A METHOD OF PRODUCING A COMPOSITE BODY BY COALESCENCE AND THE COMPOSITE BODY PRODUCED

Abstract: A method of producing a composite body by coalescence, wherein the method comprises the steps of a) filling a pre-compacting mould with composite material in the form of powder, pellets, grains and the like, b) pre-compacting the material at least once and c) compressing the material in a compression mould by at least one stroke, where a striking unit emits enough kinetic energy to form the body when striking the material inserted in the compression mould, causing coalescence of the material. A method of producing a composite body by coalescence, wherein the method comprises compressing material in the form of a solid composite body in a compression mould by at least one stroke, where a striking unit emits enough energy to cause coalescence of the material in the body. Products obtained by the inventive methods.

Description: AMETHOD OFPRODUCINGA COMPOSITEBODYBY COALESCENCE AND THE COMPOSITEBODYPRODUCED The invention concerns a method of producing a composite body by coalescence as well as the composite body produced by this method. STATE OF THE ART In WO-A1 -9700751, an impact machine and a method of cutting rods with the machine is described. The document also describes a method of deforming a meial body. The method utilises the machine described in the document and is characterised in that a metallic material either in solid form or in the form of powder such as grains, pellets and the like, is fixed preferably at the end of a mould, holder or the like and that the material is subjected to adiabatic coalescence by a striking unit such as an impact ram, the motion of the ram/being effected by a liquid. The machine is thoroughly described in the WO document. In WO-A1 -9700751, shaping of components, such as spheres, is described. A metal powder is supplied to a tool divided in two parts, and the powder is supplied through a connecting tube. The metal powder has preferably been gas-atomized. A rod passing through the connecting tube is subjected to impact from the percussion machine in order to influence the material enclosed in the spherical mould. However, it is not shown in any embodiment specifying parameters for how a body is produced according to this method. The compacting according to this document is performed in several steps, e.g. three. These steps are performed very quickly and the three strokes are performed as described below. 1 Stroke 1: an extremely light stroke, which forces out most of the air from the powder and orients the powder particles to ensure that there are no great irregularities. Stroke 2: a stroke with very high energy density and high impact velocity, for local adiabatic coalescence of the powder particles so that they are compressed against each other to extremely high density. The local temperature increase of each particle is dependent on the degree of deformation during the stroke. Stroke 3: a stroke with medium-high energy and with high contact energy for final shaping of the substantially compact material body. The compacted body can thereafter be sintered. In SE 9803956-3 a method and a device for deformation of a material body are described. This is substantially a development of the invention described in WO- Al-9700751. In the method according to the Swedish application, the striking unit is brought to the material by such a velocity that at least one rebounding blow of the striking unit is generated, wherein the rebounding blow is counteracted whereby at least one further stroke of the striking unit is generated. The strokes according to the method in the WO document, give a locally very high temperature increase in the material, which can lead to phase changes in the material during the heating or cooling. When using the counteracting of the rebounding blows and when at least one further stroke is generated, this stroke contributes to the wave going back and forth and being generated by the kinetic energy of the first stroke, proceeding during a longer period. This leads to further deformation of the material and with a lower impulse than would have been necessary without the counteracting. It has now shown that the machine according to these mentioned documents does not work so well. For example are the time intervals between the strokes, which they mention, not possible to obtain. Further, the document does not comprise any embodiments showing that a body can be formed. OBJECT OF THE INVENTION The object of the present invention is to achieve a process for efficient production of products from composite at a low cost. These products may be both medical devices such as medical implants or bone cement in orthopaedic surgery, instruments or diagnostic equipment, or non medical devices such as tools, insulator applications, crucibles, spray nozzles, tubes, cutting edges, jointing rings, ball bearings and engine parts. Another object is to achieve a composite product of the described type. It should also be possible to perform the new process at a much lower velocity than the processes described in the above documents. Further, the process should not be limited to using the above described machine. SHORT DESCRIPTION OF THE INVENTION It has surprisingly been found that it is possible to compress different composites according to the new method defined in claim 1. The material is for example in the form of powder, pellets, grains and the like and is filled in a mould, pre-compacted and compressed by at least one stroke. The machine to use in the method may be the one described in WO-A1-9700751 and SE 9803956-3. The method according to the invention utilises hydraulics in the percussion machine, which may be the machine utilised in WO-A1 -9700751 and SE 9803956- 3. When using pure hydraulic means in the machine, the striking unit can be given such movement that, upon impact with the material to be compressed, it emits sufficient energy at sufficient speed for coalescence to be achieved. This coalescence may be adiabatic. A stroke is carried out quickly and for some materials the wave in the material decay in between 5 and 15 milliseconds. The hydraulic use also gives a better sequence control and lower running costs compared to the use of compressed air. A spring-actuated percussion machine will be more complicated to use and will give rise to long setting times and poor flexibility when integrating it with other machines. The method according to the invention will thus be less expensive and easier to carry out. The optimal machine has a large press for pre-compacting and post-compacting and a small striking unit with high speed. Machines according to such a construction are therefore probably more interesting to use. Different machines could also be used, one for the pre- compacting and post-compacting and one for the compression. SHORT DESCRIPTION OF THE DRAWINGS On the enclosed drawings Figure 1 shows a cross sectional view of a device for deformation of a material in the form of a powder, pellets, grains and the like, and Figures 2-9 are diagrams showing results obtained in the embodiments described in the examples. The figures comprising the suffix a, b or c show the absolute density as a function of impact energy, while the figures without suffix show the relative density as a function of impact energy. DETAILED DESCRIPTION OF THE INVENTION The invention concems a method of producing a composite body by coalescence, wherein the method comprises the steps of a) filling a pre-compacting mould with composite material in the form of powder, pellets, grains and the like, b) pre-compacting the material at least once and c) compressing the material in a compression mould by at least one stroke, where a striking unit emits enough kinetic energy to form the body when striking the material inserted in the compression mould, causing coalescence of the material. The pre-compacting mould may be the same as the compression mould, which means that the material does not have to be moved between the step b) and c). It is also possible to use different moulds and move the material between the steps b) and c) from the pre-compacting mould to the compression mould. This could only be done if a body is formed of the material in the pre-compacting step. The device in Figure 1 comprises a striking unit 2. The material in Figure 1 is in the form of powder, pellets, grains or the like. The device is arranged with a striking unit 3, which with a powerful impact may achieve an immediate and relatively large deformation of the material body 1. The invention also refers to compression of a body, which will be described below. In such a case, a solid body 1, such as a solid homogeneous composite body, would be placed in a mould. The striking unit 2 is so arranged, that, under influence of the gravitation force, which acts thereon, it accelerates against the material 1. The mass m of the striking unit 2 is preferably essentially larger than the mass of the material 1. By that, the need of a high impact velocity of the striking unit 2 can be reduced somewhat. The striking unit 2 is allowed to hit the material 1, and the striking unit 2 emits enough kinetic energy to compress and form the body when striking the material in the compression mould. This causes a local coalescence and thereby a consequent deformation of the material 1 is achieved. The deformation of the material 1 is plastic and consequently permanent. Waves or vibrations are generated in the material 1 in the direction of the impact direction of the striking unit 2. These waves or vibrations have high kinetic energy and will activate slip planes in the material and also cause relative displacement of the grains of the powder. It is possible that the coalescence may be an adiabatic coalescence. The local increase in temperature develops spot welding (inter-particular melting) in the material which increases the density. The pre-compaction is a very important step. This is done in order to drive out air and orient the particles in the material. The pre-compaction step is much slower than the compression step, and therefore it is easier to drive out the air. The compression step, which is done very quickly, may not have the same possibility to drive out air. In such case, the air may be enclosed in the produced body, which is a disadvantage. The pre-compaction is performed at a minimum pressure enough to obtain a maximum degree of packing of the particles which results in a maximum contact surface between the particles. This is material dependent and depends on the softness and melting point of the material. The pre-compacting step in the Examples has been performed by compacting with an axial load of about 117680 N. This is done in the pre-compacting mould or the final mould. According to the examples in this description, this has been done in a cylindrical mould, which is a part of the tool, and has a circular cross section with a diameter of 30 mm, and the area of this cross section is about 7 cm 2 . This means that a pressure of about 1.7 x 10 8 N/m 2 has been used. For hydroxyapatite the material may be pre-compacted with a pressure of at least about 0.25 x 10 8 N/m 2 , and preferably with a pressure of at least about 0.6 x 10 8 N/m 2 . The necessary or preferred pre-compaction pressure to be used is material dependent and for a softer composite it could be enough to compact at a pressure of about 0.2 x 10 8 N/m 2 . Other possible values are 1.0 x 10 8 N/m 2 , 1.5 x 10 8 N/m 2 . The studies made in this application are made in air and at room temperature. All values obtained in the studies are thus achieved in air and room temperature. It may be possible to use lower pressures if vacuum or heated material is used. The height of the cylinder is 60 mm. In the claims is referred to a striking area and this area is the area of the circular cross section of the striking unit which acts on the material in the mould. The striking area in this case is the cross section area. In the claims it is also referred to the cylindrical mould used in the Examples. In this mould the area of the striking area and the area of the cross section of the cylindrical mould are the same. However, other constructions of the moulds could be used, such as a spherical mould. In such a mould, the striking area would be less than the cross section of the spherical mould. The invention further comprises a method of producing a composite body by coalescence, wherein the method comprises compressing material in the form of a solid composite body (i.e. a body where the target density for specific applications has been achieved) in a compression mould by at least one stroke, where a striking unit emits enough energy to cause coalescence of the material in the body. Slip planes are activated during a large local temperature increase in the material, whereby the deformation is achieved. The method also comprises deforming the body. The method according to the invention could be described in the following way. 1) Powder is pressed to a green body, the body is compressed by impact to a (semi)solid body and thereafter an energy retention may be achieved in the body by a post-compacting. The process, which could be described as Dynamic Forging Impact Energy Retention (DFIER) involves three mains steps. a)Pressuring The pressing step is very much like cold and hot pressing. The intention is to get a green body from powder. It has turned out to be most beneficial to perform two compactions of the powder. One compaction alone gives about 2- 3% lower density than two consecutive compactions of the powder. This step is the preparation of the powder by evacuation of the air and orientation of the powder particles in a beneficial way. The density values of the green body is more or less the same as for normal cold and hot pressuring. b)Impact The impact step is the actual high-speed step, where a striking unit strikes the powder with a defined area. A material wave starts off in the powder and interparticular melting takes place between the powder particles. Velocity of the striking unit seems to have an important role only during a very short time initially. The mass of the powder and the properties of the material decides the extent of the interparticular melting taking place. c)Energy retention The energy retention step aims at keeping the delivered energy inside the solid body produced. It is physically a compaction with at least the same pressure as the pre-compaction of the powder. The result is an increase of the density of the produced body by about 1-2%. It is performed by letting the striking unit stay in place on the solid body after the impact and press with at least the same pressure as at pre-compaction, or release after the impact step. The idea is that more transformations of the powder will take place in the produced body. According to the method, the compression strokes emit a total energy corresponding to at least 100 Nm in a cylindrical tool having a striking area of 7 cm 2 in air and at room temperature. Other total energy levels may be at least 300, 600, 1000, 1500, 2000, 2500, 3000 and 3500 Nm. Energy levels of at least 10 000, 20 000 Nm may also be used. There is a new machine, which has the capacity to strike with 60 000 Nm in one stroke. Of course such high values may also be used. And if several such strikes are used, the total amount of energy may reach several 100 000 Nm. The energy levels depend on the material used, and in which application the body produced will be used. Different energy levels for one material will give different relative densities of the material body. The higher energy level, the more dense material will be obtained. Different materials will need different energy levels to get the same density. This depends on for example the hardness of the material and the melting point of the material. According to the method, the compression strokes emit an energy per mass corresponding to at least 5 Nm g in a cylindrical tool having a striking area of 7 cm in air and at room temperature. Other energies per mass may be at least 20 Nm/g, 50 Nm/g, 100 Nm g, 150 Nm/g, 200 Nm/g, 250 Nm/g, 350 Nm/g and 450 Nm/g. There may be a linear relationship between the mass of the sample and the energy needed to achieve a certain relative density. However, for some materials the relative density may be a function of the total impact energy. These values will vary dependent on what material is used. A person skilled in the art will be able to test at what values the mass dependency will be valid and when there may be a mass independence. The energy level needs to be amended and adapted to the form and construction of the mould. If for example, the mould is spherical, another energy level will be needed. A person skilled in the art will be able to test what energy level is needed with a special form, with the help and direction of the values given above. The energy level depends on what the body will be used for, i.e. which relative density is desired, the geometry of the mould and the properties of the material. The striking unit must emit enough kinetic energy to form a body when striking the material inserted in the compression mould. With a higher velocity of the stroke, more vibrations, increased friction between particles, increased local heat, and increased interparticular melting of the material will be achieved. The bigger the stroke area is, the more vibrations are achieved. There is a limit where more energy will be delivered to the tool than to the material. Therefore, there is also an optimum for the height of the material. When a powder of a composite material is inserted in a mould and the material is struck by a striking unit, a coalescence is achieved in the powder material and the material will float. A probable explanation is that the coalescence in the material arises from waves being generated back and forth at the moment when the striking unit rebounds from the material body or the material in the mould. These waves give rise to a kinetic energy in the material body. Due to the transmitted energy a local increase in temperature occurs, and enables the particles to soften, deform and the surface of the particles will melt. The inter-particular melting enables the particles to re-solidify together and dense material can be obtained. This also affects the smoothness of the body surface. The more a material is compressed by the coalescence technique, the smoother surface is obtained. The porosity of the material and the surface is also affected by the method. If a porous surface or body is desired, the material should not be compressed as much as if a less porous surface or body is desired. The individual strokes affect material orientation, driving out air, pre-moulding, coalescence, tool filling and final calibration. It has been noted that the back and forth going waves travels essentially in the stroke direction of the striking unit, i. e. from the surface of the material body which is hit by the striking unit to the surface which is placed against the bottom of the mould and then back. What has been described above about the energy transformation and wave generation also refer to a solid body. In the present invention a solid body is a body where the target density for specific applications has been achieved. The striking unit preferably has a velocity of at least 0.1 m/s or at least 1.5 m/s during the stroke in order to give the impact the required energy level. Much lower velocities may be used than according to the technique in the prior art. The velocity depends on the weight of the striking unit and what energy is desired. The total energy level in the compression step is at least about 100 to 4000 Nm. But much higher energy levels may be used. By total energy is meant the energy level for all strokes added together. The striking unit makes at least one stroke or a number of consecutive strokes. The interval between the strokes according to the Examples was 0.4 and 0.8 seconds. For example at least two strikes may be used. According to the Examples one stroke has shown promising results. These Examples were performed in air and at room temperature. If for example vacuum and heat or some other improving treating is used, perhaps even lower energies may be used to obtain good relative densities. The composite may be compressed to a relative density of 60 %, preferably 65 %. More preferred relative densities are also 70 % and 75 %. Other preferred densities are 80 and 85 %. Densities of at least 90 and up to 100 % are especially preferred. However, other relative densities are also possible. If a green body is to be produced, it may be enough with a relative density of about 40-60 %. Load bearing implants need a relative density of 90 to 100 % and in some biomaterials it is good with some porosity. If a porosity of at most 5 % is obtained and this is sufficient for the use, no further post-processing is necessary. This may be the choice for certain applications. If a relative density of less than 95 % is obtained, and this is not enough, the process need to continue with further processing such as sintering. Several manufacturing steps have even in this case been cut compared to conventional manufacturing methods. The method also comprises pre-compacting the material at least twice. It has been shown that this could be advantageous in order to get a high relative density compared to strokes used with the same total energy and only one pre-compacting. Two compactions may give about 1-5 % higher density than one compacting depending on the material used. The increase may be even higher for some materials. When pre-compacting twice, the compacting steps are performed with a small interval between, such as about 5 seconds. About the same pressure may be used in the second pre-compacting. Further, the method may also comprise a step of compacting the material at least once after the compression step. This has also been shown to give very good results. The post-compacting should be carried out at at least the same pressure as the pre- compacting pressure, i.e. 0,25 x 10 8 N/m 2 . Other possible values are 1.0 x 10 8 N/m 2 . Higher post-compacting pressures may also be desired, such as a pressure which is twice the pressure of the pre-compacting pressure. For hydroxyapatite the pre- compacting pressure should be at least about 0.25 x 10 N/m and this would be the lowest possible post-compacting pressure for hydroxyapatite. The pre-compacting value has to be tested out for every material. A post-compacting effects the sample differently than a pre-compacting. The transmitted energy, which increases the local temperature between the powder particles from the stroke, is conserved for a longer time and can effect the sample to consolidate for a longer period after the stroke. The energy is kept inside the solid body produced. Probably the "lifetime" for the 11 material wave in the sample increases and it can affect the sample for a longer period and more particles can melt together. The after compaction or post- compaction is performed by letting the striking unit stay in place on the solid body after the impact and press with at least the same pressure as at pre-compacting, i.e. at least about 0.25 x 10 N/m hydroxyapatite. More transformations of the powder will take place in the produced body. The result is an increase of the density of the produced body by about 1-4 %. Also this possible increase is material dependent. When using pre-compacting and/or after compacting, it could be possible to use lighter strokes and higher pre- and/or after compacting, which would lead to saving of the tools, since lower energy levels could be used. This depends on the intended use and what material is used. It could also be a way to get a higher relative density. To get improved relative density it is also possible to pre-process the material before the process. The powder could be pre-heated to e.g. ~200-300 °C or higher depending on what material type to pre-heat. The powder could be pre-heated to a temperature which is close to the melting temperature of the material. Suitable ways of pre-heating may be used, such as normal heating of the powder in an oven. In order to get a more dense material during the pre-compacting step vacuum or inert gas could be used. This would have the effect that air is not enclosed in the material to the same extent during the process. The body may according to another embodiment of the invention be heated and/or sintered any time after compression or post-compacting. A post-heating is used to relax the bindings in the material (obtained by increased binding strain). A lower sintering temperature may be used owing to the fact that the compacted body has a higher density than compacts obtained by other types of powder compression. This is an advantage as a higher temperature may cause decomposition or transformation of the constituting material. The produced body may also be post-processed in some other way, such as by HIP (Hot Isostatic Pressing). Further, the body produced may be a green body and the method may also comprise a further step of sintering the green body. The green body of the invention gives a coherent integral body even without use of any additives. Thus, the green body may be stored and handled and also worked, for instance polished or cut. It may also be possible to use the green body as a finished product, without any intervening sintering. This is the case when the body is a bone implant or replacement where the implant is to be resorbed in the bone. Before processing the composite could be homogenously mixed with additives. Predrying of the granulate could also be used to decrease the water content of the raw material. Some composites do not absorb humidity, while other composites easily absorb humidity which can disturb the processing of the material, and decrease the homogeneity of the worked material because a high humidity rate can raise steam bubbles in the material. The composite material consists of at least two phases, the matrix and the reinforcement. The purpose of the matrix is to integrally bind the reinforcement together so that the load is effectively introduced in the material. It protects the reinforcement from adverse environmental effects and gives the composite material its outer surface appearance. The reinforcement normally carries the load or enhances a certain property of the matrix material. The matrix may be metallic, polymeric or ceramic in origin. The reinforcement could be in many different shapes. Commonly the reinforcement is in the form of chopped or continuos fibre, whiskers, platelets or particles. The reinforcement may by metallic, polymeric or ceramic as well. The composite matrix may be chosen from the group comprising a metallic, polymeric or ceramic material such as stainless steel, aluminium alloy, titanium, UHMWPE, PMMA, PEEK, rubber, alumina, zirconia, silicon carbide, hydroxyapatite or silicon nitride. The composite may contain reinforcements from the group comprising carbon, metals, glass or ceramics such as alumina, silica, silicon nitride, zirconia, silicon carbide. The compression strokes need to emit a total energy corresponding to at least 100 Nm in a cylindrical tool having a striking area of 7 cm 2 for oxides. The same value for nitrides, carbides and other composites is also 100 Nm. The compression strokes need to emit an energy per mass corresponding to at least 5 Nm/g in a cylindrical tool having a striking area of 7 cm for composites. It has been shown earlier that better results have been obtained with particles having irregular particle morphology. The particle size distribution should probably be wide. Small particles could fill up the empty space between big particles. The composite material may comprise a lubricant and/or a sintering aid. A lubricant may be useful to mix with the material. Sometimes the material needs a lubricant in the mould, in order to easily remove the body. In certain cases this could be a choice if a lubricant is used in the material, since this also makes it easier to remove the body from the mould. A lubricant cools, takes up space and lubricates the material particles. This is both negative and positive. Interior lubrication is good, because the particles will then slip in place more easily and thereby compact the body to a higher degree. It is good for pure compaction. Interior lubrication decreases the friction between the particles, thereby emitting less energy, and the result is less inter-particular melting. It is not good for compression to achieve a high density, and the lubricant must be removed for example with sintering. Exterior lubrication increases the amount of energy delivered to the material and thereby indirectly diminishes the load on the tool. The result is more vibrations in the material, increased energy and a greater degree of inter-particular melting. Less 14 material sticks to the mould and the body is easier to extrude. It is good for both compaction and compression. An example of a lubricant is Acrawax C, but other conventional lubricants may be used. If the material will be used in a medical body, the lubricant need to be medically acceptable, or it should be removed in some way during the process. Polishing and cleaning of the tool may be avoided if the tool is lubricated and if the powder is preheated. A sintering aid may also be included in the material. The sintering aid may be useful in a later processing step, such as a sintering step. However, the sintering aid is in some cases not so useful during the method embodiment, which does not include a sintering step. The sintering aid may be yttrium oxide, alumina or magnesia or some other conventional sintering aid. It should, as the lubricant, also be medically acceptable or removed, if used in a medical body. In some cases, it may be useful to use both a lubricant and a sintering aid. This depends on the process used, the material used and the intended use of the body which is produced. In some cases it may be necessary to use a lubricant in the mould in order to remove the body easily. It is also possible to use a coating in the mould. The coating may be made of for example TiNAl or Balinit Hardlube. If the tool has an optimal coating no material will stick to the tool parts and consume part of the delivered energy, which increase the energy delivered to the powder. No time-consuming lubricating would be necessary in cases where it is difficult to remove the formed body. A very dense material, and depending on the material, a hard material will be achieved, when the composite material is produced by coalescence. The surface of the material will be very smooth, which is important in several applications. 15 If several strokes are used, they may be executed continually or various intervals may be inserted between the strokes, thereby offering wide variation with regard to the strokes. For example, one to about six strokes may be used. The energy level could be the same for all strokes, the energy could be increasing or decreasing. Stroke series may start with at least two strokes with the same level and the last stroke has the double energy. The opposite could also be used. The highest density is often obtained by delivering a total energy with one stroke. If the total energy instead is delivered by several strokes a lower relative density may be obtained, but the tool is saved. A multi-stroke can therefore be used for applications where a maximum relative density is not necessary. Through a series of quick impacts a material body is supplied continually with kinetic energy which contributes to keep the back and forth going wave alive. This supports generation of further deformation of the material at the same time as a new impact generates a further plastic, permanent deformation of the material. According to another embodiment of the invention, the impulse, with which the striking unit hits the material body, decreases for each stroke in a series of strokes. Preferably the difference is large between the first and second stroke. It will also be easier to achieve a second stroke with smaller impulse than the first impulse during such a short period (preferably approximately 1 ms), for example by an effective reduction of the rebounding blow. It is however possible to apply a larger impulse than the first or preceding stroke, if required. According to the invention, many variants of impacting are possible to use. It is not necessary to use the counteracting of the striking unit in order to use a smaller impulse in the following strokes. Other variations may be used, for example where the impulse is increasing in following strokes, or only one stroke with a high or low 16 impact. Several different series of impacts may be used, with different time intervals between the impacts. A composite body produced by the method of the invention, may be used in medical devices such as medical implants or bone cement in orthopaedic surgery, instruments or diagnostic equipment. Such implants may be for example skeletal or tooth prostheses. According to an embodiment of the invention, the material is medically acceptable. Such materials are for example suitable composites, such as hydroxyapatite and zirconia. A material to be used in implants needs to be biocompatible and haemocompatible as well as mechanically durable, such as hydroxyapatite and zirconia or other suitable composites. The body produced by the process of the present invention may also be a non medical product such as tools, insulator applications, cmcibles, spray nozzles, tubes, cutting edges, jointing rings, ball bearings and engine parts. Here follows several applications for some of the reinforced matrix materials. Applications for silicon nitride are cmcibles, spray nozzles, tubes, cutting edges, jointing rings, ball bearings and engine parts. Alumina is a good electrical insulator and has at the same time an acceptable thermal conductivity and is therefore used for producing substrates where electrical components are mounted, insulation for ignition plugs and insulation in the high-tension areas. Alumina is also a common material type in orthopaedic implants, e.g. femoral-head in hip prostheses. Hydroxyapatite is one of the most important biomaterials extensively used in orthopaedic surgery. Common applications for zirconia are cutting tools, components for adiabatic engines and it is also a common material type in orthopaedic implants, e.g. femoral-head in hip prostheses. The invention thus has a big application area for producing products according to the invention. When the material inserted in the mould is exposed to the coalescence, a hard, smooth and dense surface is achieved on the body formed. This is an important feature of the body. A hard surface gives the body excellent mechanical properties such as high abrasion resistance and scratch resistance. The smooth and dense surface makes the material resistant to for example corrosion. The less pores, the larger strength is obtained in the product. This refers to both open pores and the total amount of pores. In conventional methods, a goal is to reduce the amount of open pores, since open pores are not possible to get reduced by sintering. It is important to admix powder mixtures until they are as homogeneous as possible in order to obtain a body having optimum properties. A coating may also be manufactured according to the method of the invention. One composite coating may for example be formed on a surface of a composite element of another composite or some other material. When manufacturing a coated element, the element is placed in the mould and may be fixed therein in a conventional way. The coating material is inserted in the mould around the element to be coated, by for example gas-atomizing, and thereafter the coating is formed by coalescence. The element to be coated may be any material formed according to this application, or it may be any conventionally formed element. Such a coating may be very advantageously, since the coating can give the element specific properties. A coating may also be applied on a body produced in accordance with the invention in a conventional way, such as by dip coating and spray coating. It is also possible to first compress a material in a first mould by at least one stroke. Thereafter the material may be moved to another, larger mould and a further composite material be inserted in the mould, which material is thereafter 18 compressed on top of or on the sides of the first compressed material, by at least one stroke. Many different combinations are possible, in the choice of the energy of the strokes and in the choice of materials. The invention also concerns the product obtained by the methods described above. The method according to the invention has several advantages compared to pressing. Pressing methods comprise a first step of fonning a green body from a powder containing sintering aids. This green body will be sintered in a second step, wherein the sintering aids are burned out or may be burned out in a further step. The pressing methods also require a final working of the body produced, since the surface need to be mechanically worked. According to the method of the invention, it is possible to produce the body in one step or two steps and no mechanical working of the surface of the body is needed. W en producing a prothesis according to a conventional process a rod of the material to be used in the prothesis is cut, the obtained rod piece is melted and forced into a mould sintered. Thereafter follows working steps including polishing. The process is both time and energy consuming and may comprise a loss of 20 to 50 % of the starting material. Thus, the present process where the prothesis may be made in one step is both material and time saving. Further, the powder need not be prepared in the same way as in conventional processes. By the use of the present process it is possible to produce large bodies in one piece. In presently used processes it is often necessary to produce the intended body in several pieces to be joined together before use. The pieces may for example be joined using screws or adhesives or a combination thereof. A further advantage is that the method of the invention may be used on powder carrying a charge repelling the particles without treating the powder to neutralize the charge. The process may be performed independent of the electrical charges or surface tensions of the powder particles. However, this does not exclude a possible use of a further powder or additive carrying an opposite charge. By the use of the present method it is possible to control the surface tension of the body produced. In some instances a low surface tension may be desired, such as for a wearing surface requiring a liquid film, in other instances a high surface tension is desired. The invention may comprise the following steps of pretreatment, posttreatment and powder preparation: Pre-treatment of as-received powders Use of the as-received powder without any pre-treatment. This excludes any addition of pressing aid or sintering aid. This also excludes automatic filling of the pressing tool since the flow properties are so poor. Ball milling followed by a. freeze granulation and freeze-drying or b. spray-drying or c. brick-drying and sieve granulation d. rotary-evaporation and sieve drying. These pre-treatments allow additions of pressing and sintering aids as well as automatic tool filling. To achieve proper suspension properties (low viscosity at high particle concentration) a dispersant or pH-adjustment is needed. It may also be possible to use automatic tool filling without pressing aids. Pre-forming by a. slip casting, b. centrifugal casting, c. pressure casting or d. filter pressing. All methods need a dispersant and they allow addition of sintering aids. It is also possible to add binder to support the green strength. Loading of preformed bodies in the machine may be done manually. Otherwise, a special arrangement, that softly place the body in the punch, should be used. Pre-forming by uniaxial pressing. This is used as one operation sequence in the machine. Pre-forming by wet or dry CIP (cold isostatic pressing). This can be used as one operation sequence before the coalescing machine. Pressing aids and sintering aids There are many options regarding pressing aids. In conventional pressing a mix of two compounds are generally used. One is a polymer that will act as a binder, for example PVA, PEG or Latex. The other compound is a low M w polymer (PEG) or a fatty acid (glycerol or similar) that will act as plasticizer and promote the pressing operation. PEG is often a better choice as softener since glycerol is more hydroscopic and can alter the pressing properties. The binder is used to give sufficient green strength, however, when the method of the invention is used the binder may often be excluded since it is, at least partly, decomposed and enough rigidity is achieved by the high-energy compression. Binder is sometimes also used in slip casting to make the green body less brittle and enable green machining. However, slip cast bodies most often have enough strength to be handled without binder. Binder addition also affects the slip casting process by lower casting rate. The binder can also segregate towards the mould surface. Regarding sintering aids, alumina can be conventionally sintered without. However, small amount of MgO (0.05 wt%) is often used and can enable complete densification and also inhibit critical grain growth. Also other oxides, like CaO and Y 2 0 3 , are used but then in larger amounts. The need of any sintering aid depends on how far the material is densified by the process and the need of post-sintering. The addition may also need to fulfil the requirements for biomaterial applications. For Si 3 N 4 , wide variations of sintering aids are used depending on sintering technique and the application. The amount is in the range of 2-10 wt% based on powder. More powerful sintering (HP or HIP) and high-temperature applications requires lower amounts. Common sintering aids are A1 2 0 3 , Y 2 0 3 , Si0 2 , MgO and Yb 2 0 3 in various portions and combinations. Note that Si 3 N 4 already contains some Si0 2 on the particle surfaces (can be increased by calcination) that will take part in the liquid phase formation during sintering. Here it may also be necessary to consider the requirements for biomaterials. Another aspect is the state of the sintering aids. It can be as fine powder (most often used) but also as salt or sols. Sols is stable dispersions of extremely small particles (10-100 nm) that sometimes are adsorbed on the particle surfaces and also act as a dispersing agent. Sols are only available for some few oxides such as A1 2 0 3 , Y 2 0 3 or Si0 2 . The advantage of using sols is the homogeneous distribution of the sintering aids that potentially can be achieved. This makes it possible to reduce the amount of addition for the sintering performance. The same can be for salts but high ion concentration reduces the stability of powder suspensions that need to be considered. Machine arrangements - Pressing conditions Pre-heating of powder and tool to support the compaction and reduce the energy input. Note that the level of temperature needs to be adapted to any present pressing aid so that it does not decompose or lose its performance. This concept is successfully used for metal powder but may also be applied for ceramics. It is believed that metal particles get softer and then deform more easily even though the temperature is far from the melting point. For ceramics the main advantage is the possibility to reduce the energy input. It is not reasonable to believe that any softening will occur. Apply vacuum to the tool. This should support and enable complete densification by removing air and decomposed organic additives. However, this may increase the costs. It may also be possible too apply another atmosphere. Apply grease to the mould surface. This may reduce the need to add such to the powder, complete or partly. The need of pressing aid added to the powder appears to be more critical for ceramics. Use of different tool materials. Especially it is possible to use surface treatment or deposition (CVD, PVD or plasma spraying) of a surface layer to reduce friction and/or wear. Post heat treatment A heat treatment after the machine operation is often needed for ceramics. A post- sintering will enable sufficient densification. The most common sintering/densification methods are a. pressureless sintering (PS) b. gas-pressure sintering (GPS) c. hot-pressing (HP) d. glass-encapsulated hot-isostatic pressing (glass-HIP) e. pressureless sintering and post-HIP (post-HIP) f. pulse electric current sintering (PECS) Conventional pressureless sintering schedules for the specific ceramic will often be adequate. However, this will depend on the degree of compaction reached in the machine Here follow some Examples to illustrate the invention. EXAMPLES This study was performed with all of the three types of matrices, i.e. metallic, ceramic and polymeric. Two metallic matrices, aluminium alloy and titanium both reinforced with chopped carbon fibre were tested. The polymeric matrices tested herein were UHMWPE, PMMA and PEEK, all reinforced with chopped carbon fibres. Further, rubber reinforced with alumina powder, stainless steel powder and silicone carbide powder were also tested in the polymeric matrix group. Zirconia powder reinforced alumina constituted the ceramic matrix composite. Nine composite types were chosen to investigate. Some composite types are of interest within the implants industry, e.g. UHMWPE reinforced with carbon fibres or PEEK reinforced with carbon fibres. The other composite types were chosen because they represent a certain group within the material group composites. They have either a big application area, or have a big series manufactured today with other manufacturing processes. These composite types are polymer or ceramic matrix reinforced with fibres or particles. The investigation performed herein is mainly a energy -density study. The goal is to obtain a relative density of >95 %. In that case desired material properties could be obtained without further post-processing. If a relative density of <95 % is obtained after this manufacturing process, it is possible to continue with a post-processing to obtain 100 % and desired material properties. The objective of this study was to study the interaction between the constituents of the composite and to determine the energy intervals for which a green body and solid bodies are obtained. Further, the ambition was also to get knowledge on how processing parameters affect the composite material properties. The study was mainly performed as an energy - density study. Preparation of powder The pure metal and polymer matrix powder, were initially dry-mixed for 10 minutes to obtain a homogeneous particle size distribution in the powder. The reinforcement particles was added and second dry-mixing was carried out for an additional 10 minutes to obtain a homogeneous particle size distribution between the matrix powder and the reinforcement material. The alumina powder was freeze granulated. To begin with the powder was ground to form a dispersion or a suspension before mixing. The main advantage of using a suspension is that the attraction forces between powder particles are less, which means that it is easier to separate powder particles and disintegrate agglomerates. The suspension is sieved before different granulation processes. The particle separation can be better controlled by adding dispersion additives to the suspension. A dispersion additive is surface active elements that are absorbed on the particles and raise repulsion forces between the particles. There are approximately 0.2-0.3 weight % dispersion additives in a suspension that are driven out during the sintering process in conventional powder pressing. Carbon fibre used in the tests is a common reinforcement material. Carbon fibre is manufactured by melt or solution spinning. The fibres are drawn and oxidised to crosslink. The fibres are then carbonised at an elevated temperature in a pyrolysis process. Graphitization is then carried out at a temperature above 1000 °C to eliminate impurities and enhance crosslinking. The fibres are finally surface treated with a size to enhance interaction with the matrix material. 25 Description In all batches an external lubricant consisting of Acrawax C was used in the mould. The first sample in all batches included in the energy studies was only pre- compacted with an axial load of 117680 N . The following samples were f i rst pre- compacted, and thereafter compressed with one impact stroke. The impact energy performed in this study was between 300 and 3000 Nm (some series were stopped at a lower impact energy), and each impact energy step interval was 300 Nm. After each sample had been manufactured, all tool parts were dismounted and the sample was released. The diameter and the thickness were measured with electronic micrometers, which rendered the volume of the body. Thereafter, the weight was established with a digital scale. All input values from micrometers and scale were recorded automatically and stored in separate documents for each batch. Out of these results, the density 1 was obtained by taking the weight divided by the volume. To be able to continue with the next sample, the tool needed to be cleaned, either only with acetone or by polishing the tool surfaces with an emery cloth to get rid of the material rests on the tool. To easier establish the state of a manufactured sample three visibility indexes are used. Visibility index 1 corresponds to a powder sample, visibility index 2 corresponds to a brittle sample and visibility index 3 corresponds to a solid sample. The theoretical density is either taken from the manufacturer or calculated by taking all included materials weighed depending on the percentage of the specific material. The relative density is obtained by taking the obtained density for each sample divided by the theoretical density. The theoretical density of the composites are determined by the rule of mixture and the constituents theoretical densities. Density 2, measured with the buoyancy method, was performed with all samples. Each sample was measured three times and with that three densities were obtained. Out of these densities the median density was taken and used in the figures. The samples were measured with a short buoyancy method. Each sample was measured one time. First in air (mi) and then in water (m 2 ). Density 2 was obtained by dividing mi with (m r m 2 ) Sample dimensions The dimensions of the manufactured sample in these tests is a disc with a diameter of -30.0 mm and a height between 5-10 mm. The height depends on the obtained relative density. If a relative density of 100 % should be obtained the thickness is 5.00 mm for all metal types. The volume fraction reinforcement was 20% for all tested composites. In the moulding die (part of the tool) a hole with a diameter of 30.00 mm is drilled. The height is 60 mm. Two stamps are used (also parts of the tool). The lower stamp is placed in the lower part of the moulding die. Powder is filled in the cavity that is created between the moulding die and the lower stamp. Thereafter, the impact stamp is placed in the upper part of the moulding die and strokes are ready to be performed. Example 1 - Metal matrix composites Aluminium alloy and titanium reinforced with chopped carbon fibres were compressed by high speed forming using the HYP 35-18 impact unit. The properties of the constituents are given in table 1. Figures 2 and 3 show the two metal matrix composites in the same graph. The graphs shows relative density as a function of impact energy per mass and of total impact energy. Figures 2a,b are diagrams showing the absolute density as a function of the impact energy per mass for each of the composites. Figures are diagrams showing the absolute density as a function of the total impact energy for each of the composites. The maximum relative densities and its corresponding values are given in table 2 for the two composites. Table 1 Table 2 It can be seen that a higher relative density is obtained for the Al-alloy matrix composite. The Al-alloy reaches also higher energy per mass du to its lower density. However, the densities for the two composites at the same energy level per mass are close to the same. Studying the same graphs for the pure material shows that the aluminium-alloy material reaches higher densities faster than the titanium for the same impact energy per mass. It might be reasonable to think that the 28 reinforcement reduces the difference in density for the same impact energy per mass and that the titanium curve therefore could be extrapolated following the aluminium curve. The Al-alloy matrix composite reaches a plateau at 210 Nm/g, while the titanium matrix composite still has a positive inclination on the curve up to 210 Nm/g which is the highest energy level tested for the composite. Density 1 could be rendered for the samples except those with irregular diameter. The big difference between density 1 and density 2 depends on two things. Density 1 could in most cases be well determined because the samples were intact. This curve, density 1, should therefore be considered as approximate. Density 2 was measured with an alternative buoyancy method that normally is suited to solid bodies, but due to the brittleness of the samples this method was used instead. Water penetrated into the pores of the samples and that made this method imprecise. That makes also density 2 somewhat imprecise. But it gives an indication of the densities of the samples. The densities are shown as absolute density instead of relative density in figures 2a,b and 3a,b because the real theoretical density is probably different to each sample depending on the volume fraction that could differ between the samples. Carbon fibre reinforced titanium Carbon reinforced titanium composite is a partly polymer and partly metal composite material. Solid titanium is produced conventionally by casting and thereafter forging. Titanium can also be produced to solid phase by sintering of a pre-compacted green body. These two materials are tested as a composite to investigate if it is possible to obtain chemical bonding between these two material groups and if it is possible to obtain a mix of both material groups' material properties. Titanium is a very interesting material du to its relative low density compared to steel and corrosive resistance. However pure titanium has mechanical properties inferior the steel. The composite combination could be interesting in applications where the materials both typical properties are desired. No solid samples was obtained already after pre-compacting. The first obtained body was obtained at 300 Nm or at an impact energy per mass of 21.6 Nm/g for which the density of 3.4 g/cm 3 was obtained. The highest density of 3.7 g/cm 3 was obtained at 2700 Nm or 195 Nm/g. All samples had visibility index 2 except for the pre-compacted sample which did not form a solid sample. The samples were tough but could be broken by hand. Samples at the higher energy levels when broken, disintegrated and it could be observed that the carbon fibres was crushed into fine particles. A transformation from individual constituents to a body would occur in the range of 0 to 300 Nm. Carbon fibre reinforced aluminium alloy Carbon reinforced aluminium alloy composite is a partly polymer and partly metal composite material. Solid aluminium alloy is produced conventionally by casting and thereafter cold and warm forming and extrusion. Aluminium alloy can also be produced to solid phase by sintering of a pre-compacted green body. The main object to of this composite study is to investigate if a material body of these two materials could be obtained and if a chemical bonding between the carbon fibre and Aluminium alloy can possibly be obtained. Aluminium alloy is a very interesting material du to its relative low density compared to steel and corrosive resistance. However the aluminium alloy has mechanical properties inferior the steel. The composite combination could be interesting in applications where the materials both typical properties are desired e.g. stiffened aluminium parts. No solid samples was obtained already after pre-compacting. The first obtained body was obtained at 1800 Nm or at an impact energy per mass of 207 Nm/g for which a density of 2.3 g/cm 3 was obtained. The highest density of 2.4 g/cm 3 was obtained at 2700 Nm or 310 Nm/g. Visibility index 2 was not reached until 1800 Nm of impact energy. The formed samples were tough but could be broken by hand. Samples at the higher energy levels when broken, disintegrated and it could be observed that the carbon fibres was cmshed into fine particles. A transformation from individual constituents to a body would occur in the range of 0 to 300 Nm. The samples varied in surface appearance. Some appeared with a metal surface other dark and porous from the carbon fibre. Example 2 - Polymer matrix composites The polymer matrix composites could be divided into two sub groups. Three thermoplastic polymer matrices, UHMWPE, PMMA and PEEK, are reinforced with chopped carbon fibres and compressed using the HUP 35-18 unit. The properties of the constituents are given in table 3 and table 4. The volume fraction fibre was 20 %. The second subgroup is three mbber matrix composites. The three reinforcement alternatives were silicone carbide, alumina and stainless steel. The reinforcement morphology was powder form, see table 4. Figures 4 and 5 show the three polymer matrix composites in the same graph plotted as relative density as a function of impact energy per mass and of total impact energy, respectively. The maximum relative densities and its corresponding values are given in table 5 for the thermoplastic matrix composites. The mbber matrix composites are compiled in table 6. The results shows that the best result is obtained for the PEEK matrix composite. This composite gives densities at 99% of the theoretical. The UHMWPE and the PMMA do only reach 84 and 93 % relative density respectively. Further, the PEEK matrix composite reaches visibility index 3 for samples above 1500 Nm impact energy. Visibility index 3 was nerve obtained for the other two thermoplastic matrix composites. Further these two also needed high impact energy before a body sample was obtained. Energy border from powder to body samples for the PMMA and UHMWPE could be identified. The PMMA composite obtained a body at 2400 Nm and the UHMWPE obtained a first body sample at 1500 Nm. Table 3 Table 4 Table 5 32 Table 6 Carbon fibre reinforced UHMWPE A carbon reinforced UHMWPE composite is a polymer-polymer based composite material. Solid UHMWPE is produced conventionally by different types of hot forming pressure methods and extrusion. These two materials are tested as a composite to investigate if it is possible to obtain chemical bonding between these two material groups and if it is possible to obtain a mix of both material groups' material properties. UHMWPE is a very interesting material in the orthopaedic industry where is is used in the acetabular component or as parts in other orthopaedic applications. The composite combination could be interesting in applications where the UHMWPE's mechanical properties could be enhanced. The main object to of this composite study is to investigate if a sample of these two material groups together can be obtained, and if a chemical bonding between the carbon fibre and UHMWPE can possibly be obtained. Density was only performed using the density 1 method. The samples below 1500 Nm did not hold together in one body as it was removed form the tool. Above 1500 Nm samples were obtained corresponding to visibility index 2. The samples were tough but could be broken by hand. The black carbon fibres could easily be identified in the white UHMWPE matrix and were clearly visible on the samples surfaces. The fibres seamed not to be broken, not even for the sample produced for the highest energies. In non of the samples a shift in material phase could be identified. The processing minimum and maximum densities with corresponding energy are given in table 5. As a sample is produced the density did not increase as the impact energy increased, and consequently impact speed was increased. The difference between minimum and maximum density was 0.03 g/cm 3 or 3.4 %. No bonding between the constituents or in the matrix material was observed. The samples disintegrated if the samples were touched to hard. Carbon fibre reinforced PMMA A carbon reinforced PMMA composite is a polymer-polymer based composite material. Solid PMMA is produced conventionally different types of hot forming and extmsion processes to net or near net shape products. PMMA is a very interesting material in the orthopaedic industry where is is used as a bone cement. The composite combination could be interesting in applications where the PMMA's mechanical properties could be enhanced. The particle size distribution of the PMMA powder was : <250micron 5% 250 - 355micron 5% 355 - 500micron 10% 500 - 710micron 45% <710micron 35% combination could be interesting in applications where the materials both typical properties are desired. No solid samples was obtained already after pre-compacting. The first obtained body was obtained at 300 Nm or at an impact energy per mass of 21.6 Nm/g for which the density of 3.4 g/cm 3 was obtained. The highest density of 3.7 g/cm 3 was obtained at 2700 Nm or 195 Nm/g. All samples had visibility index 2 except for the pre-compacted sample which did not form a solid sample. The samples were tough but could be broken by hand. Samples at the higher energy levels when broken, disintegrated and it could be observed that the carbon fibres was cmshed into fine particles. A transformation from individual constituents to a body would occur in the range of 0 to 300 Nm. Carbon fibre reinforced aluminium alloy Carbon reinforced aluminium alloy composite is a partly polymer and partly metal composite material. Solid aluminium alloy is produced conventionally by casting and thereafter cold and warm forming and extmsion. Aluminium alloy can also be produced to solid phase by sintering of a pre-compacted green body. The main object to of this composite study is to investigate if a material body of these two materials could be obtained and if a chemical bonding between the carbon fibre and Aluminium alloy can possibly be obtained. Aluminium alloy is a very interesting material du to its relative low density compared to steel and corrosive resistance. However the aluminium alloy has mechanical properties inferior the steel. The composite combination could be interesting in applications where the materials both typical properties are desired e.g. stiffened aluminium parts. No solid samples was obtained already after pre-compacting. The first obtained body was obtained at 1800 Nm or at an impact energy per mass of 207 Nm/g for 30 The samples below 2400 Nm did not hold together in one body as it was removed form the tool. Above 2400 Nm samples were obtained corresponding to visibility index 2. The three samples that were formed into bodies were tough but could be broken by hand. The black carbon fibres could be identified in the PMMA matrix and were visible on the samples surfaces. Individual PMMA particles could also be seen but they had turned dark shaded. This shading of the PMMA particles could also be noted for samples not forming a body. The fibres seamed to be broken as the energy increased. Non of the samples a shift in material phase could be identified. For the samples produced above 2400 Nm the density did not increase as the impact energy increased, and consequently as the impact speed was increased. The difference between minimum and maximum density was 0.04 g/cm 3 or 3.3 %, see figure . No bonding between the constituents or in the matrix material was observed. The samples disintegrated if the samples were touched to hard. Carbon reinforced PEEK A carbon reinforced PEEK composite is a polymer-polymer based composite material. Solid PEEK is produced conventionally different types of hot forming processes to net or near net shape products. These two materials are tested as a composite to investigate if it is possible to obtain chemical bonding between these two material groups and if it is possible to obtain a mix of both material groups' material properties. PEEK is a very interesting material for the orthopaedic industry where it could be used in parts of high mechanical stress. The composite combination could be interesting in applications where the PEEK'S mechanical properties could be enhanced. The main object to of this composite study is to investigate if a sample of these two material groups together can be obtained, and if a chemical bonding between the carbon fibre and PEEK can possibly be obtained. The constituents was initially mixed for 10 minutes to obtain a well blended composite. The properties of the powders are shown in Tables 3 and 4. All samples held together in one body after they were removed form the tool. Above 1500 Nm solid samples, visibility index 3, were obtained. The samples were tough but and could not be broken by hand. Samples below 1500 Nm could be broken by hand. The black carbon fibres could easily be identified in the beige PEEK matrix and were clearly visible on the samples surfaces. The PEEK matrix material turned more grey for the solid samples. The fibres seamed not to be broken so much as the energy increased. The processing minimum and maximum densities with corresponding energy is given in table 2. The density increases initially as the energy is increased after pre-compacting. At approximately 1500 Nm the density reaches a plateau and no significant change in density could be observed as the impact energy was increased further The total increase in energy from the first produced body was 0.09 g/cm 3 or 7 %. The highest energy 1.35 g/cm 3 corresponds to 99 % relative density. No chemical bonding between the constituents or in the matrix material was observed. The surface fibres could be scratched off. The density measurement by the density 1 and density 2 methods matched very well and the density-energy curve was relative stable indicating that a good blend between the constituents was obtained. Alumina reinforced mbber Alumina-rubber composite is a partly ceramic and partly polymer composite material. Solid alumina is produced conventionally by solid phase sintering and is normally a completely densified material. Alumina is an electrical isolator and in the mean time it has an acceptable conductivity. Common application is as an insulator in electrical applications. Alumina is also a common material type in orthopaedic implants, e.g. femoral-head in hip prostheses. Alumina is chemical inert and stable material in many environment. The strength and wear strength are high. 36 Rubber is machined as a thermoplastic and thereafter cross linked chemically by vulcanising at high temperature. The cross links consist of either sulphur or the same simple links as in the chain molecules. Rubber is a common material in many industries, e.g. car industry. These two materials are tested as a composite to investigate if it is possible to obtain chemical bonding between these two material groups and if it is possible to obtain a mix of both material groups' material properties. Ceramic is brittle and extremely hard material, while mbber is elastic and ductile. The combination could be 0 interesting in applications where both typical properties are desired, e.g. paper industry. The alumina powder was freeze granulated. The properties of the poders used are given in Table 7. 5 Table 7 Figures 6 and 7 show relative density as a function of impact energy per mass and of total impact energy. The following described phenomena could be seen for all 0 curves. All samples in batch 1 and batch 2 had visibility index 2. In batch 2 all samples were brittle due to the alumina part. Density 1 could be 5 rendered for the samples except those with irregular diameter. There was no notable 37 phase change in any sample. The alumina part seemed to be compressed powder while the mbber was well densified. The big difference between density 1 and density 2 depends on two things. Density 1 could in most cases be well determined because the samples were intact. But there was a problem with the elasticity of the samples, due to the mbber, and therefore were thickness and diameter difficult to measure. Therefore should this curve, density 1, be considered as approximate. Density 2 is measured with an alternative buoyancy method that normally is suited to solid bodies, but due to the brittleness 0 of the samples this method was used instead. Water penetrated into the pores of the samples and that makes this method imprecise. That makes also density 2 imprecise. But there is an indication of the densities of the samples. The densities are shown as absolute density instead of relative density in figures 6a 5 and 7a because the real theoretical density is probably different for each sample. Table 8 shows the results obtained. Table 8 0 Stainless steel reinforced mbber ss 316L-rubber composite is a partly metal and partly polymer composite material. ss 316L is a corrosion resistant metal type. That makes it suitable in humid 38 environment where corrosion resistance is required, ss 316L is also a common material type in orthopaedic implants, e.g. femoral-head in hip prostheses. Rubber is machined as a thermoplastic and thereafter cross linked chemically by vulcanising at high temperature. The cross links consist of either sulphur or the same simple links as in the chain molecules. Rubber is a common material in many industries, e.g. car industry. These two materials are tested as a composite to investigate if it is possible to obtain chemical bonding between these two material groups and if it is possible to obtain a mix of both material groups' material properties. Metal is a hard material group, especially comparing with rubber that is extremely elastic. The combination could be interesting in applications where both typical properties are desired. The powder properties are given in Table 9. Table 9 Rubber was mixed with pure ss 316L, which rendered badly mixed powder. The density of ss 316L is 7.9 gcm-3, while the density of mbber is 0.99 gcm-3. Besides the particle size of ss 316L is < 150 micron while rubber is -500 micron. The particles of ss 316L did sink to the bottom extremely fast due to these two differences. Directly after the mixing process some of the ss 316L was separated from the mbber at the bottom of the powder container. That made it difficult to 39 obtain the right proportion between ss 316L and mbber particles. The problem continued while filling up the moulding die before compacting process. Most of the mbber was first poured into the moulding die before the ss 316L. That made most of the ss 316L stay on the top of the coming sample. A stick was used to stir in the mould which made the ss 316L to sink and spread out more even in the sample. If the stirring was too long almost all ss 316L sank to the bottom instead of the moulding die. To sum up, it was difficult to obtain a homogeneous powder mix with these two material types due to too big differences. The powder types were mixed for 15 minutes. Figures 1-3 show relative density as a function of total impact energy, impact energy per mass and impact velocity. The following described phenomena could be seen for all curves. The samples had visibility index 2 and 3. The three first samples were brittle due to the ss 316L part. Density 1 could be measured for the samples except those with irregular diameter. There was a notable phase change between the third and the fourth sample. The densities are shown as absolute density instead of relative density in figures 6b and 7b because the real theoretical density is probably different for each sample. When the powder were poured into the moulding die the powders was mixed again because the powder blend of mbber and metal tended to separate into where the metal part sunk to the bottom of the mould, which probably is due to the big difference i density and particle size between the two constituents, see table 9. Silicon carbide reinforced mbber 40 Silicone carbide-rubber composite is a partly ceramic and partly polymer composite material. Solid silicone carbide is produced conventionally by solid phase sintering and is normally a completely densified material. There exists four types of silicone carbides, where sintered silicone carbide is one of them. At 1300-1500 °C silicone carbide has the highest strength of all construction ceramics. At lower temperatures silicone nitride has the highest strength. There exists no glass phase in silicone carbide material (except some pressure sintered materials) and that makes the creep resistance at high temperatures extremely good. Common application are e.g. wear components and cutting tools. 10 Rubber is machined as a thermoplastic and thereafter cross linked chemically by vulcanising at high temperature. The cross links consist of either sulphur or the same simple links as in the chain molecules. Rubber is a common material in many industries, e.g. car industry. 5 These two materials are tested as a composite to investigate if it is possible to obtain chemical bonding between these two material groups and if it is possible to obtain a mix of both material groups' material properties. Ceramic is brittle and extremely hard material, while mbber is elastic and ductile. The combination could be 0 interesting in applications where both typical properties are desired. Rubber was mixed for 10 minutes with pure silicone carbide. The powder properties are given in Table 10. Table 10 41 Figures 6 and 7 show relative density as a function of impact energy per mass and of total impact energy. The following described phenomena could be seen for all curves. All samples had visibility index 2. All samples were brittle due to the silicone carbide part. Density 1 could be rendered for the samples except those with irregular diameter. There was no notable phase change in any sample. The silicone carbide part seemed to be compressed powder while the mbber was well densified. The densities are shown as absolute density instead of relative density in figures 6c and 7c because the real theoretical density is probably different for each sample. Example 3 - Ceramic matrix composites The ceramic composite constituents are pure alumina and zirconia. The powder used was pre-processed by granulation of pure alumina and zirconia powder with included additives. The granulation process used was freeze granulation. Alumina-zirconia composite is a ceramic composite material. Solid alumina and zirconia are both produced conventionally by solid phase sintering and is normally a completely densified material. Alumina is an electrical isolator and in the mean time it has an acceptable conductivity. Common application is as an insulator in electrical applications. Alumina is also a common material type in orthopaedic implants, e.g. femoral-head in hip prostheses. Alumina is chemical inert and stabile material in many environment. The strength and wear strength are high, and with a 42 mix with zirconia the fracture toughness increases and correspondingly also the strength. Zirconia exists in one stabilised form and in one partial stabilised form. The used zirconia in this test is partial stabilised where (3 mol %) yttrium oxide is added. This combination of these material types renders one of the strongest ceramic material. The obtained properties, like fracture toughness, strength and wear resistance, are higher than other oxide ceramics. The thermal expansion of zirconia is closer to the values of metals. The high strength decreases already at 300 °C and the yttrium oxide stabilised zirconia is sensitive for humid at 250 °C. Common applications are tools for metals, scissors, components for adiabatic motors, but also a common material type in orthopaedic implants, e.g. femoral-head in hip prostheses. Earlier test results - with other ceramic materials - have shown that it is more difficult to high-speed form ceramic powder compared with metal powder. The obtained material body was brittle and the density level reached 68 %. The main object to of both pure alumina-zirconia and where processing additives have been added is to obtain a solid material body with a relative density level over 99 %. It is probably not possible to reach a 100 % relative density due to the fact that the forming process is not performed in an inert environment. That does neither render the same values of material properties nor microstructure as a material body compacted with conventional methods . The powder used in batch 1 is pre-processed by granulation of pure alumina and zirconia powder without any additives (binder and plasticiser). The powder used in batch 2 is a pre-processed by granulation of a pure alumina and zirconia powder where additives are added. The powder properties are given in Table 11. 43 Table 11 Batch 1 did not work out successfully. There was only powder with small clumps obtained. The result of batch 1 is mentioned in this report as well, but by experience of this result batch 2 became in focus as a represent of the composite alumina- zirconia. Therefore only the results obtained for batch 2 are included in Table 12. Table 12 Figures 8 and 9 show relative density as a function of impact energy per mass and of total impact energy. The following described phenomena could be seen for all curves. In batch 2 all samples had visibility index 2. All samples were brittle, but density 1 could be rendered for most of the them. Some of the samples fell apart directly after the removal and density 1 could not be measured. There was no notable phase change in any of the samples. They all seemed to be compressed powder, but with a better green strength compared with the pure alumina-zirconia composite. 44 The big difference between density 1 and density 2 depends on two things. Density 1 could be well determined because the samples were intact. Both thickness and diameter could together with the weight possibly render the right density. Density 2 is measured with a method that normally is suited to solid bodies but due to the brittleness of the samples this method was used instead. Water penetrated into the pores of the samples and that makes this method imprecise. Therefore should this curve, density 2, be considered as approximate. Inspecting the density curve drawn form the density 1 measurements, which would be the most accurate, a small density trend could be identified. The increase from 57 % relative density to approximately 71 % at 262 Nm/g has not reached a plateau. Therefor it my be possible to increase the density for increased impact energies. Discussion To obtain a good composite material the reinforcement particle must be will impregnated in the matrix, the interaction between reinforcement and matrix must be good and the reinforcement particles must be well dispersed in the matrix. This are three parameters cmcial for the outcome of the composite properties and ability of processing. The metal and polymer matrix composites tested herein showed to be very difficult to blend to a homogeneous distribution and to preserve the blend between the constituents. The reason for this is probably caused by the large differences between reinforcement and matrix particle size and densities. Small and heavy particles will fall through light and bulky particles. The aluminium-alloy matrix composite shows higher densities than the titanium matrix sample. This would also be expected since it has been shown that a pure aluminium powder obtains higher densities than the titanium. It would also be expected that it requires more energy for a reinforced material to reach a certain density compared with the pure material if the reinforcement are harder, has higher melting temperature and are stiffer. It is reasonable to think that the reinforcement 45 particles absorbs more energy per volume than the matrix. Accordingly, the purpose of the reinforcement is to carry the load and energy the material is subjected to. Interesting is that the PEEK/CF composite became solid bodies since PEEK has a much higher melting temperature than the UHMWPE and the PMMA. On the other hand the PEEK powder particles are smaller than for the other two enhancing the powder distribution around the fibres and therefore the densification is increased. The chemical compositions of the two constituents may also be of such that interaction is enhanced. The mbber particles in these composites was actually much larger than the reinforcement particles. Hence the opposite of what previously has been discussed as to be necessary to obtain a good composite. In this case the small and hard reinforcement particles will at best stick to the large rubber particle. It could be assumed that this would interfere with the rubber particle migration and therefor it will be difficult to obtain a composite with a solid or 100% densified matrix material and with well dispersed reinforcement particles. The theoretical density is determined with a specific volume fracture of reinforcement and matrix. The irregular curves show that probably the volume fracture of reinforcement and matrix is not as the theoretical, which may be due to poor blending between the two constituents. This will make the theoretical density different in each sample. The differences between the density 1 and density 2 measurement methods could be explained by the fact that the samples did not hold together entirely. When measuring using density method 1 parts that has com off is mot included in the weight but accounted for in the volume calculation of a cylinder specimen. Ceramic material has high melting temperature compared with metal or polymer materials. Alumina and zirconia melt at 2050 °C respectively 2500-2600 °C compared to stainless steel 1427 °C. It is probably easier to compress a ceramic 46 material with small particles during a fast lapse of increased temperatur e powder particles are too big the only thing that will happen is that the part t cles to smaller particles instead of reacting and melt together. Small grams g t ve a higher strength in the material body, but decrease the fracture toughness. If there are covalent bonds between two ions(e. g . between AlandOλhigh energy between the two ions. Instead they are dislocated further to one of the , n. f toe an i„n bond the electron cloud is between the two ions and less energy level ,s reouired. Therefore alumina, zirconia and o er ceramic powder, that have cova,ent bond, might be more difficult to solidified. Due to the high melting temperature and hardness of both alumina (2050 , 1600- °0;0HV)a n re onia( 2 500- 2 600 ,1250-1350HV)i tiS p rob a bl ynece, S ar to laseie energy required to formasolid material body.which is poss t ble by atmepowdΪrandprocessthewholecompresingprocesinasutoundmg ed temper. Probably is also an atmosphere, e.g vacuum, necessary to avoid possible air inclusions in the mater i al. over the prior art. lay require acuumor an inert gas to produce a body of extreme purty or htgh 47 density. Thus, although the use of additives, vacuum and inert gas are not required according to the invention the use thereof is not excluded. Other modifications of the method and product of the invention may also be possible within the scope of the following claims. 48

Claims: Claims 1. A method of producing a composite body by coalescence, characterised in that the method comprises the steps of a) filling a pre-compacting mould with composite material in the form of powder, pellets, grains and the like, b) pre-compacting the material at least once and c) compressing the material in a compression mould by at least one stroke, where a striking unit emits enough kinetic energy to form the body when striking the material inserted in the compression mould, causing coalescence of the material. 2. A method according to claim 1, characterised in that the pre-compacting mould and the compressing mould are the same mould. 3. A method according to any of the preceding claims, characterised in that the material is pre-compacted with a pressure of at least about 0.25 x 10 8 N/m 2 , in air and at room temperature. 4. A method according to claim 3, characterised in that the material is pre- compacted with a pressure of at least about 0.6 x 10 8 N/m 2 . 5. A method according to any of the preceding claims, characterised in that the method comprises pre-compacting the material at least twice. 6. A method of producing a composite body by coalescence, characterised in that the method comprises compressing material in the form of a solid composite body in a compression mould by at least one stroke, where a striking unit emits enough energy to cause coalescence of the material in the body. 7. A method according to any of claims 1-5 or claim 6, characterised in that the compression strokes emit a total energy corresponding to at least 100 Nm in a cylindrical tool having a striking area of 7 cm 2 in air and at room temperature. 8. A method according to claim 7, characterised in that the compression strokes emit a total energy corresponding to at least 300 Nm in a cylindrical tool having a striking area of 7 cm 2 . 49 9. A method according to claim 8, characterised in that the compression strokes emit a total energy corresponding to at least 600 Nm in a cylindrical tool having a striking area of 7 cm 2 . 10. A method according to claim 9, characterised in that the compression strokes emit a total energy corresponding to at least 1000 Nm in a cylindrical tool having a striking area of 7 cm 2 . 11. A method according to claim 10, characterised in that the compression strokes emit a total energy corresponding to at least 2000 Nm in a cylindrical tool having a striking area of 7 cm 2 . 12. A method according to any of claim 1-5 or claim 6, characterised in that the compression strokes emit an energy per mass corresponding to at least 5 Nm/g in a cylindrical tool having a striking area of 7 cm in air and at room temperature. 13. A method according to claim 12, characterised in that the compression strokes emit an energy per mass corresponding to at least 20 Nm/g in a cylindrical tool having a striking area of 7 cm 2 . 14. A method according to claim 13, characterised in that the compression strokes emit an energy per mass corresponding to at least 100 Nm/g in a cylindrical tool having a striking area of 7 cm 2 . 15. A method according to claim 14, characterised in that the compression strokes emit an energy per mass corresponding to at least 250 Nm/g in a cylindrical tool having a striking area of 7 cm 2 . 16. A method according to claim 15, characterised in that the compression strokes emit an energy per mass corresponding to at least 350 Nm/g in a cylindrical tool having a striking area of 7 cm . 17. A method according to any of the preceding claims, characterised in that the composite is compressed to a relative density of at least 60 %, preferably 65 %. 18. A method according to claim 17, characterised in that the composite is compressed to a relative density of at least 70 %, preferably 75 %. 50 19. A method according to claim 18, characterised in that the composite is compressed to a relative density of at least 80 %, preferably at least 85 % and especially at least 90 % up to 100 %. 20. A method according to any of the preceding claims, characterised in that the method comprises a step of post-compacting the material at least once after the compression step. 21. A method according to any of the preceding claims, characterised in that the composite matrix is chosen from the group comprising metallic, ceramic and polymeric materials.. 22. A method according to claim 21 , characterised in that the reinforcing phase in the composite is chosen from the group comprising carbon, glass, metal, polymeric and ceramic material. 23. A method according to claim 21, characterised in that the composite matrix is chosen from the group comprising UHMWPE , PMMA, nitrile mbber, aluminium alloys and titanium. 24. A method according to any of the preceding claims, characterised in that the body produced is a medical implant, such as a skeletal or tooth prosthesis. 25. A method according to any of the preceding claims, characterised in that the method comprises a step of post-heating and/or sintering the body any time after the compression or the post-compacting. 26. A method according to any of the preceding claims, characterised in that the body produced is a green body. 27. A method of producing a body according to claim 27, characterised in that the method also comprises a further step of sintering the green body. 28. A method according to any of the preceding claims, characterised in that the material is a medically acceptable material. 29. A method according to any of the preceding claims, characterised in that the material comprises a lubricant and/or a sintering aid. 30. A method according to claim 6, characterised in that the method also comprises deforming the body. 31. A product obtained by the method according to any of claims 1-30. 51 32. A product according to claim 31, characterised in being a medical device or instrument. 33. A product according to claim 31, characterised in being a non medical device. 52

Inventors: OLSSON KENT, OLSSON, KENT
Applicants: CK MAN AB UB, JIANGU LI, OLSSON KENT, CK MANAGEMENT AB UB, JIANGU, LI, OLSSON, KENT
Application year: 2001
Main classification: B21J5
IPC codes: A61L27, B22F3, B22F7, B28B3, B29C43, B29K23, B29K33, B29K103, B29K105, B29L31, B30B11, C22C1