Title of Invention

COMPOSITE BODIES AND METHOD OF THEIR PRODUCTION

Abstract

ABSTRACT: Disclosed herein is an invention concerns with a composite body consisting of a substrate body of hard metal, cermet, steel or ceramic and at least one metallic carbo-nitride hard metal layer, and a method for the manufacture of this carbo-nitride hard material layer. According to the invention, the metallic carbo-nitride layer is deposited through a CVD process, wherein the metal or the metals of the carbo-nitride layer consists of two or more elements of the IVa to Via groups of the periodic table. For the production of this layer, carbon and nitrogen-donors are introduced in the CVD gas phase, which produces a C-N molecule group.

Full Text

The invention concerns with a compound body, consisting of a substrate body of hard metal, cermet, steel or ceramic and at least of a metal carbo-nitride hard material layer. The invention concerns further with a method for the production of multi-component, especially quaternary, hard material layers, with at least two metals from the group Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and W. Hard material-coated substrate bodies are known as per the state-of-the-art. Through the coated hard material layer, if necessary as multi-layer coating, a wear-resistant surface layer can be combined with tough and mechanically highly loaded basic bodies. Basically, for the coating of the hard material layers, two different methods, viz., the so-called Chemical Vapour Deposition (CVD) or the Physical Vapour Deposition (PVD) are applied. Especially, with cutting tools for metal cutting of work pieces, such layers are known for extending the useful life of the cutting tools. Usual protecting coatings consist, for example, of TiC, TiN and/or aluminium oxide. It is also possible to coat readily with the layer sequence of TiN, Ti (C,N) on a substrate body with any given C:N mixture ratios. For the production of wear-resistant layers for cutting tools made of high-speed steels, PVD method is applied, while CVD method is preferably employed for cutting tools made out of hard metals. Both the methods have advantages and disadvantages. Whereas, PVD layers can be produced right from about 400 deg, C, further higher temperatures are required in the CVD method, which, as a rule, lie in the range of 1000 deg. C. Thus, it follows that temperature-sensitive substrates are coated pvd method, and of course, with this coating variant, a direct all-round coating of complex-shaped bodies is difficult and expensive. In "Surface and Coatings Technology", 33, (1987) Pp. 91 to 103, characteristics of tertiary nitrides and carbo-nitrides of the metals titanium, zirconium, hafinium, vanadium, niobium, chromium and aluminium, produced through cathode pulverising (sputtering). are analysed. High values of micro-hardnes could be obtained with layers made of (Zr, Ti) (C, N), (Zr, Ti) ,(C,N), (Nb, Ti) (C,N) as well as (Hf, Ti)C, and (Hf, Ti)C. Moreover, a method is known from DE-Al-25 05 009 for the coating of inorganic substrates with carbides, nitrides and/or carbonitrides of iron, boron, silicon or of the transition metals of the IVa to VIa secondary groups of the periodic Table through direct thermal reaction of the metals or derivatives thereof with substances providing carbon and nitrogen, if necessary in the presence of further additions, with which, as carbon-and nitrogen suppliers, the compounds can be used, amongst others, which contain the cyanide groups, with a triple bond between carbon and nitrogen. Aceto-nitrile is known as one of these compounds. The coating can be made through the CVD process. The compoxmds described are, exclusively, mono-metal carbides, nitrides, or carbo-nitrides, whereby, it has resulted, during the course of further study and research of the method given in this paper, that the zr(C, N) is not producible as per this method. In all the cases, the deposition rates per time unit lie very low. From here, it can be seen that the aim of the present invention is to produce composite bodies of the named in the beginning, whose coating produces a very uniform surface layer, especially for the production of pre-formed sintered tools, whose outer contours must remain unaltered to the maximum extent through the coating. Further, it is the aim of the present invention to provide a method, with which it is possible to procure multi-component hard material layers with at least two metals of the Groups IVa to VIa as carbo-nitride layers. A high layer growth is to be envisaged, in order to minimize the coating time correspondingly. The aim with reference to the composite bodies is achieved through the characteristic combination as per Claim 1. The new composite body consists of a hard metal, cermet, steel, or ceramic substrate body, and at least one oxygen-free metal carbo-nitride hard metal layer, whereby the metal consists of two or more elements of the IVa and VIa groups. The carbo-nitride hard metal layer must be coated through CVD method by building a single phase layer having homogeneous structure and lattice constants. Preferably, the metal carbo-nitride layer must be formed as quaternary layer of the general formula (Ml, M2) (C,N), whereby Ml and M2 are different metals of the IVa to VIa groups mentioned, preferably of the IVa and/or Va groups. As per a concrete version of the invention, the coated layer possesses the composition described in Claim 3 or Claim 4. For example, the hard material layers from the material system Ti-zr-C-N have characteristic values, which exceed the characteristics of the simple binary compounds TiC, zrC, TiN and ZrN considerably. As already elaborated in the literature mentioned in the beginning, viz. "Surface and Coatings Technology", 33 (1987), Pp. 91 to 103, the tertiary mixed carbides (Ti, Zr)C produce already higher hardness values than the binary carbides TiC and ZrC. Mixed carbides of the type (Ti, Zr)C consist of a homogeneous phase, and have the same cubic crystal structure as their binary components. This titanium and the zirconium are distributed themselves in statistical form in the places of the sub-lattice of the metallic atom. Similar is the case with the mixed nitrides of the type (Ti, Zr)N, wherein especially hard layers are received with a ratio of Ti and zr atoms of about 70 : 30 at.-% Still higher hardnesses were also observed, with a metalloid nitrogen was substituted simultaneously partly by carbon, wherein likewise single phase hard material of the type (Ti, Zr) (C,N) was foxmd, whose metallic atoms are distributed statistically in a sub-lattice, and whose metalloid C and N are likewise distributed randomly in the other sub-lattice. Analogous observations can be made with the material system Ti-Hf-C-N, in which the zirconium is replaced by the element hafnium. Here again, hardness values were observed, which exceed considerably those of the binary carbides and nitrides. Of course, the hard material layers mentioned could be produced only through the PVD method, as thin-layered coatings at high cost. Surprisingly, it has resulted in that, a deposition of the multi-component hard material layers shown in Claim 1 is possible through the CVD method, and that the precipitated multi-component layers produce an especially low surface reference. Especially, composite bodies must be addressed, which produce a hard metal substrate body, in which one or more layers must be coated by CVD process, of which at least one is a multi-metal carbo-nitride hard metal layer. In contrast to high-speed steels, hard metals can be exposed to higher temperatures without damage to the lattice structure. The CVD method is basically described in the literature. In order, e.g., to produce a TiC layer, it is known as per the state-of-the art, to introduce a gas mixture of TiC 14, CH4 and H2 (as transport gas) under about 1000 deg. C over the substrate being coated. Corresponding is valid for the production of TiN layers, with which, instead, Ch4N2 is applied. If CH4 and N2 are introduced simultaneously in the gas phase, then Ti (C,N) results. With all the carbide-, nitride- and carbo-nitride- layers, however, compounds with only one single metal are involved. It is explained, thus, that the simuhaneous introduction of TiC 14, ZrC14, CH4, N2 and H2 in the gas phase of the reaction space does not lead to the desired quaternary compounds (Ti ,Zr) (C,N). It is in turn explained, thus that the chemical equilibrium of the reaction is determined by the energy balance G, which is called the free reaction enthalpy (or, Gibbs energy). Fig. 1 shows such G values with respect to the temperature for CVD reactions, with which the solid materials TiC, TiN, ZrC and ZrN result. The chemical equilibrium of the reactions mentioned Ues around so much on the right side, so much the corresponding G values are. With temperatures of 1300 deg. k, these values are much lower with the reactions for TiC and TiN than in the cases of ZrC and ZrN. With the introduction of gas mixtures containing titanum tetra-chloride as also zirconium tetra-chloride in the reaction space, TiC and TiN layers result necessarily, as well as through solid state reactions Ti (C, N), but no carbide or nitride of zirconium or titanium-zirconium-carbo-nitride. As found out surprisingly, quaternary carbo-nitride layers can be especially obtained by maintaining special process conditions through CVD process. The present invention also comprises composite bodies with many layers of carbides, nitrides and/or carbo-nitrides of Ti, Cr, Hf, especially TiC, Ti (C, N), TiN, and/or A12-03 and atleast one multi-metal carbo-nitride layer. Preferably, composite bodies, according to the invention, are applied as tools, especially, cutting tools for metal working. The aim of the present method of the invention is achieved through the characterstic combination of Claim 7. According to the invention, the multi-component hard material layers are coated through CVD process, whereby the gas phase contains, besides H2 and/or Ar (as transport gas) and metal chlorides, also carbon and nitrogen donors, with a reaction temperature of between 700 deg. C and 1100 deg. C, and preferably under pressure of between 5 KPa and 100 KPa, these carbon and nitrogen donors producing a C-N molecule group. This C-N molecule group is preferably a cyanide group with a triple bond between carbon and nitrogen, whose distance lies between 0.114 and 0.118 nm at room temperature. As such, aceto-nitrile offers carbon and nitrogen donors. The mixture can however, contain also CN molecule groups with a sunple C-N bond. In the mixture concerned, from which the carbo-nitride hard material is precipitated, any compounds of this type are in principle known as per the state-of-the-art, and are described, e.g., in DE-Al-25 05 009. Other gas media can also be introduced in the reaction vessel, which are in position for building the CN cyanide groups with reaction temperature. While holding these specifications, it is also possible to bring in both metals in the hard material layer, while building corresponding single phase carbo-nitride, as against the presumption contained in the state-of-the-art, with simultaneous introduction of two or more metal chlorides, that only to bring those with the comfortable thermo-chemical data with the layer formation for reaction deposition. Surprisingly, with simultaneous presence of ZrC14 and TiC14 e.g., deposition rates resulted, which lie many times higher than the deposition rates which resulted with the presence of only one metal chloride in the gas phase in the CVD process. The method according to the invention is used preferably for the deposition of hard material layer (Ti, Zr) (C, N). It can however be applied successfully to the quaternary system (Ti, Hf) (C, N). In a corresponding maimer, instead of the zirconium tetra-chloride, hafnium tetra-chloride must be introduced in the gas phase. However, it is also possible to apply other chlorides of the elements vanadium, niobium, tantalum and chromium. Specially suitable materials, which can release CN cyanide radicle under the reaction temperature, are organic compounds like hydrogen cyanide CHN, cynamide H2N-CN, cyanogen NC-CN, cyanoacetylene HC-C-CN and the acetonitrile CH3-CN already mentioned. The bond length of the CN groups lie between 0.114 and 0.118 nm. It is also possible to produce quaternary hard metal material layers of the type (Ti, Zr) (C, N) with those materials whose molecules produce simple C-N bonds. Here, belong compounds like methylamine H3C-NH2 and ethylenediamine NH2-CH2-CH2-NH2. In such mixtures, however, the zirconium tetra-chloride is not transformed fully. Examples of various versions of the invention, also in comparison with the depositions, which are known as per the state-of-the art, are described in the following paragraphs. For the studies, a C VD apparatus with a reaction vessel made out of a heat-resistant steel alloy was applied, in which about 600 throw-away inserts (of size 12.4X 12.4 X 4 mm) can be coated simultaneously. The temperature can be held to values upto 1100 deg C, and the internal pressure between 500 and 100 Kpa. Using a mixing device, mixtures of different gases can be dozed and introduced exactly in the reaction chamber. The main constituent of the introduced gas is hydrogen. Titanium tetra-chloride in gas form is obtained by the evaporation of liquid titanium chloride, Zirconium chloride in gas form was obtained by transition of HCl gas over chips of metallic zirconium. The heating of samples until the coating temperature follows respectively in an inert gas temperature e.g. of argon. The cooling of the resulting coating is carried out under a hydrogen atmosphere. Experiment 1 (State- of the Art): With a temperature of 1010 deg C and a pressure of 30Kpa, a mixture of 1.5% Ti C14, 1.2 % ZrC14, 15% N2, Bal. H2 is introduced for duration of 180 min. in the reaction chamber. After cooling the samples were collected and analysed. The layers deposited on the hard metal substrates arranged in the reaction chamber were between 7 to 10 microns thick, depending on the position in the reaction chamber. Through an X-ray diffraction and analyses with a electron beam micro-wave, it could be ascertained that the deposited layers consisted Ti (C, N). The zirconium content in this layer was less than 1% on the contrary. In the exhaust tubes, there was a solid coating of zirconium chloride. The production of quaternary carbo-nitrites is not possible by this method. The hardness of the deposited titanium carbo-nitride layer was determined using a micro-hardness testing device, which amounted to 2350 HV05 (Vickers hardness with 50G load). Experiment -2: In constant to Experiment 1, aceto-nitrile CH3-CN was supplied instead of ch4 and N2, in a quantity of 3.5%. The pressure amounted to 8 Kpa. After coating for 3 hours, between 9 to 12 micron thick metallic grey layers were formed. It was ascertained with X-ray method that the deposited layer material consisted of a homogenous face-centered cubic phase with a lattice constant of 0.4365 nm. Through electron wave macro-analysis, it was found that the layers have a formula composition of (TiO.64-ZrO.36) (C0.62-NO. 38). In addition, still unavoidable contaminations in oxygen (under 0.3%) and in cobalt (0.6% near the boundary surface between the hard metal substrate and the coated layer) were ascertained. In contrast with the previously described first experiment, no coatings of zirconium chloride were found in the exhaust tube, so that a nearly full-fledged reaction of the ZrC14 supplied can be achieved. The micro hardness values measured on the various throw-away inserts lay between 2800 and 3400 HV05, therefore considerably over the micro-hardness values, which the Ti (C, N) layers producible by the state-of -the art have. The quaternary layer produced through the CVD process possessed a high surface finish, i.e. a relatively flat surface with minimum roughness depth. Experiment 3: Instead of the zirconium chloride ZrC14 applied in the Experiment 2, here hafnium chloride HfC14 is supplied in the same quantity. 9 to 13 micron-thick hard material layers were formed on the hard metal substrates, these layers likewise consisting of a homogenous face-centred cubic phase with a lattice constant of 0.4401 nm, the analysis resulted in a formula composition of (Ti0.67-Hfo).33) (C0.58-No.42). Micro hardness values of between 2920 and 3550 were measured. Experiment 4: Corresponding to the conditions described in Experiment 2, instead of acetonitile, a gas with simples C-N bond is applied, viz, methylamine. The quaternary hard material layers produced possessed a face-centred cubic structure. The composition corresponding to the formula (Ti0.86-Zr0.14) (C0.72-No. 18) produce, however, in comparison with the coating which was obtained as per experiment 2, a lower zirconium content, as also the same input quantity of ZrC14 was applied. Experiment-5: To begin with, a coating of about 1-micron-thick titanium nitride was deposited from a gas mixture of 1.5% TiC14, 25% N2, balance H2. Thereafter, an 8-micron thick layer of a hard material (Ti, Zr) (C, N) corresponding to the description for the Experiment 2 was deposited. The final layer was deposited from a gas mixture of 2 % A1C13, 5% Co2 and 93% H2 gas phase, corresponding to a thickness of 1 to 5 microns. The layer sequence thereby reads: TiN-(Ti, Zr), (C, N)-A1203; the substrate body was a hard metal (WC-CO). The throw-away inserts so produced were applied for comparative nachinability experiments. The coated thro-away inserts which are received as per the different experiments were proved on a turning machine, here, an abrasively behaving cast steel having a hardness of 320 HB was machined. The throw-away inserts had a specifications CNMG. 120412. The following settings were maintained during the experiment: Cutting speed: 100 m/min; Cutting depth: 1.5 mm; Feed : 0.28 mm/rev Throw -away inserts with nearly same coating thickness of 10 microns were selected for these comparative tests. The life until the reaching of wear width of 0.3 mm was determined. The results are given in the following table: In a further experiment, a series of throw-away inserts were manufactured, which produce a hard metal substrate body and a multi-layer coating. The multilayer coatings had the layer sequence described in Experiment 5, and the sample bodies were throw-away inserts of the geometry CNMG 120412. The present experiments under the same conditions of experiment as described earlier produced the following results: Also, with multi-layer coated throw-away inserts, of which one coating was a multi-component coating-here(Ti, Zr) (C, N)-better wear characteristics can be achieved with chip-forming metal cutting tools. We Claim: 1. Composite body consisting of one hard metal, cermet, steel or ceramic substrate body and at least metal carbo-nitride hard material layer, is this characterized in that, the metal of the metallic carbo-nitride layer contains two or more elements of the group Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W, and that the metallic carbo-nitride is coated by a CVD process through building of a single phase layer. 2. Composite body as claimed in claim 1, wherein at least one metal carbo-nitride layer is formed as quaternary layer (Ml, M2) (C, N), wherein Ml and M2 are different metals, preferably of the group Ti, Zr, Hf, Nb and Ta. 3. Composite body as claimed in claim 1 and 2, wherein the deposited layer produces the composition [Ti(X), Zr (l-X)] [C(y), N(l-Y)]with 0.4 4. Composite body as claimed in claim 1 and 2, wherein the deposited layer produces the composition [Ti(X), Zr (1-X)3 [C(y), N(l-Y)] with 0.4 5. Composite body as claimed in any one of the claim 1 to 4, wherein the substrate body is covered with layers of carbides, nitrides and or/carbo-nitrides of Ti, Zr, Hf, especially TiC, Ti (C, N), TiN and /or A1203, and at least one multi-metal carbo-nitride layer. 6. Composite body as claimed in any one of the claim 1 to 4, wherein this is built as tool, especially cutting tool metal cuttmg work. 7. Method for the production of multi-component especially quaternary, carbo nitride hard material coatings with at least two metals from the group Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and w, by known CVD process characterized is that the coatmg of the hard material layer is carried out at a temperature of between 700° C and 1100°C and preferably with a pressure of between 5kPa and 100kPa and wherein the gas phase, in addition to H2 and /or Ar as well as chlorides of the above mentioned metals, contains also carbon-and nitrogen donors, which produce a C-N molecule group. 8. Method as claimed in claim 7, wherein the C-N molecule group contains a cyanide group contains a cyanide group C-N with triple bond between the carbon and the nitrogen, whose distance in room temperature amounts to between 0.114 and 0.118 nm, preferably under the application of acetonitrile. 9. Method as claimed in claimed in claim 7 or 8, wherein the C-N molecule group contains molecule groups with a simple bond between the carbon and the nitrogen. 10. Method as claimed in claimed in claim 7 to 9, wherein the hard material layer consists of (Ti, Zf) (C, N) or (Ti, Hf) (C, N).

Documents:

1606-mas-1996 abstract duplicate.pdf

1606-mas-1996 abstract.pdf

1606-mas-1996 claims duplicate.pdf

1606-mas-1996 claims.pdf

1606-mas-1996 correspondence others.pdf

1606-mas-1996 correspondence po.pdf

1606-mas-1996 description (complete) duplicate.pdf

1606-mas-1996 description (complete).pdf

1606-mas-1996 form-1.pdf

1606-mas-1996 form-26.pdf

1606-mas-1996 form-4.pdf