Hard-coated body and method for production thereof

Technical field [0001] The invention relates to bodies coated with a hard material in a single or multilayer system which comprises at least a coating of hard material Ti1-xAlxN, and a method for their preparation. The coating according to the invention can be used in tools made of steel, cemented carbides, cermets and ceramics, such as drills, milling cutters and cutting inserts. The coated bodies according to the invention have improved abrasion and oxidation resistance.

Background Art [0002] The preparation of wear resistant coatings in specific areas of the Ti-Al-N material system is known from WO 03/085152 A2, respectively. It is possible to obtain monophasic TiAlN coatings with NaCl structure with AlN content up to 67%.

These coatings obtained using PVD have an afcc network constant between 0.412 nm and

0.424 nm (R. Cremer, M. Witthaut, A. von Richthofen, D. Neusclnitz, Fresenius J. Anal. Chem. 361 (1998) 642-645). Such cubic TiAlN coatings have relatively high hardness and abrasion resistance. At AlN contents> 67%, there is mainly a mixture of cubic and hexagonal TiAlN and at AlN contents> 75%, only hexagonal wurcite structure, softer and resistant to abrasion.

[0003] It is also known that the oxidation resistance of cubic TiAlN coatings increases with increasing AlN content (M. Kawate, A. Kimura, T. Suzuki, Surface and Coatings Technology 165 (2003) 163-167). Scientific literature on the preparation of TiAlN using PVD shows, however, that above 750 ° C in practice it is not possible to obtain more single-phase cubic TiAlN coatings with a high AlN content or in the phases Ti1xAlxN ox> 0.75 there is always a hexagonal wurcite structure (K. Kutschej, PH Mayrhofer, M. Kathrein, C. Michotte, P. Polcik, C. Mitterer, Proc. 16th Int. Plansee Seminar, May 30 - June 3, 2005, Reutte, Austria, Volume 2, pp. 774-788).

[0004] It has also been shown that using plasma CVD, one-phase hard coatings Ti1-xAlxN ox up to 0.9 can be obtained (R. Prange, Diss. RTHW Aachen, 1999, Fortschritt-Berichte VDI, 2000, vol. 5, No. 576 as well as O Kyrylov et al., Surface and Coating Techn. 151-152 (2002) 359-364). However, the inadequate homogeneity of the coating composition and the relatively high chlorine content of the coating are disadvantageous. In addition, the process is complicated and expensive.

[0005] According to JP 2001 341008 A, a titanium aluminum nitride coated tool is known, consisting of a tool body and a monolayer or multilayer titanium aluminum nitride coating, which contains at least titanium, aluminum and nitrogen, the crystal structure of the titanium aluminum nitride coating has a cubic structure, the titanium aluminum nitride coating has tensile stress and the chlorine content in the titanium aluminum nitride coating is 0.01 to 2% by weight. However, the introduction of aluminum into the TiAlN cubic crystal lattice is limited. The crystalline constant obtained with reflection (111) for this TiAlN coating was 0.41358 nm.

[0006] For the production of known coatings from Ti1-xAlxN hard materials, the PVD method or plasma CVD method according to the prior art has been used, which occur 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). The disadvantage of these methods is that coating is a problem with complex component geometry. PVD is a highly guided method, and plasma CVD ensures high plasma homogeneity because the plasma power density has a direct effect on the coating Ti / Al ratio. In PVD methods used almost exclusively in industry, it is not possible to obtain single-phase cubic Ti1-xAlxN coatings at x> 0.75.

[0007] Where reference is made to cubic TiAlN coatings with a metastable structure, obtaining the CVD process at high temperatures> 1000 ° C is essentially impossible, because at temperatures above 1000 ° C a mixture of TiN and hexagonal AlN is formed.

[0008] It is also known from US 6,238,739 B1 that by thermal CVD method without plasma support, Ti1-xAlxN ox coatings between 0.1 and 0.6 can be obtained in a temperature range between 550 ° C and 650 ° C when a gas mixture is used aluminum chlorides and titanium chloride as well as NH3 and H2. A disadvantage of this special thermal CVD method is also limiting the stoichiometry of the coating to x <0.6 and limiting the temperature to 650 ° C. Low coating temperature leads to high chlorine content in the coating up to 12% atoms, which is harmful to the coating (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 [0009] The invention defines the object of achieving clearly improved abrasion and oxidation resistance by using bodies with hard material coatings having at least a single-layer or multi-layer system that contain at least one coating of hard material Ti1-xAlxN.

[0010] This object is achieved by the features of the patent claim.

[0011] Bodies with a coating of hard materials are characterized in that they are coated with at least one coating of hard material Ti1-xAlxN obtained using CVD without plasma excitation, which has a single-phase coating with a cubic structure of NaCl with a stoichiometric factor x> 0.75 up to x = 0.93 and afcc network constant between 0.412 nm and 0.405 nm or is a multi-phase coating of hard material Ti1-xAlxN, whose main phase consists of Ti1-xAlxN with a cubic NaCl structure with a stoichiometric coefficient x> 0.75 to x = 0.93 and an afcc lattice constant between 0.412 nm and 0.405 nm, with the next phase being AlN with wurcite structure. Further characteristics of the Ti1-xAlxN hard material coating are that the chlorine content is only between 0.05 and 0.9% of atoms, and the hardness value of the Ti1-xAlxN hard material coating / coatings is in the range from 2500 HV to 3800 HV .

Preferably, the chlorine content of the Ti1-xAlxN hard material coating (s) is in the range of only 0.1 to 0.5% atoms and the oxygen content is in the range of 0.1 to 5% atoms [0012] According to the invention, Ti1-xAlxN hard coatings contain up to 30% by mass of amorphous coating components.

[0013] The coating applied to the bodies of the invention has an increased hardness of between 2500 HV to 3800 HV and a markedly improved oxidation resistance, which was achieved by increasing the AlN content of the Ti1-xAlxN cubic phase, a combination of hardness and oxidation resistance not yet achieved which achieves very good wear resistance especially at high temperatures.

[0014] For the preparation of the body, the invention includes a method characterized in that the body is coated in the reactor at temperatures ranging from 700 ° C to 900 ° C using CVD without plasma excitation, with titanium halides, aluminum halides and reactive halides being used as precursors. nitrogen compounds that were mixed at elevated temperatures.

[0015] NH3 and / or N2H4 can be used as the reactive nitrogen compound.

[0016] The precursors were preferably mixed immediately upstream of the deposition zone.

[0017] Mixing of the precursors of the invention was carried out at temperatures in the range from 150 ° C to 900 ° C.

[0018] The coating is preferably carried out at a pressure in the range of 10² Bye to 10⁵Pa.

[0019] Using the method of the invention, Ti1-xAlxN coatings having a NaCl structure can be obtained in a comparatively simple CVD thermal process at temperatures between 700 ° C and 900 ° C and a pressure between 10² Bye a. 10⁵ Pa. Using this method, it is also possible to obtain known Ti1-xAlxN coating compositions with x <0.75 as well as new compositions with x> 0.75 which cannot be obtained in any other way. The method also allows for homogeneous coating of components with complex shapes.

Embodiments of the Invention [0020] In the following, the invention is explained in more detail in the embodiments.

Example 1 [0021] Hard metal WC / Co cutting inserts were coated with Ti1-xAlxN using the thermal CVD method of the invention. Then a gas mixture [at a rate] of 20 ml / min AlCl3, 3.5 ml / min TiCl4, 1400 ml / min H2, 400 ml / min argon at 800 ° C and into the wall heating reactor with 75 mm internal diameter. pressure of 1 kPa.

[0022] On the second gas introduction, a mixture of 100 ml / min NH3 and 200 ml / min N2 was introduced into the reactor. Mixing of both gas streams took place at a distance of 10 cm from the substrate carrier. After a coating time of 30 minutes, a black-gray coating 6 μm thick was obtained.

[0023] Using the frequently occurring x-ray analysis of the coating thickness, only the cubic phase Ti1-xAlNN was observed (see X-ray diffraction pattern Il. 1).

[0024] The resulting network constant was afcc = 0.4085 nm. The ratio of Ti: Al atoms determined by WDX was 0.107. Chlorine and oxygen contents were also determined, which were 0.1% atoms for Cl and 2.0% atoms for O.

[0025] Calculations of the stoichiometric coefficient gave x = 0.90. The coating thickness of 3070 HV [0.05] was measured using a Vickers indenter. The Ti1-xAlxN coating is resistant to oxidation up to 1000 ° C.

Example 2 [0026] Si3N4 cutting ceramic cutting inserts were coated with a 1 μm thick titanium coating using a known standard CVD method at 950 ° C. Then a black-gray coating was applied by the CVD method of the invention using the gas mixture described in example 1 at a pressure of 1 kPa and a temperature of 850 ° C.

[0027] X-ray film thickness analysis showed that there is a heterogeneous mixture of Ti1-xAlxN with NaCl structure and AlN with wurcite structure. From the obtained X-ray diffraction pattern from Fig. 2, the cubic Ti1-xAlxN hexagonal particles AlN (wurtzite structure) with h are characteristic. The content of cubic Ti1xAlxN predominates in the coating.

[0028] The cubic phase lattice obtained was afcc = 0.4075 nm. The second, hexagonal AlN phase has network constants a = 0.3107 nm and c = 0.4956 nm. The hardness of the coating determined using a Vickers indenter is 3150 HV [0.01]. The Ti1xAlxN two-phase coating is resistant to oxidation up to 1050 ° C.

Mirosława Ważyńska Patent attorney