A method for removing a ni cr al y si coating from a turbine blade surface

Abstract

The present application relates to a kind of methods for removing turbine blade surface NiCrAlYSi coating, step one, the inner cavity of part and non-coating covering surface are sealed with wax, dry solidification;Step two, the coating surface of part treated in step one is wiped with organic solvent, so that surface is clean and pollution-free;Step three, preparation NiCrAlYSi coating removal solution;Step four, the part treated in step three is cleaned, the coating is polished with white clean cloth and is cleaned with flowing cold water;Step five, wax cleaning, the protective wax on the part treated in step four is removed using air furnace heating;Step six, cleaning and drying, the inner and outer surface of the part treated in step five is cleaned and dried.The present application can economically and effectively remove turbine blade surface NiCrAlYSi coating, and has no effect on turbine blade high-temperature alloy matrix.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of removing the oxidation-resistant coating of the hot end part such as the directional crystallization turbine blade of an aero-engine, and particularly relates to a method for removing the NiCrAlYSi coating on the surface of a turbine blade. BACKGROUND

[0002] The turbine blade of an aero-engine is subjected to the impact and erosion of high-temperature gas during operation. In order to improve the high-temperature oxidation resistance and corrosion resistance of the blade, the NiCrAlYSi coating is coated on the surface of the blade. However, due to the unstable state of the equipment, the surface state of the part and other reasons, the appearance or performance of the NiCrAlYSi coating may be out of standard during the preparation process, and the coating may be damaged due to accidental knocking during the turnover and assembly process of the part, and thus the coating that does not meet the requirements needs to be removed and recoated. At present, many coating removal methods have defects. The mechanical polishing process is easy to cause the unqualified wall thickness of the blade, and the coating removal efficiency of the chemical removal process is low. For example, the coating removal time of the hydrochloric acid + rudding solution is up to 5 hours, and in addition, the substrate is obviously corroded. SUMMARY

[0003] To solve the above technical problems, the present application provides a method for removing the NiCrAlYSi coating on the surface of a turbine blade, and the specific technical solutions are as follows.

[0004] A method for removing the NiCrAlYSi coating on the surface of a turbine blade, comprising the following steps:

[0005] Step one, the inner cavity and non-coating covered surface of the part are sealed with wax, and dried and solidified;

[0006] Step two, the coating surface of the part treated in step one is wiped with an organic solvent to make the surface clean and free of pollution;

[0007] Step three, a NiCrAlYSi coating removal solution is prepared, and the part treated in step two is placed in the solution for treatment, and the parts are independent and do not block each other;

[0008] Step four, the part is taken out every ten minutes, the part treated in step three is cleaned, the coating surface is polished with a white clean cloth, and is cleaned with flowing cold water. If there is residual coating, the part is continuously placed in the solution for pickling until the surface is free of coating;

[0009] Step five, wax cleaning, the protective wax on the part treated in step four is removed by heating in an air furnace;

[0010] Step six, cleaning and drying, the surface and inner cavity of the part treated in step five are washed with flowing water until clean and dried.

[0011] The chemical method for removing the NiCrAlYSi coating on the surface of the turbine blade based on directional crystallization has the preferred scheme that the NiCrAlYSi coating removal solution is prepared by 300 mL / L to 500 mL / L of nitric acid and 8 g / L to 10 g / L of sodium chloride.

[0012] When the coating does not react or no bubbles are generated, 4 g / L of sodium chloride is added.

[0013] The method for removing the NiCrAlYSi coating on the surface of the turbine blade has the preferred scheme that the specific gravity of the nitric acid is 1.42 g / cm 2 .

[0014] The method for removing the NiCrAlYSi coating on the surface of the turbine blade has the preferred scheme that the chemicals in the NiCrAlYSi coating removal solution are all chemically pure.

[0015] The method for removing the NiCrAlYSi coating on the surface of the turbine blade has the preferred scheme that the processing temperature of the NiCrAlYSi coating removal solution is 18 DEG C to 30 DEG C.

[0016] The method for removing the NiCrAlYSi coating on the surface of the turbine blade has the preferred scheme that the processing time of the NiCrAlYSi coating removal solution is 15 min to 30 min.

[0017] The method for removing the NiCrAlYSi coating on the surface of the turbine blade has the preferred scheme that in the fifth step, the air furnace is heated to 300 DEG C to 400 DEG C.

[0018] Compared with the prior art, the method has the following beneficial technical effects:

[0019] (1) The process method is convenient for observation, the coating removal process is violent, no reaction occurs after the coating is removed, and no bubbles are generated on the bare substrate.

[0020] (2) Compared with the mechanical polishing method, the method basically does not affect the blade wall thickness, so that the blade wall thickness is not over-thinned, and the blade is not scrapped due to the coating removal by the existing mechanical method.

[0021] (3) Compared with other chemical methods, the method is completely different from the nitric acid + hydrochloric acid solution, the operation is simple, the reaction rate is controllable by controlling the addition of sodium chloride, the blade substrate is basically not corroded, the coating removal time is short, no special equipment is needed, the solution adjustment method is simple, and the service life is long.

[0022] The technology is applied to removal of the turbine blade NiCrAlYSi coating, can economically and effectively remove the turbine blade surface NiCrAlYSi coating, and has no influence on the turbine blade high-temperature alloy base.

[0023] The technology can be popularized and applied to removal of oxidation-resistant coatings of other parts, realizes repeated use of the parts, reduces the cost, effectively guarantees the service life, reliability and economy, and has a broad market prospect. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The micro-morphology diagram after the coating is removed. DETAILED DESCRIPTION

[0025] The application is further illustrated in combination with Figure 1 and the examples.

[0026] Implementation 1

[0027] The turbine blade with the material of DZ125 alloy is removed from the surface NiCrAlYSi coating with the thickness of 25 microns by using the chemical method, and the removal steps are as follows:

[0028] Step one, the inner cavity and tenon of the blade are wax-sealed to protect the non-coating area, so that the solution does not contact the tenon and the inner cavity;

[0029] Step two, the surface of the blade coating is wiped with an organic solvent to remove the mark traces and oil stains, and the oil removal effect is verified to ensure the surface cleaning;

[0030] Step three, the pickling solution is prepared: nitric acid 300 mL / L, sodium chloride 8 g / L;

[0031] Step four, the part is placed in the solution, and the parts are independent without mutual shielding, and the part is taken out every ten minutes, the surface is polished with a scouring pad, if there is residual coating, the part is continuously placed in the solution for pickling, until the surface is free of coating, when the coating does not react or no bubbles are generated, the sodium chloride is added according to 4 g / L;

[0032] Step five, after the part surface is checked by naked eye without coating, the wax of the part tenon and other parts is removed, and then the part is placed in the air furnace and heated to 300 DEG C;

[0033] Step six, the part surface and the inner cavity are washed with flowing water until clean and dry;

[0034] Step seven, the part is disassembled, and the surface of the part is observed by Figure 1 It can be found that the part surface is free of residual coating.

[0035] Step eight, after wet sandblasting, the hot coloring verification is performed, the body is blue, and there is no residual coating.

[0036] Implementation 2

[0037] The present application uses chemical method to remove the surface NiCrAlYSi coating with thickness of 30μm of turbine blade made of DZ125 alloy, and the removing steps are as follows:

[0038] Step one, the inner cavity and tenon of the blade are waxed to protect the non-coating area, so as to ensure that the solution does not contact the tenon and the inner cavity;

[0039] Step two, the coating surface of the blade is wiped with organic solvent to remove marks and oil stains, and the oil removal effect is verified to ensure the surface is clean;

[0040] Step three, prepare the pickling solution: nitric acid 500mL / L, sodium chloride 10g / L;

[0041] Step four, put the part into the solution, and the parts are independent without mutual shielding, take out the part after about ten minutes, polish the surface with a scouring pad, if there is residual coating, continue to put it into the solution for pickling, until there is no coating on the surface, when the coating does not react or no bubbles are generated, add 4g / L of sodium chloride;

[0042] Step five, after the part surface is checked by naked eye without coating, remove the wax from the tenon and other parts of the part, and then put it into the air furnace to heat to 400℃.

[0043] Step six, rinse the surface and inner cavity of the part with flowing water until clean and dry.

[0044] Step seven, disassemble the part, and the surface of the part has no residual coating;

[0045] Step eight, after wet sandblasting, perform hot coloring verification, the body is blue, and there is no residual coating.

Claims

1. A method of removing a NiCrAlYSi coating from the surface of a turbine blade, characterized in that: It comprises the following steps: Step one, the inner cavity and non-coating surface of the part are sealed with wax, and dried and solidified; Step two, the coating surface of the part treated in step one is wiped with organic solvent to make the surface clean and free of pollution; Step three, a NiCrAlYSi coating removal solution is prepared, and the part treated in step two is put into the solution for treatment, and the parts are independent and not shielded from each other; The NiCrAlYSi coating removal solution is prepared from nitric acid 300 mL / L-500 mL / L and sodium chloride 8 g / L-10 g / L; When the coating does not react or no bubbles are generated, sodium chloride 4 g / L is added; The specific gravity of the nitric acid is 1.42 g / cm 2 ; The chemicals in the NiCrAlYSi coating removal solution are all chemically pure; The treatment temperature of the NiCrAlYSi coating removal solution is 18-30°C; The treatment time of the NiCrAlYSi coating removal solution is 15-30 min; Step four, the part is taken out every ten minutes, the part treated in step three is cleaned, the coating surface is polished with white clean cloth, and is cleaned with flowing cold water, if there is residual coating, it is continuously put into the solution for pickling until the surface is free of coating; Step five, wax cleaning, the protective wax on the part treated in step four is removed by air furnace heating; wherein the air furnace is heated to 300-400°C; Step six, cleaning and drying, the surface and inner cavity of the part treated in step five are washed with flowing water until clean and dried.

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