JP4492503B2 - Surface treatment method - Google Patents

Description

  The present invention relates to a surface treatment method for forming a coating layer on a surface of a member in order to improve corrosion resistance and wear resistance.

  In order to improve the corrosion resistance and wear resistance of the member, surface treatment techniques for forming a coating layer on the surface of the member include thermal spraying, plasma powder overlaying (hereinafter referred to as “PTA method”), chemical vapor deposition (hereinafter referred to as “ "CVD method").

  In the thermal spraying method, the material powder for forming the coating layer is put into a heat source such as a plasma jet or a combustion flame, and in the PTA method, it is melted and accelerated in the heat source and sprayed onto the surface of the member to be treated. Form a layer. In such a thermal spraying method or PTA method, it is possible to form a relatively thick coating layer with a material having a relatively high melting point. However, voids inside the coating layer due to deposition of material powder, peeling due to the difference in thermal expansion between the coating layer and the member to be processed, and thermal deformation due to heat input to the member to be processed when forming the coating layer There are problems such as dust collection due to low adhesion efficiency.

  On the other hand, the CVD method evaporates a material for forming a coating layer in a vacuum, and deposits the evaporated material on the surface of a member to be processed. With such a CVD method, it is possible to form a coating layer made of a relatively dense and thin film. However, since it is necessary to process the member to be processed in the vacuum chamber, there are problems such as inability to perform on-site construction and relatively low adhesion between the coating layer and the member to be processed.

  As a method for solving these problems, surface treatment is performed by melting the electrode by discharge generated when a voltage is applied between the electrode and the member to be treated, and forming a coating layer on the surface of the member to be treated by the melted electrode component. There is a technique (for example, see Patent Documents 1-5).

  In Patent Document 1, a voltage is applied between an electrode disposed at a predetermined interval and a member to be processed in a state of being immersed in a processing liquid made of deionized water to which a nonionic surfactant is added. It is disclosed that discharging is performed by doing so. By depositing the electrode component melted by the discharge on the surface of the member to be processed, a relatively dense coating layer can be formed, and voids inside the coating layer can be reduced. In addition, the thickness of the coating layer to be formed can be adjusted by changing the output of the applied voltage. Patent Document 2 discloses that a discharge is performed by applying a voltage between an electrode and a member to be processed while blowing a working fluid toward the discharge space.

  However, in the methods such as Patent Documents 1 and 2, it is necessary to perform the treatment while the electrode and the member to be treated are immersed in the machining liquid or while the machining liquid is blown toward the discharge space. The treatment cannot be performed in medium or pure water.

  On the other hand, in the surface treatment technique as proposed in Patent Documents 3-5, the coating layer can be formed without using a working fluid. Patent Document 3 discloses that a discharge is generated by forming a space between an electrode and a member to be processed (that is, a space where discharge is performed) in an inert gas atmosphere to form a coating layer. Moreover, in patent document 4, using an electrode which has a base metal element as a main component, and applying a voltage between an electrode and a to-be-processed member, a discharge can be generated in an air atmosphere and a coating layer can be formed. It is disclosed. On the other hand, in Patent Document 5, a coating layer is formed from the dissolved electrode component by applying a voltage between the electrode and the member to be processed in a state where the tip of the electrode is in contact with the member to be processed. Is disclosed.

JP 2000-256875 A (page 3-5, FIG. 1) WO99 / 44780 (6th page, Fig. 3) JP-A-9-108834 (page 3-4, FIG. 1) Japanese Patent Laying-Open No. 2003-194988 (page 3-5, FIG. 1) Japanese Unexamined Patent Publication No. 2003-1478 (page 4, FIG. 1)

  In a surface treatment technique in which an electrode is dissolved by discharge to form a coating layer with an electrode component, heat is generated in a member to be treated by performing the surface treatment. When the amount of heat input to the member to be processed is increased, there is a case where thermal deformation or a change in the structure forming the member is caused, and further, the member that has been irradiated with radiation may be cracked. For this reason, in the surface treatment technology for forming the coating layer by conventional discharge as proposed in Patent Documents 3-5, the amount of heat input to the member to be treated depends on the discharge time, the pulse width of the pulse to be applied, and the like. Control is disclosed.

However, as in the conventional surface treatment technology for forming a coating layer by electric discharge, the amount of heat input can be controlled only by controlling the amount of heat input by the discharge time, the pulse width of the applied pulse, the energization interval, etc. It is difficult to suppress the influence of Moreover, even if the influence of the heat input on the member to be processed can be suppressed, the required performance (such as the erosion resistance of the member to be processed and the hardness of the coating layer cross section, which is an index of wear resistance and erosion resistance) It may not be possible to obtain a coating layer having For example, in Patent Document 3 or the like, there is a possibility that voids and cracks due to oxygen contamination remain, and the coating layer thickness is as thin as several μm, and a coating layer having the required performance cannot be obtained. There is. Accordingly, there is a need for a surface treatment technique that can form a coating layer having the required performance while suppressing the influence of heat input on the member to be treated.

  The subject of this invention is providing the surface treatment method which can form the coating layer which has sufficient erosion resistance, suppressing the influence to the to-be-processed member by heat input.

In order to solve the above problems, the surface treatment method of the present invention is to apply a voltage between a member to be treated and the electrode to generate a pulse discharge to melt the electrode, and melt the electrode component on the surface of the member to be treated. A surface treatment method for forming a coating layer, wherein the voltage applied to the electrode is 300 V to 1000 V, the pulse frequency is 500 Hz to 1000 Hz, the pulse width is 50 μm to 100 μm, and the coating layer is formed. The scanning speed of the electrode moving on the surface of the member to be processed is 500 mm / min or more and 2000 mm / min or less , and the electrode is discharged in a state where the electrode is held at a position where the distance between the electrode and the member to be processed is 50 μm or more and 300 μm or less. The difference between the thermal expansion coefficient and the thermal expansion coefficient of the member to be treated is within ± 20% .

  According to the surface treatment method of the present invention, it is possible to form a coating layer having sufficient erosion resistance while suppressing the influence of heat input on the member to be treated.

The inventor applied the voltage between the conductive member to be processed and the electrode to generate a pulse discharge to form a coating layer of the electrode component on the surface of the member to be processed. investigated. In particular, the construction conditions for forming a coating layer having sufficient erosion resistance while suppressing the influence of heat input on the member to be treated were examined, and the examination results are shown below. The distance between the electrode and the member to be processed is referred to as standoff. The voltage means the maximum value of the pulse voltage applied to the electrode.

  From the results of investigation by the inventor, it is desirable that the voltage of the applied pulse is 300 V to 1000 V, the pulse frequency is 500 Hz to 1000 Hz, the pulse width is 50 μm to 100 μm, and the standoff is 50 μm to 300 μm. all right.

If the applied pulse voltage is less than 300V, the pulse frequency is less than 500Hz, the pulse width is less than 50μm, or the standoff is less than 50μm, non-contact discharge is performed. I can't. On the other hand, when the applied pulse voltage is greater than 1000 V, the pulse frequency is greater than 1000 Hz, or the pulse width is greater than 100 μm, the discharge is not a pulse but a continuous discharge, that is, an arc discharge. End up. In addition, when the standoff is larger than 300 μm, the discharge cannot be performed when the pulse voltage is in the range of 300V to 1000V.

  Furthermore, the inventor studied the operation speed of the electrode and obtained new knowledge. That is, it was found that the scanning speed of the electrode is preferably 500 mm / min or more and 2000 mm / min or less.

If the scanning speed is slower than 500 mm / min, the amount of heat input to the member to be processed becomes large and deformation occurs. On the other hand, if the scanning speed is faster than 2000 mm / min, unevenness occurs in the formation of the coating layer. That is, it was confirmed that the influence of heat input to the member to be processed can be sufficiently suppressed by setting the scanning speed to 500 mm / min or more. Moreover, it was confirmed that the occurrence of unevenness in the formation of the coating layer can be suppressed by setting the operation speed to a scanning speed of 2000 mm / min or less. Here, when unevenness occurs in the formation of the coating layer, the surface roughness of the coating layer (unevenness on the surface of the coating layer) increases. When the surface roughness is large, the valley portion of the coating layer becomes thin. The coating layer formed by the surface treatment technique applied in the present invention includes a mixed layer with the member to be processed, but this mixed layer is easily eroded, and when the mixed layer is exposed directly from the valley of the coating layer, Erosion progresses locally. Accordingly, the surface roughness of the coating layer is preferably small. By controlling the operation speed to 2000 mm / min or less, it is possible to suppress the occurrence of unevenness in the formation of the coating layer, so that the surface roughness of the coating layer can be made sufficiently small, and direct mixing is also performed in the valley portion of the coating layer. The layer is not exposed. Therefore, when the pulse discharge is generated between the member to be processed and the electrode component coating layer is formed on the surface of the member to be processed, the electrode scanning speed is set to 500 mm / min or more and 2000 mm / min or less. Thus, it is possible to form a coating layer having sufficient erosion resistance while suppressing the influence of heat input on the member to be processed.

  In addition, it turned out that it is desirable that the flow volume of the inert gas to eject is 20 L / min or more and 100 L / min or less.

  If the flow rate of the inert gas to be ejected is less than 20 L / min, the surrounding atmosphere is caught in the portion where the coating layer is formed, and the coating layer is oxidized. On the other hand, if the flow rate of the inert gas to be ejected is higher than 100 L / min, the temperature of the surface portion of the member to be treated that forms the coating layer is lowered, causing opening cracks.

  In the surface treatment technique in which the electrode is dissolved by discharge and the coating layer is formed with the dissolved electrode component, heat is generated in the member to be treated by performing the surface treatment. When the amount of heat input to the member to be processed becomes large, there is a case where an influence such as a thermal deformation or a change in the structure forming the member or a crack in the member irradiated with radiation may occur. For this reason, it is desirable to form the coating layer with an amount of heat input to the member to be processed being 1 KJ / cm or less.

  Moreover, in order to improve the corrosion resistance and wear resistance of the member to be processed, it is necessary to set the strength and thickness of the coating layer to desired values. Specifically, it is desirable that the Vickers hardness is 400 Hv or more and the thickness is 5 μm or more and 500 μm or less. In order to set the Vickers hardness of the coating layer to 400 Hv or higher, an electrode formed of a material having a Vickers hardness of 400 Hv or higher can be used.

  Since the coating layer was formed under the conditions satisfying these construction conditions, the test results are shown below. Table 1 shows each construction condition. Table 2 shows the characteristics of the coating layer formed under these construction conditions. In addition, the hardness of the coating layer shown in Table 2 is an average value obtained by measuring any 10 locations in the cross section of the coating layer using a micro Vickers hardness tester. The thickness of a coating layer is the average value which measured arbitrary 10 places from the cross-sectional image of a coating layer. The amount of heat input to the member to be processed was calculated by the product of the voltage E of the pulse applied to the electrode, the current I, the pulse width τ, the frequency f and the reciprocal of the scanning speed V, that is, the amount of heat input = EIτf / V.

From the above test results, by setting the scanning speed of the electrode to 500 mm / min or more and 2000 mm / min or less, the surface roughness can be made sufficiently small 10 μm, and the opening crack width is 1
It can be set to μm or less (PT detection or less). That is, it is possible to form a coating layer having sufficient erosion resistance while suppressing the influence of the heat input on the member to be processed.

  Furthermore, by applying the above-mentioned construction conditions, a coating layer having a Vickers hardness of 400 Hv or more, an internal porosity of 5% by volume or less, and a thickness of 5 μm or more and 500 μm or less has a heat input to the member to be processed of 1 KJ / It can be formed below cm. Therefore, it is possible to form a coating layer having sufficient corrosion resistance and wear resistance while suppressing the influence of the heat input on the member to be processed.

In addition, the inventor verified the influence of the distance (standoff) between the electrode that governs the characteristics of the coating layer and the member to be processed on the transition mode in the surface treatment technique of the present invention. The verification results are shown below. FIG. 1 is a diagram illustrating a result of verifying an influence of a standoff on a transition form. As shown in FIG. 1, when the standoff is 0 and the electrode and the member to be processed are in contact with each other, a short circuit occurs, so that (1) contact is transferred. When the standoff increases, (2) discharge is impossible until a voltage that can break the insulation between the electrode and the site to be processed (hereinafter referred to as “critical voltage value”) is reached. The critical voltage value varies depending on conditions such as the electrode, the site to be treated, and the inert gas, but is about 300 V in practical use. When a voltage of 300 V is applied to the electrodes, discharge can be performed while maintaining the standoff at about 50 μm, and (3) non-contact transition is performed. In addition, the standoff which can be discharged increases with the increase in voltage. The material droplet melted from the electrode becomes a vapor, moves through the non-contact space, and is deposited on the surface of the coating layer. However, it is necessary to suppress the heat input to 1 KJ / cm or less so as not to cause thermal deformation or deterioration of the material to be processed. Since the amount of heat input increases with the voltage value, the acceptable voltage value is about 1000V.

Furthermore, the inventor considers the relationship between the voltage and the standoff, and regarding the coating layer formed by appropriately selecting the electrode, the holding mechanism, and the member to be processed, the construction conditions, the opening defect, and the surface roughness. And the relationship with the erosion weight. The results will be described below. Here, the construction conditions are the ratio of the thermal expansion coefficient between the electrode and the member to be processed, the voltage, and the standoff. Voltage and standoff are factors that determine the transition pattern. The opening defect means a crack having a width of 1 μm or more that can be detected by a penetrant flaw detection test on the surface of the coating layer. The surface roughness means the unevenness on the surface of the coating layer, that is, the height difference between the valley and the mountain. The erosion weight refers to a weight at which the coating layer is eroded by spraying high pressure jet water on the coating layer. The formed coating layer preferably has no opening defect. It is desirable that the surface roughness and erosion weight are small.

The measurement results are shown in Table 3 and FIG. FIG. 2 is a diagram showing the measurement results of the surface roughness of the coating layer formed by the surface treatment technique. Moreover, Table 3 has shown the construction conditions of test number (1)-(3) in FIG. 2, (1)-(3) in Table 3 is test number (1)-in FIG.
Correspond to the construction conditions of (3).

  Comparing the construction conditions (1) and (2), it can be seen that opening cracks can be eliminated by setting the ratio of the thermal expansion coefficient within 20%, and as a result, the erosion weight is reduced by 50%. In the process of forming the coating layer, an opening crack may occur due to a difference in thermal expansion between the coating layer and the member to be processed. In the case of the thermal spraying method, if the crack is formed at the boundary between the coating layer and the member to be processed, the coating layer may fall off. Therefore, in order to alleviate thermal strain, measures are taken to insert an intermediate layer between the coating layer and the member to be processed. However, in the case of the surface treatment technology applied in the present invention, this method cannot be handled because the thickness is thin and the mixing ratio of the members to be treated is high. Therefore, setting the ratio of the thermal expansion coefficient within 20% is an effective measure for suppressing opening cracks. Moreover, erosion progresses from the opening crack of the surface of a coating layer, and drops the inside of a coating layer. Therefore, erosion can be suppressed by suppressing opening cracks.

  In addition, when the construction conditions (2) and (3) are compared, the surface roughness is within 10 μm by setting the voltage to 300 V above the critical value and the standoff to 100 μm. As a result, the erosion weight is further increased. It can be seen that it decreases by 50%. The coating layer is formed in a non-contact transition by applying a voltage higher than the critical value and taking a standoff. This reduces the surface roughness as shown in FIG. When the surface roughness is large, the valley portion becomes thin. The coating layer formed by the surface treatment technique applied in the present invention includes a mixed layer with the member to be treated. This mixed layer is a portion that is easily eroded. Therefore, the mixed layer is exposed directly from the valley portion of the coating layer, and erosion proceeds locally from here. However, when the surface roughness is 10 μm or less, the coating layer is thick even in the valley, and the mixed layer is not directly exposed. Thereby, erosion can be suppressed. That is, it is considered that forming the coating layer under the construction condition (3) is a desirable condition for suppressing erosion.

  A first embodiment of the present invention will be described with reference to FIGS. In this embodiment, a coating layer is formed on a steam turbine blade which is a member to be processed.

First, the surface treatment apparatus 1 used in the present invention will be described. FIG. 3 is a schematic configuration diagram of the surface treatment apparatus of the present embodiment. FIG. 4 is an enlarged view of a torch portion of the surface treatment apparatus of FIG. The surface treatment apparatus 1 supports a torch 5 to which an electrode 3 is attached, a torch 5 and a scanning arm 7 for moving the torch 5 to perform a scanning operation, a scanning arm driving mechanism 9 for driving the scanning arm 7, and the like. Is provided. Furthermore, the surface treatment apparatus 1 is used for rotating the first power supply 13, the scanning arm drive mechanism 9, and the electrode 3 that are voltage application means for applying a voltage between the electrode 3 and the member 11 to be processed. A second power source 15 for supplying power to the electrode rotating mechanism provided in the torch 5, a gas cylinder 17 for supplying an inert gas injected from the torch 5 around the power source 3, and the like are also provided.

  The electrode 3 is dissolved from the tip end side by discharge with the member to be processed 11, and a coating layer is formed on the surface of the member to be processed 11 by the dissolved components of the electrode 3. Electrode 3 is an iron alloy including stainless steel and high chromium steel, a nickel alloy including inconel, a zirconium alloy including zirconium, a titanium alloy including titanium, an aluminum alloy including aluminum, a magnesium alloy including magnesium, and a manganese alloy including manganese. , A molybdenum alloy containing molybdenum, and a cobalt alloy alloy material containing cobalt. The electrode 3 can also be formed of a metal carbide material containing tungsten carbide, chromium carbide, or titanium carbide. Further, it can be formed by a mixture of these alloy materials, a mixture of metal carbide materials, a mixture of alloy materials and metal carbide materials, or the like.

The torch 5 supports the electrode 3 in a state where the electrode 3 and the first power supply 13 are electrically connected via the power cable 19. A cover 23 is attached to the torch 5 so as to protrude from the torch 5 and surround the electrode 3. The cover 23 has a tapered shape in which the diameter gradually increases toward the tip of the electrode 3 (that is, the opening of the cover 23). Further, the torch 5 is connected to the gas cylinder 17 via the gas pipe 21. The inert gas supplied from the gas cylinder 17 passes through the gas pipe 21 and the gas flow path formed in the torch 5 from the space in the cover 23 (that is, around the electrode 3) to the surface of the member 11 to be processed. Erupted toward the. 3 and 4, the cover 23 is shown in cross section.

  The torch 5 has a non-contact distance between the electrode 3 and the member 11 to be processed, and an electrode rotation mechanism (not shown) that rotates the electrode 3 with the central axis along the extending direction of the rod-shaped electrode 3 as a rotation axis. An electrode holding mechanism for holding a state in which discharge occurs. Driving means such as a motor and an actuator included in the electrode rotation mechanism are each electrically connected to the second power supply 15 via the power cable 27.

  The electrode holding mechanism will be described with reference to FIGS. FIG. 5 is a cross-sectional view of an electrode holding mechanism in which a mechanism for holding the distance between the electrode and the member to be processed in a non-contact and dischargeable state is incorporated in the torch portion. FIG. 6 is a diagram schematically illustrating the behavior of the cover according to the shape of the member to be processed. The torch 5 is formed in a cylindrical shape whose one end is closed by a cover 23, and an elastic member is provided on the end surface of the cover 23 to prevent the inert gas 25 from flowing out. A gas pipe 21 is inserted through the cap 29, and the gas pipe 21 communicates with the space in the torch 5. Even if the member to be processed 11 is not a flat surface but a three-dimensional complicated shape, the formation of a gap between the cover 23 and the member to be processed 11 can be suppressed by the expansion and contraction of the packing 35 as shown in FIG. A power cable 19 is also inserted through the cap 29, and the power cable 19 is electrically connected to the electrode 3. A power cable 27 is electrically connected to an actuator (not shown) that rotates the cam 31. In the conventional surface treatment technology for forming a coating layer by electric discharge, the coating layer is formed by bringing the electrode and the member to be processed into contact with each other, but it has been difficult to obtain a smooth coating layer. In particular, since blades such as turbines and pumps have a three-dimensional curved surface, more precision is required to scan the electrode 3 while maintaining contact. On the other hand, in the surface treatment apparatus of the present invention, the electrode can be scanned without contact by the electrode holding mechanism, so that a smooth coating layer can be obtained even with a turbine having a three-dimensional aspect.

  The opening 37 of the torch 5 is a tapered nozzle whose diameter gradually decreases toward the opening, and the electrode 3 protrudes from the center of the opening. Thereby, when the inert gas is supplied from the gas cylinder 17, the inert gas 25 is jetted from the periphery of the electrode 3 toward the surface of the member to be processed 11, and this inert gas 25 is applied to the surface of the member to be processed 11. Oxidation of the coating layer 18 to be formed is suppressed.

  The scanning arm 7 is formed of a rod-like member having a torch 5 fixed at one end and the other end fixed to a scanning arm drive mechanism 9. The scanning arm drive mechanism 9 is composed of a manipulator-like device having a plurality of joints, slide mechanisms, and the like, and positioning operation of the torch 5 and scanning operation for moving the torch 5 in a desired direction along the surface of the processing target member 11. Etc.

  Two power cables 19 are connected to the first power supply 13, and one power cable 19 is electrically connected to the electrode 3 and the other power cable 19 is electrically connected to the member 11 to be processed. The first power supply 13 can apply a pulse when applying a voltage between the electrode 3 and the member 11 to be processed, and can adjust the frequency and width of the pulse in addition to the adjustment of the voltage. It is desirable that the first power supply 13 and the second power supply 15 have a function of displaying information such as values and frequencies related to the power to be supplied.

  Hereinafter, with reference to FIG. 7, a description will be given of a work procedure when performing surface treatment (that is, formation of the coating layer 18) on the steam turbine blade that is the member to be processed 11. FIG. 7 is a flowchart showing a procedure of surface treatment work when the surface treatment technique of the present invention is applied to a steam turbine blade. In the present embodiment, the coating layer 18 is formed in the plant for the steam turbine blade in use in the plant or the like.

  First, when an order to start repair work is given (step 101), the operation of the plant is stopped (step 102), and the container in which the steam turbine blade as the member to be treated 11 is stored is opened (step 103). . After step 103, data is acquired from the damage database 39 containing damage data acquired at the time of inspection or the like, and the damage state of the repaired portion 41 is grasped (step 104).

  After step 104, equipment necessary for the surface treatment such as the surface treatment apparatus 1 is installed (step 105). Thereafter, the construction data (for example, the scanning speed necessary for forming the coating layer 18 having the required thickness and the number of times of scanning at the same location) constructed from the past results, the electrode 3 and the member 11 to be processed. Data is acquired from the construction database 43 that stores data such as the voltage, frequency, width, and interval of pulses applied to the steam turbine blade, and construction conditions are set based on the obtained data (step 106).

  After preparation is completed in step 106, the coating layer 18 is formed in order to repair the repaired portion 41 of the steam turbine blade, which is the member 11 to be processed, by the surface treatment apparatus 1 (step 107).

  Here, the operation of the surface treatment apparatus 1 in step 107 will be described. FIG. 8 is a flowchart showing the operation of the surface treatment apparatus in the first embodiment. As shown in FIG. 8, when the surface treatment apparatus 1 receives a command to start operation (coating layer formation start) (step 201), it is necessary to form the coating layer 18 having a preset required thickness. Based on the scanning speed, the number of scans at the same location, and the voltage, frequency, width, interval, etc. of the pulse applied between the electrode 3 and the steam turbine blade, During this period, a pulse is applied (step 202), and scanning of the electrode 3 is started (step 203).

  When the tip of the electrode 3 approaches the surface of the steam turbine blade due to the application of the pulse in step 202 and the distance between the surface of the steam turbine blade and the electrode 3 becomes equal to or less than the dielectric breakdown distance (step 205), the discharge condition is satisfied. Then, a discharge is generated between the steam turbine blade and the electrode 3 (step 206), and the distance between the electrode 3 and the member to be processed 11 is maintained so as to maintain the state (step 203). In this way, by discharging between the steam turbine blade that is the member to be treated 11 and the electrode 3, the tip of the electrode 3 is dissolved, and the components of the dissolved electrode 3 are the components of the steam turbine blade that is the member to be treated 11. A coating layer 18 is formed on the surface.

Further, in step 204, while performing such rotational movement of the electrode 3, the electrode 3 is scanned in the x-axis direction shown in FIG. 8 until the preset range is completed. When scanning of the scanning range in the x-axis direction (formation range of the coating layer 18) is completed (step 207), the electrode 3 is preliminarily placed in the direction in which the tip of the electrode 3 faces (that is, the y-axis direction shown in FIG. 8). Move by the set distance (step 208). Then, Step 204 to Step 208 are repeated until the formation of the coating layer 18 within a preset range in the y-axis direction is completed (Step 209).

  In step 209, when the formation of the coating layer 18 in a predetermined range in the y-axis direction is completed, the electrode 3 is moved by a predetermined distance in the thickness direction of the steam turbine blade (that is, the z-axis direction). (Step 210). Thereafter, steps 204 to 210 are repeated until the formation of the coating layer 18 up to a preset range in the z-axis direction is completed (that is, until the formation of the coating layer 18 having a preset thickness is completed). Then, scanning in the x-axis direction, movement in the y-axis direction, and further movement in the z-axis direction are performed (step 211). When the range in the z-axis direction ends in step 211, the entire preset range has been scanned, so that the application of pulses and the scanning of the electrode 3 in the x-axis direction are stopped (steps 212, 213 and 214). ) And the formation of the coating layer 18 is completed (step 215). As described above, the work of Step 107 is performed through Steps 201 to 215.

Here, the coating layer forming operation (step 107) is performed under the above-described construction conditions. That is, the voltage of the applied pulse is 300 V to 1000 V, the pulse frequency is 500 Hz to 1000 Hz, the pulse width is 50 μm to 100 μm, and the standoff is 50 μm to 300 μm. Also, the scanning speed of the electrode is 500 mm / min or more and 2000
Not more than mm / min. By carrying out the construction under such construction conditions, it is possible to form a coating layer having sufficient erosion resistance while suppressing the influence of the heat input on the member to be processed. More preferably, the applied pulse voltage is 400 V, the pulse frequency is 500 Hz, the pulse width is 100 μm, and the operation speed of the electrode is 1000 mm / min.

  The standoff is 50 μm or more and 300 μm or less. By setting it as such construction conditions, appropriate discharge can be performed. More preferably, the standoff is 50 μm.

  Furthermore, it is preferable to select the electrode 3 so that the difference in thermal expansion coefficient between the electrode 3 and the member to be processed 11 is within ± 20%. By using such an electrode, since the surface roughness of the coating layer can be reduced, the occurrence of opening cracks on the surface of the coating layer 18 can be suppressed. In consideration of the corrosion resistance and wear resistance of the member to be treated, when a high hardness coating layer is required, an electrode having a high hardness can be used. For example, an electrode formed of a material having a Vickers hardness of 400 Hv or more can be used.

  In step 107, the coating layer 18 is formed until a predetermined construction request (for example, the number of scans at the same location) is satisfied so that the coating layer 18 having a necessary thickness in a predetermined range is formed. If the construction request set in advance is satisfied, the operation of forming the coating layer 18 by the surface treatment apparatus 1 is finished (step 108).

  After step 108, the thickness and range of the actually formed coating layer 18 are inspected (step 109). If the proper coating layer 18 is not formed at the repair location 41 of the steam turbine blade that is the member to be processed 11, that is, if it is not properly repaired, Step 107 to Step 109 are repeated again. If the formation of the proper coating layer 18 is confirmed in step 109, the equipment such as the surface treatment apparatus 1 is removed (step 110), and the container is closed (step 111). Then, the operation of the plant is resumed (step 112), and the repair work is finished (step 113).

  According to the present embodiment, since the coating layer having sufficient erosion resistance can be formed while suppressing the influence of heat input on the member to be processed, the corrosion resistance and wear resistance due to the formation of the coating layer can be improved.

  A second embodiment of the present invention will be described with reference to FIG. In this embodiment, a coating layer is formed on an unused steam turbine blade, which is a member to be processed, in a production factory or the like. FIG. 9 is a flowchart showing a procedure of surface treatment work when the surface treatment technique of the present invention is applied to a steam turbine blade.

  The procedure for forming the coating layer in the present example is the same as the procedure for forming the coating layer in Example 1, except that steps 102, 103, 111, and 112 in the procedure for forming the coating layer in Example 1 are not performed.

  When a covering layer work start command is issued (step 101), data is acquired from the damage database 45 containing the covering data forming the covering layer 18 such as a design drawing, and the damage state of the damaged portion is grasped (step 104). .

After step 104, equipment necessary for the surface treatment such as the surface treatment apparatus 1 is installed (step 105). And data are acquired from the construction database 43 which accommodated the construction data constructed | assembled from the past results, and construction conditions are set based on the acquired data (step 106). After step 106, the surface treatment apparatus 1 forms the coating layer 18 on the steam turbine blade that is the member to be treated 11 (step 107). The formation of the coating layer 18 is performed until a predetermined construction request (for example, the number of scans at the same location) is satisfied so that the coating layer 18 having a necessary thickness is formed in a predetermined range. When the construction request is satisfied, the forming operation of the coating layer 18 by the surface treatment apparatus 1 is finished (step 108).

  In step 107, as in the first embodiment, the coating layer 18 is formed according to the above-described construction conditions (applied pulse voltage, frequency, width, standoff, electrode operation speed, etc.). By performing construction under such construction conditions, it is possible to form a coating layer having sufficient erosion resistance while suppressing the influence of heat input on the member to be treated.

  After step 108, the thickness and range of the actually formed coating layer 18 are inspected (step 109). If the appropriate coating layer 18 is not formed, steps 106 to 109 are repeated again. If the formation of the proper coating layer 18 is confirmed in step 109, the equipment such as the surface treatment apparatus 1 is removed (step 110), and the coating operation is terminated (step 113).

  According to the present embodiment, since the coating layer having sufficient erosion resistance can be formed while suppressing the influence of heat input on the member to be processed, the corrosion resistance and wear resistance due to the formation of the coating layer can be improved. In addition, since the coating layer can be formed in the atmosphere, it is also possible to repair the processed material that is actually used in facilities such as plants, which can reduce the construction cost and time required for the repair. it can.

  A third embodiment of the present invention will be described with reference to FIGS. In this embodiment, a coating layer is formed on the blades 53a of the internal pump 53 provided in the reactor pressure vessel 51 of the improved boiling water nuclear power plant. FIG. 10 is a diagram schematically showing a construction example by the surface treatment apparatus in the present embodiment. FIG. 11 is an enlarged view of a torch portion of the surface treatment apparatus in FIG.

  The scanning arm drive mechanism 9 and the scanning arm 7 of the surface treatment apparatus 1 are formed in a shape suitable for inserting the scanning arm 7 into the reactor pressure vessel 51 and bringing the torch 5 to the position of the internal pump 53. To do.

  In order to perform the surface treatment in the reactor pressure vessel 51, the construction is performed in the reactor water collected at the bottom of the reactor pressure vessel 51. At this time, since the reactor water hinders discharge, the torch 5 is provided with a cover 55 having a shape suitable for construction in water. As shown in FIG. 10, the cover 55 is formed in a tapered shape whose diameter becomes smaller toward the tip of the electrode 3. Since the distance between the inner peripheral surface of the cover 55 and the outer peripheral surface of the electrode 3 in the opening of the cover 55 is narrower than the other portions of the cover 55, the flow rate of the inert gas ejected from the cover 55 is increased. Can do. Inert gas phase space is formed between the tip of the electrode 3 and the processing portion of the blade 53a serving as the member to be processed by the inert gas ejected from the gas ejection port which is the opening of the cover 55. Therefore, the discharge can be generated by bringing the tip of the electrode 3 closer to the surface of the processing portion of the blade 53a to be equal to or less than the dielectric breakdown distance.

  As described above, the surface treatment apparatus 1 can be applied to repair of a member to be treated in various apparatuses and facilities by changing the shape of the scanning arm driving mechanism and the scanning arm. Further, by forming the shape of the cover attached to the torch into a tapered shape whose diameter becomes narrower toward the tip of the electrode 3, a coating layer is formed even in a liquid that prevents discharge, such as pure water. It becomes possible. Thus, the surface treatment technology of the present invention can be applied not only to steam turbine blades but also to various members that require improved corrosion resistance and wear resistance, such as pump blades and gas turbine blades. .

  According to the present embodiment, since the coating layer having sufficient erosion resistance can be formed while suppressing the influence of heat input on the member to be processed, the corrosion resistance and wear resistance due to the formation of the coating layer can be improved. In addition, a coating layer can be formed in a liquid that prevents discharge, such as pure water.

The figure which shows the result of having verified the influence which standoff has on a transfer form. The figure which shows the measurement result of the surface roughness of the coating layer formed by the surface treatment technique. The schematic block diagram of the surface treatment apparatus of a 1st Example. The enlarged view of the torch part of the surface treatment apparatus of a 1st Example. Sectional drawing of the electrode holding | maintenance mechanism incorporating the mechanism for hold | maintaining the distance of an electrode and a to-be-processed member in the state which can be discharged in non-contact. The figure which shows typically the behavior of the cover according to the shape of the to-be-processed member. The flowchart which shows the procedure of the surface treatment work of a 1st Example. The flowchart which shows operation | movement of the surface treatment apparatus of a 1st Example. The flowchart which shows the procedure of the surface treatment work of a 2nd Example. The figure which shows typically the construction example by the surface treatment apparatus of a 3rd Example. The enlarged view of the torch part of the surface treatment apparatus of a 3rd Example.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Surface treatment apparatus, 3 ... Electrode, 5 ... Torch, 7 ... Scanning arm, 9 ... Scanning arm drive mechanism, 11 ... To-be-processed member, 18 ... Covering layer, 23 ... Cover.

Claims (3)

A surface treatment method in which a voltage is applied between a member to be treated and an electrode to generate a pulse discharge to melt the electrode and form a coating layer of the molten electrode component on the surface of the member to be treated. ,
The voltage applied to the electrode is 300 V or more and 1000 V or less, the frequency of the pulse is 500 Hz or more and 1000 Hz or less, and the width of the pulse is 50 μm or more and 100 μm or less,
Ri der scanning speed is less 500 mm / min or more 2000 mm / min of the electrodes to move said member to be processed surface at the time of forming the coating layer,
The discharge is performed in a state where the electrode is held at a position where the distance between the electrode and the member to be processed is 50 μm or more and 300 μm or less,
The surface treatment method is characterized in that the difference in thermal expansion coefficient of the electrode from the thermal expansion coefficient of the member to be treated is within ± 20% . The surface treatment method according to claim 1, wherein an amount of heat input to the member to be treated when forming the coating layer is 1 KJ / cm or less. 3. The surface according to claim 1, wherein the voltage applied to the electrode is 400 V, the frequency of the pulse is 500 Hz, the width of the pulse is 100 μm, and the scanning speed of the electrode is 1000 mm / min. Processing method.

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