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CN-121870002-B - High-temperature alloy casting method for gas turbine blade

CN121870002BCN 121870002 BCN121870002 BCN 121870002BCN-121870002-B

Abstract

The invention relates to the technical field of high-temperature alloy precision casting, and discloses a high-temperature alloy casting method of a gas turbine blade, which comprises the steps of sequentially carrying out lanthanum nitrate dip-coating pretreatment and ammonium carbonate curing treatment on the inner wall of a shell, and converting lanthanum nitrate into a lanthanum carbonate solid interface layer in situ; sequentially dip-coating lanthanum borate surface layer slurry and gadolinium oxide isolation layer slurry on a solidified layer to complete shell preparation, dewaxing, sintering at high temperature to solidify the shell, pouring high-temperature alloy metal liquid into the shell, forming metallurgical bonding between a lanthanum borate surface layer and the surface of a casting, leaving a lanthanum borate active layer on the surface of a blade after unshelling, and carrying out oxalate-phosphate composite sealing treatment on pores of the surface layer of the blade. The invention realizes the integration of casting molding and CMAS-resistant protective layer formation, the metallurgical combination of the protective layer and the blade matrix has high bonding strength, the micropores on the surface layer of the blade are effectively sealed, and the CMAS infiltration channel is blocked.

Inventors

  • ZHENG YONGSHUAI

Assignees

  • 辽宁汉文动力科技有限责任公司

Dates

Publication Date
20260512
Application Date
20260320

Claims (10)

  1. 1. A method of superalloy casting for a gas turbine blade, comprising the steps of: performing dip-coating pretreatment on the inner wall of the shell by using a lanthanum nitrate solution to form a lanthanum nitrate precursor thin layer; immersing the shell in an ammonium carbonate solution to enable the lanthanum nitrate precursor thin layer to be converted into an insoluble lanthanum carbonate solid layer in situ, rinsing to remove byproducts and drying; Sequentially dip-coating lanthanum borate surface layer slurry and gadolinium oxide isolation layer slurry on a lanthanum carbonate solid layer, and dip-coating outer layer support shell slurry to complete shell preparation; Dewaxing the shell, sintering at high temperature, thermally decomposing lanthanum carbonate into lanthanum oxide, and diffusing the lanthanum oxide and a lanthanum borate surface layer at high temperature to form chemical combination; Pouring nickel-based superalloy metal liquid into the shell, carrying out interfacial chemical reaction on the lanthanum borate surface layer and the surface of the casting, generating a rare earth aluminate bonding layer on the surface of the casting, and forming metallurgical bonding between the lanthanum borate surface layer and the surface of the casting; during unshelling, the metallurgical bonding strength between the lanthanum borate surface layer and the casting is higher than the interface bonding strength between the lanthanum borate surface layer and the gadolinium oxide isolation layer, the gadolinium oxide isolation layer is peeled off along with the outer layer supporting shell, and the lanthanum borate surface layer is reserved on the surface of the blade.
  2. 2. The method for casting the superalloy of the gas turbine blade according to claim 1, wherein the mass fraction of the lanthanum nitrate solution is 5% -15%, the dip-coating time is 30-60 s, and the solution is drained for 1-2 min after being taken out.
  3. 3. The high-temperature alloy casting method of the gas turbine blade according to claim 1, wherein the mass fraction of the ammonium carbonate solution is 8% -12%, the soaking time of the shell in the ammonium carbonate solution is 5-15 min, and the rinsing is carried out for 2-3 times by adopting deionized water.
  4. 4. The method for casting the high-temperature alloy of the gas turbine blade according to claim 1, wherein the D50 particle size of lanthanum borate powder in the lanthanum borate surface layer slurry is not more than 5 mu m, the adhesive is aluminum sol, the mass fraction of Al 2 O 3 in the aluminum sol is 20% -30%, the mass ratio of the lanthanum borate powder to the aluminum sol is 2:1-3:1, the lanthanum borate surface layer slurry is dip-coated for 12 channels, and the lanthanum borate surface layer slurry is drained for 12min after being taken out.
  5. 5. The method for casting the high-temperature alloy of the gas turbine blade according to claim 1, wherein the D50 particle size of gadolinium oxide powder in the gadolinium oxide isolation layer slurry is not more than 5 mu m, the adhesive is aluminum sol, the mass fraction of Al 2 O 3 in the aluminum sol is 20% -30%, the mass ratio of the gadolinium oxide powder to the aluminum sol is 2:1-3:1, the gadolinium oxide isolation layer slurry is dip-coated for 12 times, and the gadolinium oxide isolation layer slurry is drained for 12 minutes after each time.
  6. 6. The method for casting a superalloy for a gas turbine blade according to claim 1, wherein the high temperature sintering temperature is 900-1100 ℃ and the holding time is 13h.
  7. 7. The method for casting a superalloy for a gas turbine blade according to claim 1, wherein the casting of the nickel-based superalloy molten metal into the shell is performed by a vacuum directional solidification process or a vacuum single crystal casting process, and the casting temperature of the molten metal is 1400-1500 ℃.
  8. 8. The method of casting a superalloy for a gas turbine blade according to claim 1, further comprising the step of performing an oxalate-phosphate composite blocking treatment of the blade skin pores after unshelling, comprising: Immersing the blade casting into a mixed solution containing gadolinium nitrate and aluminum dihydrogen phosphate, taking out, and drying at low temperature to fix Gd 3+ and aluminum dihydrogen phosphate in the surface layer pores of the blade; And immersing the blade in an ammonium oxalate solution, in-situ reacting Gd 3+ in the pores with the permeated oxalate ions to generate insoluble gadolinium oxalate, depositing the insoluble gadolinium oxalate in the pores, taking out and drying, and curing the gadolinium oxalate and aluminum phosphate gel in the pores on the surface layer of the blade to form an oxalate-phosphate composite sealing film, so as to seal the casting residual micropores on the surface layer of the blade.
  9. 9. The method for casting a superalloy for a gas turbine blade according to claim 8, wherein the mixed solution contains gadolinium nitrate 3-5% by mass and aluminum dihydrogen phosphate 4-6% by mass; The immersion time of the blade casting in the mixed solution is 10-30 min; the low-temperature drying temperature is 50-80 ℃ and the drying time is 0.5-1 h.
  10. 10. The method for casting a superalloy for a gas turbine blade according to claim 8, wherein the mass fraction of the ammonium oxalate solution is 2% -3%; The immersion time of the vane in the ammonium oxalate solution is 5-15 min; And drying at 80-120 ℃ for 12h after taking out.

Description

High-temperature alloy casting method for gas turbine blade Technical Field The invention relates to the technical field of high-temperature alloy precision casting, in particular to a high-temperature alloy casting method of a gas turbine blade. Background Gas turbine blades are exposed to high temperature gas environments containing Calcium Magnesium Aluminum Silicate (CMAS) for extended periods of time under high temperature and pressure conditions. CMAS melts at the service temperature of the blade, permeates the surface layer of the blade and reacts with the surface material of the blade in a chemical corrosion way, so that the early failure of the blade is caused, and the service life and the reliability of the gas turbine are seriously affected. In the existing casting process of the high-temperature alloy blade, blade casting molding and CMAS corrosion resistant protective coating application belong to two mutually independent process chains, namely, after the blade is cast and unshelled, the protective coating is independently applied by a thermal spraying method and the like. In order to integrate the CMAS-resistant protection function into a casting process, the existing thought is to perform rare earth nitrate activation pretreatment on the inner surface of a shell in the preparation process of the shell so as to enhance the chemical binding force between a subsequent functional slurry layer and a shell matrix and enable the functional slurry layer to remain on the surface of a blade after casting, however, rare earth nitrate is a water-soluble salt, the pretreatment layer is continuously washed and dissolved by a water-based or alcohol-based solvent in the subsequent multi-functional slurry sequential dip-coating process, a large amount of rare earth nitrate is lost, the functional slurry layer is attached to the shell wall only by physical adhesion, and the aim of protecting function integration is difficult to achieve. Disclosure of Invention The invention provides a high-temperature alloy casting method for a gas turbine blade, which solves the technical problems of low bonding strength of a CMAS (CMAS) resistant protective coating and a blade matrix and CMAS infiltration caused by unsealed micropores on the surface layer of the blade in the related technology. The invention provides a high-temperature alloy casting method of a gas turbine blade, which comprises the following steps: performing dip-coating pretreatment on the inner wall of the shell by using a lanthanum nitrate solution to form a lanthanum nitrate precursor thin layer; immersing the shell in an ammonium carbonate solution to enable the lanthanum nitrate precursor thin layer to be converted into an insoluble lanthanum carbonate solid layer in situ, rinsing to remove byproducts and drying; Sequentially dip-coating lanthanum borate surface layer slurry and gadolinium oxide isolation layer slurry on a lanthanum carbonate solid layer, and dip-coating outer layer support shell slurry to complete shell preparation; Dewaxing the shell, sintering at high temperature, thermally decomposing lanthanum carbonate into lanthanum oxide, and diffusing the lanthanum oxide and a lanthanum borate surface layer at high temperature to form chemical combination; Pouring nickel-based superalloy metal liquid into the shell, carrying out interfacial chemical reaction on the lanthanum borate surface layer and the surface of the casting, generating a rare earth aluminate bonding layer on the surface of the casting, and forming metallurgical bonding between the lanthanum borate surface layer and the surface of the casting; during unshelling, the metallurgical bonding strength between the lanthanum borate surface layer and the casting is higher than the interface bonding strength between the lanthanum borate surface layer and the gadolinium oxide isolation layer, the gadolinium oxide isolation layer is peeled off along with the outer layer supporting shell, and the lanthanum borate surface layer is reserved on the surface of the blade. Preferably, the lanthanum nitrate solution is 5% -15% by mass, the dip-coating time is 30-60 s, and the lanthanum nitrate solution is drained for 1-2 min after being taken out. Preferably, the mass fraction of the ammonium carbonate solution is 8% -12%, the soaking time of the shell in the ammonium carbonate solution is 5-15 min, and the rinsing is carried out for 2-3 times by adopting deionized water. Preferably, the D50 particle size of lanthanum borate powder in the lanthanum borate surface layer slurry is not more than 5 mu m, the adhesive is aluminum sol, the mass fraction of Al 2O3 in the aluminum sol is 20% -30%, the mass ratio of the lanthanum borate powder to the aluminum sol is 2:1-3:1, the lanthanum borate surface layer slurry is dip-coated for 1-2 times, and the drying is carried out for 1-2 minutes after each time. Preferably, the D50 particle size of gadolinium oxide powder in the gadolinium oxide isolation la