Processing method of monofilament SiC fiber reinforced Ti2AlNb composite high-temperature fastener

Abstract

The application belongs to the field of SiC fiber reinforced titanium-aluminum matrix composite structural part processing, and particularly relates to a processing method of single-fiber SiC fiber reinforced Ti2AlNb composite high-temperature fastener. The fastener is prepared by using the precursor wire method and the hot isostatic pressing process. The internal composite reinforced core of the fastener is composed of single-fiber SiC fiber and a Ti2AlNb alloy substrate prepared by magnetron sputtering. The external part of the fastener is a Ti2AlNb alloy sheath structure. The composite material and the sheath are densified and formed by hot isostatic pressing. The processing method of the fastener takes coaxial processing of the composite reinforced core and the external sheath as the goal, proposes a processing reference determination method, formulates processing procedures and process parameters in combination with the structural characteristics of the fastener and the processing methods of various parts, and ensures high-quality processing quality of the composite high-temperature fastener. The internal fiber of the fastener prepared by the application is coaxially distributed with the external sheath, so that the composite material in the fastener can exert excellent bearing capacity.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of SiC fiber reinforced titanium-aluminum matrix composite structural part processing, and particularly relates to a processing method of single-fiber SiC fiber reinforced Ti2AlNb composite high-temperature fastener. BACKGROUND

[0002] In high-speed aircraft, high-temperature fasteners are important parts for ensuring the safe connection between components. The existing high-temperature fasteners adopt high-temperature alloy structures, and the material strength and temperature resistance are important bases for part selection. Due to the large amount of fasteners used in aircraft, the structural weight of the parts is one of the problems that must be considered in aircraft design and performance improvement. The high-temperature alloy has a large density, and the total weight of the fasteners used in some components is relatively large, even exceeding the weight of the components themselves, which is not conducive to the power improvement of the aircraft. Therefore, the demand for weight reduction of high-temperature fasteners is imminent. Continuous single-fiber SiC fibers have high specific strength, high specific modulus and good high-temperature performance along the fiber axis, and are suitable for preparing unidirectional selective reinforced components. The high-temperature fastener prepared by using SiC fiber reinforced Ti2AlNb composite material can be used above 800 DEG C. Compared with high-temperature alloy fasteners, the structure can be reduced by more than 35% under the same specification and stress conditions. Therefore, using SiC f / Ti2AlNb composite material to replace high-temperature alloy fasteners is an inevitable development trend for high-performance aircraft to achieve structural weight reduction and performance improvement.

[0003] The preparation method of the single-fiber SiC fiber reinforced Ti2AlNb composite high-temperature fastener adopts the precursor wire method + hot isostatic pressing + machining forming process. Among them, the fastener processing quality is one of the key processes for determining the optimal bearing capacity of the composite material. The composite fastener has a "sandwich" structure, and the integrity and coaxiality of the internal reinforcing core are closely related to the performance of the fastener. The composite fastener is not suitable for the conventional metal fastener extrusion forming method, and the coaxiality of the internal reinforcing core and the outer sleeve, the surface without obvious oxidation, the good bonding between the internal fibers and the interface, and other processing qualities must be ensured during the processing of the composite fastener. SUMMARY

[0004] The purpose of the present application is to provide a processing method of single-fiber SiC fiber reinforced Ti2AlNb composite high-temperature fastener. For the "sandwich" structure of the composite fastener, a processing reference positioning method is proposed, and the fastener processing sequence, the processing equipment suitable for the composite material component in the multi-processing procedure and the key process parameters are specified. The composite high-temperature fastener processed by the present application meets the key technical requirements of the coaxiality of the internal reinforcing core and the outer sleeve, the surface without obvious oxidation, the good bonding between the internal fibers and the interface, and other processing qualities. The composite high-temperature fastener is used to replace the high-temperature alloy fastener, and the structure can be reduced by more than 35% under the same specification and stress conditions.

[0005] To achieve the above object, the technical scheme adopted by the present application is as follows:

[0006] A processing method of monofilament SiC fiber reinforced Ti2AlNb composite high-temperature fastener, the method comprising the following steps:

[0007] (1) determining the fastener processing reference, taking the axial center range of the fastener blank after hot isostatic pressing as the reference processing area, clamping and fixing one end of the SiC f / Ti2AlNb composite high-temperature fastener blank after hot isostatic pressing on the numerical control lathe to carry out reference alignment; select three circumferences in the middle region of the blank axis, which are the blank axial center circumference and two circumferences at a distance of x from the center, and the value of x is in the range of 10% to 20% of the length of the blank; each circumference is divided into 4 points at intervals of 90° for table alignment, and when the diameter deviation of two points at intervals of 180° is ≯0.05mm, it is considered that the processing reference adjustment is completed;

[0008] (2) after determining the reference, punch and fix the free end of the fastener blank; then use the numerical control lathe to process the fastener screw and thread by turning, the cutting amount is 0.1mm to 0.5mm, the feed rate is 10mm / min to 30mm / min, and the blank rotation speed is 400rad / min to 1500rad / min;

[0009] (3) use a diamond wire cutting machine to cut off the excess length at both ends of the fastener, cut off the length of the thread tail and the bolt head to meet the length requirement of the drawing, and the wire speed of the diamond wire cutting is 0.2mm / min to 2.0mm / min;

[0010] (4) use a milling machine to process the fastener bolt head to the structure of the drawing.

[0011] The processing method of the monofilament SiC fiber reinforced Ti2AlNb composite high-temperature fastener is suitable for precision machining of SiC f / Ti2AlNb composite high-temperature fasteners prepared by precursor filament method + hot isostatic pressing process.

[0012] The processing method of the monofilament SiC fiber reinforced Ti2AlNb composite high-temperature fastener, the inside of the fastener is a SiC f / Ti2AlNb composite reinforced core, and the outside of the fastener is a Ti2AlNb alloy sheath, the SiC f / Ti2AlNb composite reinforced core and the Ti2AlNb alloy sheath are densified and formed by hot isostatic pressing; wherein, the SiC fThe Ti2AlNb composite material reinforcing core is composed of single SiC fiber and Ti2AlNb alloy substrate prepared by a magnetron sputtering technology, the Ti2AlNb alloy substrate is coated on the periphery of each single SiC fiber, and the single SiC fiber is uniformly distributed in the Ti2AlNb alloy substrate.

[0013] In the processing method of the single SiC fiber reinforced Ti2AlNb composite material high-temperature fastener, after the fastener processing reference is determined in the processing process of the single SiC fiber reinforced Ti2AlNb composite material high-temperature fastener blank, the SiC f The Ti2AlNb composite material reinforcing core is coaxially processed with the Ti2AlNb alloy sheath outside the fastener, and coaxial distribution is realized.

[0014] In the processing method of the single SiC fiber reinforced Ti2AlNb composite material high-temperature fastener, the SiC f The size and fiber volume fraction of the Ti2AlNb composite material reinforcing core.

[0015] In the processing method of the single SiC fiber reinforced Ti2AlNb composite material high-temperature fastener, the fastener bolt head is completed by using a milling process, and is processed into a hexagonal or countersunk structure according to the requirements of the drawing.

[0016] The design idea of the application is:

[0017] Firstly, the processing method of the single SiC fiber reinforced Ti2AlNb composite material high-temperature fastener is different from the processing method of the metal fastener, and the fastener reference positioning method is proposed according to the sandwich structure of the composite material, so that the coaxial processing of the composite material reinforcing core inside the fastener and the outer sheath is ensured.

[0018] Secondly, the processing method of the single SiC fiber reinforced Ti2AlNb composite material high-temperature fastener is clear about the processing equipment and key process parameters used in each process in the processing process according to the structural characteristics of the composite material.

[0019] Thirdly, the processing method of the single SiC fiber reinforced Ti2AlNb composite material high-temperature fastener is clear about the processing equipment and key process parameters used in each process in the processing process according to the structural characteristics of the composite material. f The Ti2AlNb composite material high-temperature fastener has excellent performance, the coaxiality of the reinforcing core inside the fastener and the outer sheath is good, the surface is not obviously oxidized, the internal fiber and the interface are well combined, the same specification high-temperature alloy fastener can be replaced, and the structure weight reduction of more than 35% can be realized.

[0020] The application has the following advantages and beneficial effects:

[0021] 1. This invention proposes a processing method for high-temperature fasteners made of monofilament SiC fiber reinforced Ti2AlNb composite material, which realizes the coaxial processing of composite material reinforcing core and outer sleeve, ensuring that the high-temperature fasteners made of composite material can exert optimal load-bearing capacity.

[0022] 2. The high-temperature fasteners of SiC fiber-reinforced Ti2AlNb composite material processed by this invention, based on the material structural characteristics, specify the applicable processing equipment and key process parameters for the processing steps. The high-temperature fasteners of composite materials processed by this method have no obvious oxidation on the surface and good bonding between the internal fibers and the interface, thus meeting the processing quality requirements of composite fasteners. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the blank structure after hot isostatic pressing of a high-temperature fastener made of SiC fiber reinforced Ti2AlNb composite material.

[0024] In the figure, 11-SiC f / Ti2AlNb composite material reinforced core, 12-Ti2AlNb alloy sheath.

[0025] Figure 2 This is a cross-sectional view of a high-temperature fastener blank made of SiC fiber reinforced Ti2AlNb composite material.

[0026] In the figure, 21 represents a single-filament SiC fiber, 22 represents a Ti2AlNb alloy matrix, and 12 represents a Ti2AlNb alloy sheath.

[0027] Figure 3 This is a schematic diagram showing the machining reference for a high-temperature fastener blank made of SiC fiber reinforced Ti2AlNb composite material after being clamped on a lathe.

[0028] Figure 4 This is a schematic diagram of the screw and thread processing of a high-temperature fastener blank made of SiC fiber reinforced Ti2AlNb composite material.

[0029] Figure 5 This diagram illustrates the length of the end face of a high-temperature fastener blank made of SiC fiber-reinforced Ti2AlNb composite material removed using diamond wire cutting.

[0030] Figure 6 This is a schematic diagram of milling bolt heads on a high-temperature fastener blank made of SiC fiber-reinforced Ti2AlNb composite material.

[0031] Figure 7 This is a photograph of a high-temperature fastener made of SiC fiber-reinforced Ti2AlNb composite material. Detailed Implementation

[0032] In the specific implementation process, for SiC fBased on the "sandwich" structure characteristics and composite material properties of high-temperature fasteners made of Ti2AlNb composite materials, this invention proposes a processing method for high-temperature fasteners made of monofilament SiC fiber reinforced Ti2AlNb composite materials. Aiming at coaxial machining of the composite material reinforcing core and outer sheath, a method for determining the machining datum is proposed. Combining the structural characteristics of the fastener and the machining methods of each part, machining procedures and process parameters are formulated to ensure high-quality machining of the high-temperature composite material fasteners. The specific machining process is as follows: First, the machining datum of the fastener is determined, with the axial center range of the fastener blank after hot isostatic pressing as the datum machining area. One end of the blank is clamped and fixed using a CNC lathe. The axial center circumference of the fastener blank is taken, and together with two circumferences x-lengths from the center circumference, they are used as the machining datum circumference. The value of x ranges from 10% to 20% of the blank length. Each circumference is divided into four points for dial indicator alignment. The criterion for determining the datum is that the diameter deviation between two points on the same circumference is ≤0.05mm. After determining the datum, the free end of the fastener blank is drilled and fixed. The fastener screw and thread are then machined using a CNC lathe. A diamond wire EDM machine is used to remove the thread tail and bolt head length to meet the drawing requirements. Finally, a milling machine is used to machine the fastener bolt head to the structure specified in the drawing.

[0033] SiC prepared by the method of the present invention f The Ti2AlNb composite high-temperature fastener features coaxial distribution of internal fibers and outer sheath, ensuring excellent load-bearing capacity of the composite material. The composite material cross-section at the bolt head tip and thread tail end is flat, with no obvious oxide layer, and the fiber-matrix interface is well-bonded. This overcomes the current technical bottleneck of lacking processing methods for composite high-temperature fasteners, avoiding the problem of reduced load-bearing capacity caused by fiber exposure on the component surface or poor core coaxiality due to misalignment of the internal composite reinforcement core. This invention guides the development of SiC... f High-quality machining of Ti2AlNb composite high-temperature fasteners: High-temperature fasteners made of composite materials processed using this method can replace existing high-temperature alloy fasteners, achieving a weight reduction of more than 35%.

[0034] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0035] like Figures 1-2 As shown, the high-temperature fastener blank of SiC fiber-reinforced Ti2AlNb composite material is prepared by the pilot wire method + hot isostatic pressing process, and the fastener interior is SiC. f / Ti2AlNb composite material reinforced core 11, fastener exterior is Ti2AlNb alloy sheath 12, SiC f The Ti2AlNb composite reinforcing core 11 and the Ti2AlNb alloy cladding 12 are formed by hot isostatic pressing. Among them, SiC... fThe Ti2AlNb composite material reinforcing core 11 is composed of single-filament SiC fibers 21 and Ti2AlNb alloy matrix 22 prepared by magnetron sputtering technology. The Ti2AlNb alloy matrix 22 covers the periphery of each single-filament SiC fiber 21, and the single-filament SiC fibers 21 are uniformly distributed in the Ti2AlNb alloy matrix 22.

[0036] Example 1

[0037] In this embodiment, a method for processing a high-temperature fastener made of monofilament SiC fiber reinforced Ti2AlNb composite material includes the following steps:

[0038] (1) As Figure 3 As shown, the high-temperature fastener blank (specifications) of SiC fiber reinforced Ti2AlNb composite material after hot isostatic pressing is shown. The blank is clamped on a CNC lathe, and three circumferences are selected at 10mm intervals in the middle area for machining datum alignment. The diameter deviation of each circumference is 0.008mm.

[0039] (2) Figure 4 As shown, the free end of the fastener blank is drilled and fixed. The screw and thread of the fastener blank are machined using a CNC lathe with a cutting amount of 0.2 mm, a feed rate of 20 mm / min, and a blank rotation speed of 1000 rad / min.

[0040] (3) Figure 5 As shown, using a diamond wire EDM machine, 8mm is cut off from each end of the fastener blank, with a wire feed rate of 0.5mm / min. The end face of the fastener blank is removed by diamond wire EDM to remove the length excess. The composite material cut by this method has a flat cross-section, no obvious oxide layer on the surface, and good bonding between the fiber and the matrix interface.

[0041] (4) Figures 6-7 As shown, a milling machine is used to mill the head of the fastener bolt into a hexagonal structure.

[0042] This embodiment addresses the structural characteristics of composite materials by specifying the processing equipment and key process parameters for multiple machining steps. During processing, appropriate process parameters are employed, and the machining sequence for fastener screws, threads, and bolt heads is proposed to reduce the impact of residual stress on fastener performance. The monofilament SiC fiber-reinforced Ti2AlNb composite material obtained by this method exhibits no obvious oxide layer and good surface finish, solving problems such as oxidation and discoloration of the component surface and adjacent areas caused by wire EDM, and interface damage and cracking of the composite material caused by turning.

[0043] The results of the implementation show that this invention proposes a method for processing high-temperature fasteners made of monofilament SiC fiber-reinforced Ti2AlNb composite materials. The SiC fasteners processed by this method...f The high-temperature fasteners made of Ti2AlNb composite material ensure coaxial machining of the internal composite material and the external sheath, with no obvious oxidation on the fastener end face and good bonding between the fiber and the matrix interface, ensuring that the composite material exerts its reinforcing effect during service. The SiC processed by the method of this invention... f Ti2AlNb composite high-temperature fasteners can replace high-temperature alloy fasteners for safe use in harsh high-temperature environments.

Claims

1. A method for processing high-temperature fasteners made of monofilament SiC fiber reinforced Ti2AlNb composite material, characterized in that, The method includes the following steps: (1) Determine the fastener machining datum. The axial center range of the fastener blank after hot isostatic pressing is taken as the datum machining area. The hot isostatic pressed SiC f The Ti2AlNb composite high-temperature fastener blank is clamped and fixed at one end on a CNC lathe for datum alignment. Three circles are selected in the middle area of ​​the blank's axial direction: the central circle of the blank's axial direction and two circles at a distance x from the center. The value of x ranges from 10% to 20% of the blank's length. Each circle is divided into four points at 90° intervals for dial indicator alignment. When the diameter deviation between two points at 180° intervals is ≤0.05mm, the machining datum adjustment is considered complete. (2) After determining the reference, the free end of the fastener blank is fixed by drilling; then the fastener screw and thread are machined by CNC lathe with a cutting amount of 0.1mm to 0.5mm, a feed rate of 10mm / min to 30mm / min, and a blank rotation speed of 400rad / min to 1500rad / min. (3) Use a diamond wire cutting machine to cut off the excess length at both ends of the fastener, and cut off the thread tail and bolt head length to meet the length requirements of the drawing. The diamond wire cutting feed rate is 0.2mm / min~2.0mm / min. (4) Use a milling machine to machine the head of the fastener bolt to the structure shown in the drawing; This method is applicable to SiC prepared by the precursor wire method combined with hot isostatic pressing. f Precision machining of high-temperature fasteners made of Ti2AlNb composite material; the fastener interior is SiC. f / Ti2AlNb composite material reinforced core, fasteners are externally clad in Ti2AlNb alloy, SiC f The Ti2AlNb composite reinforcing core and Ti2AlNb alloy cladding are formed by hot isostatic pressing; among them, SiC f The Ti2AlNb composite material reinforcing core is composed of single-filament SiC fibers and a Ti2AlNb alloy matrix prepared by magnetron sputtering technology. The Ti2AlNb alloy matrix covers the periphery of each single-filament SiC fiber, and the single-filament SiC fibers are evenly distributed in the Ti2AlNb alloy matrix. During the machining of high-temperature fastener blanks made of monofilament SiC fiber reinforced Ti2AlNb composite material, after determining the fastener machining datum, the SiC content inside the fastener is ensured. f The Ti2AlNb composite material reinforcing core and the Ti2AlNb alloy cladding on the outside of the fastener are coaxially machined to achieve coaxial distribution.

2. The processing method of the high-temperature fastener of monofilament SiC fiber reinforced Ti2AlNb composite material according to claim 1, characterized in that, Design the SiC inside the fastener as needed f / Ti2AlNb composite material reinforcing core size and fiber volume fraction.

3. The processing method of the high-temperature fastener of monofilament SiC fiber reinforced Ti2AlNb composite material according to claim 1, characterized in that, The heads of the fastener bolts are finished by milling, and are machined into hexagonal or countersunk structures according to the drawings.

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