Alloy powder for laser additive repair of beryllium bronze and additive repair method thereof

Abstract

This invention discloses an alloy powder for laser additive repair of beryllium bronze and its additive repair method, belonging to the field of laser additive repair. The alloy powder composition is Ni 29-33%, Co 10-15%, Fe≤0.9%, Mn≤1.2%, O≤0.03%, with the balance being Cu. This invention optimizes the content of Ni and Co elements by increasing their content and eliminating Be elements, ensuring safety during large-scale powder preparation and use, while improving the wear resistance of the repaired surface and the bonding performance between the substrate and the additive repair layer. The repair process of this invention utilizes a small-diameter spot, high-energy-density laser additive repair to effectively reduce the heat-affected zone, minimize deformation, and improve repair quality. The method of this invention significantly reduces the repair cycle.

Description

Technical Field

[0001] This invention relates to the field of laser additive repair, specifically to an alloy powder for laser additive repair of QBe2 beryllium bronze and its additive repair method. Background Technology

[0002] QBe2 is a ternary alloy containing small amounts of beryllium (1.8%-2.1% by mass) and nickel (0.2%-0.5% by mass). After quenching, cold working, and aging treatment, the alloy exhibits high strength, hardness, and elastic limit, as well as low elastic hysteresis, good elastic stability, fatigue resistance, corrosion resistance, wear resistance, non-magnetic properties, high electrical and thermal conductivity, and does not generate sparks upon impact. It is an important material with excellent comprehensive performance in industry, and is a high-elasticity and high-strength structural and functional material, widely used in the manufacture of elastic sensitive elements in electrical appliances, electronic instruments, and meters.

[0003] Currently, aircraft pistons made of beryllium bronze (QBe2 alloy) in aviation equipment are subject to wear from high-strength steel parts during use. Because QBe2 beryllium bronze is less hard than high-strength steel, these parts wear down during operation, reducing performance and increasing aircraft safety risks. Furthermore, the large number of these parts used on aircraft means that damage occurs in batches, making replacement and repair costly and time-consuming, severely impacting production efficiency. Repair layers obtained through brushing and thermal spraying are mechanically bonded, not metallurgically bonded, and are only suitable for surface repair, unable to repair damaged areas. Brazing joints have weak bonding strength, and fusion welding repairs such as argon arc welding have a large heat-affected zone (>1.5mm). In comparison, laser additive repair, with its high energy density, low heat input, fast crystallization speed, fine grain size, and superior mechanical properties, is increasingly being used for repairing damaged aviation components.

[0004] Currently, additive repair of beryllium bronze mainly focuses on arc welding. For example, application number 202510182065.0, "A Method for Repairing Inner Wall Damage of Beryllium Bronze Piston Parts," discloses a scheme for additive repair of beryllium bronze using cold welding. Cold welding is a type of arc welding, and its energy density is much lower than that of laser. Therefore, the width of the heat-affected zone in its repair area is greater than that in laser additive repair. At the same time, the grain size of its repair area is larger than that of the laser additive repair area. Therefore, the mechanical properties of its repair joint are lower than those of the laser additive repair joint.

[0005] Beryllium is a group 2 element in the second period of beryllium bronze. Beryllium and its compounds are highly toxic. If broken bronze is used to prepare powder and carry out restoration, it is easy to cause harm to the human body during the powder making process. For example, beryllium dust and fumes are highly toxic to the human body when inhaled and can lead to lung diseases. Beryllium bronze powder has not yet been seen on the market.

[0006] Therefore, providing an alloy powder for laser additive repair of QBe2 beryllium bronze and its additive repair method is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0007] In view of this, the present invention provides an alloy powder for laser additive repair of QBe2 beryllium bronze and the additive repair method thereof, which meets the needs of damage repair of beryllium bronze parts.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] An alloy powder for laser additive repair of beryllium bronze comprises the following elements by mass percentage: Ni 29-33%, Co 10-15%, Fe≤0.9%, Mn≤1.2%, O≤0.03%, with the balance being Cu.

[0010] This invention determines the powder composition for laser additive repair based on the chemical composition, heat treatment process, and stress conditions of QBe2 beryllium bronze materials. Be acts as a precipitation hardening element in beryllium bronze, forming nanoscale precipitates in the copper matrix through solution-aging treatment, thereby achieving high strength. Considering the highly toxic nature of Be, it needs to be removed. Ni and Co elements can improve the room temperature tensile strength and wear resistance of copper alloys.

[0011] Furthermore, the particle size of the alloy powder is 53μm-150μm, and the proportion of the component with particle size <53μm is ≤5%, and the proportion of the component with particle size >150μm is ≤5%.

[0012] Furthermore, the aforementioned alloy powder is prepared using either gas atomization or plasma rotating electrode method.

[0013] This invention also provides an additive repair method for damaged beryllium bronze parts, which uses the aforementioned laser additive repair alloy powder for beryllium bronze, and includes the following steps: (1) Cleaning of the area to be repaired: Mechanically grind the end face of the damaged part to be repaired to remove the oxide layer, ensuring that the metal luster is exposed and the surface is clean, and then clean with acetone; (2) Defect removal: After confirming the defect by fluorescence detection, use aluminum foil to protect the parts of the part that can be irradiated by the laser except for the area to be repaired, to prevent the laser irradiation from damaging the substrate of other parts during the repair process.

[0014] (3) Laser additive repair of beryllium bronze parts, the specific laser parameters are as follows: Carrier gas: 99.999% high-purity argon; Powder for laser restoration: Alloy powder for laser additive restoration of beryllium bronze; Laser power: 1200-1400W; Scanning speed: 8-10 mm / s; Spot diameter: 1-1.2mm; Powder feeder speed: 0.5-0.8 r / min; Powder delivery gas flow rate: 4-6 L / min; Protective gas flow rate: 18-20 L / min; Overlap rate: 40%-50%; (4) During the laser additive repair process, for each additive repair layer, when the temperature of the molten pool is between 750℃ and 850℃, laser micro-forging is used to forge the molten pool. After the laser micro-forging is completed, when the interlayer temperature drops below 40℃, the next layer is repaired by laser additive repair. (5) After the laser additive repair is completed, the parts are placed in a vacuum heat treatment furnace for tempering; (6) The tempered parts are machined to standard dimensions; (7) After machining, fluorescent flaw detection is performed and no cracks are found, thus completing the additive repair of damaged beryllium bronze parts.

[0015] Furthermore, in step (4), the thickness of each additive repair layer is no more than 0.3 mm.

[0016] Furthermore, the parameters of the laser micro-forging are: laser wavelength 1064 nm, pulse width 8 ns, frequency 5-10 Hz, pulse laser energy 1-1.2 J, and spot size 1.5 mm.

[0017] The entire repair process of this invention adopts a cycle of "additive manufacturing - laser micro-forging with a melt pool temperature of 750℃-850℃ - additive manufacturing with an interlayer temperature of less than 40℃" until the final formed sample is formed; among them, the temperature of the middle melt pool is monitored by an infrared thermometer.

[0018] Furthermore, after the interlayer temperature in step (4) drops below 40°C, the surface of the additive repair layer is cleaned by mechanical grinding to remove the oxide layer, ensuring that the metal luster is exposed and the surface is clean. Then, it is cleaned with acetone and then the next layer is added to repair.

[0019] Furthermore, the tempering method in step (5) involves holding the furnace at 280-330℃ for 2-4 hours, followed by furnace cooling; the vacuum degree of the tempering is 6.67×10⁻⁶. -3 Pa -6.67×10 -2 Pa.

[0020] The beneficial effects of this invention are as follows: 1. This invention develops and prepares a novel laser additive repair powder specifically for QBe2 alloys. By optimizing the content of Ni and Co elements and eliminating Be elements, this invention ensures safety during mass production and use of the powder while improving the wear resistance of the repaired surface and the bonding performance between the substrate and the additive repair layer. Nickel primarily enhances the strength and hardness of the copper alloy through "solid solution strengthening." Nickel atoms can dissolve extensively in the copper lattice, forming an infinite copper-nickel solid solution. Since the radius of nickel atoms differs from that of copper atoms, they replace copper atoms in the lattice, causing lattice distortion. These distorted regions create elastic stress fields within the lattice. When dislocations causing material deformation attempt to pass through these stress field regions, they are strongly hindered, making movement difficult and requiring greater external force to continue. Macroscopically, this manifests as a significant increase in the material's strength and hardness.

[0021] Cobalt has very low solid solubility in copper, which decreases sharply with decreasing temperature, creating conditions for precipitation strengthening. The process involves solution treatment followed by aging treatment, strengthening the copper alloy through the precipitation of phases such as (CoNi)Cu4. In the early stages of formation, these precipitates maintain a coherent relationship with the copper matrix, leading to severe lattice distortion at the interface and generating a strong stress field. When dislocation lines encounter these hard, fine, and uniformly distributed precipitate particles during their movement, they cannot cut through them directly but must bend and bypass them, requiring a significant amount of additional energy. This, in turn, increases the strength and hardness of the copper alloy. Cobalt also refines grains (grain boundaries are another obstacle to dislocation movement) and suppresses the segregation of other elements, further enhancing strength.

[0022] 2. The present invention uses a small-diameter spot high-energy-density laser additive repair process to effectively reduce the heat-affected zone, reduce deformation, and improve repair quality.

[0023] 3. In the laser additive repair process of this invention, after each additive layer, when the temperature of the molten pool is in the range of 750℃-850℃, the molten pool is forged by laser micro-forging process, which effectively improves the density of the repair layer and thus improves the mechanical properties of the repair joint.

[0024] 4. After the laser additive repair is completed, the part is placed in a vacuum heat treatment furnace for tempering. While relieving stress, a strengthening phase can be precipitated in the repair layer, thereby improving the mechanical properties of the repair joint. Attached Figure Description

[0025] Figure 1 Flowchart of alloy powder and additive repair method for laser additive repair of QBe2 beryllium bronze; Figure 2 Schematic diagram of room temperature tensile testing for laser additive repair of QBe2 beryllium bronze Figure 3 A schematic diagram of laser additive repair for friction and wear of QBe2 beryllium bronze. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Example 1 An additive repair method for damaged beryllium bronze parts includes the following steps: (1) Cleaning of the area to be repaired: Mechanically grind the end face of the damaged part to be repaired to remove the oxide layer, ensuring that the metal luster is exposed and the surface is clean, and then clean with acetone; (2) Defect removal: After confirming the defect by fluorescence detection, use aluminum foil to protect the parts of the part that can be irradiated by the laser except for the area to be repaired, to prevent the laser irradiation from damaging the substrate of other parts during the repair process.

[0028] (3) Laser additive repair of beryllium bronze parts, the specific laser parameters are as follows: Carrier gas: 99.999% high-purity argon; Powder for laser restoration: Alloy powder for laser additive restoration of beryllium bronze; Laser power: 1400W; Scanning speed: 10mm / s; Spot diameter: 1.2mm; Powder feeder speed: 0.7 r / min; Powder delivery air flow rate: 5L / min; Protective gas flow rate: 19 L / min; Overlap rate: 50%; (4) During the laser additive repair process, for each additive repair layer, when the molten pool temperature is 800℃, laser micro-forging is used to forge the molten pool. The laser wavelength is 1064 nm, the pulse width is 8 ns, the frequency is 8 Hz, the pulse laser energy is 1.2 J, and the spot size is 1.5 mm; the thickness of each additive repair layer is no more than 0.3 mm. (5) After the laser micro-forging is completed, wait for the interlayer temperature to drop below 40°C and then use mechanical grinding to clean the surface of the additive repair layer to remove the oxide layer, ensuring that the metal luster is exposed and the surface is clean. Then clean with acetone and then add the next layer. (6) After laser additive repair is completed, the parts are placed in a vacuum heat treatment furnace for tempering, specifically at 320℃ for 4 hours, and then cooled with the furnace; the vacuum degree of tempering is 6.67×10 -3 Pa -6.67×10-2 Pa; (7) The tempered parts are machined to standard dimensions; (8) After machining, fluorescent flaw detection is performed and no cracks are found, thus completing the additive repair of damaged beryllium bronze parts.

[0029] Among them, five schemes for designing and preparing alloy powder for laser additive repair of beryllium bronze in step (3) are as follows: Option 1: Ni 29%, Co 10%, Fe 0.6%, Mn 0.8%, O 0.03%, balance Cu.

[0030] Option 2: Ni 29%, Co 14%, Fe 0.6%, Mn 0.8%, O 0.03%, balance Cu.

[0031] Option 3: Ni 30%, Co 14%, Fe 0.6%, Mn 0.8%, O 0.03%, balance Cu.

[0032] Option 4: Ni 30%, Co 15%, Fe 0.6%, Mn 0.8%, O 0.03%, balance Cu.

[0033] Option 5: Ni 33%, Co 15%, Fe 0.6%, Mn 0.8%, O 0.03%, balance Cu.

[0034] Experimental Example 1: Verification of Material-Level Mechanical Properties Currently, the failure mechanism of lead-bronze aircraft parts manufactured with QBe2 alloy in the aviation maintenance field is mainly friction and wear. Therefore, material-level testing is conducted to examine the bonding performance between the repair layer and the substrate, as well as the friction and wear performance of the repair layer. Based on this, and according to repair requirements, the bonding performance of the QBe2 alloy repair should not be less than 90% of that of the base material, and its wear resistance should be superior to that of the base material. Laser additive repair powder is then applied to the QBe2 alloy substrate, such as... Figure 2 , Figure 3 Room temperature tensile specimens and friction and wear specimens were prepared, and the performance of the specimens was tested. The results of the performance comparison are shown in Table 1.

[0035] Table 1

[0036] Performance comparison showed that using the alloy powder of this invention for laser additive repair resulted in a maximum tensile strength of 91.64% of that of the substrate. At the same time, the friction coefficient of the laser repair layer was lower than that of the substrate, indicating that the wear resistance of the repair layer was superior to that of the substrate.

[0037] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. An alloy powder for laser additive repair of beryllium bronze, characterized in that, It includes the following elements by mass percentage: Ni 29-33%, Co 10-15%, Fe ≤0.9%, Mn ≤1.2%, O ≤0.03%, with the balance being Cu.

2. The alloy powder for laser additive repair of beryllium bronze according to claim 1, characterized in that, The alloy powder has a particle size of 53μm-150μm, and the proportion of components with a particle size <53μm is ≤5%, and the proportion of components with a particle size >150μm is ≤5%.

3. A method for additive repair of damaged beryllium bronze parts, characterized in that, The method of using the laser additive repair alloy powder for beryllium bronze as described in claim 1 or 2 includes the following steps: (1) Cleaning of the area to be repaired: Mechanically grind the end face of the damaged part to be repaired to remove the oxide layer, ensuring that the metal luster is exposed and the surface is clean, and then clean with acetone; (2) Defect removal: Protect the parts of the part that can be irradiated by the laser, except for the area to be repaired, with aluminum foil; (3) Laser additive repair of beryllium bronze parts, the specific laser parameters are as follows: Carrier gas: 99.999% high-purity argon; Powder for laser repair: alloy powder; Laser power: 1200-1400W; Scanning speed: 8-10 mm / s; Spot diameter: 1-1.2mm; Powder feeder speed: 0.5-0.8 r / min; Powder delivery gas flow rate: 4-6 L / min; Protective gas flow rate: 18-20 L / min; Overlap rate: 40%-50%; (4) During the laser additive repair process, for each additive repair layer, when the temperature of the molten pool is between 750℃ and 850℃, laser micro-forging is used to forge the molten pool. After the laser micro-forging is completed, when the interlayer temperature drops below 40℃, the next layer is repaired by laser additive repair. (5) After the laser additive repair is completed, the parts are placed in a vacuum heat treatment furnace for tempering; (6) The tempered parts are machined to standard dimensions; (7) After machining, fluorescent flaw detection is performed and no cracks are found, thus completing the additive repair of damaged beryllium bronze parts.

4. The additive repair method for damaged beryllium bronze parts according to claim 3, characterized in that, In step (4), the thickness of each additive repair layer shall not exceed 0.3 mm.

5. The additive repair method for damaged beryllium bronze parts according to claim 3 or 4, characterized in that, The parameters of the laser micro-forging are: laser wavelength 1064 nm, pulse width 8 ns, frequency 5-10 Hz, pulse laser energy 1-1.2 J, and spot size 1.5 mm.

6. The additive repair method for damaged beryllium bronze parts according to claim 3, characterized in that, After the interlayer temperature drops below 40°C in step (4), the surface of the additive repair layer is cleaned by mechanical grinding to remove the oxide layer, ensuring that the metal luster is exposed and the surface is clean. Then, it is cleaned with acetone and then the next layer is added to repair.

7. The additive repair method for damaged beryllium bronze parts according to claim 3, characterized in that, The tempering method in step (5) is to hold at 280-330℃ for 2-4 hours, and then cool it with the furnace; the vacuum degree of the tempering is 6.67×10. -3 Pa -6.67×10 -2 Pa.

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