Electroplated carbon fiber reinforced wide-gap brazing filler metal and preparation method thereof

Abstract

The invention relates to a method for preparing Ni-Cr-Fe-Si-W-Nb-Ta-Cf series wide-gap brazing filler metal with high mechanical property by doping electroplated carbon fibers. The method is characterized in that electroplated carbon fibers are used as a reinforcing phase for improving the mechanical property of the brazing filler metal to be doped into a mixture of the brazing filler metal and alloy powder, and the electroplated nickel metal carbon fiber reinforced wide-gap brazing filler metal with the high mechanical property is prepared. Based on the method, the novel Ni-Cr-Fe-Si-W-Nb-Ta-Cf series wide-gap brazing filler metal is prepared, high-temperature stretching and high-cycle fatigue tests show that when 1.33 wt% of nickel-plated carbon fibers are added, the tensile strength of a brazed joint is the highest, and the elongation at break of the wide-gap brazed joint is obviously improved based on the toughening effect of the carbon fibers. The tensile strength of the brazing filler metal added with 1.33% (wt) of nickel-plated carbon fibers is 401.64 MPa under the condition of 650 DEG C, and the fatigue limit is 260 MPa when the high-cycle fatigue life reaches 107 cycles; and the tensile strength corresponding to 900 DEG C is 360.04 MPa, and the fatigue limit is 160 MPa when the high-cycle fatigue life reaches 107 cycles.

Description

Technical Field

[0001] The invention relates to the field of brazing material research and development, and specifically to a method for preparing an electroplated carbon fiber reinforced wide-gap brazing brazing material. The electroplated nickel metal carbon fiber reinforced wide-gap brazing brazing brazing material prepared by the method can significantly improve the high-temperature mechanical properties of wide-gap brazing joints based on the toughening effect of carbon fiber. Background Art

[0002] In view of the presence of high-hardness, brittle, low-melting-point eutectic products in nickel-based wide-gap brazed joints, and the tendency of composition segregation of elements in the joint structure, it is easy to cause obvious differences in microhardness between phases and uneven distribution, resulting in insufficient toughness. Therefore, based on the bridging mechanism toughening theory of fibrous reinforcement, chopped carbon fibers are selected to improve the toughness of wide-gap brazed joints. At the same time, the negative temperature effect (negative temperature coefficient, NTC) of carbon fibers is utilized. The radial expansion and axial contraction at high temperature can further consolidate the joint structure, improve the thermal strength of the joint, and thus enhance the high-temperature mechanical properties of the nickel-based wide-gap brazed joints.

[0003] The present invention is a method for preparing Ni-Cr-Fe-Si-W-Nb-Ta-C with high mechanical properties by doping electroplating carbon fiber. f The invention discloses a method for wide gap brazing of brazing filler metal. Based on the method, the invention prepares a new type of Ni-Cr-Fe-Si-W-Nb-Ta-C f It is a wide gap brazing filler metal. High temperature tensile and high cycle fatigue tests show that the mechanical properties of wide gap brazing joints can be significantly enhanced by doping nickel-plated carbon fibers. Summary of the invention

[0004] The purpose of the present invention is to meet the development needs of a new generation of brazing technology, overcome the shortcomings of existing wide-gap brazing technology, and provide a method for preparing an electroplated carbon fiber reinforced wide-gap brazing filler metal that can significantly improve the high-temperature mechanical properties of the brazed joint.

[0005] To achieve the above object, the present invention is implemented through the following technical solutions:

[0006] The invention provides a method for preparing an electroplated fiber reinforced wide gap brazing filler metal, taking the preparation of an electroplated nickel metal carbon fiber reinforced wide gap brazing filler metal as an example.

[0007] The method for preparing the nickel-plated metal carbon fiber reinforced wide gap brazing filler metal comprises the following steps:

[0008] Step 1: Prepare the plating solution. The plating solution consists of 123 g / L nickel sulfate (NiSO4·6H2O), 30 g / L boric acid (H3BO3), 32 g / L nickel chloride (NiCl2·6H2O), and sodium dodecyl sulfate (C 12 H 25 NaO4) 0.12g / L. Nickel sulfate is used as the main source of nickel ions in the nickel plating layer, boric acid is used to adjust the pH value of the solution, and pH test paper is used to maintain the pH value of the solution between 3 and 4, and nickel chloride is used as an anode active agent.

[0009] Step 2: Electroplating of carbon fiber with nickel. During electroplating, the solution temperature is controlled between 20 and 40°C, the cathode of the power supply is connected to the carbon fiber, and the anode is connected to the pure nickel test piece. The anode is dissolved to replenish nickel ions in the electroplating solution, and the current density is 0.6A / dm 2 , the plating time is 5 minutes. Figure 1 This is a real picture of nickel-plated carbon fiber. Figure 2 SEM image and EDS spectrum of nickel-coated carbon fiber.

[0010] Step 3: Cut the carbon fiber with nickel plating into short carbon fiber with a length of less than 1 mm, mix it into a mixture of Ni-Cr-Fe-Si-W-Nb-Ta brazing material and Hastelloy X alloy powder, and prepare electroplated nickel metal carbon fiber reinforced wide gap brazing brazing material.

[0011] The mechanical properties of the prepared solder are characterized as follows:

[0012] Figure 3 The stress-strain curves of wide gap brazed joints with different contents of nickel-plated carbon fiber. The tensile strengths of the joints corresponding to the nickel-plated carbon fiber contents of 0.66%, 0.93%, 1.33%, 4% and 6.66% are 428.53MPa, 468.96MPa, 544.71MPa, 488.20MPa and 323.96MPa, respectively. According to the tensile test results, when the content of nickel-plated carbon fiber is within 1.33%, the tensile strength of the brazed joint increases with the increase of the nickel-plated carbon fiber content; when the content of nickel-plated carbon fiber exceeds 1.33%, the joint strength decreases significantly with the increase of the nickel-plated carbon fiber content. With the continuous increase of the nickel-plated carbon fiber content, the strength of the brazed joint presents a single-peak distribution characteristic, indicating that the doping of nickel-plated carbon fiber in the wide gap brazed joint is beneficial to the improvement of its tensile strength.

[0013] Figure 4 and 5The stress-strain curves of undoped nickel-plated carbon fiber, doped nickel-plated carbon fiber and Hastelloy X parent material at 650℃ and 900℃, respectively. The tensile strengths at 650℃ are 359.71MPa, 401.64MPa and 720.20MPa, respectively; the tensile strengths at 900℃ are 322.51MPa, 360.04MPa and 663.84MPa, respectively. The tensile strengths of the two wide gap brazed joints and the parent material decrease with increasing temperature. At 650℃, the strengths of the wide gap brazed joints of undoped nickel-plated carbon fiber and doped nickel-plated carbon fiber are about 49.95% and 55.68% of the parent material; at 900℃, the strengths of the wide gap brazed joints of undoped nickel-plated carbon fiber and doped nickel-plated carbon fiber are about 48.58% and 54.24% of the parent material. It can be seen that the tensile strength of the wide gap brazed joint of doped nickel-plated carbon fiber is about 40MPa higher than that of the joint of undoped nickel-plated carbon fiber.

[0014] Figure 6 The high cycle fatigue SN curve of the wide gap brazed joint at 650℃. At 650℃, the fatigue life of the wide gap brazed joint containing nickel-plated carbon fiber reaches 260MPa when the fatigue stress limit reaches 107 cycles, while the fatigue life of the wide gap brazed joint without doping reaches 220MPa when the fatigue stress limit reaches 107 cycles. The difference between the two is 40MPa, indicating that the doped nickel-plated carbon fiber significantly improves the fatigue life of the joint. There are two main reasons: First, the added nickel-plated carbon fiber significantly improves the tensile properties of the joint. The interface cracking and fiber pull-out of the nickel-plated carbon fiber can effectively improve the toughness of the joint, which hinders the initiation and expansion of fatigue cracks. Second, carbon fiber has a negative temperature coefficient. It shrinks axially and expands radially under high temperature conditions, which can further consolidate the density of the joint structure, thereby improving the thermal strength and thermal stability of the joint. At the same time, the radial expansion of the carbon fiber can resist the further derivation of tissue defects around the joint into crack sources. In addition, the carbon fiber itself has high strength and a low stress level for high-cycle fatigue. Fatigue cracks are difficult to penetrate nickel-plated carbon fiber, resulting in crack deflection when the fatigue crack encounters nickel-plated carbon fiber, further improving the toughness of the joint. Therefore, brazed joints doped with nickel-plated carbon fiber can significantly improve high-temperature fatigue performance.

[0015] Figure 7 The high cycle fatigue SN curve of the wide gap brazed joint of nickel-doped carbon fiber at 900℃. Under 900℃, only the high cycle stress fatigue performance of the wide gap brazed joint of nickel-doped carbon fiber is characterized. It can be seen that the fatigue stress limit reaching 107 cycle life is 160MPa, which is 100MPa lower than the fatigue limit reaching 107 at 650℃. Description of the drawings:

[0016] Figure 1 Nickel plating for carbon fiber surface

[0017] Figure 2 Surface morphology of carbon fiber before and after nickel plating (a) Surface morphology and energy spectrum results of carbon fiber without nickel plating (b) Surface morphology and energy spectrum results of carbon fiber after nickel plating

[0018] Figure 3 Stress-strain curves of wide gap brazed joints of carbon fibers with different nickel contents

[0019] Figure 4 Stress-strain curves of 650℃ wide gap brazing joints with / with nickel-plated carbon fiber and base material.

[0020] Figure 5 Tensile stress-strain curves of wide gap brazed joints with / with nickel-plated carbon fiber and base material at 900℃.

[0021] Figure 6 High cycle fatigue SN curve of wide gap brazed joint at 650℃

[0022] Figure 7 High cycle fatigue SN curve of wide gap brazed joint with nickel-doped carbon fiber at 900℃ Specific implementation method:

[0023] The present invention is now further described in conjunction with specific implementation examples:

[0024] Preparation of nickel-plated carbon fiber doped Ni-Cr-Fe-Si-W-Nb-Ta wide gap brazing filler metal, the preparation method is as follows:

[0025] The plating solution consists of 123 g / L nickel sulfate (NiSO4·6H2O), 30 g / L boric acid (H3BO3), 32 g / L nickel chloride (NiCl2·6H2O), and sodium dodecyl sulfate (C 12 H 25 NaO4) 0.12g / L. Nickel sulfate is used as the main nickel ion provider in the nickel plating layer. The main function of boric acid is to adjust the pH value of the solution. The pH value of the plating solution is adjusted to between 3 and 4 using pH test paper. Nickel chloride is used as an anode activator. During electroplating, the solution temperature is controlled between 20 and 40°C. The cathode of the power supply is connected to the carbon fiber, and the anode is connected to the pure nickel test piece. The anode dissolves to replenish nickel ions in the plating solution. The current density is 0.6A / dm 2 The electroplating time is 5 minutes. The carbon fiber with nickel coating is cut into short carbon fiber with a length of less than 1 mm, mixed with the mixture of brazing material and Hastelloy X alloy powder, and used to prepare wide gap brazing joints.

Claims

1. A method for preparing an electroplated carbon fiber reinforced wide gap brazing filler metal, taking the preparation of nickel-plated carbon fiber doped Ni-Cr-Fe-Si-W-Nb-Ta wide gap brazing filler metal as an example, the preparation method comprises the following steps: Step 1: Prepare the plating solution. The plating solution consists of 123 g / L nickel sulfate (NiSO4·6H2O), 30 g / L boric acid (H3BO3), 32 g / L nickel chloride (NiCl2·6H2O), and sodium dodecyl sulfate (C 12 H 25 NaO4) 0.12g / L. Nickel sulfate is used as the main source of nickel ions in the nickel plating layer, boric acid is used to adjust the pH value of the solution, and pH test paper is used to maintain the pH value of the solution between 3 and 4, and nickel chloride is used as an anode active agent. Step 2: Electroplating of carbon fiber with nickel. During electroplating, the solution temperature is controlled between 20 and 40°C, the cathode of the power supply is connected to the carbon fiber, and the anode is connected to the pure nickel test piece. The anode is dissolved to replenish nickel ions in the electroplating solution, and the current density is 0.6A / dm 2 , the electroplating time is 5 minutes. Figure 1 is a physical picture of carbon fiber electroplating nickel. Step 3: Cut the carbon fiber with nickel plating into short carbon fiber with a length of less than 1 mm, mix it into a mixture of Ni-Cr-Fe-Si-W-Nb-Ta brazing material and Hastelloy X alloy powder, and prepare electroplated nickel metal carbon fiber reinforced wide gap brazing brazing material.

2. The method for preparing the electroplated carbon fiber reinforced wide gap brazing filler metal according to claim 1, characterized in that: Electroplated carbon fiber is used as a reinforcing phase to improve the mechanical properties of the brazing filler metal and is doped into a mixture of the brazing filler metal and alloy powder to prepare an electroplated nickel metal carbon fiber reinforced wide gap brazing filler metal with high mechanical properties.

3. The method for preparing the electroplated carbon fiber reinforced wide gap brazing filler metal according to claim 1, characterized in that: In step 2, a metal layer is electroplated on the carbon fiber to be doped into the solder.

4. The method for preparing the electroplated carbon fiber reinforced wide gap brazing filler metal according to claim 1, characterized in that: In step 3, the electroplated carbon fiber is chopped short, and then the chopped electroplated carbon fiber is mixed into the mixture of solder and alloy powder as a mechanical property enhancement phase.

5. Based on a method for preparing electroplated carbon fiber reinforced wide gap brazing brazing filler metal, a nickel-plated short carbon fiber Ni-Cr-Fe-Si-W-Nb-Ta-C with high mechanical properties was prepared. f Wide gap brazing filler metal.

6. A nickel-plated chopped carbon fiber Ni-Cr-Fe-Si-W-Nb-Ta-C with high mechanical properties as claimed in claim 5 f Wide gap brazing filler metal, characterized in that: Nickel-plated chopped carbon fibers are used as reinforcement phase to improve the mechanical properties of the brazing filler metal.

7. A nickel-plated chopped carbon fiber Ni-Cr-Fe-Si-W-Nb-Ta-C with high mechanical properties as claimed in claim 5. f Wide gap brazing filler metal, characterized in that: When 1.33% (wt) nickel-plated carbon fiber is added, the tensile strength of the brazed joint is the highest, and the elongation at break of the wide gap brazed joint is significantly improved based on the toughening effect of the carbon fiber.

8. A nickel-plated chopped carbon fiber Ni-Cr-Fe-Si-W-Nb-Ta-C with high mechanical properties as claimed in claim 5 f Wide gap brazing filler metal, characterized in that: Under the condition of 650℃, the tensile strength of the brazed joint prepared by adding 1.33% (wt) nickel-plated carbon fiber to the brazing material is 401.64MPa; the corresponding tensile strength at 900℃ is 360.04MPa.

9. A nickel-plated chopped carbon fiber Ni-Cr-Fe-Si-W-Nb-Ta-C with high mechanical properties as claimed in claim 5 f Wide gap brazing filler metal, characterized in that: The fatigue limit of the wide gap brazing joint with 1.33% (wt) nickel-plated carbon fiber added at 650°C is 260MPa when the high cycle fatigue life reaches 107 cycles; the fatigue limit of the wide gap brazing joint at 900°C is 160MPa when the high cycle fatigue life reaches 107 cycles.

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