EP1154033A2 - Member for material and heat transport and manufacturing method - Google Patents

Abstract

Component comprises a base body with a coating produced by vacuum plasma spraying, in which powder particles are melted to form a pore structure and the amount of open and closed pores is adjusted by the degree of melting. An Independent claim is also included for a process for the production of a component. Preferred Features: The base body has recesses with opposite facing surfaces inclined to each other so that their surface normals cut. The recesses are V-shaped and have a concave cross-section. The base body is formed as a half shell with the concave surfaces forming a coating surface. The coating has a thickness of 10-2000 microns .

Description

The present invention relates to components for mass and heat transport with a base body and with a layer supporting a material and heat transport on at least a component surface.

Furthermore, the invention relates to methods for producing a component for material and Heat transport with provision of a base body, with a base body a layer that supports material and heat transport is applied.

Arrangements for the transport of liquids, using capillary forces, are well known. Such capillary structure layers can be made using different methods be built up, for example by known sintering techniques or by plasma spraying of powder particles.

A heat pipe, and a method for its production, for the transport of heat from an evaporation area to a condensation area, with a capillary structure within the heat pipe, is known from DE-A1 197 17 235. The one described there Capillary structure is created by thermal plasma spraying of powder particles and has an open-pored capillary structure layer. For this purpose, powder particles with a average particle size in the range of about 30 microns to about 300 microns used.

Basically, an arrangement as known from DE-A1 197 17 235 is for Heat pipes are particularly suitable, particularly with regard to their porosity, as they are caused by the plasma spraying used there is generated by powder particles. To use a heat pipe Building up the inner coating is also proposed in DE-A1 197 17 235, two To provide half-shells with a capillary layer on the inside. Then be the two half-shells or the two cylinder halves are joined flat with their edges, so that there is a tube coated on the inside.

Based on the prior art described above, the present Invention, the object of an arrangement for transporting liquids under Utilization of capillary forces of the type specified in the introduction so that a Material and heat transport with a higher transport capacity can take place with it, as well a corresponding method for building up a corresponding capillary structure layer specify for such an arrangement.

This task is solved by a component for material and heat transport with one Base body and with a layer supporting a material and heat transport at least one component surface, which is characterized in that the coating is generated by a vacuum plasma spraying process, using powder particles for production a pore structure are melted on the surface and by the degree of melting the proportion of open and closed pores is set.

According to the method, the object is achieved in that the coating by a vacuum plasma spraying process is generated, the powder particles to produce a Pore structure are melted on the surface and by the degree of melting the proportion of open and closed pores is set.

In one embodiment of the invention, the degree of melting is accordingly the individual powder particles set the porosity. Depending on the requirements of the shift and in particular with regard to the area of application, a suitable proportion of open and closed pores formed.

In particular with a vacuum plasma spraying process to apply the powder particles to the base body can apply by changing various process parameters Pore structure can be influenced. Here is the particle size distribution of the used ones To name powder fractions. Through the defined admixture of powder particles with a small diameter compared to the powder portion with a maximum diameter, more pores can be closed because such fine powder particles are stronger melt in the surface area as the particles with large particle diameter. On Another parameter is the electrical power that is injected into the plasma. By Increasing the electrical power makes the plasma hotter and the powder particles in the Surface melted more.

A porosity can already be achieved with the formation of a layer of powder particles, which is useful for certain applications for mass and heat transport. Such a layer would have a thickness that corresponds approximately to the diameter of the powder particles.

Partially closed pores are preferably formed, which face towards the base body are more closed.

An important parameter for setting and influencing the proportion of open and / or closed pores, in particular of closed pores, is the pressure. In principle, work should therefore be carried out in a vacuum, ie in the range from approximately 5 x 10 ³ Pa to 3 x 10 ⁴ Pa.

Another parameter to consider is the appropriate spray distance between Flame and base body. The larger this distance is chosen, the higher the resulting one Porosity. However, the distance must not be chosen so large that the melted Particles do not already solidify superficially before they hit the base body hit.

If distances between flame / plasma and base body are specified, refer this at the end of each burner.

In terms of a gradient between open pores and closed pores, it is preferred that viewed in the direction of the thickness of the layer to be applied one Half should be closed-pore than the other half, the closed Pores point towards the base body, while the open-pored side faces the free surface forms.

By continuously changing the process parameters immediately during the Plasma spraying, as well as a change in the powder fraction in relation to the proportion of fine-grained Powder compared to the proportion of larger powder particles can be a continuous gradient of the porosity can be obtained over the layer thickness. Preferably the porosity should be adjusted so that the ratio of the total Pore volume fraction to the total volume of the layer changes from 0 to 80%; the preferred The range is between 10 to 50%.

In addition, a dense base layer can be applied at the start of spraying, by setting the parameters so that either the entire powder particles are melted, or a correspondingly high proportion of fine powder is mixed in, so that this results in the dense base layer.

A vacuum high-frequency plasma spray process is preferred as the plasma spray process used. This makes it possible, in comparison to flame spraying or DC plasma spraying to melt relatively coarse-grained powders (> 50 µm); in a vacuum Cannot Print Using High Frequency Plasma Spraying only the length of the plasma flame, but also the heat transfer between Plasma and powder particles can be checked.

The starting powder used should preferably be one whose particle size is in the range from 10 μm to 800 μm, a range between 100 μm and 250 μm to be emphasized as a particularly preferred range. Investigations have further shown that a powder fraction should be used which comprises particles in a diameter range between a minimum particle diameter d _min and a maximum particle diameter d _max , which meets the following requirement: Δd d a Max <0.35 where d _a ^max indicates the powder particle diameter that forms the largest portion in the selected powder fraction, and wherein Δd represents the range of fluctuation of the particle diameter around the largest particle diameter.

For simplification, the rule can also be followed for d _a ^max : d a Max = d min + d Max 2

In order to achieve a partially open pore structure, the degree of melting m of the surface layer of the particles should comply with the regulation m = d - d s * d consequences,
where d denotes the particle diameter and
where d _s * denotes the diameter of the remaining solid core, where applies to m 5% <m ≤60%.

To produce the at least partially closed pore structure, the surface layer of the particles is melted, the degree of melting m again being the requirement m = d - d s * d is sufficient, but with 10% <m ≤ 100%.

Suitable pore radii should be applied to the respective layers applied to the Base bodies are between 25 µm and 200 µm. The thickness of the coating can vary depending on Type of base body and the requirements, in the range from 10 µm to 2000 µm lie. Powders made of metals or metal alloys are preferably used; it is but it is also possible to use ceramic materials, as these are specified using the Process can also be processed due to the achievable high temperatures.

A ceramic coating over metallic powder can be advantageous if the metallic Base material should be protected against corrosion and the base material nevertheless should conduct heat well.

However, a ceramic coating can also have a very positive effect on heat and mass transfer influence, especially in the condensation of vapors. Because of poor wetting the ceramic can namely achieve the particularly advantageous drop condensation become.

In order to increase the heat transfer performance, at least one can be in the base body Groove in the material and heat transport direction to be formed by the powder particles while maintaining the cross-sectional shape of the groove.

In this way it is possible to use a porous capillary structure by injection molding To produce channels or grooves, also called arteries. This combination is particularly advantageous since areas of high capillarity with such low pressure losses can be linked efficiently. The possibility of producing porous functional layers in which channels or grooves are directly incorporated, leads to the fact that such arrangements with high heat and mass transfer performance can be produced very inexpensively.

When building up the porous layer on the base layer, into which one or more Groove (s) are incorporated, care should be taken that the powder particles are one size have such that the cross-sectional shape of the groove is only covered, i.e. the free The cross section of the groove should be obtained after the layer has been sprayed on. One is preferred V-shaped groove used.

Such a groove should therefore have an opening width that is smaller than the middle Particle diameter of the powder of the layer applied thereon.

The groove can be milled into the base body or etched into it.

The above-mentioned grooves can be in a desired number in the base body be trained, run in different directions and with cross connections among themselves.

In order to produce the specified layer with a pore structure, powder particles are preferably used used, which melted on the surface during the coating process become. The degree of melting can then open and / or partially closed pore structure can be set. Furthermore, by the degree of melting the pore structure is provided with a gradient in which the Seen in the thickness of the layer, a more open or closed pore structure is produced. This can be done in that the degree of melting of the surface of the powder particles, which are applied in layers to produce the capillary structure layer, are melted to a greater or lesser degree in the surface. Prefers a layer is created, the pores of which face towards the radially inner side are more closed than towards the radially outer side, i.e. towards the free surface.

It has been shown that porous layers are advantageous using a high-frequency plasma spraying process can be generated, this being done even more preferably in a vacuum becomes. With the high-frequency plasma spraying process, a defined melting process can be carried out the surface layer of the individual powder particles. The process parameters can simply in terms of performance, pressure in the coating chamber, Flame distance to the layer, can be changed to change the degree of melting Surface and thus to change the pore structure. Also makes the choice the particle size is a factor influencing the pore structure. The particle sizes should be in the range of 10 µm to 800 µm, with a particle size between 100 µm and 250 µm is preferable. The pore radius of each pore that is between the fused powder particles should be in the range of 20 microns up to 500 µm.

If distances between flame / plasma and base body are specified, refer this at the end of each burner.

To promote the formation of an open pore structure, particles should be in the fraction area 0.7 ≤ d min d Max <1 be used.

In order to promote the formation of a closed pore structure, particles in the fraction range of d min d Max <0.7 be used.

Preferred pressure ranges which are set in the coating chamber during vacuum plasma spraying are 8 · 10 ³ Pa to 2 · 10 ⁴ Pa, preferably 1 · 10 ⁴ Pa to 1.7 · 10 ⁴ Pa. It is precisely in this pressure range that it is ensured that the negative influence of oxidative reactions is largely prevented; a predominantly laminar plasma jet can be set in this pressure range, which results in a uniform melting. In addition, the heat transfer is large enough to control the controlled melting of the particle surface. In order to reduce residual oxygen and the formation of oxide on the individual powder particles, which reduces the strength of the layer, and in order to be able to control pore structure formation even better, plasma spraying should take place in a protective gas atmosphere, in particular with the appropriate reducing agent, such as hydrogen.

Preferred process parameters in vacuum plasma spraying are a pressure of 5 · 10 ³ Pa to 3 · 10 ⁴ Pa and a power of 5 to 50 kW to create an open pore structure, while a pressure range of 1 · 10 ⁴ Pa to 5 · 10 ⁴ Pa and a power of 7 to 50 kW can be set to create a closed pore structure.

It has also proven advantageous to warm up the base body before coating, especially at temperatures in the range of a few 100 ° C; this will the deposition of the powder particles is favorably influenced, i.e. for example, there will be cracks avoided between base body and layer.

Further advantageous configurations of both the component and the method are shown in the respective subclaims 2 to 29 and 31 to 34.

Figur 1

eine schematische Darstellung im Schnitt eines Teils eines Basiskörpers mit einer darauf aufgebrachten, einlagigen, porösen Schicht,

Figur 2

eine Schnittdarstellung entsprechend der Figur 1 mit einer dreilagigen Schicht,

Figur 3

eine der Figur 2 entsprechenden Darstellung mit einer zusätzlichen Nut im Basiskörper,

Figur 4

ein rohrförmiges Bauteil mit einer Außenbeschichtung, wobei für einen größenmäßigen Vergleich eine 1-Pfennig-Münze zu sehen ist,

Figur 5

eine Rasterelektronenmikroskopaufnahme einer Oberflächenschicht, wie sie auf einem Bauteil entsprechend Figur 4 aufgebracht ist, und

Figur 6

eine graphische Darstellung der Partikeldurchmesserverteilung der zum Plasmaspritzen eingesetzten Pulverfraktionen.

Various exemplary embodiments are explained below with reference to the drawing. The accompanying drawings show in detail

Figure 1

1 shows a schematic representation in section of a part of a base body with a single-layer, porous layer applied thereon,

Figure 2

2 shows a sectional illustration corresponding to FIG. 1 with a three-layer layer,

Figure 3

2 shows a representation corresponding to FIG. 2 with an additional groove in the base body,

Figure 4

a tubular component with an outer coating, a 1 Pfennig coin being shown for a size comparison,

Figure 5

a scanning electron microscope image of a surface layer, as applied to a component according to Figure 4, and

Figure 6

a graphic representation of the particle diameter distribution of the powder fractions used for plasma spraying.

Figure 1 shows schematically a base body 1, on which a single-layer layer of powder particles 2 is sprayed on. Since the individual powder particles 2 are controlled only in one Are melted surface area, the shape of the individual powder particles 2nd essentially maintained. The powder particles can be considered with a suitable Throughput are applied to the base body 1 in such a way that they melt together, so that 2 pores are formed between the base body 1 and the powder particles. These pores arise in particular when powder fractions with particles are present relatively large particle diameter can be used.

Figure 2 shows a sectional view corresponding to Figure 1 with a three-layer Layer, i.e. the powder particles are layered on top of each other. Because the individual powder particles only superficially before hitting the base body 1 or the one below it lying powder particles 2 are melted, they essentially keep their Shape so that 2 defined pores 3 form between the individual powder particles. This pore structure can be determined by the degree of melting on the one hand Powder particle size distribution, on the other hand, which is particularly immediate during a Vacuum high frequency plasma spraying can be changed, in addition about the pressure set in the plasma spraying system and the power with which the system is operated, adjusted or influenced. So it is possible during the Plasma spraying to increase the proportion of fine powder with a small diameter, so that the pores close, while for a higher porosity the powders with larger ones Radius can be changed. Furthermore, the degree of melting of the surface be increased so that the individual powder particles melt together more strongly, so that in contrast to an open porosity, the individual pores are closed become. The porosity is preferably gradually starting from the base layer 1 to the Increased outside, so that on the one hand in the area of the base body high strength can be achieved.

As explained at the beginning, a particularly suitable starting powder of the regulation should be used Δd d a Max <0.35 are enough; the relationships between d _a ^max , Δd, d _min (minimum particle diameter d) and d _max (maximum particle diameter d) are shown in FIG. 6, depending on the percentage of the respective powder particle diameter that is present in a starting powder.

Figure 3 shows a structure according to Figure 2, but with two additional, V-shaped grooves 4 which are formed in the surface of the base body 1. This Grooves 4 form capillaries below the porous layer; they are completely through the powder particles 2 covered. Since the opening width of the grooves 4 is less than the particle diameter the bottom layer, the grooves are not closed, i.e. their free Cross section is completely preserved.

Figure 4 shows an 8 mm stainless steel sheet, which is by means of high-frequency plasma spraying was produced. A powder made of a nickel-based alloy was sprayed on in one Grain size of -160 + 125 µm. The layer thickness is approx. 500 µm. The coating was at a pressure between 100 and 200 mbar (at a distance of 320 mm) carried out. The electrical power was between 15 - 20 kW. As plasma gases were Argon and hydrogen were used in a total of 140 SLPM.

FIG. 5 shows a scanning electron microscope image of the surface layer of the one in FIG 4 component shown in a 30-fold magnification. Based on this shot is clearly recognizable that the structuring of the layer, in particular the surface, it happens that the particles are melted on the surface and by the Degree of melting largely resembles the shape of the original, spherical particle was maintained. The proportion of molten material connects the particles with each other and strengthens shift cohesion. Such a structured layer, in particular Surface, promotes heat and mass transfer.

Claims (34)

Component for material and heat transport with a base body and with a layer supporting a material and heat transport on at least one component surface, characterized in that the coating is produced by a vacuum plasma spraying method, powder particles for producing a pore structure being melted on the surface and by the degree of Melting the proportion of open and closed pores is set. Component according to claim 1, characterized in that the base body is structured on its coating surface with depressions, the depressions comprising opposing surfaces which are inclined to one another such that their surface normals intersect. Component according to claim 1, characterized in that the depressions are V-shaped in cross section. Component according to claim 1, characterized in that the depressions have a concave cross section. Component according to claim 1, characterized in that the base body is designed as a half-shell, the concave surface forming a coating surface. Component according to claim 1, characterized in that partially closed pores are formed which are more closed towards the base body. Component according to claim 6, characterized in that viewed in the direction of the thickness of the layer, one half of the layer is closed-pore and the other half of the layer is open-pore. Component according to Claim 1, characterized in that the porosity has a gradient as seen over the thickness of the layer. Component according to Claim 8, characterized in that the porosity changes in such a way that the ratio of the total proportion of hollow volume to the total volume of the layer is 0 to 80%. Component according to claim 9, characterized in that the ratio of the total void volume to the total volume of the layer is 10 to 50%. Component according to claim 1, characterized in that an essentially dense base layer is applied to the base body, which has no porosity. Component according to claim 1, characterized in that the coating is produced by a high-frequency vacuum plasma spraying process. Component according to claim 1, characterized in that the thickness of the coating is 10 µm to 2000 µm. Component according to claim 3, characterized in that the depressions comprise at least one groove running in the material and heat transport direction, which is covered by the powder particles while maintaining the cross-sectional shape of the groove. Component according to claim 14, characterized in that the groove is V-shaped. Component according to claim 14 or 15, characterized in that the groove has an opening width which is smaller than the average particle diameter of the powder of the layer applied thereon. Component according to claim 14, characterized in that the groove is milled into the base body. Component according to claim 14, characterized in that the groove is etched in the base body. Component according to Claim 7, characterized in that the powder throughput quantity is in the range from 4 to 100 g / min, preferably from 10 to 50 g / min. Component according to claim 1, characterized in that the coating is formed by at least one layer of powder particles, such that the layer has a thickness which corresponds approximately to the diameter of the powder particles. Component according to Claim 1, characterized in that the particle size of the starting powder is in the range from 10 µm to 800 µm, preferably between 100 µm and 250 µm. Component according to Claim 21, characterized in that a powder fraction is used which comprises particles in a diameter range between a minimum particle diameter d _min and a maximum particle diameter d _max , which satisfies the following requirement: Δd d a Max <0.35 where d _a ^max indicates the powder particle diameter which forms the largest proportion in the powder fraction mentioned, and where Δd represents the range of fluctuation of the particle diameter around this particle diameter. Component according to claim 22, characterized in that approximately d a Max = d min + d Max 2 applies. Component according to Claim 21, characterized in that the surface layer of the particles is melted on in order to produce the at least partially open pore structure, the degree of melting m satisfying the following requirement: m = d - d s * d in which d: particle diameter d _s *: remaining solid core with 5% <m < 60%. Component according to Claim 21, characterized in that the surface layer of the particles is melted on in order to produce the at least partially closed pore structure, the degree of melting m satisfying the following requirement: m = d - d s * d in which d: particle diameter d _s *: remaining solid core with 10% <m ≤ 100%. Component according to claim 1, characterized in that the powder is formed from metals and / or metal alloys. Component according to Claim 13, characterized in that a coating layer formed from ceramic powder is applied to the layer built up from the metal powder and / or the metal powder alloy. Component according to claim 21, characterized in that in order to produce the at least partially open pore structure, particles in the fraction area 0.7 ≤ d min d Max <1 are used. Component according to claim 21, characterized in that, in order to produce the closed pore structure, particles in the fraction area d min d Max <0.7 A process for producing a component for mass and heat transport while providing a base body, a layer supporting a mass and heat transport being applied to the base body, characterized in that the coating is produced by a vacuum plasma spray process, the powder particles being superficial to produce a pore structure are melted and the proportion of open and closed pores is set by the degree of melting. A method according to claim 30, characterized in that a vacuum high-frequency plasma spraying method is used. A method according to claim 30, characterized in that the spraying takes place under a protective gas atmosphere, in particular an argon atmosphere. A method according to claim 30, characterized in that a reducing agent, in particular hydrogen, is added to the protective gas atmosphere. A method according to claim 30, characterized in that a pressure of 5 · 10 ³ to 3 · 10 ⁴ Pa and an output of 5 to 50 kW are set during the plasma spraying in order to produce an open pore structure.

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