Title of Invention

HARD-MATERIAL-COATED BODIES AND METHOD FOR THEIR PRODUCTION

Abstract

The invention relates to hard-coated bodies with a single- or multi-layer system containing at least one Ti1-xAlxN hard layer and a method for production thereof. The aim of the invention is to achieve a significantly improved wear resistance and oxidation resistance for such hard-coated bodies. Said hard-coated bodies are characterised in that the bodies are coated with at least one Ti1-xAlxN hard layer, generated by CVD without plasma stimulation present as a single-phase layer with cubic NaCl structure with a stoichiometric coefficient x > 0.75 to x = 0.93 and a lattice constant afcc between 0.412 nm and 0.405 nm, or as a multi-phase layer, the main phase being Ti1-xAlxN with a cubic NaCl structure with a stoichiometric coefficient x > 0.75 to x = 0.93 and a lattice constant afcc between 0.412 nm and 0.405 nm, with Ti1-xAlxN with a wurtzite structure and/or as TiNx with NaCl structure as further phase. Another feature of said hard layer is that the chlorine content is in the range of only 0.05 to 0.9 atom %. The invention further relates to a method for production of the body, characterised in that the body is coated in a reactor at temperatures from 700 °C to 900 °C by means of CVD without plasma stimulation with titanium halides, aluminium halides and reactive nitrogen compounds as precursors, mixed at elevated temperatures. Said coating can be applied to tools made from steel, hard metals, cermets and ceramics, such as drills, millers and indexable inserts.

Full Text

FORM 2 THE PATENT ACT 1970 (39 of 1970) & The Patents Rules, 2003 COMPLETE SPECIFICATION (See Section 10, and rule 13) 1. TITLE OF INVENTION HARD-MATERIAL-COATED BODIES AND METHOD FOR THEIR PRODUCTION 2. APPLICANT(S) a) Name : FRAUNHOFER-GESELLSCHAFT ZUR FOERDERUNG DER ANGEWANDTEN FORSCHUNG E.V. b) Nationality : GERMAN Company c) Address : HANSASTRASSE 2 7C, 8 0686 MUENCHEN GERMANY 3. PREAMBLE TO THE DESCRIPTION The following specification particularly describes the invention and the manner in which it is to be performed : - Technical Field The invention relates to hard-material-coated bodies having a single-layer or multilayer layer system that contains at least one Ti1-XA1XN hard material layer, and a method for their production. The coating according to the invention can be used, in particular, for tools made of steel, hard metals, cermets, and ceramics, such as drills, milling cutters, and cutting inserts. The bodies coated according to the invention have improved friction-wear resistance and oxidation resistance. State of the Art The production of friction-wear protection layers in certain regions of the material system Ti-Al-N is already known, in accordance with WO 03/085152 A2. In this connection, it is possible to produce monophase TiAIN layers having the NaCl structure, at A1N contents up to 67%. These layers, which are produced by means of PVD, have lattice constants afcc between 0.412 run and 0.424 nm (R. Cremer, M. Witthaut, A. von Richthofen, D. Neuschutz, Fresenius J. Anal. Chem. 361 (1998) 642-645). Such cubic TiAIN layers possess a relatively great hardness and friction-wear resistance. In the case of A1N contents > 67%, however, a mixture of cubic and hexagonal TiAIN is formed, and at an A1N proportion > 75%, only the softer wurtzite structure, which is not resistant to friction wear, is formed. It is also known that the oxidation resistance of cubic TiAIN layers increases with an increasing A1N content (M. Kawate, A. Kimura, T. Suzuki, Surface and Coatings Technology 165 (2003) 163-167). However, the scientific literature concerning TiAIN production by means of PVD indicates the view that practically no monophase cubic TiAIN layers having a high proportion of A1N can be formed any more above 750°C, i.e. that in the case of Ti1-XA1XN phases where x > 0.75, the hexagonal wurtzite structure will always be present (K. Kutschej, P.H. Mayrhofer, M. Kathrein, C. Michotte, P. Polcik, C. Mitterer, Proc. 16th Int. Plansee Seminar, May 30 - June 03, 2005, Reutte, Austria, Vol. 2, p. 774 - 788). It was also already found that monophase Ti1-XA1XN hard material layers with x up to 0.9 can be produced by means of plasma CVD (R. Prange, Diss. RTHW Aachen, 1999, Fortschritt-Berichte VDI [Progress Reports of the Association of German Engineers], 2000, Series 5, No. 576, as well as O. Kyrylov et al., Surface and Coating Techn. 151-152 (2002) 359-364). However, a disadvantage in this connection is the insufficient homogeneity of the layer composition, and the relatively high chlorine content in the layer. Furthermore, conducting the process is complicated and requires a lot of effort. For the production of the known Ti1-XA1XN hard material layers, PVD methods or plasma CVD methods are used, according to the state of the art, which methods are operated at temperatures below 700°C (A. Horling, L. Hultman, M. Oden, J. Sjolen, L. Karlsson, J. Vac. Sci. Technol. A 20 (2002)5, 1815 - 1823, as well as D. Heim, R. Hochreiter, Surface and Coatings Technology 98 (1998) 1553 - 1556). It is a disadvantage of these methods that coating complicated component geometries presents difficulties. PVD is a very targeted process, and plasma CVD requires a high level of plasma homogeneity, since the plasma power density has a direct influence on the Ti/Al atom ratio of the layer. With the PVD methods which are almost exclusively used industrially, it is not possible to produce monophase cubic Ti1-XA1XN layers with x > 0.75. Since cubic TiAlN layers are a metastable structure, production with conventional CVD methods, at high temperatures > 1000°C is fundamentally not possible, because a mixture of TiN and hexagonal A1N is formed at temperatures above 1000°C. In accordance with US 6,238,739 Bl, it is also known that Ti1-XA1XN layers with x between 0.1 and 0.6 can be obtained in the temperature range between 550°C and 650°C, by means of a thermal CVD process, without plasma support, if a gas mixture of aluminum chlorides and titanium chlorides, as well as NH3 and H2, is used. The disadvantage of this special thermal CVD method also consists in the restriction to a layer stoichiometry x £ 0.6 and the restriction to temperatures below 650°C. The low coating temperature leads to high chlorine contents in the layer, up to 12 at.-%, which are harmful for use (S. Anderbouhr, V. Ghetta, E. Blanquet, C. Chabrol, F. Schuster, C. Bernard, R. Madar, Surface and Coatings Technology 115 (1999) 103 - 110). Disclosure of the Invention The invention is based on the task of achieving significantly improved friction wear resistance and oxidation resistance in the case of hard-material-coated bodies having a one-layer or multi-layer layer system that contains at least one Ti1-XA1XN hard material layer. This task is accomplished with the characteristics of the claims. The hard-material-coated bodies according to the invention are characterized in that they are coated with at least one Ti1-XA1XN hard material layer produced by means of CVD, without plasma stimulation, which layer is present as a monophase layer in the cubic NaCl structure, with a stoichiometry coefficient x > 0.75 up to x = 0.93, and a lattice constant afCC between 0.412 nm and 0.405 nm, or that is a multiphase Ti1-XA1XN hard material layer whose main phase consists of Ti1-XA1XN having a cubic NaCl structure, with a stoichiometry coefficient x > 0.75 up to x = 0.93, and a lattice constant afcc between 0.412 nm and 0.405 nm, whereby Ti1-XA1XN in the wurtzite structure and/or TiNx in the NaCl structure are contained as an additional phase. A further characteristic of this Ti1-XA1XN hard material layer consists in the fact that its chlorine content lies in the range between only 0.05 and 0.9 at.-%. It is advantageous if the chlorine content of the Ti1-XA1XN hard material layer(s) lies in the range of only 0.1 to 0.5 at.-%, and the oxygen content lies in the range of 0.1 to 5 at.-%. The hardness value of the Ti1-XA1XN hard material layer(s) lies in the range of 2500 HV to 3800 HV. According to the invention, up to 30 mass-% amorphous layer components can be contained in the Ti1-XA1XN hard material layer(s). The layer that is present on the bodies, according to the invention, with its great hardness between 2500 HV to 3800 HV, and with a clearly improved oxidation resistance as compared with the state of the art, which is achieved by means of the high A1N proportion in the cubic Ti1-XA1XN phase, has a combination of hardness and oxidation resistance that has not been achieved until now, which results in very good friction-wear resistance, particularly at high temperatures. For the production of the bodies, the invention includes a method that is characterized in that the bodies are coated in a reactor, at temperatures in the range of 700°C to 900°C, by means of CVD, without plasma stimulation, whereby titanium halogenides, aluminum halogenides, and reactive nitrogen compounds are used as precursors, which are mixed at elevated temperature. According to the invention, NH3 and/or N2H4 can be used as reactive nitrogen compounds. It is advantageous if the precursors are mixed in the reactor, directly ahead of the deposition zone. Mixing of the precursors is carried out, according to the invention, at temperatures in the range of 150°C to 900°C. The coating process is advantageously carried out at pressures in the range of 102 Pa to 105 Pa. Using the method according to the invention, it is possible to produce Ti1-XA1XN layers having the NaCl structure by means of a comparatively simple thermal CVD process, at temperatures between 700°C to 900°C, and pressures between 102 Pa and 105 Pa. Both the Ti1-XA1XN layer compositions that were previously known, with x 0.75, which cannot be produced with any other method, can be obtained using the method. The method allows homogeneous coating even of complicated component geometries. Embodiments of the Invention In the following, the invention will be explained in greater detail using exemplary embodiments. Example 1 A Ti1-xAlxN layer is deposited onto WC/Co hard metal cutting inserts, by means of the thermal CVD method according to the invention. For this purpose, a gas mixture of 20 ml/min AlCl3, 3.5 ml/min TiCl4, 1400 ml/min H2, 400 ml/min argon is introduced into a hot-wall CVD reactor having an inside diameter of 75 mm, at a temperature of 800°C and a pressure of 1 kPa. A mixture of 100 ml/min NH3 and 200 ml/min N2 is passed into the reactor by way of a second gas feed. Mixing of the two gas streams takes place at a distance of 10 cm ahead of the substrate carrier. After a coating time of 30 minutes, a gray-black layer having a thickness of 6 urn is obtained. Only the cubic Ti1-xAlxN phase is found by means of the X-ray thin-layer analysis carried out with sweeping incidence (see X-ray diffractogram, Fig. 1). The lattice constant that is determined amounts to afcc = 0.4085 nm. The atom ratio Ti:Al determined by means of WDX amounts to 0.107. The contents of chlorine and oxygen, which were also determined, amount to 0.1 at.-% for CI and 2.0 at.-% for O. Calculation of the stoichiometric coefficient yields x = 0.90. A hardness of the layer of 3070 HV[0.05] is measured by means of a Vickers indenter. The Ti1-XA1XN layer is oxidation resistant in air up to 1000°C. Example 2 First, a titanium nitride layer having a thickness of 1 \im is applied to cutting inserts made of Si3N4 cutting ceramic, by means of a known standard CVD process, at 950°C. Afterwards, a gray-black layer is deposited with the CVD method according to the invention, using the gas mixture described in Example 1, a pressure of 1 kPa, and a temperature of 850°C. X-ray thin-layer analysis shows that here, a heterogeneous mixture of Ti1-XA1XN, having the NaCl structure and AIN having the wurtzite structure is present. In the X-ray diffractogram of Fig. 2 that was determined, the reflexes of the cubic Ti1-XA1XN are indicated with c, and those of the hexagonal AIN (wurtzite structure) are indicated with h. The proportion of the cubic Ti1-XA1XN in the layer predominates. The lattice constant of the cubic phase that is determined amounts to afcc = 0.4075 ran. The second, hexagonal AIN phase has lattice constants of a = 0.3107 ran, and c = 0.4956 ran. The hardness of the layer, determined by means of a Vickers indenter, amounts to 3150 HV[0.01]. The biphase Ti1-XA1XN layer is oxidation-resistant in air up to 1050°C. WE CLAIM: 1. Hard-material-coated bodies having a single-layer or multi-layer layer system that contains at least one Ti1-XA1XN hard material layer produced by means of CVD without plasma stimulation, wherein the Ti1-XA1XN hard material layer is present as a monophase layer in the cubic NaCl structure, with a stoichiometry coefficient x > 0.75 up to x = 0.93, and a lattice constant afcc between 0.412 nm and 0.405 ran, or wherein the Ti1-XA1XN hard material layer is a multiphase layer whose main phase consists of Ti1-XA1XN having a cubic NaCl structure, with a stoichiometry coefficient x > 0.75 up to x = 0.93, and a lattice constant afcc between 0.412 nm and 0.405 nm, and Ti1-XA1XN in the wurtzite structure and/or TiNx in the NaCl structure are contained as an additional phase, and wherein the chlorine content of the Ti1-XA1XN hard material layer lies in the range between 0.05 and 0.9 at.-%. 2. Hard-material-coated bodies according to claim 1, characterized in that the chlorine content of the Ti1-XA1XN hard material layer(s) lies in the range of 0.1 to 0.5 at.-%. 3. Hard-material-coated bodies according to claim 1, characterized in that the oxygen content of the Ti1-XA1XN hard material layer(s) lies in the range of 0.1 to5at.-%. 4. Hard-material-coated bodies according to claim 1, characterized in that the hardness value of the Ti1-XA1XN hard material layer(s) lies in the range of 2500 HV to 3800 HV. 5. Hard-material-coated bodies according to claim 1, characterized in that the Ti1-xAlxN hard material layer(s) contain(s) 0 to 30 mass-% amorphous layer components. 6. Method for the production of hard-material-coated bodies having a single-layer or multi-layer layer system that contains at least one Ti1-XA1XN hard material layer, characterized in that the bodies are coated in a reactor, at temperatures in the range of 700°C to 900°C, by means of CVD, without plasma stimulation, whereby titanium halogenides, aluminum halogenides, and reactive nitrogen compounds are used as precursors, which are mixed at elevated temperature. 7. Method according to claim 6, characterized in that NH3 and/or N2H4 are used as reactive nitrogen compounds. 8. Method according to claim 6, characterized in that the precursors are mixed in the reactor, directly ahead of the deposition zone. 9. Method according to claim 6, characterized in that mixing of the precursors is carried out at temperatures in the range of 150°C to 900°C. 10. Method according to claim 6, characterized in that the coating process is carried out at pressures in the range of 102 Pa to 105 Pa. ABSTRACT The invention relates to hard-coated bodies with a single- or multi-layer system containing at least one Ti1-XA1XN hard layer and a method for production thereof. The aim of the invention is to achieve a significantly improved wear resistance and oxidation resistance for such hard-coated bodies. Said hard-coated bodies are characterised in that the bodies are coated with at least one Ti1-XA1XN hard layer, generated by CVD without plasma stimulation present as a single-phase layer with cubic NaCl structure with a stoichiometric coefficient x > 0.75 to x = 0.93 and a lattice constant afcc between 0.412 nm and 0.405 nm, or as a multi-phase layer, the main phase being Ti1-XA1XN with a cubic NaCl structure with a stoichiometric coefficient x > 0.75 to x = 0.93 and a lattice constant afcc between 0.412 nm and 0.405 nm, with Ti1-XA1XN with a wurtzite structure and/or as TiNx with NaCl structure as further phase. Another feature of said hard layer is that the chlorine content is in the range of only 0.05 to 0.9 atom %. The invention further relates to a method for production of the body, characterised in that the body is coated in a reactor at temperatures from 700 °C to 900 °C by means of CVD without plasma stimulation with titanium halides, aluminium halides and reactive nitrogen compounds as precursors, mixed at elevated temperatures. Said coating can be applied to tools made from steel, hard metals, cermets and ceramics, such as drills, millers and indexable inserts. To, The Controller of Patents, The Patent Office, Mumbai

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