the IV., V. and VI. Subgroup of the Periodic System of the Elements, formed from these hard materials Mixed phases, from W2-A1203, boron carbide, silicon carbide, silicon nitride, carbon with diamond-like properties, cubic boron nitride in the form of monolayers and layer combinations.

The most common coating processes are chemical vapor deposition (CVD process) and physical vapor deposition (PVD process), where CVD processes dominate because of their low costs.

Chemical vapor deposition shows particularly favorable properties produced boron-containing hard materials, as they are, for. B. in DD-PS 144 930 described are. In DE-OS 226 31 10 it is proposed in 'Ditancarbonitridschichten carbon and to replace some or all of the nitrogen with boron or silicon. The DE-OS 251 72 88 recommends highly wear-resistant layers from representatives of IV. - VI. Subgroup of the periodic table of the elements with carbon and / or nitrogen and / or boron and / or silicon.

In DE-OS 232 36 52 a CVD process is described, according to which Titanium halide with a boron and / or nitrogen source to form a hard titanium compound is implemented, which has a wear-reducing effect in the form of a hard material layer.

European patent application 6 534 includes a CVD process produced layer combination, which in the transition from a TiN layer to an external one TiB2 layer contains a Ti (BN) layer.

All of the above suggestions include the possibility of manufacturing of hard material compounds preferably using the CVD process made of titanium, boron and Nitrogen in the form of hard materials with a wear-reducing effect.

According to the chemical formation conditions applicable for this combination This creates the compounds titanium nitride and titanium diboride. The formation of a Ti (BN) phase is according to the study of Samsonov and Petrash (Metalloved. Obr. Lietallov (1955) No. 6 pp. 19-24) is possible insofar as up to 8 vol>% TiB2 in TiN dissolve, while a reverse solubility is not given.

The proposed hard material coatings of the titanium-boron-nitrogen system are consequently, if they are above the solubility limit of the TiB2 in the TEN, Mixtures of TiN and TiB2. According to the authors mentioned above, the for the Properties relevant to wear resistance, e.g. obtained by co-deposition Layer additively from the phase components. Such layers of the titanium-boron-nitrogen system their properties are between TiN and TiB2.

French patent specification No. 237 05 51 describes wear-resistant ones Titanium boron nitride layers with the composition TiBxNy, where x = 0.05 - 0.80 0.025 - 0.40 at.

and 1 <x + y (1.25 should be. Such layers are made by chemical Vapor deposition in low pressure ranges from 60 to 100 Torr and at temperatures from 1050-1500 ° C obtained. Depending on the boron halogenide / hydrogen molar ratio, the nitrogen partial pressure, the deposition temperature and the pressure in the aforementioned In the area, one- and two-phase layers with different properties are created. When using atmospheric pressure (normal pressure), however, no layers, but powdery precipitate is generated.

The separated phases have slightly changed lattice constants face-centered cubic titanium nitride and hexagonal titanium diboride isomorphic, from which it can be concluded that more boron is dissolved in the titanium nitride than Semsomov and Petrash indicate and nitrogen is dissolved in the titanium diboride phase.

For the production of the titanium boron nitride layers according to FR-PS 27 70 551 necessary temperatures and separation times lead due to the high mobility of the boron atoms cause the hard metal substrate to be borated, causing changes occur in the structure of the structure, which the practical value of such coated hard metal body can affect. According to investigations by Riehle ("Investigations on the Boriding of hard metals "Final report 1974, Technical University of Dresden, Materials Science Section) the components react under such conditions of hard metal to borides. The boride formation takes place initially with the binder metal phase z. B.

to cobalt boride and preferably at 2 temperatures) 1050 ° C. also below Participation of the carbidic hard material phases with the precipitation of carbon to so-called # -borides. Such a boronization of the adhesive metal base body leads to a considerable reduction in the breaking strength of the coated hard metal body, which i.a. Poor performance when it is used for machining in the interrupted Cut (Frtisen).

It is also known the oxidation resistance of coated To improve hard metals by means of oxygen-containing top layers. So in the U.S. Patent No. 401 86 31 discloses a titanium oxynitride layer and in US Pat DE-AS 196 46 02 oxygen- and nitrogen-containing carbide layers of the elements of IV., V. and VI. Subgroup of the Periodic Table of the Elements recommended for this purpose. In terms of resistance to oxidation, pure achieved an even better effect Aluminum oxide and zirconium oxide top layers, as they are in DE-AS 225 37 45 and the European patent application No. 3 18 05 with different intermediate layers be proposed.

The invention is based on the object for the surface coating layers of titanium-boron-nitride compounds known from cemented carbide bodies in their properties such as hardness, abrasion resistance, adhesive strength, breaking strength and oxidation resistance u and the manufacturing process for the same To further develop surface layers.

This object is achieved according to the invention in that the surface layer consists of titanium-boron-oxynitride of the general formula TiBxOyNz, where x = 0.30 to 0.75, y = 0.05 to 0.25 and x + y + z = 0.98 to 113.

For reasons of strength properties and an economically justifiable one Coating effort, it has proven to be useful that the layer thickness the 'ditan-boron-oxynitride layer is 2 to 12 µm.

The composition of the titanium-boron-oxynitride layer can also be used can be continuously changed within the boundaries of the geekenen.

Another modification of the properties of the surface layer is also possible because the titanium-boron-oxynitride layer with layers of carbides, Nitrides, silicides of the IV. To VI. Subgroup of the PSE, their mixed phases, with Aluminum oxide, zirconium oxide, boron carbide, silicon nitride, carbon with diamond-like ones Properties and / or boron nitride is combined.

According to a preferred method for producing the invention Surface layer can be applied in a TiCl4-N2-H2 gas mixture under a pressure from 90 - 120 kPa at 1280 - 1350 K pretreated cemented carbide bodies during and after lowering the temperature to 1100 - 1200 K under the same pressure by a Post-treatment in one of 2-2.5% by volume TiCl4, 0.02-0.2 volt BCl3, 25-35% by volume N2 and 60 - 75 vol = »H2 existing gas atmosphere, the 0.005 to 0.04 vol% H20 is added, a titanium-boron-oxynitride layer according to the general formula TiBxOyNz are formed.

The titanium-boron-oxynitride layer applied to cemented carbide bodies has particularly good properties for metal cutting when in general Formula TiBxOyNz x = 0.30 - 0.75, y = 0.05 - 0.25 and 0.98 = x + y + z = 1.3.

In the plants that are considered for carrying out the process dre the surface coating after chemical vapor deposition is it expedient if the H20 additive is introduced into the gas atmosphere via the H2 gas stream will.

For the implementation of the process, it has proven to be advantageous if in the gas mixture for the pretreatment and / or in the gas atmosphere for the Post-treatment H2 is partially replaced by Ar.

A useful addition to the process design according to the invention is also seen in the fact that the cemented carbide body before the pretreatment in Ar can be heated and cooled in N2 after the aftertreatment.

The coating method according to this invention can also be used with others Coating process for applying additional layers of carbides, Nitrides, silicides of the IV. To VI. Subgroup of PSE, aluminum oxide, zirconium oxide, Boron carbide, silicon nitride, carbon with diamond-like properties and / or Boron nitride can be combined.

When combined with other coating processes, by separate execution of the individual process sections the titanium-boron-oxynitride layer can be applied as a top layer, base layer and / or intermediate layer.

Due to the resistance to temperature changes of the titanium-boron-oxynitride layer the process should be carried out in such a way that the layer thickness depends on the structure of the Layer system as monolayer, double layer, multiple layer or multi-layer is between 0.2 and 12 jim.

Titanium boroxynitride layers of the composition TiBxOyNz have in comparison higher hardness than the hard materials known from the titanium-boron-carbon system, higher abrasion resistance, higher oxidation resistance and higher breaking strength. Correspondingly coated hard metal base bodies are more wear-resistant, in particular in the machining of short-chipping ferrous materials, high and low alloyed Steels, superalloys and non-ferrous materials. They have e.g. micro-hardness on, which is considerably higher than that of the previously from the system Tltan-Bor-Oxygen-Nitrogen known lie. Using particularly thick, for the hardness measurement along and across the The direction of growth of specially produced model layers was determined by different Composition of the 'l'itanboroxinittidschicht micro-hardness mhflOOp 4500 - 5400 found. For example, on titanium boroxynitride layers, TiB0.70 ° 0.10N0.22 mh100p 4700 and TiB0.40 ° 0.22N0.51 mh100 @ 5300 measured.

The comparatively low separation temperatures of 1100 - 1250 K, preferably 1130-1180 K, for the production of the titanium boroxynitride layer according to the invention and their high rate of formation largely prevent the diffusion of Boron into the hard metal backing and form the prerequisite for the formation of a super fine grain structure. In addition to the chemical composition, the result special wear-reducing properties from this preferably X-ray amorphous Layer structure. The growth rate is within the above limits for the separation temperature and gas composition between 0.05 and 0.20 µm per minute.

In contrast to titanium boron nitride, as in the French patent 237 05 51 is proposed, titanium boroxynitride can also be used at pressures above 100 Torr, preferably at atmospheric pressure, as a firmly adhering layer on hard metal substrates directly or in a manner known per se Separate hard metal substrates provided with other hard material layers.

The high separation rates and the low separation temperatures form the prerequisite for the usually undesirable boronization of the hard metal base the formation of borides in the binder metal phase is completely absent or only slightly deep is demonstrable. A combined hard material deposition and simultaneous boronization the hard metal base, comes out of the gas phase due to the low amount of boron not a.

Depending on the intended use, concentration gradients of the Boron, oxygen and nitrogen within the layer in the aforementioned Limits the properties of the titanium boroxynitride layers can be varied. Be like that the highest hardness with approximately equal proportions of boron and nitrogen and the highest oxidation resistance achieved with oxygen cells of y = 0.1 - 0.2. The combination of the titanium boron nitride layer with other hard material layers can require higher concentrations of nitrogen in the border areas if carbide or nitride layers are combined or require higher oxygen contents, if is combined with oxide layers.

For the combination of titanium boron nitride layers with other plastic layers all hard material layers known per se come with a wear-reducing effect in Prague, preferably carbides, nitrides, silicides of the IV., V. and VI.

Subgroup of the Periodic System of the Elements, their mixed phases Aluminum oxide, zirconium oxide, boron carbide, silicon nitride, carbon with diamond-like ones Properties and / or boron nitride.

The invention is explained in more detail below using two exemplary embodiments are: Example 1: Inserts made of a conventional K10 hard metal were in a Reactor heated to 1320 K under inert gas and 20 min with a gas mixture, consisting treated from Ar-H2-TiCl4-C6H6. After that, benzene was replaced by nitrogen and then set a gas mixture which has the following composition: 32, 74 vol% N2 65.00 vol% H2 2.14 vol% TiCl4 0.10 vol% BCl3 0.02 volS 1120 at the same time the temperature was reduced from 1320 K to 1200 K.

The inserts were in this atmosphere at one pressure of 105 kPa for 40 min at 1200 K and then treated in the reactor in a stream of nitrogen cooled down.

These indexable inserts had a closed double layer, consisting of a 3 µm thick TiC layer and a 4 µm thick X-ray amorphous layer Titanium boroxynitride layer of the composition TiB0.40 ° 0.12N0.51. The titanium boron nitride layer has a micro hardness of mh100p 5300.

The practical value of the layer is determined in a milling test: test conditions Single tooth cutter: 1st test: Material GGL 20 v = 224 m / min a = 2 mm s = 0.4 mm z milling tool FPXH 315-22 insert TNGN 2204 ZD criterion flank wear B 0.8 mm K20 carbide K10 / K20 hard metal K10 / K20 hard metal uncoated tall Ti (CN) TiC / TiB 0.40 ° 0.12N TiN-coated 0.51-coated Tool life in 1.5 2.5 3.5 m B in mm 0.86 0.75 0.70 2nd test: material, Tool, insert as in text 1 v = 140 m / min a ~ 2 mm s = 0.5 mm z criterion of flank wear = 1.0 mm K20 hard metal K10 / K20 hard K10 / K20 hard metal uncoated metal Ti (CN) TiC / TiB0.40 ° 0.12N TiN-coated 0q51 -coated tool life in 2.0 3.0 5.0 m B in mm 0.93 0.86 0.98 Example 2: Indexable inserts made from a conventional K20 hard metal were heated to 1320 K in a reactor under inert gas. After that, these were Treated conventionally for 40 min in a H2-N2-TiCl4 atmosphere. Then became a gas mixture adjusted with the following composition: 32.64 VolwN2 65.00 Vol% H2 2.14 Vol% TiCl4 0.02 volts 1120 and at the same time lowered the temperature to 1200 K.

The indexable inserts were in this atmosphere for 40 minutes Treated 1200 K and then cooled in the reactor in a stream of nitrogen. These Indexable inserts have a closed double layer, consisting of one 4 µm thick TiN layer and a 4 µm thick titanium boron oxynitride layer with the Composition TiB0.70 o0.10N0.22. The titanium boron nitride layer had a microhardness from mh100p 4700 * These indexable inserts were coated with a titanium nitride coating in the usual way Indexable insert compared in the turning test: AG / workpiece: longitudinal turning of a shaft (smooth cut) Material: GGL 22 HB = 1800 Nmm Cutting speed: v = 120mmin-1 Feed: s = 0.3 mmU-1 depth of cut: a = 2 mm Wear criterion: Flank wear B = 0.5 m Results as tool life in minutes: Conventionally TiN-coated inserts = 32 min WSP coated according to the invention = 72 min hard material layers described were radiographically, metallographically on the oblique and cross section and with the electron beam microprobe to clarify the phase distribution, the layer thickness and the layer structure analyzed.

Claims (12)

P a t e n t a n s p r it c h e 1. Surface layers made from ditanium boron nitride compounds for cemented carbide bodies, in particular cutting inserts, made from carbides of metals the IV. to VI. Subgroup of the PSE with binding metal of the iron group characterized by that the surface layer of titanium-boron-oxynitride of the general formula TiBxOyNz where x = 0.30 to 0.75, y = 0.05 to 0.25 and x + y + z = 0.98 to 1.3 be. 2. Surface layers according to claim 1, characterized in that the thickness of the titanium-boron-oxynitride layer is 2 to 12 µm. 3. Surface layers according to claims 1 and 2, characterized in that that the composition of the titanium-boron-oxynitride layer is within the given Boundaries are continuously changing. 4. Surface layers according to Claims 1 to 3, characterized in that that the titanium-boron-oxynitride layer with layers of carbides, nitrides, silicides the IV. to VI. Subgroup of the PSE, their mixed phases, with aluminum oxide, zirconium oxide, Boron carbide, silicon nitride, carbon with diamond-like properties and / or Boron nitride is combined. 5. Process for the production of surface layers from titanium-boron compounds on sintered carbide bodies, in particular on cutting plates, according to claims 1 to 4 by chemical vapor deposition in one of TiCl4, BCl3, N2 and H2 Reaction atmosphere, characterized in that the in one TiCl4-N2-H2 gas mixture sintered carbide bodies pretreated under a pressure of 90 - 120 kPa at 1280 - 1350 K. during and after lowering the temperature to 1100 to 1200 K under the same pressure by post-treatment in one of 2 - 2.5 vol TiCl4, 0.02 - 0.2 vol BCl3, 25 - 35 vol% N2 and 60 - 75 vol% H2 existing gas atmosphere, which is 0.005 to 0.04 vol * H20 is added, a titanium-boron-oxynitride layer according to the general Formula TiExOyNz is formed. 6. The method according to claim 5, characterized in that in the general formula Ti3xOyNz of the titanium-boron-oxynitride layer applied to the cemented carbide body x = 0.30-0.75, y = 0.05-0.25 and 0.98 = x + y + z = 1.3. 7. The method according to claims 5 and 6, characterized in that that the H20 additive is introduced into the gas atmosphere via the H2 gas stream. 8. The method according to claims 5 to 7, characterized in, that in the gas mixture for the pretreatment and / or in the gas atmosphere for the Post-treatment H2 is partially replaced by Ar. 9. The method according to claims 5 to 8, characterized in that that the cemented carbide body is heated before the pretreatment in Ar and after the Post-treatment can be cooled in N2. 10. The method according to claims 5 to 9, characterized by the Combination with other coating processes for the application of additional Layers of carbides, nitrides, silicides of the IV. To VI. Subgroup of PSE, aluminum oxide, zirconium oxide, boron carbide, silicon nitride, Carbon with diamond-like properties and / or boron nitride. 11. The method according to claims 5 to 10, characterized in that that the titanium-Eor-oxynitride layer as a top layer, base layer and / or intermediate layer is applied. 12. The method according to claims 5 to 11, characterized in that that the layer thickness depends on the structure of the layer system as a monolayer, double layer, Multi-layer or multi-layer between 0.2 and 12, im lies.