Heat-resisting plate having a cooling structure and method of manufacturing it

Abstract: Heat-resisting composite plate (14) useful in various beam devices employing high temperature plasma or high energy particles. It has cooling pipes (12) embedded within a thermally sprayed layer (13) of the same material as the metallic plate (11) on at least one face of the plate. The arrangement facilitates location of the cooling pipes whilst reducing frequency of faults. The cooling pipes can be partially located in recesses and/or subjected to low temperature brazing. It is preferred to infiltrate the sprayed thermal layer with a metal such as copper, for further improvement in thermal conductivity.

Description: This invention relates to a heat-resisting plate having a cooling structure that can be employed in various types of beam device for handling high-temperature plasma or high-energy particles, and to a method of manufacturing it. Examples of beam devices that handle high-temperature plasma or high-energy particles are fusion reactors or accelerators. In all such beam devices, the interior of the structural member that handles the high temperature plasma or high energy particles is exposed to extremely high temperature. A heat-resisting plate having a cooling structure is therefore employed for structural members handling such high temperature plasma or high energy particles, see for example the article "Net plasma facing components" in Fusion Engineering and Design, vol. 11, no 1/2, June 1989, pages 125-137. The heat-resisting plate having a cooling structure may be of the type wherein the body of the heat-resisting plate is cooled by passing cooling water through cooling pipes which are mounted by brazing to the body of the heat-resisting plate, or the type wherein the body of the heat-resisting plate is cooled by passing cooling water through passages for flow of cooling water formed in the body of the heat-resisting plate. However, a heat-resisting plate with cooling pipes mounted on it is subject to the following inconveniences. Specifically, it is difficult to mount the cooling pipes on to the heat-resisting plate body by brazing, and cracks appear in the vicinity of the mounting joint interface. This is due to the difference in the materials of the heat-resisting plate body and of the cooling pipes. Typically, the high melting point metals tungsten W or molybdenum Mo are employed for the material of the heat-resisting plate body, while stainless steel is used for the material of the cooling pipes. There was therefore the problem that cooling pipes made of stainless steel melted when it was sought to fix them securely by brazing. Brazing therefore had to be performed at a temperature such that the stainless steel cooling pipes were not melted. A further problem was the occurrence of cracks in the vicinity of the brazed joint interface due to the different linear expansion coefficients of the material of the cooling pipes and the material of the heat-resisting plate body. On the other hand, in the case of a heat-resisting plate bored with passages to allow the flow of cooling water in the heat-resisting plate body, the material of the passages and the material of the heat-resisting plate body is the same. However, since tungsten W or molybdenum Mo is employed as the material of the heat-resisting plate body, there were problems regarding corrosion resistance to the cooling water. An object of this invention is to provide a heat-resisting plate equipped with a cooling structure wherein cooling pipes can be comparatively easily mounted on the heat-resisting plate body whilst reducing the possibility of generation of cracks in the vicinity of the mounting joint interface, and which yet still provides good corrosion resistance with respect to the cooling water. A further object of this invention is to provide a method of manufacturing a heat-resisting plate having a cooling structure as described above. The objects of this invention described above are achieved by the means and steps described below. A heat-resisting plate having a cooling structure employed in high temperature portions of equipment exposed to high temperature is constituted of: a plate-shaped metallic substrate having prescribed thickness and consisting essentially of a metallic substrate formed of a metal selected from the group consisting of Ti, Cr, Co, Ni, Cu, Fe, Zr, Nb, Mo, Ta, W and alloys of these; cooling pipes for passage of cooling water arranged with prescribed spacing on one or both sides of this metallic substrate; and a plasma sprayed layer which is of the same material as the material of the metallic substrate and formed on the face of the metallic substrate where the cooling pipes are arranged, being formed so as to embed the cooling pipes. One method of manufacturing heat-resisting plate having a cooling structure employed in high temperature portions of equipment exposed to high temperature comprises: a substrate preparation step wherein a metallic substrate consisting of a metal selected from the group consisting essentially of Ti, Cr, Co, Ni, Cu, Fe, Zr, Nb, Mo, Ta, W and their alloys is processed to the shape of a plate having a prescribed thickness, and arranged at a prescribed location on a production line; a cooling pipe arrangement step wherein cooling pipes are arranged at prescribed locations on the surface of the metallic substrate; a thermal spray layer formation step wherein a plasma sprayed layer of the same material as the substrate is formed on the surface where the cooling pipes are arranged on the metallic substrate, to a degree such as to embed the cooling pipes; and a finish processing step for elimination of irregularity and warping of the thermal spray layer surface. In order that the invention may be illustrated, more easily understood and readily carried into effect, embodiments thereof will now be described purely by way of non-limiting example only, and wherein: Fig. 1 is a process diagram showing a first embodiment of the heat-resisting plate, Fig. 2 is a perspective view of a heat-resisting plate according to the first embodiment, Fig. 3 is a diagram of an embodiment in the case where a plasma spray layer is provided on the back face of a heat-resisting plate also according to the first embodiment, Fig. 4 is a process diagram showing a second embodiment, Fig. 5 is a diagram showing brazing of a cooling pipe in the second embodiment, Fig. 6 is a diagram of an embodiment including a plasma spray layer on the back face of a heat-resisting plate according to the second embodiment, Fig. 7 is a process diagram of a third embodiment of a heat-resisting plate, Fig. 8 is a perspective view of a heat-resisting plate also according to the third embodiment, Fig. 9 is a process diagram showing a fourth embodiment of a heat-resisting plate, Fig. 10 is a diagram of an embodiment using brazing material coated on to the cooling pipes of the fourth embodiment, Fig. 11 is a flow chart showing an embodiment of a method of manufacturing the heat-resisting plate, Fig. 12 is a diagram showing plasma spray layer formation, Fig. 13 is a diagram showing infiltration, Fig. 14 is a graph showing tensile strength performance of the sprayed coating, Fig. 15 is a graph showing adhesion strength performance of the sprayed coating, Fig. 16 is a graph showing thermal conductivity performance of heat-resisting plate, Fig. 17 is a graph showing the warping performance of heat-resisting plate , and Fig. 18 is a graph showing the heat-resisting cycle performance of heat-resisting plate according to this invention. Embodiments of this invention are described below with reference to the drawings. Fig. 1 is a process diagram showing a first embodiment of the heat-resisting plate of this invention. A heat-resisting plate according to this first embodiment has cooling pipes mounted on one side of the metallic substrate by plasma spraying. In more detail, as shown in Fig. 1A, first of all, a metallic substrate 11 is processed to the form of a plate, and is arranged at a prescribed location in a manufacturing line. For this metallic substrate, Ti, Cr, Co, Ni, Cu, or Fe, Zr, Nb, mo, Ta, W or alloys of these may be employed. Hereinbelow, the use of Mo will be described. Next, as shown in Fig. 1B, a plurality of cooling pipes 12 are arranged at prescribed positions on the upper surface of metallic substrate 11. These cooling pipes 12 are preferably arranged at equal intervals. Also, in arranging cooling pipes 12, if required, the joint faces of cooling pipes 12 contacting metal substrate 11 can be brazed. This results in more secure mounting than in the case where cooling pipes 12 are not brazed to metallic substrate 11. This brazing is to ensure that cooling pipes 12 do not move in the subsequent step of forming a plasma spayed layer 13. It is not performed with the object of mounting cooling pipes 12 on to metallic substrate 11, which was the purpose of the conventional brazing. Such brazing can therefore be unelaborate and low temperature brazing is sufficient and therefore preferred. There is therefore no possibility of such brazing melting cooling pipes 12 or of generating cracks in the vicinity of the brazing joint interface. Hereinbelow, in this invention, such "brazing" will refer to low temperature brazing. As shown in Fig. 1C, when arrangement of the cooling pipes 12 on to metallic substrate 11 is completed, mounting of cooling pipes 12 on to metallic substrate 11 is performed by thermal spraying. In more detail, plasma spray layer 13 is formed to a depth such as to embed cooling pipes 12 on the face of metallic substrate 11 on which cooling pipes 12 are arranged. This formation of layer 13 embeds cooling pipes 12 in the layer 13, thereby securely mounting cooling pipes 12 on metallic substrate 11. Formation of layer 13 is performed by plasma spraying. The material of layer 13 is the same as that of metallic substrate 11. In this first embodiment, metallic substrate 11 consists of Mo, so plasma spray layer 13 is also formed of Mo. Formation of heat-resisting plate 14 prior to finish processing is performed by formation of plasma sprayed layer 13 on metallic substrate 11. Prior to finish processing, the plasma sprayed layer surface of heat-resisting plate 14 contains irregularities and shows warping due to the plasma spraying. Finish processing is therefore performed so as to eliminate the warping of heat-resisting plate 14 prior to such finish processing and to eliminate irregularities of the plasma sprayed layer surface. Fig. 2 is a perspective view showing a heat-resisting plate 14 of this invention formed in this way. Since heat-resisting plate 14 according to this first embodiment has cooling pipes 12 mounted on to metallic substrate 11 by plasma spraying, there is no possibility of cracks being generated in the vicinity of the brazing joint interface. This plasma spraying produces warping of the heat-resisting plate 14 before finish processing. In order to alleviate this warping, as shown in Fig. 3, a plasma spray layer 13 is formed on the back face on the opposite side of metallic substrate 11 to that on which metallic pipes 12 are mounted. The warping produced by plasma spraying can thereby be alleviated. Fig. 4 is a process diagram showing a second embodiment of this invention. In this second embodiment, Mo is employed as metallic substrate 11 as in the first embodiment, and cooling pipes 12 are mounted by plasma spraying on the front face of metallic substrate 11. The difference with respect to the first embodiment lies in that, in the arrangement of cooling pipes 12, recesses 15 are provided for the arrangement of cooling pipes 12, maintaining a prescribed spacing on the front face of metallic substrate 11. Specifically, as shown in Fig. 4A, as in the first embodiment, a metallic substrate 11 is prepared by processing to a plate shape. Then, as shown in Fig. 4B, recesses 15 are provided for the arrangement of cooling pipes 12 maintaining a prescribed spacing on the front face of metallic substrate 11. Cooling pipes 12 are then arranged in these recesses 15 as shown in Fig. 4C. In this case, as in the first embodiment, if required, the surfaces where cooling pipes 12 join metallic substrate 11 can be brazed. Fig. 5 is a diagram of such brazing. Brazing is carried out with the introduction of brazing material 16 between cooling pipes 12 and recesses 15 provided in metallic substrate 11. Arrangement of cooling pipes 12 on metallic substrate 11 can thereby be made more secure than if brazing is not performed. As mentioned above, since such brazing is low temperature brazing, there is no possibility of cooling pipes 12 melting, or of generation of cracks in the vicinity of the mounting joint interface. Next, mounting of cooling pipes 12 on to metallic substrate 11 is performed by plasma spraying in the same way as in the first embodiment. Specifically, as shown in Fig. 4D, plasma spray layer 13 is formed on the face of metallic substrate 11 where cooling pipes 12 are arranged, to a degree sufficient to embed cooling pipes 12. This formation of plasma spray layer 13 results in secure mounting of cooling pipes 12 on to metallic substrate 11, owing to the embedding of cooling pipes 12 in thermal spray layer 13. Formation of plasma spray layer 13 is achieved by plasma spraying. For the material of the layer 13, the same material as metallic substrate 11 is employed. Since, in this first embodiment, metallic substrate 11 consists of Mo, spray layer 13 also consists of Mo. Forming of plasma spray layer 13 on to metallic substrate 11 completes the formation of heat-resisting plate 14 apart from finish processing. Prior to finish processing, heat-resisting plate 14 has irregularities in the upper surface of the plasma spray layer and warping produced by the plasma spraying. The finish processing is performed in order to eliminate warping of this unfinished heat-resisting plate 14 and irregularities of the surface of the plasma spray layer. Since the plasma spraying produces warping in the heat-resisting plate 14 prior to finish processing, as shown in Fig. 6, a plasma spray layer 13 may be formed on the back face of metallic substrate 11 opposite to the side on which metallic pipes 12 are mounted, in order to alleviate such warping. The warping due to plasma spraying can thereby be alleviated. Next, Fig. 7 is a process diagram showing a third embodiment of this invention. This third embodiment is the same as the first embodiment in that Mo is employed as the metallic substrate 11 and in that cooling pipes 12 are mounted by plasma spraying on the front face of metallic substrate 11. However, it differs from the first embodiment in that cooling pipes 12 are also mounted by plasma spraying on the back face of metallic substrate 11. That is, cooling pipes 12 are mounted by plasma spraying on both faces of metallic substrate 11. In the same way as in the first embodiment, a plate-shaped metallic substrate 11 is prepared as shown in Fig. 7A and cooling pipes 12 are arranged on the front face of metallic substrate 11 as shown in Fig. 7B. These cooling pipes 12 are then mounted by plasma spraying as sown in Fig. 7C. Then, as shown in Fig. 7D, cooling pipes 12 are arranged also on the rear face of metallic substrate 11 and, as shown in Fig. 7E, these cooling pipes 12 arranged on the rear face of metallic substrate 11 are also mounted by plasma spraying. After this, finish processing is performed. It is not necessarily essential for the number of cooling pipes 12 arranged on the back face to be identical with the number of cooling pipes 12 mounted on the front face, but it is preferable that they should be the same number. As in the case of the first embodiment, in the arrangement of cooling pipes 12, the face of cooling pipes 12 contacting metallic substrate 11 may be attached by low temperature brazing. The same material is used for both the metallic substrate 11 and plasma spray layer 13 e.g. Mo. Fig. 8 is a perspective view of a heat-resisting plate 14 obtained in this way. The heat-resisting plate 14 shown in Fig. 8 is a heat-resisting plate employed as the accelerating electrode of an accelerator. A plurality of through-holes 17 are therefore provided in this heat-resisting plate 14 to permit passage of accelerated particles. In cases where it is not necessary to permit passage of accelerated particles, there is no need to provide through-holes 17 in heat-resisting plate 14. With this third embodiment, the amount of warping of heat-resisting plate 14 prior to finish processing can be reduced, owing to the mounting of cooling pipes 12 on both faces of metallic substrate 11. In particular, if the same number of cooling pipes 12 is arranged on both faces, and the thickness of plasma spray layer 13 is the same, warping of heat-resisting plate 14 prior to finish processing can be practically eliminated. Fig. 9 is a process chart showing a fourth embodiment of this invention. This fourth embodiment is the same as the third embodiment in that Mo is employed as metallic substrate 11 and cooling pipes 12 are mounted on both faces of metallic substrate 11 by plasma spraying. The difference from the third embodiment lies in that, in arrangement of cooling pipes 12, recesses 15 are provided for arrangement of cooling pipes 12 maintaining prescribed spacing, on both faces of metallic substrate 11. In this fourth embodiment also, like the third embodiment, a plate-shaped metallic substrate 11 is provided as shown in Fig. 9A. Then, as shown in Fig. 9B, recesses 15 are provided for arrangement of cooling pipes 12 on both faces of metallic substrate 11. As shown in Fig. 9C, cooling pipes 12 are arranged in recesses 15 on the front face of metallic substrate 11 and, as shown in Fig. 9D, cooling pipes 12 are mounted on the front face of metallic substrate 11 by plasma spraying. After this, as shown in Fig. 9E, cooling pipes 12 are arranged also in recesses 15 on the back face of metallic substrate 11, and, as shown in Fig. 9F, cooling pipes 12 arranged on the back face of metallic substrate 11 are also mounted by plasma spraying. After this, finish processing is performed. It is not essential for the number of cooling pipes 12 arranged on the back face to be the same as the number of cooling pipes 12 mounted on the front face, but it'is desirable that their number should be the same. The same material, for example, Mo, is employed as the material of metallic substrate 11 and plasma spray layer 13. Regarding the arrangement of cooling pipes 12, as in the third embodiment, if required, the joint faces where cooling pipes 12 contact metallic substrate 11 may be attached by low temperature brazing. This low temperature brazing can be as shown in Fig. 5. However, it is alternatively possible, as shown in Fig. 10, to apply a coating of brazing material 16 beforehand to the circumferential surface of cooling pipes 12. Ni can be employed as brazing material 16. Brazing material 16 thereby provides a heat stress relaxation agent between metallic substrate 11 and cooling pipes 12 and between plasma spray layer 13 and cooling pipes 12. With this fourth embodiment, in addition to the benefits of the third embodiment, mis-positioning of cooling pipes 12 when thermal spraying is performed is eliminated. Next, Fig. 11 is a flow chart showing an embodiment of the method of manufacturing the heat-resisting plate of this invention. In more detail, a method of manufacturing heat-resisting plate according to this embodiment comprises a metallic substrate preparation step S1, cooling pipe arrangement step S2, plasma spray layer formation step S3, infiltration step S4, and finish processing step S5. In metallic substrate preparation step S1, metallic substrate 11 is processed to plate shape, and positioned at a prescribed location on a production line. As this metallic substrate, Ti, Cr, Co, Ni, Cu, Fe, Zr, Nb, Mo, Ta or W, and alloys of these, can be employed. In cooling pipe arrangement step S2, a plurality of cooling pipes 12 are arranged in prescribed positions on metallic substrate 11. In the arrangement of these cooling pipes 12, if required, recesses 15 may be provided for arrangement of cooling pipes 12. Also, if required, the joint surface of cooling pipes 12 may be brazed to metallic substrate 11. The circumferential surface of cooling pipes 12 may be coated beforehand with brazing material 16. Preferably, cooling pipes 12 are arranged with equal spacing. Cooling pipes 12 may be positioned on one face or both faces of metallic substrate 11. In plasma spray forming step S3, the cooling pipes 12 are mounted on metallic substrate 11 by plasma spraying. That is, a plasma spray layer 13 is formed on metallic substrate 11 to a degree sufficient to embed cooling pipes 12 on the surface on which cooling pipes 12 are arranged. By this formation of plasma spray layer 13, cooling pipes 12 are embedded in plasma spray layer 13, thereby securely mounting cooling pipes 12 on metal substrate 11. Plasma spray layer 13 is formed by plasma spraying. The material used for plasma spray layer 13 is the same as the material of metallic substrate 11. In infiltration step S4, the infiltration material, which is a low melting point heat conductive material, is deposited on spray layer 13 by an infiltration process. The reason for performing an infiltration step is to eliminate pores 18 and/or cracks 19 formed in the interior of spray layer 13. That is, in the spray layer 13 formed by plasma spraying by thermal spray equipment 20 shown in Fig. 12, pores 18 or cracks 19 are present, and pores 18 due to poor adhesion are also present at the periphery of cooling pipes 12. Plasma spray layer 13 is therefore infiltrated with a low melting point heat conductive material in order to eliminate these pores 18 or cracks 19. For such infiltration material Cu, Ag, Pb, A1 or the like can be used. In the experiments carried out by the inventors, the density of thermal spray layer 13 obtained by plasma spraying was normally about 85% to 95% of the density of Metallic substrate 11. In other words, it contained about 5% to 15% pores 18 or cracks 19. Furthermore, on examining these pores 18 or cracks 19 by the mercury pressure method, it was found that 88% to 98% of pores 18 or cracks 19 were open pores or cracks connected to the outside. This shows that pores 18 or cracks 19 can conveniently be filled in by a subsequent step of infiltration in an infiltration material. Also it was found that, in the plasma spraying process, pores 18 are generated in the region between the cooling pipes 12 and metallic substrate 11 where the spray material cannot penetrate. These pores 18 are also open pores. Fig. 13 is a diagram showing infiltration of spray layer 13 in infiltration material. First of all, infiltration material 22 is spread on the bottom of a crucible 21 in a hydrogen atmosphere for infiltration. Then, heat-resisting plate 14 prior to finish processing is placed in crucible 21 with spray layer 13 facing downwards. Heating is then performed by a heater 23 up to a temperature sufficient to melt infiltration material 22 e.g. 1100 °C. Wettability with the molten infiltration material 22 is thereby improved, since the oxide present on the metallic substrate 11 and contained in the spray layer 13 is decomposed. Infiltration material 22 therefore penetrates into pores 18 and cracks 19 in spray layer 13 by capillary action, with the result that pores 18 and cracks 19 are filled with infiltration material 22. The strength of spray layer 13 is improved since infiltration material 22 has high ductility. In finish processing step S5, finish processing is performed in order to eliminate irregularities of the surface of spray layer 13 by removing unrequired infiltration material 22 adhering to metallic substrate 11. Irregularities are produced when infiltration is performed due to adhesion of excess infiltration material 22 to metallic substrate 11, and also in the surface of spray layer 13 that is used to mount cooling pipes 12 by plasma spraying. Finish processing is therefore performed to eliminate these. Next, Fig. 14 shows the tensile strength performance of spray layer 13. The experimental method for measurement of this tensile strength was to superimpose end-to-end two Mo mandrels 24 of diameter 45 mm and length 50 mm, forming a sprayed coating 25 of width 80 mm, thickness 2 mm on the circumferential surface around this superimposed portion, and to measure the tensile strength (Mpa) by applying respective forces F (9807 N/min) in the directions of the arrows. Fig. 14 shows the results of measurement performed five times on sprayed coating 25 respectively for the case where only a Mo sprayed coating was provided and for the case where the Mo sprayed coating was infiltrated with Cu. It can be seen that in the case where the coating was a Mo sprayed coating only, the tensile strength was lower and its variability was greater than in the case where the Mo sprayed coating was infiltrated with Cu. Fig. 15 shows a graph of the adhesion strength of spray layer 13. The experimental method of finding this adhesion strength was to prepare two Mo mandrels 24 of diameter 40 mm, length 40 mm forming a sprayed coating 25 of 0.5 mm on one of the Mo mandrels 24, and to mount the other Mo mandrel 24 on this portion using epoxy adhesive 26. The adhesive strength (Mpa) was then measured by applying respective forces F (9807 N/min) in the directions of the arrows. Fig. 15 shows the results of measurements in respect of a sprayed coating 25 performed five times, respectively for the case of Mo sprayed coating only, and for the case where a Mo sprayed coating was infiltrated with Cu. As shown in Fig. 14, the behaviour of the adhesive strength was the same as that of the tensile strength in that the adhesive strength was lower and its variability greater for a coating consisting only of Mo sprayed coating than for a coating consisting of Mo sprayed coating subjected to cu infiltration. Fig. 16 is a graph showing the thermal conductivity performance of a heat-resisting plate 14. The ordinate shows the thermal conductivity (W/m.K), while the abscissa shows the results of five measurements in each case using respectively a Mo plasma spray layer only, and a Mo plasma spray layer infiltrated with Cu. It can be seen that in the case of this thermal conductivity performance also, the performance of a heat-resisting plate with a Mo spray layer infiltrated with Cu is raised, and variability of the performance is reduced. Next, Fig. 17 is a graph showing the warping performance of a metallic substrate 11 formed with a plasma spray layer 13. Specifically, Fig. 17 shows the warp performance of heat-resisting plate 14 when provided with various different spray layers 13 on a metallic substrate 11 of thickness 4 mm, size 300 mm x 300 mm. The central area of heat-resisting plate 14 was taken as the reference position, and the height of the edge portions of heat-resisting plate 14 relative to this reference position was measured; this is the deformation amount. The deformation amount (mm) is shown along the ordinate, while the distance from the reference position at the centre of heat-resisting plate 14 is shown along the abscissa. Characteristic curve C1 is the characteristic curve for an embodiment in which cooling pipes 12 are mounted by plasma spray layer 13 on one face of metallic substrate 11, as shown in Fig. 1 or Fig. 4. Characteristic curve C2 is a characteristic curve for an embodiment in which cooling pipes 12 are mounted by thermal spray layer 13 on one face of metallic substrate 11, as shown in Fig. 3 or Fig. 6, and a plasma spray layer 13 of half the thickness of the plasma spray layer 13 on the front face is formed on the back face. Characteristic curve C3 is the characteristic curve of an embodiment in which cooling pipes 12 are mounted by plasma spray layer 13 on one face of metallic substrate 11, as shown in Fig. 3 or Fig. 6, and a plasma spray layer 13 of the same thickness as the thermal spray layer 13 on the front face is formed on the back face. Characteristic curve C4 is the characteristic curve of an embodiment in which cooling pipes 12 are mounted by spray layer 13 on both faces of metallic substrate 11 as shown in Fig. 7 or Fig. 9. As can be seen from these characteristic curves, in order to perform without difficulty finish processing to eliminate warp generated in heat-resisting plate 14, it is desirable to provide a spray layer on the back face when cooling pipes 12 are mounted by spray layer 13 on one face only of metallic substrate 11, or to mount cooling pipes 12 by spray layer 13 on both faces of metallic substrate 11. Fig. 18 is a graph showing the heat-resisting cycle performance of a heat-resisting plate 14. H1 is the performance of a heat-resisting plate 14A wherein cooling pipes 121 are mounted by spray layer 13 on both faces of metallic substrate 11. H2 is the performance of heat-resisting plate 14B wherein the circumferential surfaces of cooling pipes 12 are precoated with Ni as a brazing material, and such cooling pipes 12 are mounted on both faces of metallic substrate 11 by spray layer 13. H3 is the performance of a heat-resisting plate 14C wherein the circumferential surfaces of cooling pipes 12 are coated beforehand with Ni as a brazing material, these cooling pipes 12 are mounted on both faces of metallic substrate 11 by means of plasma spray layer 13, and wherein through-holes 17 are provided in metallic substrate 11. The heat-resisting cycle test is performed by intermittently heating the upper faces of these heat-resisting plates 14a, 14b and 14c in a condition with cooling water flowing in cooling pipes 12 of these heat-resisting plates 14a, 14b and 14c. Specifically, the temperature of the front faces of heat-resisting plates 14a, 14b and 14c is raised to the prescribed temperature, when this is reached, heating is stopped, and heating is again performed when the temperature has reached the value which it had when heating was commenced. This heating and cessation of heating are carried out repetitively in sequence. The number of times of heating until leakage occurs of the cooling water flowing through cooling pipes 12 is determined. Tests were performed with prescribed temperatures of 300 °C, 600 °C and 900 °C. The result was that although heat-resisting plate 14A could withstand four heating cycles at 300 °C, in the case of heating to 600 °C and 900 °C, cooling pipes 12 showed cracks after a single cycle, resulting in leakage of cooling water. Heat-resisting plate 14B showed no leakage of cooling water for ten heating cycles at 300 °C, and was able to withstand five cycles at 600 °C and three heating cycles at 900 °C. Heat-resisting plate 14C showed no leakage of cooling water for ten heating cycles at 300 °C and 600 °C, and was able to withstand seven cycles at 900 °C. As can be seen from these characteristics, the heat-resisting cycle performance was improved by performing coating with the brazing material Ni on the circumferential surface of cooling pipes 12 of heat resisting plate 14. Also, the heat-resisting cycle performance of heat-resisting plate 14 provided with through-holes 17 was even further improved. However, heat-resisting plates 14 provided with through-holes 17 in metallic substrate 11 are restricted to applications which require through-holes 17 e.g. for use as the electrode of an accelerator. As described above, according to this invention, the cooling pipes are mounted by plasma spraying on to the metallic substrate, so the cooling pipes can be mounted comparatively easily on to the metallic substrate. Specifically, there is no possibility of cracks being generated in the vicinity of the mounting joint interface, nor of the cooling pipes being melted. Also, since good adhesion can be obtained between the cooling pipes and the plasma sprayed layer, large heat-resisting plates can be manufactured. Furthermore, since the cooling water flows through cooling pipes which are separate from the metallic substrate, heat-resisting plates of excellent corrosion resistance to cooling water can be obtained.

Claims: Heat-resisting plate (14) having a cooling structure for use in a high temperature region of equipment exposed to high temperature, the plate comprising: a plate-shape metallic substrate (11) of pre-determined thickness, said metallic substrate consisting essentially of a metal from the following elements Ti, Cr, Co, Ni, Cu, Fe, Zr, Nb, Mo, Ta, and W, and alloys of two or more of such elements, spaced apart cooling pipes (12) provided on at least one face of said metallic substrate, through which cooling water can flow, and a plasma sprayed layer (13) formed on the face of said metallic substrate where said cooling pipes are arranged, said layer (13) being of the same material as the arranged, said layer being of the same material as the material of said metallic substrate, and which is effective to embed said cooling pipes. Heat-resisting plate according to claim 1 wherein spaced recesses (15) are provided on at least one side of said metallic substrate (11), said cooling pipes (12) being located in said recesses. Heat-resisting plate according to either preceding claim wherein an additional layer (13) of said material is provided on that face of said metallic substrate which is at the back of said one face. Heat-resisting plate according to any preceding claim including cooling pipes (12) arranged on a front face and also on a back face of said metallic substrate (11), said layer (13) being provided on both faces of said substrate. Heat-resisting plate according to claim 4 wherein spaced recesses (15) are provided on both the front and back faces of said metallic substrate, the cooling pipes (12) located respectively in said recesses. Heat-resisting plate according to claim 4 or 5 wherein the number of said cooling pipes (12) on the said one face of said metallic substrate (11) is the same as the number of cooling pipes on the back face thereof. Method of making a heat-resisting plate (14) having a cooling structure provided with cooling passages through the interior and through which cooling water can flow, whereby it can cool itself, and which plate is useful in a high temperature region of equipment exposed to high temperature, which method comprises the following steps: a substrate preparation step wherein a metallic substrate (11) consisting essentially of a metal from the following elements: Ti, Cr, Co, Ni, Cu, Fe, Zr, Nb, Mo, Ta, W and an alloy of two or more said elements is provided in or formed to the shape of a plate of predetermined thickness; a cooling pipe arrangement step wherein cooling pipes (12) are arranged at spaced locations on one face of said metallic substrate (11); a plasma sprayed layer (13) formation step wherein a layer of the same material as the metallic substrate is plasma sprayed on said one face such as to embed said cooling pipes; and a finish processing step to reduce any irregularity and/or warping in the surface of the sprayed layer. Method according to claim 7, wherein during the substrate preparation step, recesses (15) for receiving cooling pipes (12) are formed at spaced locations on the substrate (11). Method according to claim 7 or 8, wherein during the cooling pipe arrangement step, said cooling pipes (12) are mounted on said metallic substrate (11) by low-temperature brazing after said cooling pipes have been arranged in prescribed locations on said metallic substrate. Method according to any one of claims 7 to 9, wherein a coating (16) of brazing material is applied to the circumferential surfaces of the cooling pipes. Method as claimed in any one of claims 7 to 10, further including an infiltration step after plasma spraying comprising insertion of the layered substrate into a crucible containing infiltration material whereby said plasma sprayed layer (13) contacts said infiltration material such that infiltration material infiltrates into said layer by heating in a suitable atmosphere; said finish processing step reducing any irregularity and/or warping of the surface of said layer that has been infiltrated with said infiltration material. Method as claimed in claim 11, wherein the infiltration material comprises one or more of: copper, lead, silver or aluminium.

Inventors: ISHIWATA YUTAKA, ITOH YOSHIYASU, TAMURA MASATAKA, ISHIWATA, YUTAKA, ITOH, YOSHIYASU., TAMURA, MASATAKA, Ishiwata, Yutaka, c/o Intellectual Property Div., ITOH, YOSHIYASU, C/O INTELLECTUAL PROPERTY DIV., Tamura, Masataka, c/o Intellectual Property Div.
Applicants: TOSHIBA KK, KABUSHIKI KAISHA TOSHIBA
Application year: 1992
Main classification: G21B1
IPC codes: H05H7, F28F13, G21B1