Method of chemical pretreatment of a lightweight jet engine fan blade

• US 6,544,002 B1
• Filed: 11/07/2001
• Issued: 04/08/2003
• Est. Priority Date: 11/07/2001
• Status: Expired due to Fees

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Lin, Wendy Wen-Ling, Rosenzweig, Mark Alan, Evans, Kathryn Ann, Schworm, Jeffrey Lynn, Evans, Charles Richard
• Primary Examiner(s): Look, Edward K.
• Assistant Examiner(s): MCALEENAN, JAMES M
• Application Number:
  US10/039,394
• Time in Patent Office: 517 Days
• Field of Search: 416/224, 416/233, 416/241.A, 416/229.A, 416/243, 416/DIG.2, 416/DIG.5, 298/892, 427/377, 427/532, 427/585, 428/613, 428/256, 428/469, 428/408
• US Class Current: 416/224
• CPC Class Codes: F01D 5/147 Construction, i.e. structural features, e.g. of weight-saving hollow blades F01D5/148, F01D5/16 and F01D5/20 take precedence; blade shape F01D5/141; blades with cooling or heating channels or cavities F01D5/18; heating, heat-insulating or cooling means on blades F01D5/18
• CPC Class Codes: F01D 5/28 Selecting particular materials; Particular measures relating thereto; Measures against erosion or corrosion
• CPC Class Codes: F04D 29/023 especially adapted for elastic fluid pumps
• CPC Class Codes: F04D 29/324 Blades
• CPC Class Codes: F05D 2230/90 Coating; Surface treatment manufacture with deposition of material F05D2230/30
• CPC Class Codes: F05D 2300/43 Synthetic polymers, e.g. plastics; Rubber
• CPC Class Codes: Y02T 50/60 Efficient propulsion technologies, e.g. for aircraft
• CPC Class Codes: Y10T 29/4932 Turbomachine making
• CPC Class Codes: Y10T 428/12479 Porous [e.g., foamed, spongy, cracked, etc.]
• CPC Class Codes: Y10T 428/30 Self-sustaining carbon mass or layer with impregnant or other layer

Abstract

A grit blasting and alkaline etch surface pretreatment that is applied to a metallic airfoil. The metallic airfoil includes pockets or cavities that have been fabricated into the airfoil to reduce the weight of the airfoil. The pretreatment includes grit blasting the surface of the pockets or cavities, followed by washing the airfoil and treating the airfoil in an alkaline etch bath. After any remaining solution from the bath is neutralized and within twenty-four hours of the end of the pretreatment, primer is applied to the surface of the pockets or cavities. After the primer is applied to the surface of the pockets, a lightweight resin is injected into the pockets and bonds to the primer forming a mechanical bond with good fracture toughness at elevated temperatures.

Claims

1. A method of producing an aircraft engine blade, comprising an airfoil portion and a dovetail portion, and having at least one pocket in the airfoil portion, comprising the steps of:

providing an aircraft engine fan blade having at least one pocket in the airfoil portion;

grit blasting a surface of the airfoil portion having at least one blade pocket with a preselected type of grit, at a preselected size and at a preselected pressure to effect a uniform surface finish;

washing the surface with a solvent that is miscible in water and has a volatility sufficient to accelerate the removal of liquid from the surface without leaving a stain;

drying the surface by removing the solvent;

immersing the airfoil portion of the blade in an alkaline etch bath while agitating the etch bath to further effect a uniform surface finish;

removing the airfoil portion of the blade from the bath without allowing the airfoil portion of the blade to dry;

neutralizing the alkaline solution on the surface of the airfoil portion of the blade;

washing the surface with a solvent;

drying the surface wherein the solvent is removed from the surface of the airfoil portion of the blade without forming stains;

applying a primer to the at least one pocket of the airfoil portion of the blade;

curing the primer;

injecting a polymeric resin into the at least one pocket; and

curing the resin.

2. The method of claim 1, wherein the alkaline etch bath further comprises a preselected concentration of NaOH and a predetermined iron concentration.

3. The method of claim 2, wherein the concentration of NaOH is about 360 grams to about 480 grams per liter of deionized water and the concentration of iron is about 0.05 to about 0.15 grams per liter of deionized water.

4. The method of claim 3, wherein the NaOH solution is TURCO 5578 in deionized water.

5. The method of claim 1, wherein the step of neutralizing further comprises the step of:

immersing the airfoil portion of the blade in a deionized water bath at a preselected temperature for a preselected period of time.

6. The method of claim 1, wherein the step of neutralizing further comprises the step of:

immersing the airfoil portion of the blade in an acid solution, having a predetermined concentration, at a preselected temperature for a preselected period of time.

7. The method as in claim 6, wherein the step of neutralizing further comprises the step of:

immersing the airfoil portion of the blade in a deionized water bath at a preselected temperature for a preselected period of time after immersion in the acid solution.

8. The method of claim 1, wherein the step of neutralizing further comprises the steps of:

immersing the airfoil portion of the blade in a deionized water bath at a preselected temperature for a preselected period of time,

immersing the airfoil portion of the blade in a nitric acid solution, having a predetermined concentration, at a preselected temperature for a preselected period of time.

9. The method of claim 8, wherein the acid is nitric acid having a predetermined concentration.

10. The method of claim 9, wherein the nitric acid has a concentration of about 1% to about 15% by mass in deionized water.

11. The method of claim 1, wherein each washing step includes a solvent selected from the group consisting of ethanol, propanol, methanol and isopropyl alcohol.

12. The method of claim 11, wherein the solvent is isopropyl alcohol.

13. The method of claim 1 wherein the type of grit is selected from the group consisting of oxides of refractory metals.

14. The method of claim 13 wherein the grit is selected from the group consisting of Al₂O₃, SiO, ZrO₂.

15. The method of claim 14 wherein the grit is Al₂O₃.

16. The method of claim 15 wherein the size of the grit used is in the range of about 120 grit to about 180 grit.

17. The method of claim 16 wherein the pressure used for the grit blasting is in the range of about 40 psi to about 60 psi.

18. An aircraft engine fan blade having at least one pocket fabricated into the airfoil portion manufactured by the process of claim 1.

19. An aircraft engine fan blade having at least one pocket, said at least one pocket being filled with a resin, wherein the fracture toughness between the resin and metal surfaces of the pocket is characterized as being at least 4.4 in-lbs/in².