EP1119429B1 - Method for producing components by metallic powder injection moulding - Google Patents

Abstract

The invention relates to a method for producing components by metallic powder injection moulding of metallic powder parts coated with a binding agent in an injection mould. According to said method the metallic powder parts of a titanium alloy are used to produce components having a complex shape. During the production of the components, the stages production of the metallic powder parts for the titanium alloy, preparation of the feed-stocks with a binding agent, release of the binding agent and sintering are carried out exclusively in an ultrapure protective atmosphere of protective gas and/or in the absence of air and/or under vacuum. The metallic powder parts and the binding agent ingredients are such that they are poor in impurities. The sinter support for the components is configured in such a way that during sintering of the components the free slip of the surface of the sinter support for the components positioned thereon remains intact.

Description

The invention relates to a method for producing components by metal powder injection molding of powder-coated metal powder parts with the characteristics of the in the Preamble of claim 1 genus described.

Complex shaped components have long been used in medium and large quantities Automotive engineering, in aviation as moving parts and in off-shore applications and also needed in medical technology, for example for implants. It is about complex components with dimensions that go into the millimeter range can. As a rule, such complexly shaped components are machined Processes prepared, such as by milling, turning and grinding. As materials come, for example, low-alloy, high-alloy or corrosion-resistant Steels, high-speed steels, superalloys, alloys with magnetic properties, Hard metals and other materials not listed in question. When using a cutting process for the production of complex shaped components, in particular when using hard, high-strength materials for the component when milling, turning and grinding the disadvantage that high tool wear arises in the production and thus corresponding costs. Complex component geometries require a lot of work, which increases the unit price. Certain complicated Structures can only be realized with the help of extreme effort. This is particularly true towards thin parts, such as thin axes, which are due to the mechanical Load when milling, turning and grinding the part of the risk of damage subject. When using a manufacturing technique such as milling, turning and grinding there is generally a high loss of material and therefore corresponding costs. Furthermore is the surface of the finished complex-shaped components with an unacceptable Surface roughness, which requires special post-treatment techniques, to achieve a surface with low roughness.

Another manufacturing method for producing a complex shaped component with Small dimensions consist in the use of investment casting. The investment casting is for Every manufactured component requires a mold production, the production of which is considerable Labor required. With the help of investment casting, complex shaped can be created Components with small and very small structures that are in the range of centimeters, no longer reproduce with certainty. It also responds due to the temperature of the liquid casting, as a rule, the surface of the complex-shaped component produced with the wall surface of the mold. The resulting reaction layer on the surface The complex shaped component must be used to produce a perfect surface for example stripped. This stripping in turn leads to tight Tolerances can no longer be met. Furthermore, the mechanical properties of the casting structure, which are produced by means of investment casting, the mechanical properties inferior if the complex shaped component with the help of forging technology has been manufactured.

It is also known to manufacture complex-shaped components by means of spark erosion. The production of components with spark erosion is slow and time-consuming in front of it and is also associated with considerable costs. Restrictions on the production of complex shaped components by spark erosion also arise in that not all geometries of the component are produced by means of spark erosion can. In addition, there is of course the loss of material in the manufacture of a component on the way of spark erosion high, forced by making a Component on the way of spark erosion also the surface layer of the for Complex shaped component used material unusable and must be used with appropriate Process removed and smoothed. Making a surface with less Roughness not only requires an additional operation, but also has an effect negatively affects the adherence to high reproducibility and dimensional accuracy.

Another method for producing complex shaped components with small dimensions is given in electrochemical processing for the manufacture of such components. The electrochemical processing has the disadvantage that some component geometries cannot be designed and that basically no sharp edges are generated can. Even with electrochemical processing, the high-quality material for the production of complex shaped components, a high proportion removed and so the loss of material is considerable.

Can complex shaped components due to their special requirements Component geometry with the described methods according to the prior art, such as milling, Not turning, grinding, investment casting, spark erosion and electrochemical machining produce, you usually switch to another material or choose a different design in order to still be able to manufacture the complex-shaped component. Therefore, if you choose a different design for the complex-shaped component, the one with one of the techniques described according to the prior art can then be manufactured can, this forces a waiver of the complex for the particular purpose molded component required optimal geometry of the component. You give way to manufacturing of the complex shaped component on one for the production according to the state of the art Technically more suitable material, one deals with the disadvantage that because the changed and partly defective material properties of the changed Material, for example, the component must be dimensioned larger than that for its optimal property would be required, possibly restrictions regarding the functional properties of the component are accepted or, for example, must in the case of components intended for medical technology, material properties of a material that, for example, has poorer biocompatibility of the component in an implant means like this when replacing a well compatible titanium material by another for an implant. each some of the above limitations when choosing a different design or another material can stand alone for each application already be unacceptable.

The injection molding process for components with complex geometries has long been known made from a wide variety of plastics to produce such parts. For higher properties, such as those found in mechanical engineering and medical technology and other fields are required, those used in the injection molding process practically do not use thermoplastic and / or thermosetting materials as they do not had sufficient mechanical properties. An improvement in mechanical Properties were achieved by using powdered fillers, for example made of metal in the injection molding process and the metal content in the Injection molding compound has run as large as possible, so that now produces a metal component in which the powdered binder encloses the metal powder parts by mixing and is initially held together by this binder, the described method is referred to as metal powder injection molding. The binder metal powder is injected into a mold with an injection molding machine, after that at least partially removed the binder from the green component obtained and subjected to sintering. To achieve extremely high reproducibility with the metal powder injection molding process and dimensional accuracy to achieve, further mechanical properties of the components that are comparable to those of forged components, and

in order to achieve a homogeneous structure in the material of the component and thus in the subsequent heat treatment of the component no warpage has already occurred Titanium powder for producing heavy-duty components, such as in Automotive engineering, etc. used. Titanium is particularly advantageous for complicated molded components with small dimensions in the field of medical technology, there such components have an especially good biocompatibility as an implant. With titanium powder the required strength values of components can be complex achieve shaped structure, but is missing, for example, in safety-relevant areas A safety reserve of titanium powder for both machines and implants manufactured component in terms of functionality and against irreparable Damage due to overloading and against breakage. Complex shaped from titanium powder and with Components manufactured using the metal powder injection molding process break when the strength limit is reached without previous plastic deformation immediately (brittle fracture), which however in the majority of the applications cannot be tolerated. This essential Disadvantage of the complex shaped according to the prior art made from titanium powder Components essentially result from the fact that considerable during the manufacture of these components Amounts of contaminants such as oxygen, carbon, nitrogen and the like can be included in the material of the titanium component. With that attain Complex shaped components made from titanium powder using the metal powder injection molding process not the properties that the same component has when it is on the Ways of forging has been made.

DE 44 08 304 A1 describes sintered parts made of oxygen-sensitive, non-reducible Powders and their production via injection molding are known in the metal powder parts made of titanium serve for the production of complex shaped components, the production of oxide-free powder with exclusion of air and the feedstock production with a binder under protective gas and which also includes debinding and sintering with the exclusion of air and moisture take place.

The invention has for its object an inexpensive and for mass production to create a suitable process for the production of complex shaped components, in particular a safety reserve of the sintered component against inoperability and against irreparable damage in the event of overloading and breakage, which minimizes the uptake of contaminants in the material of the components allows during the manufacture of the components until completion, that for the prefabricated Component has a homogeneous structure, extremely high reproducibility and Has dimensional accuracy that avoids reworking of the manufactured components, which enables a low surface roughness of the finished component, and that during the production of the complex shaped excludes a distortion of the components.

The advantages of the invention are, in particular, that individual sections of the method according to the invention for the production of complex shaped components under strict Compliance with a high-purity protective atmosphere consisting of protective gas and / or air exclusion and / or vacuum takes place. This prevents that during the manufacturing process the complex shaped components contaminants with respect to the given Performance data of the component to an intolerable extent from the component be included. However, these individual manufacturing sections are partially again divided into subsections, these subsections also helping to ensure that the inclusion of contaminants in the material of the component is always a minimum is supplied, such as the metal powder parts of the selected titanium alloy and the constituents of the binder are selected in their composition in such a way that each individual material component already has the property as such has to be low in contaminants. By selecting the components of the titanium alloy and the binder becomes the proportion of unwanted contaminants set to the lowest possible starting base value, so that the during the process inevitable increase in the contaminants of the material of the component in the final sum corresponding to the selected low basic contamination of the components the titanium alloy and binder. So there is the production of the metal powder parts, also the mixture of the metal powder parts with the binder components for feedstock production under the influence of high-purity protective gas, such as argon instead of. The sintering itself takes place under a vacuum and the debinding takes place in a commercial debinding bath, for example with hexane and thus under exclusion the presence of air and thus of oxygen, carbon, nitrogen and the like as contaminants.

Every single section of the manufacturing process of the complex shaped components is that Subject to the least possible accumulation of contaminants to achieve each manufacturing step, as well as according to the production of the metal powder parts the invention has been made. For high-quality stress on the components produced a titanium alloy was selected which has the composition Ti-6Al-7Nb. The contaminants Poor metal powder parts of this titanium alloy can be made by two methods are generated, namely the Electrode Induction Melting Guiding Gasatomization process or the plasma melting induction guiding gas atomization process. The production the metal powder parts for the titanium alloy mentioned are carried out by an atomization system with argon inert gas atomization, in which the inert gas atomized metal powder parts caught in the powder can flanged gas-tight to the atomization system become. The powder jug itself is designed to be gas-tight and can be sealed in one Glove box system incorporated, which in turn is operated with argon gas, so that in the manufacture of the metal powder parts an absolutely small increase in the contaminants, such as oxygen, carbon, nitrogen, etc. during this manufacturing stage is achieved in the powder components of the component.

For the mixing of the generated in the feedstock production under the influence of protective gas Metal powder parts with the binder is also a special composition of the Binder to minimize the possibility of absorbing contaminants during the feedstock production and on the other hand to influence the remaining Binder residues in the sintered component due to the composition of the binder components selected in relation to their response to an increase in temperature in the component. Binder components are used to carry out partial debinding of the complex shaped components with low melting, decomposition and / or evaporation temperature in a proportion added to the binder that is greater than half of the total binder proportions is. The rest of the entire mixture of binder components consists of higher ones Melting, decomposing and / or evaporating temperature reacting binder components the low-melting binder components. The metal powder parts of the titanium alloy are made with binder components made of thermoplastic or thermoset polymers, with thermal gelling substances, with waxes or surface-active substances or mixtures obtained therefrom. For the production of the invention A special binder has been selected to reduce the entry of contaminants such as oxygen and to reduce the residual binder in the Component contributes.

Another procedural measure in the manufacture of highly complex components is that during the sintering these components do not shrink May enter into connection with their pad and also not through contaminants to be changed, which separates the pad on which the components at Sintering, with the same terms and conditions in the document for hot isostatic pressing apply, which is still carried out on the components after sintering can be. To prevent a reaction between the complex shaped Components and the base takes place, is therefore the sintered base for the Components designed such that the sintering of the components while the free sliding of the surface of the sintered base for the components lying on it unchanged What is preserved, for example, by designing the surface of the sintered base with a material that is resistant to reduction against the material of the components such as. Ceramic oxides happened. At the same time, the material of the surface of the Sintered base selected so that the material does not contain any contaminants at the sintering temperature emits. This design of the sintered base is a particular advantage of Invention to avoid that the complex components with often very minimal Structure on the sintered base and also not with hot isostatic pressing warp or break by sticking to the surface and also not by contaminants be contaminated with the respective pad.

Another advantage of the present invention is the selected manufacturing process of metal powder injection molding, in which the mixing of the metal powder parts with the binder components for feedstock production and also the metal injection molding of the Feedstockes in the injection molding machine take place at low temperatures, so that none Reaction of the feedstock or the binder and metal parts of the feedstock with the mixer itself or in particular not with the injection mold in the injection molding machine, so that no surfaces are created on the complex shaped components, which with the React form or with device parts and therefore do not need to be treated, that means that the surface is already in perfect condition, whereby an extremely high reproducibility and dimensional accuracy and thus a Near-net-shape production of a high-strength component is made possible. By selection a titanium alloy for production using the metal powder injection molding process for complex Components, the selected titanium alloy Ti-6Al-7Nb by means of its components which for the complex-shaped components to be produced have the required material properties, With the aid of the method according to the invention, it is possible to achieve these alloy properties during manufacture in sections and subsections until completion of the To maintain the final state of the component almost unchanged, while according to the state the technology in the manufacturing process of metal powder injection molding is usually too significant Absorption of contaminants occurs and thus an intolerable Change in the material properties of the component to be manufactured compared to the Original properties of the selected material for the production of metal powder.

The invention based on an embodiment and drawings explained in more detail.

Fig. 1

Schaubildform einer Prinzipdarstellung des Verfahrens zur Herstellung komplex geformter Bauteile mit dem Metallpulverspritzgußverfahren,

Fig. 2

die Wiedergabe eines Zugstabes, der nach der Metallpulverspritzgußtechnik hergestellt ist, vor und nach einem Zugversuch und

Show it:

Fig. 1

Diagram of a basic representation of the process for the production of complex shaped components with the metal powder injection molding process,

Fig. 2

the reproduction of a tension rod, which is made by the metal powder injection molding technique, before and after a tensile test and

From Figure 1 is in the form of a diagram only sketchy and in partial representation Production of a complex shaped component from the production of metal powder parts about the production of feedstock, metal molding, debinding and sintering shown with the finished component. In Figure 1, 2 and also in the results in Figure 3 was deliberately dispensed with the representation of a complex shaped component in order to To promote clarity and to be able to achieve clear measurement results. complex shaped components are, however, for their application in motor vehicle construction, aviation, in off-shore applications and in medical technology, e.g. in the form of implants required. The metal powder parts as a material for forming components according to the invention can be manufactured in different ways. Powder can be used once are made by mechanical alloying or mechanical crushing has been. What is required, however, is the material components of the titanium alloy to select in their composition so that each material component in the Initial state already has the property of being low in impurities. The required purity of individual material components depends on the requirements which are placed on the finished end component when it is used. Each individual material component of the metal powder parts must therefore be the one for that to be manufactured Component already have the required material properties. While above Direct powder mixing as the first way of producing metal powder parts has been described, the embodiment in Figure 1 assumes that pre-alloyed Powder is used, for example a finished alloy in the form of a rod. Metal powder parts for the production of perform complex components or a test specimen in an atomization facility by means of an argon inert gas atomization. It became an atomization plant used, specially designed for the production of high-purity titanium alloy powder has been. The atomization of the titanium alloy powder pre-alloyed in a finished alloy takes place in strict compliance with a high-purity protective atmosphere made of protective gas such as argon. This and the special design of the atomization system is the absorption of contaminants such as carbon, oxygen and Nitrogen kept very low during the atomization process. With that of the applicant The system used will have a carbon and oxygen content of the titanium alloy powder achieved with carbon: 0.01% by weight, oxygen: 0.21% by weight, these Values are only slightly above the values that each individual material component already had in the initial state, namely for carbon: 0.01% by weight and for oxygen: 0.2% by weight.

When the production of the metal powder parts for the titanium alloy by means of an atomization system done with argon inert gas atomization, it is advantageous that the atomize in inert Metal powder parts in a gas can flanged gas-tight to the atomization system to be caught. This powder can itself can be closed gas-tight executed and the powder jug is then introduced into a glove box system, which itself is operated with the protective gas argon. These measures will be taken to minimize the uptake of contaminants in the metal powder to achieve in the manufacture. The purity of contaminants used Metal powder parts for the titanium alloy is necessary for the fulfillment of the required material properties of the finished component very essential. The powder components must be less contaminated than the end product, since one in the manufacturing process of the component Minimization of the contaminants absorbed into the component can be made can, however, completely avoid the absorption of contaminants is practically impossible during the manufacturing process of the component. To the goal of high purity Reaching metal powder parts have been two different manufacturing processes of metal powder parts used for the titanium alloy. On the one hand, there was the electrode Induction melting gas atomization process applied, and on the other hand plasma melting Induction guiding gas atomization process. Different results regarding The total amount of pollutants in the manufacture of the metal powder parts are also thereby causes that when using a pre-alloyed powder in the form of a pre-alloyed According to the DIN standard, the oxygen content of 2000 µg / g is already in the finished product is predetermined, with reference to the predetermined amount of oxygen contamination those% by weight of oxygen contamination and of course also other contaminants add up that occurs during the manufacture of the metal powder parts. Due to the contamination contained in the finished alloy according to the DIN standard with contaminants it is advantageous, even the individual material components the titanium alloy, so as to take special care in the selection and the treatment of the individual components in the initial state to a better result achieve, i.e. a result that minimization already during the manufacture of the metal powder parts for example, the oxygen concentration in the initial state.

When using inert gas atomization for the production of metal powder parts Metal powder parts in a pronounced spherical shape. The spherical shape is for sintering advantageous because a high packing density of the metal powder parts due to the spherical shape of the Powder can be achieved and thus a low residual porosity of the sintered complex built component is achieved.

The amount of metal powder produced is then determined by means of a sieve chain according to the particle size of the powdered metal parts. For the production of the complex shaped components is the Use of metal powder parts with a particle size <100µm is suitable. Especially Favorable results are achieved if one preferably has a particle size of <45 μm used. The resulting loss of material in the production of metal powder is included a use of metal powder parts with a particle size <45 microns at about 70 to 75% of the metal powder parts produced in contrast to the often 90% loss of material in the production of the complex shaped components by means of machining processes. The sieved metal powder parts with a particle size> 45 µm can be used for others Use purposes so that the loss of material can still be reduced. With the actual Metal powder injection molding process and operation becomes practically one hundred percent Material utilization achieved, because then any remaining feedstock can be used can be. The surface roughness of the finished complex shaped The component depends on the powder size and is when using metal powder parts with a particle size <45 µm typically 1 µm. This means the surface of the finished, complex-shaped component is basically closed without reworking use.

The titanium alloy in rod form 1 is shown by way of example from FIG is processed into metal powder parts 2, which has already been described, that this is only one way of manufacturing the metal powder parts. In Figure 1b) follows the feedstock production, i.e. mixing the metal powder parts 2 with the binder 3 in a kneader 4 to the feedstock 5. This is followed in accordance with FIG. 1c) by metal molding of the feedstock by means of a block diagram indicated only schematically here Injection molding machine 6, to which the feedstock 5 is fed and under pressure into the injection mold 7 is injected into the shape of the component 8. The green part of the component created in this way 8 is partially delivered in the debinding in FIG. 1d) in a debinding bath 9 and then sintered according to FIG. 1e) in the chamber 10 of the sintering furnace until the finished one Component 8 is created, which for the reasons of simplification already described as Tension rod is formed, which is used at the same time for the tensile tests described later becomes. As can be seen from the overview in FIG. 1, follows after Production of the metal powder parts, the mixing of these metal powder parts with a Binder 3. These two components are mixed in a kneader 4 and into one Feedstock processed. The feedstock is therefore the mixture of the metal powder parts and the binder components used in the subsequent metal injection molding process as a molding compound be used. The binder components are thermoplastic or thermosetting Polymers, thermal gelling substances, waxes or surface-active substances or mixtures obtained therefrom are added. Can be used as binder components Polyamides, polyoxymethylene, polycarbonate, styrene-acrylonitrile copolymer, polyimide, natural Waxes and oils, thermosets, cyanates, polypropylenes, polyacetates, polyethylenes, Ethylene vinyl acetates, polyvinyl alcohols, polyvinyl chlorides, polystyrenes, polymethyl methacrylates, Anilines, water, mineral oils, agar, glycerin, polyvinyl butyryle, polybutyl methacrylates, Cellulose, oleic acids phthalates, paraffin waxes, carnauba wax, ammonium polyacrylates, Digylceride stearates and oleates, glyceryl monostearates, isopropyl titanates Lithium stearates, monoglycerides, formaldehyde, octyl acid phosphates, olefin sulfonates, Phosphate esters or stearic acid can be used.

Mixing the two components of the feedstock, i.e. the metal powder parts 2 and of the binder components takes place at elevated temperature, so that the binder components become liquid and can coat the powder particles. As a rule, you also need lubricants be added to bond the binder components and the metal powder parts prevent. The kneader 4 must ensure a sufficiently homogeneous mixing without clumping the components. By appropriate selection of the Mixing temperature and the constituents of the binder also find no chemical reaction between the binder and the metal powder during mixing. The binder 3 must also be selected in its components so that during metal injection molding there is no decomposition of the binder. In addition, the binder must also be very light can be removed from the component manufactured by means of metal powder injection molding, since he only for the temporary cohesion of the metal powder components after the metal molding serves. The binder, which always consists of several components, must be of this type be carried out so that each individual material component in the initial state itself has the property of being low in contaminants such as oxygen, nitrogen and carbon to be. Is very important for the production of a complex shaped component also with regard to the binder and its components, that they contribute to the required Maintain material properties of the component until the component is completed and not to be changed by additional intake of contaminants. For this Basically, the kneader and / or the kneading chamber is preferably of high purity Shielding gas such as argon filled to prevent contamination of the two components of the feedstock, for example with oxygen and nitrogen from the air. Due to the addition of external lubricants, the binder forms an envelope around each single metal powder part. When generating the feedstock, shear processes must ensure that that every metal powder part is covered with binder. This usually happens in so-called Z-blade mixers or also in planetary mixers. The feedstock usually shows a share of about 30 to 40 vol.% binder.

Mixing the metal powder parts of the titanium alloy and the components of the binder the feedstock production is carried out in a low temperature range. The The temperature range in feedstock production is between 50 degrees and 200 Centigrade. The constituents of the binder have a different melting, decomposition and / or evaporating temperature. Those predominate Binder ingredients that have a low melting, decomposition and / or evaporation temperature have compared to the proportion of binder components in the mixture, which have a higher different melting, decomposition and / or evaporation temperature exhibit. A binder poor in contaminants, its material constituents already have the property of being poor in the initial state to be contaminants consists of polyethylene, stearic acid, paraffin and Carnauba wax.

According to FIG. 1c), the metal injection molding of component 8 in an injection molding machine closes 6 in the injection mold 7. For metal injection molding, the in injection molding machines used in the plastics industry. The feedstock is in the Usually pelletized and inserted as a pellet in the injection molding machine if required. The exact Metal mold injection parameters such as pressure and temperature depend on the geometry of the complex shaped component and the flow properties of the feedstock. The pressure ranges from 30 to 50 bar. Metal injection molding has the advantages on, an inexpensive and excellent reproducibility of the complex shaped To enable components with small tolerances and is especially for medium to high Suitable for quantities. These advantages are particularly due to the extremely long life due to the metal injection mold, which is subject to almost no wear, so that a change in component geometry with the time and duration of use is not expected. The injection mold is manufactured conventionally. Because this manufacture but is only required once, the work involved can be high without itself to have a significant impact on a medium to high unit price. An automatic Manufacturing large numbers of components with such machines is without any Problem easy to carry out. You can also create complex shapes, such as Make threads, bores and the like with only one injection process.

The metal injection molding of the complex shaped component for the production of the green body takes place in a low temperature range. This temperature range is for metal injection molding between 60 degrees and 200 degrees Celsius. This low temperature range makes it possible to prevent the surface when selecting the binder components the injected green body reacts in the injection molding machine with the surface of the injection mold 7, which is why the surface is smooth and not again after the component is finished must be processed. This also applies, as already described, to a similar one low temperature manufacturing process in feedstock manufacturing, which is between 50 degrees and 200 degrees Celsius. Here too it can no reaction of the surface of the kneader with the resulting feedstock and therefore there are no disruptions in production. To the metal injection molding this is followed by the debinding of component 8, see FIG. 1d). It will be first partial childbirth, e.g. by thermal expulsion or in one commercial debinding bath, for example with hexane under air at light elevated temperature in the order of 40 degrees Celsius for a few hours is carried out. Large portions of the binder content are at a slightly elevated temperature removed with the help of the solvent. This heating up must be done very carefully, to avoid warping and destruction of the complex shaped component. Therefore the binder is also composed of different components that are used in different Evaporate temperatures. It will be influenced during the partial delivery of the solvent hexane, about 75% of the binder is removed from the green body, which then Bräunling is mentioned as a partially debonded component. The solvent hexane ensures that the debinding with complete exclusion of air, also of contaminants such as carbon, oxygen, nitrogen and so an accumulation of contaminants prevented in the injection molded component. Another removal of the residual binder, which can only be removed at a higher temperature and has previously been kept apart of the component prevented by thermal decomposition. Preferably done thermal decomposition in a high vacuum, but it can also take place in a pure protective gas atmosphere such as argon. After extraction, drying takes place held in argon gas. The handling of the injected components in the form of a green compact and the partially debonded components in the form of a brown must be done carefully to avoid a delay or break. The degree and homogeneity of childbirth are decisive for the further geometrical fidelity, the successful course of the Sintering and low contamination of the component with residual binder components. to Partial debinding of the complex-shaped component is therefore carried out first those binder components with low melting, decomposition and / or evaporation temperatures removed at slightly elevated temperature.

The next step in the completion of the complex-shaped components is sintering, as can be seen in FIG. 1e). During the sintering process, the component's browning undergoes a heat treatment in which the individual metal powder parts receive metallurgical contacts in the form of a welding diffusion with one another. A successful sintering process with titanium alloys and the achievement of a perfect material property of the component can only be achieved by avoiding the inclusion of additional contaminants such as oxygen, carbon and nitrogen during the sintering process in the metal powder. Therefore, the atmosphere of the chamber of the sintering furnace must have an excellent vacuum in the order of magnitude <10 ^-5 mbar, the high temperatures during sintering being unfavorable for maintaining good material properties, since at these high temperatures a particularly good absorption of impurities in the metal powder parts takes place. The temperature interval during sintering is between 1100 degrees and 1400 degrees Celsius. Production tests have shown that preferably the temperature of 1300 degrees Celsius gives an optimal result with regard to the properties of the manufactured component. Furthermore, it is necessary to avoid contamination by binder residues still contained in the brown compact, which is done by choosing a heating rate adapted to the evaporation rate of the residual binder still contained in the brown compact of the component, such as 5 K / min, so that during the heating process in the Sintering chamber of the residual binder is expelled thermally. The complex-shaped component produced after sintering has a density close to the theoretical density, namely 96%. The mechanical properties of the finished component are very similar to those of forged material with a comparable composition.

It has an important role in the flawless manufacture of complex components the sinter pad during the sintering process. The sinter pad for the complex shaped Components is therefore designed such that while sintering is being carried out of the components the free sliding of the surface of the sintered base for Components remain unchanged. The material of the sinter pad is therefore chosen so that at the sintering temperature the surface of the sintered base against the material of the components consists of reduction-resistant material, such as this is the case with ceramic oxides. It also becomes a material of the sintered base used, which releases no contaminants at the sintering temperature. By This selection of the materials of the sintered base is used when storing the complex shaped Components on the sinter pad and the one that occurs during sintering Shrinking process a distortion of the components and a possible breakage avoided.

After sintering can be achieved by a subsequent hot isostatic pressing treatment that the residual porosity of the sintered part can be brought to zero in order to thus all theoretically possible mechanical properties from the material of the component get. That is why the sintered components are made into one with high purity Protective gas such as argon equipped chamber and given at a temperature of around 850 degrees Celsius and 2000 bar gas pressure for several hours hot isostatically pressed. The high-purity protective gas argon is necessary because at these high Temperatures the tendency of the titanium alloy to absorb foreign matter is great however must be prevented. For the same reason, this is also the case with the material of the contact surface for the components in isostatic pressing ensure that this requirement the free sliding ability by training from a suitable material such as Ceramic oxides retained during pressing and that the material of the contact surface at the temperature of isostatic pressing no contaminants in the Chamber and to the components. The hot isostatic pressing process is only carried out if either the material inside the components must have no porosity or if the highest possible strengths with a density of 100% and the best possible Ductility is required for the respective application and therefore the necessary for it incurred additional costs are accepted.

The previous description of the manufacture of the complex shaped component according to the Invention and those described below and summarized in the table below Show values and evaluations of tests on a component designed as a tension rod, that it is possible with the method according to the invention not only the high strength of titanium as a component of the titanium alloy for the extreme requirements in the applications in medical technology, e.g. as an implant, in automotive and aeronautical engineering and in offshore applications from the initial state of the material for the Component and its properties in this initial state until the completion of the To obtain metal powder parts produced by the sintering process complex-shaped component, but at the same time, which is very important, that of the original titanium alloy Ti-6Al-7Nb already own high ductility until the finished complex-shaped part is obtained Obtain component by sintering. The titanium alloy Ti-6Al-7Nb was also made previously used elsewhere, but could not be useful in a metal powder injection molding process can be used without the property of stretchability the absorption of contaminants during the manufacturing process again was lost, so that the final product gained the safety reserve of the sintered Component in terms of functionality and against irreparable damage in the event of an overload of the component and against breakage in the prior art was missing. That after State of the art component made with titanium can have high strength, behaves However, the elasticity is not like a metal, it is elastic but not plastic deformable. Only through the combination of the features of the selection that is essential to the invention the titanium alloy Ti-6Al-7Nb together with the features of the Existence of a high-purity protective atmosphere during the manufacture of the metal powder Feedstock production, debinding and sintering with the help of protective gas and / or air exclusion and / or vacuum along with the selection of metal powder parts and binders that are low in contaminants, the manufacturing process metal powder parts of the titanium alloy which are low in contamination by the electrode induction Melting Gasatomization or the Plasma Melting Induction Guiding Gasatomization process, the application of a low temperature range in the manufacture of Mixing of the feedstock and in metal injection molding and also the nature of the Sinter pad with the free sliding ability of its surface and the production of the metal powder parts for the titanium alloy through an atomization system operated with argon with the downstream device for further transport of the metal powder parts in one Protective atmosphere. It is only by combining these features that, for example ductility of the tension rod shown in FIG. 2 until completion of the production received the sintering. The tension rod 8 can be seen in FIG. 2a) after completion. In Figure 2b) has been stretched with the tension rod 8 until it broke apart. It can be clearly seen from FIG. 2b that the one produced by sintering Tension rod behaved like normal metal by breaking apart before breaking apart has plastically deformed, i.e. got longer before it broke up. The ability, In addition to the elasticity, also having a plasticity creates the necessary for the application Safety reserve when installing complex shaped components according to the method according to the invention are produced.

• Sintertemperatur 1250° C, keine weiteren Behandlungen
• Sintertemperatur 1300° C, ebenfalls keinerlei zusätzliche Behandlungen
• Sintertemperatur 1300° C, anschließende heißisostatische Preßbehandlung unter Argon, 850° C/2000 bar, keine weitere Oberflächenbehandlung
• Sintertemperatur 1250 °C, heißisostatischer Preßprozeß, Oberfläche geschliffen
• Sintertemperatur 1300 °C, heißisostatischer Preßprozeß, Oberfläche geschliffen
• Sintertemperatur 1250 °C, heißisostatischer Preßprozeß, anschließende Wärmebehandlung bei 900° C /1h/in Wasser abgeschreckt + 540° C / 8h/ unter Schutzgas gekühlt. Diese Temperung entspricht der üblichen Aushärtebehandlung einer Ti-AI-V-Legierung.

In der Tabelle der Figur 3 sind die Ergebnisse für die Streckgrenze R_p, _0,2, die Zugfestigkeit R_m, die Dehnung A, Sauerstoffgehalt und Dichte, geordnet nach Behandlungsvariation aufgeführt. Die Zugversuche zeigten eine Steigerung der Festigkeit bei steigender Sintertemperatur und Dichte. Die bei 1300 Grad Celsius gesinterten und anschließend einem heißisostatischen Preßprozeß unterzogenen Proben zeigten Festigkeitswerte bei Raumtemperatur vergleichbar zu denen der geschmiedeten oder gewalzten Legierung (Streckgrenze ca. 1000 Mpa, Zugfestigkeit ca. 1060 Mpa, Dehnung ca. 17%).The measurement results of mechanical tests in the manufacture of tensile specimens of the tensile rod 8 can be seen from FIG. When producing the tensile specimens, the sintering temperatures of 1250 degrees Celsius and 1300 degrees Celsius and the surface treatment ground or not ground were varied. In some samples of the tension rod, a hot isostatic process was additionally connected in order to achieve a 100 percent density, in the other samples the density was approximately 96%. In Figure 3 tensile specimens of tensile bars are summarized, which received the following different treatment:

• Sintering temperature 1250 ° C, no further treatments
• Sintering temperature 1300 ° C, also no additional treatments
• Sintering temperature 1300 ° C, subsequent hot isostatic press treatment under argon, 850 ° C / 2000 bar, no further surface treatment
• Sintering temperature 1250 ° C, hot isostatic pressing process, surface ground
• Sintering temperature 1300 ° C, hot isostatic pressing process, surface ground
• Sintering temperature 1250 ° C, hot isostatic pressing process, subsequent heat treatment at 900 ° C / 1h / quenched in water + 540 ° C / 8h / cooled under protective gas. This tempering corresponds to the usual hardening treatment of a Ti-AI-V alloy.

In the table in FIG. 3, the results for the yield strength R _p , _0.2 , the tensile strength R _m , the elongation A, oxygen content and density are listed in order of treatment variation. The tensile tests showed an increase in strength with increasing sintering temperature and density. The samples sintered at 1300 degrees Celsius and then subjected to a hot isostatic pressing process showed strength values at room temperature comparable to those of the forged or rolled alloy (yield strength approx. 1000 MPa, tensile strength approx. 1060 MPa, elongation approx. 17%).

The oxygen content is approximately 0.25% by weight and the carbon content is approximately 0.06%. The parent alloy used for metal powder production already showed an oxygen content of 0.2% or a carbon content of 0.01%. The respective Growth is due to handling and, above all, the sintering process.

The structural examinations showed a homogeneous, fine lamellar structure from the α and β phase with an average grain size of about 150 µm. The pores have a size of maximum 10 µm, in the case of the samples subjected to a hot isostatic pressing process no pores. In addition, samples with the geometry of the Tension rod, which was produced by the method according to the invention, cutting made from forged material. This material also served as the starting alloy for metal powder production. It's about the surface treatment not a polish, but only a cut, the possible surface notches should eliminate. Since the material is ductile, the influence of surface quality should be considered the experiments do not play a major role. An electropolish was therefore avoided.

The structure in the case of the forged material is fine-grained globular, while that after material of the tension rod produced according to the invention has a fine lamellar structure. The The carbon content is approximately 0.06% by weight, the increase compared to the starting alloy is about 0.05% by weight. The oxygen content increases by a maximum of 0.06 % By weight, the starting alloy already had 0.19% by weight. The results of the Tensile tests on the tension rod 8 can be interpreted as follows. All samples show one excellent strength. Except for the case of the heat-treated sample, the measured one is Elongation in the tensile bar samples produced according to the invention is significantly higher than in the forged version. The samples sintered at 1300 degrees Celsius show on average slightly better results than those sintered at 1250 degrees Celsius Tension rods. Execution of the hot isostatic pressing process on the samples improved the strength again over 100 MPa. The strength values of a hot isostatic Pressed samples of the tension rod are comparable to those of the forged one Starting material in the form of a tension rod. The curing treatment leads to significantly higher strength, but at the same time only to a very small elongation. In summary, this means that those produced by the process according to the invention Samples of the tension rod with a suitable selection of the process characteristics made a strength comparable to that of the forged parts with a higher strength Show ductility.

LIST OF REFERENCE NUMBERS

1

Titanium alloy in rod form

2

Metal powder parts

3

binder

4

compounder

5

feedstock

6

injection molding machine

7

mold

8th

component

9

Entbinderbad

10

Chamber of the sintering furnace

rehearse Rp 0.2 [MPa] Rm [MPa] A [%] Oxygen content (wt.%) Density [% of theoretical density] forged material 981 1034 5.0 0.19 100 1250 ° C sintering temperature 796 897 12.8 0.25 96.0 1300 ° C sintering temperature 846 917 14.4 0.25 96.0 1300 ° C, HIP 1016 1059 17.8 0.25 100 1250 ° C, HIP, ground 963 1061 17.2 0.25 100 1300 ° C, HIP, ground 934 1019 20.5 0.25 100 1250 ° C, HIP, heat treated, closed 1050 1115 1.0 0.25 100

Claims (22)

1. Method for the manufacture of components by metal powder die casting from metal powder parts coated with binder in a die, followed by a binder removal and sintering of the components produced, where the metal powder parts of a titanium alloy are used for the manufacture of the complexly shaped components, each of the following sections in the manufacture of the components of producing the metal powder parts for the titanium alloy, feedstock production with a binder, binder removal and sintering take place exclusively under a high-purity inert atmosphere of inert gas and/or air exclusion and/or vacuum and the metal powder parts and binder have a law impurity level, characterized in that a subsequent compaction of the complexly shaped components takes place by hot isostatic pressing of the sintered, components in an inert gas-filled chamber, that the bearing surface for the components during hot isostatic pressing maintains a free sliding capacity by construction from a suitable material and that the material of the bearing snrface at the isostatic pressing temperatures does not give off imparities.
2. Method according to claim 1, characterized in that the individual material constituents of the titanium alloy and the binder have a composition such that each individual material constituent in the starting state already has the characteristic of a low impurity level.
3. Method according to one or more of the claims 1 to 2, characterized in that to the metal powder parts are added as binder constituents thermoplastic or duroplastic polymers, thermogelling substances, waxes or surfactants or mixtures obtained therefrom.
4. Method according to one or more of the claims 1 to 3, characterised in that for the binder are used polyamides, polyoxymethylene, polycarbonate, styrene-acrylonitrile copolymer, polyimide, natural waxes and oils, duroplastics, cyanates, polypropylenes, polyacetates, polyethylenes, ethylene-vinyl acetates, polyvinyl alcohols, polyvinyl chlorides, polystyrenes, polymethyl methacrylates, aniline, water, mineral oils, agar, glycerol, polyvinyl butyryls, polybutyl methacrylates, cellulose, oleic scuds, phthalates, paraffin waxes, carnauba wax, ammonium polyacrylates, diglyceride stearates and oleates, glycerol monostearates, isopropyl titanates, lithium stearates, monoglycerides, formaldehyde, octanoic acid phosphates, olefin sulphonates, phosphate esters or stearic acid.
5. Method according to one or more of the claims 1 to 4, characterized in that for carrying out a partial binder removal with respect to the complexly shaped components those binder constituents with a low melting, decomposing and/or evaporation temperature preponderate in the total binder constituent mixture compared with those mixture binder constituents with a higher melting, decomposing and/or evaporation temperature.
6. Method according to one or more of the claims 1 to 5, characterized in that a binder is composed of polyethylenes, stearic acid, paraffin, and carnauba wax.
7. Method according to one or more of the claims 1 to 6, characterized in that the low imparity metal powder parts of the titanium alloy are produced by the electrode induction metal gas atomization process.
8. Method according to one or more of the claims 1 to 7, characterized in that the low impurity metal powder parts are produced by the plasma melting induction guiding gas atomization process.
9. Method according to one or more of the claims 1 to 8, characterized, in that the metal powder parts for the titanium alloy are produced by an atomizing apparatus with inert gas atomization.
10. Method according to one or more of the claims 1 to 9, characterized in that the inert gas-atomized metal powder parts are corrected in a gastight powder can flanged to the atomizing apparatus, the powder can being itself constructed in a gas-tight sealable form and that the powder can is introduced into a glovebox system operated with argon gas.
11. Method according to one or more of the claims 1 to 10, characterized in that the particle size of the metal powder parts of the titanium alloy is in the range smaller than 100 µm.
12. Method according to one or more of the claims 1 to 11, characterized in that the particle size of the metal powder parts of the titanium alloy is preferably smaller than 45 µm.
13. Method according to one or more of the claims 1 to 10, characterized in that the die casting of the components takes place with die casting machines.
14. Method according to one or more of the claims 1 to 10, characterized in that the mixing of the metal powder parts of the titanium alloy and the binder during feedstock production and metal die casting of the component in each case take place in a low temperature range.
15. Method according to one or more of the claims 1 to 10 and 4, characterized in that the temperature range during feedstock production is between 50 and 200°C.
16. Method according to one or more of the claims 1 to 10, 13 and 14, characterized in that the temperature range during metal die casting is between 60 and 200°C.
17. Method according to one or more of the claims 1 to 16, characterised in that the titanium alloy is Ti-6Al-7Nb.
18. Method according to one or more of the claims 1 to 17, characterized in that the sintering substrate for the components is constructed in such a way that during the sintering of the components the free sliding capacity of the surface of the sintering substrate for the components resting thereon remains unchanged.
19. Method according to one or more of the claim 1 to 18, characterized in that the sintering substrate material gives off no impurities at the sintering temperature.
20. Method according to one or more of the claims 1 to 19, characterized in that at the sintering temperature, the sintering substrate surface is made from a material, such as e.g. ceramic oxides redaction-resistant to the material of the components.
21. Method according to one or more of the claims 1 to 20, characterized in that the complexly shaped components undergo sintering in a temperature range 1100 to 1400°C.
22. Method according to one or more of the claims 1 to 21, characterized in that the complexly shaped components are preferably sintered at a temperature of 1300°C.

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