JP5881513B2 - Method for removing coating from gas turbine member - Google Patents

Description

  The present invention relates to a coating peeling method for a gas turbine member that peels a coating layer on the surface of the gas turbine member.

  The operation temperature of gas turbines is increasing year by year for the purpose of improving efficiency. In order to cope with such a high temperature, for example, a coating layer (TBC: Thermal Barrier Coating) for the purpose of heat insulation is formed on the surface of a gas turbine member exposed to a high temperature state such as a gas turbine blade or a combustor. Is formed.

  Such a coating layer is composed of an undercoat layer made of an alloy formed on the base material of the gas turbine member, and a top coat layer made of ceramics formed on the undercoat layer.

Here, when repairing the gas turbine member after operation, after the coating layer formed on the base material of the gas turbine member is peeled off, the undercoat layer and the topcoat layer are again formed on the base material. The coating layer is regenerated by forming
For example, Patent Document 1 discloses a technique for detaching a coating layer by sequentially immersing in an alkaline cleaning liquid, water, and a weakly acidic cleaning liquid, followed by heat treatment and then immersing in a strong acidic cleaning liquid.

International Publication No. 2009/101690

  By the way, even if it is a case where the peeling method of the above coating layers is applied, especially an undercoat layer is hard to peel among coating layers. Therefore, usually, a step of removing the undercoat layer by performing a physical method such as blasting after the coating peeling method is performed.

  However, if the undercoat layer remains even after blasting or the like, it is necessary to sequentially perform steps such as immersion in the cleaning liquid again on the gas turbine member, which makes the operation complicated. It had become. Moreover, when the execution place of each process differs, the loss of time is so large that it is necessary to move the member for gas turbines, and the work has become inefficient. Furthermore, when each process is again performed on the entire gas turbine member, there is a possibility of adversely affecting the base material exposed by the peeling of the coating layer.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a coating removal method for a gas turbine member that can efficiently and reliably peel the coating layer from the gas turbine member. .

In order to solve the above problems, the present invention provides the following means.
That is, in the method for removing a coating for a gas turbine member according to the present invention, a pickling process is performed in which at least a part of the coating layer on the surface of the gas turbine member is peeled off by subjecting the gas turbine member after operation to pickling. And a gel attaching step of attaching a polymer gel impregnated with an acid to the remaining coating layer after the pickling step.

According to the coating peeling method of the gas turbine member having such characteristics, when the polymer gel is attached to the coating layer remaining in the previous step, the acid impregnated in the polymer gel is left on the coating layer where the acid is impregnated. By acting, the coating layer can be removed. Therefore, the coating layer can be removed without requiring a large facility and without moving the gas turbine member.
Furthermore, since the acid can be locally supplied to the coating layer through the polymer gel, there is no possibility of adversely affecting the base material of the gas turbine member.

  Moreover, the coating peeling method of the member for gas turbines which concerns on this invention remains on the surface of the said member for gas turbines by heating the said member for gas turbines between the said pickling process and the said gel adhesion process. It is preferable to provide a heating step for changing the color of the coating layer.

When the coating layer is discolored by heating, the remaining region of the coating layer can be easily visually confirmed.
Further, by heating the gas turbine member, the reaction rate between the acid and the coating layer in the subsequent gel adhesion process can be increased. That is, in the state where the gas turbine member is heated, the acid in the polymer gel is warmed by heat transfer from the gas turbine member by attaching the polymer gel impregnated with the acid to the remaining coating layer. . As a result, the decomposition rate of the coating layer by the acid increases, so that the coating layer can be removed more efficiently.

Here, if the polymer gel impregnated with acid is directly heated, that is, it is intended to increase the acid reaction rate by separately heating the polymer gel instead of heat conduction from the gas turbine member. In such a case, the viscosity of the polymer gel is lowered by the heating, which causes acid dripping. In this case, as a result of supplying the acid not only to the coating layer but also to the base material of the gas turbine member, the base material may be adversely affected.
On the other hand, in the present invention, the polymer gel heats only the contact portion with the gas turbine member, that is, the contact portion with the remaining coating layer, by heat conduction from the gas turbine member. As a result, the melting of the polymer gel can be minimized, the reaction rate of the acid at the contact point between the acid and the coating layer can be increased, and the coating layer can be efficiently removed. It becomes possible.

  Furthermore, it is preferable that the coating peeling method of the member for gas turbines of this invention is equipped with the blast process which performs the blast process on the surface of the said member for gas turbines between the said pickling process and the said heating process.

As a result, the coating layer remaining after the pickling treatment can be physically peeled off by blast treatment.
In addition, since the surface roughness of the base material of the gas turbine member can be increased, it is possible to firmly fix the coating layer to the base material when the coating layer is regenerated.

  According to the coating peeling method for a gas turbine member of the present invention, the acid impregnated in the polymer gel acts on the remaining coating layer, thereby efficiently and reliably peeling the coating layer from the gas turbine member. Is possible.

It is a flowchart which shows the procedure of the coating peeling method of the member for gas turbines which concerns on this invention. It is sectional drawing of the surface of the member for gas turbines as a member for gas turbines. It is sectional drawing of the surface of the member for gas turbines as a member for gas turbines, Comprising: It is a figure explaining the state after giving a pickling process and a blast process. It is sectional drawing of the surface of the member for gas turbines as a member for gas turbines, Comprising: It is a figure explaining a gel adhesion process. It is a figure explaining the gel adhesion process in the coating peeling method of the member for gas turbines concerning a modification.

Hereinafter, an embodiment of a coating peeling method for a gas turbine member according to the present invention will be described in detail with reference to FIGS. 1 to 5.
The coating peeling method of this embodiment peels the coating layer 20 (see FIG. 2) formed on the surface of the gas turbine member 10 such as a gas turbine blade (gas turbine blade, gas turbine stationary blade) or combustor, for example. Is the method.

  Since the gas turbine member 10 is exposed to a high temperature environment, a coating layer (TBC) 20 for heat insulation is formed on the surface of the base material 11. The coating layer 20 includes an undercoat layer 21 formed on the base material 11 of the gas turbine member 10 and made of an alloy, and a topcoat layer 22 formed on the undercoat layer 21 and made of ceramics. ing.

  When the gas turbine member 10 is repaired after the gas turbine is operated for a predetermined time, the coating layer 20 is peeled off from the gas turbine member 10 and then the surface of the base material 11 is coated again. Regenerate layer 20. The coating peeling method of this embodiment is used to peel the coating layer 20 from the surface of the gas turbine member 10 during such repair.

  In the coating peeling method performed for such a purpose, as shown in FIG. 1, the first hot water washing process S1, the first water washing process S2, the pickling process S3, the blasting process S8, the heating process S9, the remaining confirmation process S10, The gel adhesion step S11 is performed by sequentially applying the gas turbine member 10 after operation.

  In executing the coating peeling method according to the present embodiment, the gas turbine member 10 such as a gas turbine blade or a combustor is removed from the gas turbine after an actual operation time has elapsed from, for example, 5000 hours to 40000 hours. Then, the first hot water washing process S <b> 1 is performed on the gas turbine member 10.

  In the first hot water washing treatment S1, the gas turbine member 10 is immersed in hot water by being moved by a support means (not shown). By performing the first hot water washing process S1, oil and water-soluble substances can be removed to some extent from the scales attached to the gas turbine member 10 during operation of the gas turbine. In addition, the hot water temperature in 1st hot water washing process S1 is 50 degreeC or more and 80 degrees C or less, for example, Preferably you may be about 65 degreeC.

  After this first hot water washing process S1, a first water washing process S2 is performed. In the first water washing treatment S2, the gas turbine member 10 is washed with water. As a result, the gas turbine member 10 is rapidly cooled, so that the scale is easily peeled off from the gas turbine member 10. This 1st water washing process S2 is a process which uses water as a washing | cleaning liquid, and is performed by immersing the member 10 for gas turbines in water in this embodiment. Moreover, you may perform 1st water washing process S2 by the washing | cleaning by a pressurized water flow, or the ultrasonic cleaning which used water as the medium.

  In addition, when immersing the gas turbine member 10 in water, the gas turbine member 10 is pulled up from the water during the immersion, and the internal space of the gas turbine member 10 (for example, the internal cooling medium passage of the gas turbine blade, the combustor) It is preferable to repeat the operation of immersing in water again several times after the water in the cylinder) is discharged. Thereby, the water of the internal space of the member 10 for gas turbines can be forcedly replaced. Moreover, it is preferable to perform this 1st water washing process S2, stirring water with a stirring means.

  Next, pickling process S3 is performed. This pickling process S3 is a process of peeling at least a part of the coating layer 20 on the surface of the gas turbine member 10 by mainly performing a pickling process on the gas turbine member 10. The pickling process S3 of the present embodiment is performed by sequentially performing a coating removal process S4, a neutralization cleaning process S5, a second water washing process S6, and a second hot water washing process S7.

The coating removal process S4 is performed by immersing the gas turbine member 10 in a strongly acidic cleaning solution. By thus cleaning the gas turbine member 10 with the strong acid cleaning liquid, at least a part of the coating layer 20 of the gas turbine member 10 is removed.
Moreover, it is preferable to perform coating removal process S4, stirring a strong acidic washing | cleaning liquid, for example by stirring means, such as a bubble and a propeller. Thereby, the coating removal nonuniformity of the member 10 for gas turbines can be suppressed. As the stirring means, it is particularly preferable to use a method of introducing bubbles into the strongly acidic cleaning solution. By introducing the bubbles, the effect of assisting the removal of the coating with the strongly acidic cleaning liquid can be obtained. Moreover, the usage-amount of a strong acidic washing | cleaning liquid can be reduced, ie, a washing | cleaning waste liquid can also be reduced.

  As the strongly acidic cleaning solution, a strongly acidic aqueous solution corresponding to the type of the coating layer 20 can be used. In this embodiment, for example, hydrochloric acid or hydrogen fluoride is used. Moreover, you may add an appropriate additive to a strong acidic washing | cleaning liquid.

After the coating removal process S4, a neutralization cleaning process S5 is performed. The neutralization cleaning process S5 is a step of immersing the gas turbine member 10 in an alkaline aqueous solution, and thereby, the strongly acidic cleaning liquid remaining in the gas turbine member 10 can be neutralized. As the alkali aqueous solution may be, for example, aqueous _Na 2 CO _3.

  After this neutralization washing process S5, a second water washing process S6 is performed. In this 2nd water washing process S6, the member 10 for gas turbines is wash | cleaned with water similarly to 1st water washing process S2. Thereby, the effect that it can avoid that an acidic component and an alkali component remain in the member 10 for gas turbines is acquired.

  Next, a second hot water washing process S7 is performed after the second water washing process S6. In the second hot water washing process S7, the gas turbine member 10 is immersed in hot water as in the first hot water washing process S1. Thereby, the effect that the member 10 for gas turbines can be dried at an early stage by heating the member 10 for gas turbines is acquired.

  By performing the above four processes, the pickling process is completed. Although it is preferable that the coating layer 20 of the gas turbine member 10 is completely peeled off by this pickling treatment, a part of the coating layer 20 actually remains on the surface of the gas turbine member 10.

  Blasting process S8 is performed after such a pickling process. This blast process S8 is performed by making the fluid as a projection material collide with the surface of the member 10 for gas turbines. Specifically, sand is used as the projecting material, and the sand is sprayed toward the surface of the gas turbine with compressed air (sand blasting). As a result, the coating layer 20 remaining on the surface of the gas turbine member 10 can be peeled off. Moreover, the surface roughness of the base material 11 can be increased by spraying the projection material onto the portion where the coating layer 20 has already been peeled off by the pickling treatment and the base material 11 is exposed.

In addition, as a kind of the projection material in blast process S8, a metal type granular material, a ceramic type granular material, etc. can be used suitably. Moreover, you may employ | adopt what is called wet blasting which injects an abrasive | polishing agent etc. as a projection material.
Moreover, it is preferable that the projection speed of the projection material is set to an appropriate speed so as not to damage the surface of the base material 11 more than necessary.

  A heating step S9 is performed after such a blasting step S8. In this heating step S9, the entire gas turbine member 10 is heated by, for example, a heater. As a result, the temperature of the gas turbine member 10 itself rises, and when the coating layer 20 remains on the surface of the base material 11, the coating layer 20 changes color. That is, in this heating step S9, it is preferable to heat the gas turbine member 10 to a temperature at which the coating layer 20 changes color.

  Next, a remaining confirmation step S10 is performed after the heating step S9. In the remaining confirmation step S <b> 10, whether or not the coating layer 20 remains on the surface of the gas turbine member 10 is confirmed by an operator's visual observation. When the remaining portion of the coating layer 20 is present, the coating layer 20 is discolored by the heating step S9, so that the base material 11 and the coating layer 20 can be easily distinguished.

  Then, as a result of performing the remaining confirmation step S10, when it is determined that the coating layer 20 does not remain on the surface of the gas turbine member 10, the peeling operation ends. Thereafter, the coating layer 20 is regenerated on the surface of the gas turbine member 10.

On the other hand, as a result of performing the remaining confirmation step S10, when it is determined that the coating layer 20 remains on the surface of the gas turbine member 10, the gel adhesion step S11 is performed.
That is, although it is preferable that the coating layer 20 is completely peeled off from the surface of the gas turbine member 10 by performing the pickling step S3 and the blasting step S8, the undercoat layer 21 in the coating layer 20 is difficult to peel off. Therefore, for example, as shown in FIG. 3, the undercoat layer 21 often remains on a part of the surface of the base material 11 of the gas turbine member 10. The remaining undercoat layer 21, that is, the coating layer 20, is removed by the gel adhesion step S11.

The gel attachment step S11 is a step of attaching the polymer gel 30 impregnated with the acid to the coating layer 20 remaining on the surface of the base material 11. As the polymer gel 30, for example, a highly water-absorbing polymer such as sodium polyacrylate or polyacrylic acid polymer, or a silicon-based gel capable of absorbing moisture can be used. Such a polymer gel 30 is impregnated with an acid such as hydrochloric acid or hydrogen fluoride. That is, by immersing the polymer gel 30 in a hydrochloric acid solution and a hydrogen fluoride solution, the hydrochloric acid solution and the hydrogen fluoride solution are absorbed by the polymer gel 30.
The polymer gel 30 preferably retains its adhesiveness to some extent even after being impregnated with an acid.

  As shown in FIG. 4, the polymer gel 30 impregnated with the acid is attached only to the remaining region of the coating layer 20 on the surface of the gas turbine member 10. At this time, since the polymer gel 30 adheres to the coating layer 20 due to its own adhesiveness, it does not come off from the coating layer 20 due to dropping or the like. Moreover, since the coating layer 20 can hold an acid by its high water absorption, the acid does not cause dripping.

  The polymer gel 30 is thus attached to the coating layer 20, so that the acid in the polymer gel 30 acts on the coating layer 20 through the interface between the polymer gel 30 and the coating layer 20. To do. As a result, the coating layer 20 is gradually dissolved by the acid, and as a result, the remaining coating layer 20 can be removed from the surface of the base material 11. At this time, since the gas turbine member 10 is in a high temperature state by the heating step S9, the reaction rate of the acid can be improved and the coating layer 20 can be removed more quickly. That is, this gel adhesion step S11 is preferably performed after the heating step S9, when the gas turbine member 10 is at a higher temperature than before the heating step S9.

  Then, after the gel adhesion step S <b> 11, the remaining confirmation step S <b> 10 is performed again to check whether or not the coating layer 20 remains on the surface of the gas turbine member 10. Here, when the remaining coating layer 20 is confirmed, the gel adhesion step S11 is performed again on the remaining portion. On the other hand, when the remaining of the coating layer 20 is not confirmed, the operation is terminated, and then the regeneration process of the coating layer 20 is performed.

According to the coating peeling method as described above, when the polymer gel 30 is attached to the coating layer 20 remaining in the pickling step S3 or the blasting step S8, the acid impregnated in the polymer gel 30 remains. By acting on the coating layer 20, the coating layer 20 can be removed. Therefore, the coating layer 20 can be removed without requiring a large facility and without moving the gas turbine member 10.
That is, when it is confirmed that the coating layer 20 remains, if the pickling step S3 is performed again, a time loss occurs because the gas turbine member 10 needs to be sequentially moved to a strongly acidic aqueous solution or an alkaline aqueous solution. In addition, the work becomes complicated. On the other hand, since the gel adhesion process of this embodiment can be performed with respect to the member 10 for gas turbines regardless of a place, the coating layer 20 can be removed more smoothly.

  Further, when the pickling process is performed again, a strong acidic aqueous solution or an alkaline aqueous solution acts on the base material 11 exposed by the peeling of the coating layer 20, which may adversely affect the base material 11. There is. In this regard, in this embodiment, the acid can be locally supplied to the coating layer 20 by bringing the remaining coating layer 20 into contact with the acid via the polymer gel 30. Therefore, the exposed base material 11 is not affected.

Furthermore, in this embodiment, when the coating layer 20 is discolored by heating process S9, the residual area | region of this coating layer 20 can be confirmed visually easily.
Further, by heating the gas turbine member 10 in this way, the reaction rate between the acid and the coating layer 20 in the subsequent gel adhesion step S11 can be increased. That is, in the state where the gas turbine member 10 is heated, the polymer gel 30 impregnated with the acid is attached to the remaining coating layer 20, so that heat transfer from the gas turbine member 10 causes the polymer gel 30 to pass through the polymer gel 30. The acid is warmed. As a result, the decomposition rate of the coating layer 20 by the acid increases, so that the coating layer 20 can be removed more efficiently.

  Here, if the polymer gel 30 itself impregnated with acid is directly heated, that is, the polymer gel 30 is heated instead of heat conduction from the gas turbine member 10 to increase the acid reaction rate. In such a case, the viscosity of the polymer gel 30 decreases due to the heating. When the viscosity of the polymer gel 30 is thus reduced, not only does the polymer gel 30 easily come off from the adhesion site, but also the water absorption of the polymer gel 30 is lowered, leading to acid dripping. In this case, as a result of supplying the acid not only to the coating layer 20 but also to the base material 11 of the gas turbine member 10, the base material 11 may be adversely affected.

  On the other hand, in this embodiment, the polymer gel 30 is heated only at the contact point with the gas turbine member 10, that is, the contact point with the remaining coating layer 20, due to heat conduction from the gas turbine member 10. Is done. Thereby, melting of the polymer gel 30 can be minimized, and the reaction rate of the acid at the contact point between the acid and the coating layer 20 can be increased. Therefore, the coating layer 20 can be efficiently removed.

  In addition, since the blasting process is performed in this embodiment, the coating layer 20 remaining after the pickling process can be physically peeled off by the blasting process. In addition, since the surface roughness of the base material 11 of the gas turbine member 10 can be increased, the coating layer 20 can be firmly fixed to the base material 11 when the coating layer 20 is regenerated. .

The embodiment of the present invention has been described above, but the present invention is not limited to this, and can be appropriately changed without departing from the technical idea of the present invention.
For example, as a modification, as shown in FIG. 5, in the gel adhesion step S <b> 11, a masking 40 such as a polytetrafluoroethylene tape is applied to a portion other than the remaining coating layer 20, that is, the surface of the base material 11 exposed to the outside. You may give it. Thereby, it can avoid more reliably that the acid in the polymer gel 30 contacts the base material 11. FIG.

  Further, a corrosion inhibitor (inhibitor) may be added to the acid impregnated in the polymer gel 30. Thereby, corrosion of the base material 11 by an acid can be prevented.

DESCRIPTION OF SYMBOLS 10 Gas turbine member 11 Base material 20 Coating layer 21 Undercoat layer 22 Topcoat layer 30 Polymer gel 40 Masking S1 First hot water washing process S2 First water washing process S3 Pickling process S4 Coating removal process S5 Neutralization washing process S6 2nd water washing process S7 2nd hot water washing process S8 Blast process S9 Heating process S10 Residual confirmation process S11 Gel adhesion process

Claims (3)

A pickling process in which at least a part of the coating layer on the surface of the gas turbine member is peeled off by subjecting the gas turbine member after operation to pickling treatment;
A coating peeling method for a member for a gas turbine, comprising: a gel attaching step of attaching a polymer gel impregnated with an acid to the remaining coating layer after the pickling step.   A heating step of changing the color of the coating layer remaining on the surface of the gas turbine member by heating the gas turbine member between the pickling step and the gel adhering step is provided. The coating peeling method of the member for gas turbines of Claim 1.   3. The coating removal method for a gas turbine member according to claim 2, further comprising a blasting step of performing a blasting process on a surface of the gas turbine member between the pickling step and the heating step.

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