A method for laser-aligned brazing of vibration-damping bosses on aero-engine fan rotor blades

Abstract

This invention relates to a method for laser-aligned brazing of vibration-damping bosses on aero-engine fan rotor blades, comprising the following steps: Pre-welding preparation of the fan blade: fixing pressure-sensitive adhesive tape to the non-welding area of ​​the blade body and the boss; Brazing solder preparation: mixing Lielite hard alloy powder and brazing filler metal to form a brazing filler metal mixture powder; preparing Lielite adhesive; thoroughly mixing the prepared adhesive and brazing filler metal mixture powder to form a paste; Pre-laser alignment brazing preparation: applying the paste brazing filler metal to the boss; placing the coated blade in an environmental chamber, then evacuating the chamber and filling it with argon gas to maintain atmospheric pressure; Laser alignment brazing: using a rectangular flat-top laser, with the spot size determined by the wear-resistant boss on the blade; Post-brazing inspection: using fluorescence and X-ray inspection to check the welding quality. This invention solves the problem of uneven wear-resistant layer caused by induction brazing methods. This invention can ensure uniform distribution of hard alloy on the surface of the wear-resistant layer.

Description

Technical Field

[0001] This invention relates to the field of manufacturing vibration damping bosses for aero-engine blades, and specifically to a method for laser-aligned brazing of vibration damping bosses for aero-engine fan rotor blades. Background Technology

[0002] Fan rotor blades are critical rotating components of aero-engines, playing a vital role in delivering air to the inner and outer bypass ducts. During operation, aero-engine blades are subjected to significant centrifugal, aerodynamic, thermal, and vibration loads, with vibration loads being particularly prone to causing blade failure. To address vibration issues, fan blades typically utilize Coulomb friction damping. Damping structures are added to the blade body, increasing the clamping rigidity at both ends of the blade and raising its natural frequency. During vibration, the working surfaces of the damping structures rub against each other, absorbing vibration energy and effectively mitigating flutter. Therefore, most aero-engine fan blades, both domestically and internationally, employ damping structures.

[0003] To protect fan blades and prevent wear on the contact surfaces of the damping and vibration-damping structure due to blade vibration, a wear-resistant layer (a special hard alloy coating) is typically sprayed onto the contact surfaces. This wear-resistant layer is achieved by induction brazing a paste-like filler metal containing wear-resistant particles. The preparation of the wear-resistant layer on the blades involves multiple processes, including grinding, mixing, filler metal coating, brazing, and polishing. This process is characterized by high failure rates, short lifespans, high repair costs, and complex repair procedures. Furthermore, due to the uneven temperature distribution on the wear-resistant layer surface during induction brazing, the cemented carbide settling velocity varies significantly across different locations, ultimately resulting in uneven cemented carbide distribution on the wear-resistant layer surface. This leads to out-of-tolerance wear dimensions in the wear-resistant layer, causing abnormal vibrations in the aero-engine.

[0004] Therefore, in order to improve the efficiency of fan blade manufacturing and repair, reduce costs, and extend the reliability and service life of the wear-resistant layer of the boss, it is urgent to develop a brand-new brazing process. Summary of the Invention

[0005] This invention addresses the problem of uneven distribution of hard alloy in the wear-resistant layer caused by induction brazing of vibration-damping bosses on aero-engine fan blades. It proposes a laser-guided brazing process. This method ensures relatively uniform brazing filler metal distribution during the brazing process, significantly improving the yield rate of manufactured vibration-damping bosses for fan rotor blades.

[0006] This invention is achieved through the following technical solutions:

[0007] A method for laser-aligned brazing of vibration-damping bosses on aero-engine fan rotor blades includes the following steps:

[0008] Step 1: Preparation before fan blade welding: Fix pressure-sensitive tape to the non-welding area of ​​the blade body and boss to prevent the laser beam from damaging the blade body;

[0009] Step 2: Solder preparation: Mix Lielite cemented carbide powder and solder to ensure uniform dispersion of the cemented carbide, forming a solder mixture powder; prepare Lielite adhesive, the components of which are: acetone, xylene, butyl acetate, and acrylic resin; thoroughly mix the prepared adhesive and solder mixture powder, stirring to form a paste;

[0010] Step 3: Preparation before laser straightening brazing: Apply a paste-like brazing filler metal to the boss, being careful not to apply it onto the pressure-sensitive tape; place the coated blade in an environmental chamber, then evacuate to a pressure less than 5 × 10⁻⁶. -2 Pa, fill the environmental chamber with argon gas until the pressure is equal to atmospheric pressure;

[0011] Step 4: Laser straightening brazing: The straightening laser uses a rectangular flat-top laser with a laser power of 2000-3000W. The spot size depends on the wear-resistant protrusions on the blade.

[0012] Step 5: Post-brazing inspection: Use fluorescence and X-ray to check the welding quality.

[0013] In step two, the Lilt cemented carbide powder and the brazing filler metal are mixed in a weight ratio of 30:50.

[0014] The microstructure of the Lielite cemented carbide powder in step two is spherical.

[0015] The particle size of the Lielite cemented carbide powder in step two is 0.2-0.6 mm.

[0016] In the Lielite adhesive of step two, the ratio of acetone: xylene: butyl acetate: acrylic resin is 1:2:1:0.2.

[0017] The size of the rectangular flat-top laser spot in step four is 5×2-12×3mm.

[0018] The laser activation time in step four is 5-10 seconds.

[0019] Compared with existing technologies, the present invention has the following advantages:

[0020] 1. Traditional methods use cemented carbide powder that is irregularly ground. Irregular powder has uneven stress distribution. When powder with sharp corners appears, stress concentration occurs, which reduces the surface's wear resistance. In this invention, spherical cemented carbide powder is used, which makes the stress distribution relatively uniform during friction and wear, thus improving the surface's wear behavior.

[0021] 2. Traditional induction brazing methods suffer from uneven temperature distribution during the brazing process. Different morphologies of cemented carbide powders deposit at inconsistent rates under gravity, resulting in uneven tungsten carbide particle distribution after brazing. Since the wear-resistant properties of the wear-resistant layer are provided by carbide particles, this also easily leads to uneven wear resistance. This invention proposes for the first time a shaped laser brazing method, which achieves uniform energy distribution of the focused laser spot, allowing the brazing filler metal in the wear-resistant layer to melt simultaneously. With uniform brazing filler metal distribution, uniform cemented carbide distribution on the wear-resistant layer surface can be ensured, significantly improving the wear resistance of fan blades. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0023] The following is an illustration through specific embodiments:

[0024] Example:

[0025] The method for preparing the wear-resistant layer of a certain type of aero-engine second-stage fan blade is as follows:

[0026] Step 1: Preparation before brazing: First, use a file to smooth out any remaining solder joints and clean the area to be brazed with alcohol or acetone; fix the blade with pressure-sensitive tape to prevent the laser beam from damaging the blade.

[0027] Step 2: Preparation of brazing solder: Mix Lielite cemented carbide powder and brazing filler metal at a weight ratio of 30:50 to ensure uniform dispersion of the cemented carbide; and prepare Lielite adhesive, which consists of acetone, xylene, butyl acetate, and acrylic resin in a ratio of 1:2:1:0.2; thoroughly mix the prepared adhesive and brazing filler metal powder and stir into a paste.

[0028] Step 3: Preparation before laser straightening brazing: Apply a paste-like brazing filler metal to the boss, being careful not to apply it onto the pressure-sensitive tape; place the coated blade in an environmental chamber, then evacuate to a pressure less than 5 × 10⁻⁶. -2 Pa, fill the environmental chamber with argon gas until the pressure is equal to atmospheric pressure;

[0029] Step 4: Laser straightening brazing: The straightening laser uses a rectangular flat-top laser with a power of 2800W, a spot size of 6×2mm, and a laser on-time of 5s;

[0030] Step 5: Post-brazing inspection: The welding quality was inspected using fluorescence and X-ray examination, and no cracks or porosity defects were found.

[0031] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for laser-aligned brazing of vibration-damping bosses on aero-engine fan rotor blades, characterized in that: Includes the following steps: Step 1: Preparation before fan blade welding: Fix pressure-sensitive tape to the non-welding area of ​​the blade body and boss to prevent the laser beam from damaging the blade body; Step 2: Solder preparation: Mix Lielite cemented carbide powder and solder to ensure uniform dispersion of the cemented carbide, forming a solder mixture powder; prepare Lielite adhesive, composed of acetone, xylene, butyl acetate, and acrylic resin; thoroughly mix the prepared adhesive and solder mixture powder, stirring until a paste is formed; Step 3: Preparation before laser straightening brazing: Apply a paste-like brazing filler metal to the boss, being careful not to apply it onto the pressure-sensitive tape; place the coated blade in an environmental chamber, then evacuate to a pressure less than 5 × 10⁻⁶. -2 Pa, fill the environmental chamber with argon gas until the pressure is equal to atmospheric pressure; Step 4: Laser straightening brazing: The straightening laser uses a rectangular flat-top laser with a laser power of 2000-3000W. The spot size depends on the wear-resistant protrusions on the blade. Step 5: Post-brazing inspection: Use fluorescence and X-ray inspection to check the welding quality; In step two, the Lielite cemented carbide powder and brazing filler metal are mixed in a weight ratio of 30:50; the particle size of the Lielite cemented carbide powder is 0.2-0.6mm; and the ratio of acetone:xylene:butyl acetate:acrylic resin in the Lielite adhesive is 1:2:1:0.

2.

2. The method for laser-aligned brazing of vibration-damping bosses on aero-engine fan rotor blades according to claim 1, characterized in that: The microstructure of the Lielite cemented carbide powder in step two is spherical.

3. The method for laser-aligned brazing of vibration-damping bosses on aero-engine fan rotor blades according to claim 1, characterized in that: The size of the rectangular flat-top laser spot in step four is 5×2-12×3mm.

4. The method for laser-aligned brazing of vibration-damping bosses on aero-engine fan rotor blades according to claim 1, characterized in that: The laser activation time in step four is 5-10 seconds.