Copper-based graphite sealing material for aircraft engines and preparation method thereof

Abstract

The present invention provides a copper-based graphite sealing material for an aero-engine and a preparation method thereof, which can meet the performance requirements of a sealing bushing for an aero-engine in different directions. This material is a copper-based graphite sealing material with anisotropic lamellar graphite in a directional arrangement. The raw materials used in this material are composed, by mass percentage, of 60%-70% copper powder, 18%-32% iron powder, 6%-12% graphite, 0.01%-0.5% silicon dioxide, 0.01%-0.5% aluminum oxide and 0.01%-0.5% tungsten disulfide, with the total mass percentage of the above components being 100%. The copper powder is irregular electrolytic copper powder, wherein the Cu content is ≥99.9% and the particle size range is 48-100μm. The iron powder is porous sponge iron powder, wherein the Fe content is ≥99.9% and the particle size range is 48-100μm. The graphite is natural lamellar graphite, with a particle size range of 48-100μm and a thickness range of 8-18μm. The particle size of silicon dioxide, aluminum oxide and tungsten disulfide is 2-5μm.

Description

Technical Field

[0001] The invention belongs to the technical field of sealing materials, and in particular relates to a copper-based graphite sealing material for an aero-engine and a preparation method thereof. Background Art

[0002] The dynamic seal of an aircraft engine mainly adopts a non-contact grate seal structure, which uses the sudden expansion and contraction of the channel to increase the flow resistance to limit fluid leakage. It has the characteristics of high speed, high pressure, high vibration and special sealing medium. The grate seal consists of grate teeth as the rotor and a sealing bushing (also called sealing bushing) as the stator. Generally, in order to reduce sealing leakage and thus improve the operating efficiency of the engine, the operating clearance between the rotor and the stator needs to be minimized. During service, the clearance is affected by the radial movement caused by cumulative errors, dynamic deflection and thermal deformation, making it difficult to determine the minimum clearance during design. In order to ensure normal and stable operation when friction occurs, the sealing bushing material that allows contact friction at non-working points is generally designed to be abradable and act as a sacrificial material. The operating end clearance is reduced by rotor scraping, while keeping the grate wear to a minimum. The sealing performance and operational reliability of aircraft engine grate seals depend largely on the performance of the sealing bushing material. The material needs to have excellent tribological characteristics and lubrication conditions at the contact surface between the bushing and the rotor to protect the rotating parts from damage during service. It also needs to have appropriate physical and mechanical properties to avoid failure during service, and it needs to have good corrosion resistance to adapt to the sealing of special media.

[0003] At present, the commonly used sealing materials for grate seal bushings include: carbon / graphite sealing materials, carbon / carbon composite materials, metal alloys coated with abradable sealing coatings, powder metallurgy sealing materials, etc. Among them, copper-based graphite sealing materials are widely concerned as the preferred material for sealing medium and low temperature oil media at this stage. As a typical composite material, copper-based graphite sealing materials can be designed to meet specific requirements according to the operating conditions, and are an important research direction in the field of sealing materials. However, due to the large difference in physical properties between the copper phase and graphite and their poor lubricity, the interfacial bonding performance of the two phases is poor, which seriously affects the mechanical and tribological properties of the material and limits its application. Currently, copper-based graphite sealing materials are mainly designed and strengthened through matrix reinforcement, graphite surface treatment (see Chinese patent application CN 114000007 A), or a combination of the two methods (see Chinese patent CN 107586989B and Chinese patent CN 110791676B). These methods can significantly improve material performance, but these process methods generally have disadvantages such as complex process, unstable quality, and high cost.

[0004] Therefore, grate seal bushings used in aircraft engine oil systems must maintain low friction and wear under high-speed sliding conditions, and possess excellent mechanical properties in the diametrical direction to ensure integrity during installation and use. Leveraging the designability of composite materials, this paper has developed a copper-based graphite sealing material for aircraft engines that features a simple preparation process, a short production cycle, and is economical and reliable. Summary of the Invention

[0005] In view of the differences in performance requirements required for sealing bushings for aircraft engines in different directions, the present invention provides a copper-based graphite sealing material with oriented lamellar graphite for aircraft engines and a preparation method thereof. The material has typical anisotropy of mechanical properties and friction properties, with good mechanical properties in the direction perpendicular to the oriented arrangement of the lamellar graphite and excellent friction and wear properties in the direction parallel to the oriented arrangement of the lamellar graphite. The anisotropic characteristics of the material can simultaneously meet the performance requirements of the aircraft engine sealing material in different directions. At the same time, the preparation process is simple, the cycle is short, and stable mass production is possible.

[0006] To achieve the above objectives, the technical solutions provided by the present invention are:

[0007] The present invention provides a copper-based graphite sealing material for aircraft engines, which is special in that it is a copper-based graphite sealing material with oriented lamellar graphite.

[0008] The raw materials used for the copper-based graphite sealing material are composed of 60%-70% copper powder, 18%-32% iron powder, 6%-12% graphite, 0.01%-0.5% silicon dioxide, 0.01%-0.5% aluminum oxide and 0.01%-0.5% tungsten disulfide in terms of mass percentage, and the total mass percentage of the above components is 100%;

[0009] Because the purity and particle size of the powder will directly affect the mechanical properties and friction properties of the final product, the copper powder is irregular electrolytic copper powder, wherein the Cu content is ≥99.9% and the particle size range is 48-100 μm;

[0010] The iron powder is porous sponge iron powder, wherein the Fe content is ≥99.9% and the particle size range is 48-100 μm;

[0011] The graphite is natural lamellar graphite with a particle size range of 48-100 μm and a thickness range of 8-18 μm;

[0012] The particle sizes of the silicon dioxide, aluminum oxide and tungsten disulfide are all 2-5 μm.

[0013] Furthermore, it is composed of 60%-65% copper powder, 26%-30% iron powder, 8%-10% graphite, 0.01%-0.3% silicon dioxide, 0.01%-0.3% aluminum oxide and 0.01%-0.3% tungsten disulfide.

[0014] Furthermore, its density is 5.8-6.4 g / cm 3 The aviation engine sealing material bushing with this density can ensure that it does not cause damage to the aviation engine grate teeth during use and does not break; the hardness is 40-70HV;

[0015] Mechanical properties perpendicular to the direction of lamellar graphite arrangement: flexural strength ≥ 120MPa; compressive strength ≥ 120MPa; the mechanical properties perpendicular to the direction of lamellar graphite arrangement are higher than those parallel to the direction of graphite arrangement;

[0016] Friction performance parallel to the direction of lamellar graphite arrangement: 0.15-0.20 in dry state, 0.06-0.10 in lubricating oil medium, wear rate <2.5×10 -4 cm 3 / m; The friction performance parallel to the arrangement direction of the lamellar graphite is better than that perpendicular to the arrangement direction of the lamellar graphite.

[0017] The method for preparing the copper-based graphite sealing material for aircraft engines is special in that it comprises the following steps:

[0018] Step 1: Powder pretreatment

[0019] 1.1 Reduction treatment and drying

[0020] Before batching, the irregular electrolytic copper powder and porous sponge iron powder are reduced; the natural lamellar graphite, silicon dioxide, aluminum oxide, and tungsten disulfide powder are dried to remove moisture from the powder;

[0021] 1.2 Sieving

[0022] The treated irregular electrolytic copper powder, porous sponge iron powder and lamellar graphite are sieved respectively, and the irregular electrolytic copper powder with a size of -150 mesh to +300 mesh, the porous sponge iron powder with a size of -150 mesh to +300 mesh and the lamellar graphite with a size of -150 mesh to +300 mesh are taken for later use;

[0023] Step 2: Mix the powder

[0024] 2.1 Weigh the irregular electrolytic copper powder, porous sponge iron powder, lamellar graphite, silicon dioxide, aluminum oxide and tungsten disulfide powder treated in step 1 according to the mass ratio;

[0025] 2.2 Place irregular electrolytic copper powder, porous sponge iron powder and grinding balls into a ball mill for vacuum mixing at a ball milling speed of 100-200 r / min and a ball-to-material ratio of 1:1. After ball milling for 3-6 hours, place lamellar graphite, silicon dioxide, aluminum oxide and tungsten disulfide powder into the ball mill and continue mixing for 10-20 hours to obtain a mixed powder, ensuring uniform mixing of the components while minimizing the damage to the integrity of the component particles, especially the lamellar graphite particles.

[0026] The vacuum powder mixing chamber must maintain an absolute pressure of 50-80 kPa; the grinding balls are zirconia grinding balls with a diameter of no more than 0.5 mm;

[0027] Step 3: Molding

[0028] The molding process is carried out by compression molding or hot pressing;

[0029] The molding process of compression sintering is as follows:

[0030] Pour the mixed powder obtained in step 2 into a cylindrical mold / annular mold and press it under a pressure of 300-400 MPa. The pressing direction is perpendicular to the friction surface of the sealing bushing. The pressing speed is 0.1-0.5 mm / min and the holding time is 10-30 min. The density is 5.6-6.2 g / cm 3 Green billet of copper-based graphite sealing material;

[0031] The green blank is placed in a sintering furnace, a mixture of hydrogen and argon is used as a protective gas, the sintering temperature is 840-1000°C, and the sintering holding time is 2-3 hours to obtain a copper-based graphite sealing material;

[0032] For density <5.8g / cm 3 The samples can be re-pressed and re-fired to increase the density. The sintered samples are re-pressed at 200-300 MPa, using a mixture of hydrogen and argon as the protective gas, the sintering temperature is 760-830 ° C, the sintering time is 2-3 hours, and the density is 5.8-6.4 g / cm 3 Copper-based graphite sealing materials;

[0033] The hot pressing process is as follows:

[0034] The mixed powder obtained in step 2 is poured into a cylindrical mold / annular mold, placed in a hot pressing sintering furnace, and vacuumed to a furnace pressure of <5kPa. The sintering temperature is 700-900℃, the sintering pressure is 20-30MPa, and the holding time is 20-50min to obtain a density of 5.8-6.4g / cm 3 Copper-based graphite sealing material.

[0035] At the same time, the present invention also provides a sealing bushing for an aero-engine, the material of which is the copper-based graphite sealing material for an aero-engine.

[0036] The special feature of the above-mentioned method for preparing the sealing bushing for an aircraft engine is that, based on the above-mentioned method for preparing the copper-based graphite sealing material, a fourth step is added:

[0037] The copper-based graphite sealing material for the aircraft engine is mechanically processed according to the design drawings to obtain a finished sealing bushing for the aircraft engine.

[0038] The advantages of the present invention are:

[0039] 1. The present invention provides a copper-based graphite sealing material with oriented lamellar graphite. By optimizing the components and preparation process, a high-graphite-content copper-based graphite sealing material with oriented lamellar graphite is obtained, that is, the lamellar graphite particles are evenly distributed and oriented in the material matrix. The material has typical anisotropic characteristics and good mechanical and friction properties. It has a low friction coefficient and high wear resistance in the direction parallel to the lamellar graphite arrangement, and has excellent mechanical properties in the direction perpendicular to the lamellar graphite arrangement. It has the advantages of high strength, low friction coefficient, good wear resistance, and small wear debris. In addition, during use, there is no phenomenon of scraping layer shedding, block falling, or sticking.

[0040] 2. The present invention adds an appropriate percentage of porous sponge iron powder to the copper-based graphite sealing material, introducing a harder porous iron phase into the material. The iron phase and the graphite phase can produce a chemical metallurgical reaction at the interface to form a compound, thereby improving the bonding strength and thus improving the hardness and strength of the material; the graphite chips generated during the friction process are easily filled into the pores of the porous iron phase, thereby reducing the friction coefficient of the sealing material; the porous iron phase can limit the deformation and softening of the copper phase during the friction process, thereby improving the wear resistance of the sealing material.

[0041] 3. The present invention adopts a vacuum powder mixing process to obtain uniformly distributed powder while effectively avoiding significant damage to the morphology of the softer lamellar graphite particles.

[0042] 4. The preparation method of the present invention has a simple operation process, a short preparation cycle, is economical and reliable, is easy to implement, and is suitable for large-scale industrial production.

[0043] 5. The present invention meets the service mechanical properties of aviation engine grate sealing materials while ensuring that the sealing material has a low friction coefficient and high wear resistance on the friction surface, and has good sealing and corrosion resistance under oil and gas two-phase conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 The copper-based graphite sealing bushing of Example 1;

[0045] Figure 2 This is a metallographic image of the end face of the copper-based graphite sealing bushing in Example 1;

[0046] Figure 3 This is a metallographic image of the wall surface of the copper-based graphite sealing bushing in Example 1;

[0047] Figure 4 This is the metallographic diagram of the copper-based graphite sealing material of Comparative Example 1;

[0048] Figure 5 This is the metallographic diagram of the copper-based graphite sealing material of comparative example 2. DETAILED DESCRIPTION

[0049] The present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments:

[0050] The invention provides a copper-based graphite sealing material for aircraft engines with typical anisotropy. The copper-based graphite sealing material is composed of 60%-70% of copper powder, 18%-32% of iron powder, 6%-12% of graphite, 0.01%-0.5% of silicon dioxide, 0.01%-0.5% of aluminum oxide and 0.01%-0.5% of tungsten disulfide, and the total mass percentage of the above components is 100%.

[0051] In Examples 1-5, the copper powder is irregular electrolytic copper powder, wherein the Cu content is ≥99.9% and the particle size range is 48-100 μm; the iron powder is porous sponge iron powder, wherein the Fe content is ≥99.9% and the particle size range is 48-100 μm; the graphite is natural lamellar graphite, with a particle size range of 48-100 μm and a thickness range of 8-18 μm; the particle sizes of silicon dioxide, aluminum oxide and tungsten disulfide are all 2-5 μm.

[0052] Example 1:

[0053] This embodiment provides a sealing bushing for an aircraft engine, which is made of a copper-based graphite sealing material composed of the following components in percentage by mass: 60% irregular electrolytic copper powder, 29.8% porous sponge iron powder, 10% natural lamellar graphite, 0.05% silicon dioxide, 0.05% aluminum oxide, and 0.1% tungsten disulfide. The particle size range of the irregular electrolytic copper powder, the porous sponge iron powder, and the natural lamellar graphite is 48-100 μm, and the thickness of the lamellar graphite is 8-18 μm. The production steps are as follows:

[0054] Step 1: Powder pretreatment

[0055] (1) Before batching, irregular electrolytic copper powder and porous sponge iron powder are placed in a reduction furnace for reduction treatment;

[0056] The reduction temperature of irregular electrolytic copper powder is 370℃, the atmosphere is H2, the reduction reaction is kept at this temperature for 1.5h, and then cooled with the furnace;

[0057] The reduction temperature of the porous sponge iron powder is 650°C, the atmosphere is H2, the reduction reaction is kept warm for 1.5 hours, and then cooled with the furnace.

[0058] (2) Natural lamellar graphite, silicon dioxide, aluminum oxide, and tungsten disulfide are placed in an oven for drying to remove moisture from the powder; during the drying process, the oven temperature is raised to 150°C and kept warm for 1 hour;

[0059] (3) The treated irregular electrolytic copper powder, porous sponge iron powder and lamellar graphite are sieved separately, and the irregular electrolytic copper powder with a size of -150 mesh to +300 mesh, the porous sponge iron powder with a size of -150 mesh to +300 mesh and the lamellar graphite with a size of -150 mesh to +300 mesh are taken for later use.

[0060] Step 2: Mix the powder

[0061] The irregular electrolytic copper powder, porous sponge iron powder, lamellar graphite, silica, alumina and tungsten disulfide treated in step 1 are weighed according to the stoichiometric ratio; the irregular electrolytic copper powder, porous sponge iron powder and 0.2 mm diameter zirconia grinding balls are first placed in a ball mill for vacuum mixing, maintaining the absolute pressure in the chamber at 65 kPa, the ball milling speed at 120 r / min, the ball-to-material ratio at 1:1, and the ball milling time at 5 h; then, the lamellar graphite, silica, alumina and tungsten disulfide powders are placed in the ball mill, and the powder mixing is continued for 15 h to obtain a mixed powder.

[0062] Step 3: Molding

[0063] The mixed powder obtained in step 2 was poured into a mold and pressed at a pressure of 350 MPa. The pressing direction was perpendicular to the friction surface of the sealing bushing. The pressing speed was 0.3 mm / min and the holding time was 15 min. The density was 5.75 g / cm 3 Green billet of copper-based graphite sealing material;

[0064] The green blank is placed in a sintering furnace, a mixture of hydrogen and argon is used as a protective gas, the sintering temperature is 850° C., and the sintering holding time is 2 hours to obtain the sealing bushing blank material for the aircraft engine of this embodiment;

[0065] The main physical, mechanical and friction properties of the copper-based graphite sealing material of this embodiment are shown in Table 1.

[0066] Step 4: Machining

[0067] According to the design drawings, the sealing bushing blank material for the aircraft engine obtained in step 3 is machined to obtain the following Figure 1The metallographic diagram of the sealing bushing end face of the copper-based graphite sealing material is as follows: Figure 2 As shown, the wall metallographic diagram is as follows Figure 3 As shown, the light gray area in the metallographic image is the copper matrix, the dark gray part with dot-like pores is iron, and the black structure is graphite.

[0068] Example 2:

[0069] This embodiment provides a sealing bushing for an aircraft engine, which is made of a copper-based graphite sealing material composed of the following components in percentage by mass: 62.6% irregular electrolytic copper powder, 28% porous sponge iron powder, 9% lamellar graphite, 0.1% silicon dioxide, 0.1% aluminum oxide, and 0.2% tungsten disulfide. The particle size range of the irregular electrolytic copper powder, the porous sponge iron powder, and the natural lamellar graphite is 48-100 μm, and the thickness of the lamellar graphite is 8-18 μm. The production steps are as follows:

[0070] Step 1: Powder pretreatment

[0071] (1) Before batching, the irregular electrolytic copper powder and the porous sponge iron powder are placed in a reduction furnace for reduction treatment.

[0072] The reduction temperature of irregular electrolytic copper powder is 420℃, the atmosphere is H2, the reduction reaction is kept at this temperature for 2h, and then cooled with the furnace;

[0073] The reduction temperature of porous sponge iron powder is 670℃, the atmosphere is H2, the reduction reaction is kept warm for 1h, and then cooled with the furnace.

[0074] (2) Place natural lamellar graphite, silicon dioxide, aluminum oxide, and tungsten disulfide in an oven for drying to remove moisture from the powder. During the drying process, raise the oven temperature to 180°C and keep it warm for 1.5 hours.

[0075] (3) The treated irregular electrolytic copper powder, porous sponge iron powder and lamellar graphite are sieved separately, and the irregular electrolytic copper powder with a size of -150 mesh to +300 mesh, the porous sponge iron powder with a size of -150 mesh to +300 mesh and the lamellar graphite with a size of -150 mesh to +300 mesh are taken for later use.

[0076] Step 2: Mix the powder

[0077] The irregular electrolytic copper powder, porous sponge iron powder, lamellar graphite, silica, alumina and tungsten disulfide powder treated in step 1 are weighed according to the stoichiometric ratio; the irregular electrolytic copper powder, porous sponge iron powder and 0.2 mm diameter zirconia grinding balls are first placed in a ball mill for vacuum mixing, maintaining the absolute pressure in the chamber at 60 kPa, the ball milling speed at 180 r / min, the ball-to-material ratio at 1:1, and the ball milling time for 4 h; then the lamellar graphite, silica, alumina and tungsten disulfide powders are placed in the ball mill, and the powder mixing is continued for 12 h to obtain a mixed powder.

[0078] Step 3: Molding

[0079] The mixed powder obtained in step 2 was poured into a mold and pressed at a pressure of 400 MPa. The pressing direction was perpendicular to the friction surface of the sealing bushing. The pressing speed was 0.2 mm / min and the holding time was 10 min. The density was 5.68 g / cm 3 The green billet of copper-based graphite sealing material.

[0080] The green blank was placed in a sintering furnace, and a mixture of hydrogen and argon was used as the protective gas. The sintering temperature was 900 ° C, and the sintering holding time was 2 h. The density was 5.75 g / cm 3 Copper-based graphite sealing material sample. Since the density does not reach 5.8g / cm 3 The sintered sample was subjected to 250 MPa re-pressing, a mixture of hydrogen and argon was used as the protective gas, the sintering temperature was 800°C, and the sintering holding time was 2 hours to obtain the sealing bushing blank material for the aircraft engine of this embodiment;

[0081] The main physical, mechanical and friction properties of the copper-based graphite sealing material of this embodiment are shown in Table 1.

[0082] Step 4: Machining

[0083] According to the design drawings, the sealing bushing blank material for the aircraft engine obtained in step three is machined to obtain a finished sealing bushing.

[0084] Example 3:

[0085] This embodiment provides a sealing bushing for an aircraft engine, which is made of a copper-based graphite sealing material composed of the following components in percentage by mass: 65% irregular electrolytic copper powder, 26.7% porous sponge iron powder, 8% lamellar graphite, 0.05% silicon dioxide, 0.1% aluminum oxide, and 0.15% tungsten disulfide. The particle size range of the irregular electrolytic copper powder, the porous sponge iron powder, and the lamellar graphite is 48-100 μm, and the thickness of the lamellar graphite is 8-18 μm. The production steps are as follows:

[0086] Step 1: Powder pretreatment

[0087] (1) Before batching, the irregular electrolytic copper powder and the porous sponge iron powder are placed in a reduction furnace for reduction treatment.

[0088] The reduction temperature of irregular electrolytic copper powder is 400℃, the atmosphere is H2, the reduction reaction is kept at this temperature for 1h, and then cooled with the furnace;

[0089] The reduction temperature of porous sponge iron powder is 620℃, the atmosphere is H2, the reduction reaction is kept warm for 2h, and then cooled with the furnace.

[0090] (2) Natural lamellar graphite, silicon dioxide, aluminum oxide, and tungsten disulfide are placed in an oven for drying to remove moisture from the powder. During the drying process, the oven temperature is raised to 150°C and kept at this temperature for 1 hour.

[0091] (3) The treated irregular electrolytic copper powder, porous sponge iron powder and lamellar graphite are sieved separately, and the irregular electrolytic copper powder with a size of -150 mesh to +300 mesh, the porous sponge iron powder with a size of -150 mesh to +300 mesh and the lamellar graphite with a size of -150 mesh to +300 mesh are taken for later use.

[0092] Step 2: Mix the powder

[0093] The irregular electrolytic copper powder, porous sponge iron powder, lamellar graphite, silica, alumina and tungsten disulfide treated in step 1 are weighed according to the stoichiometric ratio; the irregular electrolytic copper powder, porous sponge iron powder and zirconia grinding balls with a diameter of 0.2 mm are first placed in a ball mill for vacuum mixing, maintaining the absolute pressure in the chamber at 80 kPa, the ball milling speed at 200 r / min, the ball-to-material ratio at 1:1, and the ball milling time for 3 hours; then the lamellar graphite, silica, alumina and tungsten disulfide powders are placed in the ball mill, and the powder mixing is continued for 10 hours to obtain a mixed powder.

[0094] Step 3: Molding

[0095] The mixed powder obtained in step 2 is poured into a mold, placed in a hot pressing sintering furnace, evacuated to a furnace pressure of 3 kPa, sintered at a temperature of 800° C., a sintering pressure of 25 MPa, and held at this temperature for 25 min. The mold is then removed from the furnace after cooling to obtain the sealing bushing blank material for the aircraft engine of this embodiment.

[0096] The main physical, mechanical and friction properties of the copper-based graphite sealing material of this embodiment are shown in Table 1.

[0097] Step 4: Machining

[0098] According to the design drawings, the sealing bushing blank material for the aircraft engine obtained in step three is machined to obtain a finished sealing bushing.

[0099] Example 4

[0100] This embodiment provides a sealing bushing for an aircraft engine. The difference from Example 1 is that the formulation is modified to include a higher percentage of copper powder and a lower percentage of iron powder. The composition includes 70% irregular electrolytic copper powder, 18% porous sponge iron powder, 11.8% lamellar graphite, 0.05% silicon dioxide, 0.05% aluminum oxide, and 0.1% tungsten disulfide.

[0101] The main physical, mechanical and friction properties of the copper-based graphite sealing material of this embodiment are shown in Table 1.

[0102] Example 5

[0103] This embodiment provides a sealing bushing for an aircraft engine. The difference from Example 1 is that the formulation is modified to include a lower percentage of graphite powder: 61.6% irregular electrolytic copper powder, 32% porous sponge iron powder, 6% lamellar graphite, 0.1% silicon dioxide, 0.1% aluminum oxide, and 0.2% tungsten disulfide.

[0104] The main physical, mechanical and friction properties of the copper-based graphite sealing material of this embodiment are shown in Table 1.

[0105] Comparative Example 1

[0106] This comparative example provides a sealing bushing for an aero-engine. Other conditions are the same as those in Example 1, except that the cold isostatic pressing process is used for forming. Figure 4 .

[0107] The main physical, mechanical and friction properties of the copper-based graphite sealing material of this comparative example are shown in Table 1.

[0108] Comparative Example 2

[0109] This comparative example provides a sealing bushing for an aero-engine. Other conditions are the same as those of Example 1, except that granular graphite with a particle size range of 48-100 μm is used instead of lamellar graphite with a particle size range of 48-100 μm and a thickness range of 8-18 μm. The metallographic structure is shown in FIG. Figure 5 .

[0110] The main physical, mechanical and friction properties of the copper-based graphite sealing material of this comparative example are shown in Table 1.

[0111] Comparative Example 3

[0112] This comparative example provides a sealing bushing for an aircraft engine. Other conditions are the same as those of Example 1. The difference from Example 1 is that the formula of this comparative example does not contain iron powder.

[0113] The main physical, mechanical and friction properties of the copper-based graphite sealing material of this comparative example are shown in Table 1.

[0114] Table 1 Comparison of physical, mechanical and friction properties of copper-based graphite sealing materials

[0115]

[0116]

[0117] It can be seen from Table 1 in combination with the embodiments and comparative examples of the present invention that the copper-based graphite sealing materials prepared in Examples 1-5 of the present invention exhibit relatively excellent mechanical properties in the direction perpendicular to the arrangement direction of the lamellar graphite and relatively excellent friction properties in the direction parallel to the arrangement direction of the lamellar graphite, meeting the use requirements of the engine sealing bushing.

[0118] Compared with Example 1, Comparative Example 1 replaces compression molding with isostatic pressing, and Comparative Example 2 replaces lamellar graphite with granular graphite; the materials obtained by Comparative Examples 1 and 2 have the same microstructure in all directions (metallographic images as shown in FIG. Figure 3 and Figure 4 The mechanical properties and friction properties in all directions are consistent, and the mechanical properties of Comparative Examples 1 and 2 are lower than those of Example 1 perpendicular to the arrangement direction of the lamellar graphite, and the friction coefficients of Comparative Examples 1 and 2 are higher than the friction coefficients of Example 1 parallel to the arrangement direction of the lamellar graphite, indicating that the anisotropic copper-based graphite sealing material with directional arrangement of lamellar graphite has better performance in a specific direction than the isotropic material under the same conditions.

[0119] Compared with Example 1, no iron phase was added in Comparative Example 3. It can be seen that the introduction of the porous iron phase not only enhances the hardness and mechanical properties of the material to a certain extent, but also reduces the friction coefficient of the material and improves the wear resistance of the material.

[0120] In summary, through the optimization of the present invention, a high-graphite-content copper-based graphite sealing material with oriented lamellar graphite is obtained, so that the material has typical anisotropy of mechanical properties and friction properties, with good mechanical properties perpendicular to the direction of oriented arrangement of lamellar graphite and excellent friction and wear properties parallel to the direction of oriented arrangement of lamellar graphite. The anisotropic characteristics of the material can simultaneously meet the performance requirements of aviation engine sealing materials in different directions.

[0121] The above description is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with this technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed in the present invention, and these modifications or replacements should all be included in the scope of protection of the present invention.

Claims

1. A copper-based graphite sealing material for aircraft engines, characterized by: It is a copper-based graphite sealing material with anisotropic lamellar graphite directional arrangement; The raw materials used in the copper-based graphite sealing material are composed of 60%-70% copper powder, 18%-32% iron powder, 6%-12% graphite, 0.01%-0.5% silicon dioxide, 0.01%-0.5% aluminum oxide and 0.01%-0.5% tungsten disulfide by mass percentage, and the total mass percentage of the above components is 100%; The copper powder is an irregular electrolytic copper powder, wherein the Cu content is ≥99.9% and the particle size range is 48-100 μm; The iron powder is porous sponge iron powder, wherein the Fe content is ≥99.9% and the particle size range is 48-100 μm; The graphite is natural lamellar graphite with a particle size range of 48-100 μm and a thickness range of 8-18 μm; The particle sizes of the silicon dioxide, aluminum oxide and tungsten disulfide are all 2-5 μm; The density of copper-based graphite sealing materials for aircraft engines is 5.8-6.4 g / cm 3 , hardness 40-70 HV; Mechanical properties perpendicular to the arrangement direction of lamellar graphite: bending strength ≥120 MPa; compressive strength ≥120 MPa; Friction performance parallel to the direction of lamellar graphite arrangement: 0.15-0.20 in dry state, 0.06-0.08 in lubricating oil medium, wear rate <2.5×10 -4 cm 3 / m.

2. The copper-based graphite sealing material according to claim 1, characterized in that: It is composed of 60%-65% copper powder, 26%-30% iron powder, 8%-10% graphite, 0.01%-0.3% silicon dioxide, 0.01%-0.3% aluminum oxide and 0.01%-0.3% tungsten disulfide.

3. The method for preparing the copper-based graphite sealing material for aviation engines according to claim 1, wherein: The following steps are involved: Step 1: Powder pretreatment 1.1 Reduction treatment and drying Before batching, the irregular electrolytic copper powder and porous sponge iron powder are reduced; the natural lamellar graphite, silicon dioxide, aluminum oxide, and tungsten disulfide powder are dried to remove moisture from the powder; 1.2 Sieving The treated irregular electrolytic copper powder, porous sponge iron powder and lamellar graphite are sieved separately, and the irregular electrolytic copper powder with a size of -150 mesh to +300 mesh, the porous sponge iron powder with a size of -150 mesh to +300 mesh and the lamellar graphite with a size of -150 mesh to +300 mesh are taken for later use; Step 2: Mix the powder 2.1 Weigh the irregular electrolytic copper powder, porous sponge iron powder, lamellar graphite, silicon dioxide, aluminum oxide and tungsten disulfide powder treated in step 1 according to the mass ratio; 2.2 Place irregular electrolytic copper powder, porous sponge iron powder, and grinding balls in a ball mill for vacuum mixing at a ball milling speed of 100-200 r / min and a ball-to-material ratio of 1:

1. After ball milling for 3-6 hours, place lamellar graphite, silicon dioxide, aluminum oxide, and tungsten disulfide powder in the ball mill and continue mixing for 10-20 hours to obtain a mixed powder. The vacuum powder mixing chamber must maintain an absolute pressure of 50-80 kPa; the grinding balls are zirconia grinding balls with a diameter not greater than 0.5 mm; Step 3: Molding The molding process is carried out by compression molding or hot pressing; The molding process of compression sintering is as follows: Pour the mixed powder obtained in step 2 into a cylindrical mold / annular mold and press it under a pressure of 300-400 MPa. The pressing direction is perpendicular to the friction surface of the sealing bushing. The pressing speed is 0.1-0.5 mm / min and the holding time is 10-30 min. The density is 5.6-6.2 g / cm 3 Green billet of copper-based graphite sealing material; The green blank is placed in a sintering furnace, a mixture of hydrogen and argon is used as a protective gas, the sintering temperature is 840-1000°C, and the sintering holding time is 2-3 hours to obtain a copper-based graphite sealing material; For density < 5.8 g / cm 3 The samples should be re-pressed and re-fired for densification. The sintered samples were re-pressed at 200-300 MPa, with a mixture of hydrogen and argon as the protective gas, a sintering temperature of 760-830 °C, and a sintering time of 2-3 h to obtain a density of 5.8-6.4 g / cm 3 Copper-based graphite sealing materials; The hot pressing process is as follows: The mixed powder obtained in step 2 was poured into a cylindrical mold / annular mold, placed in a hot pressing sintering furnace, and vacuumed to a furnace pressure of <5 kPa. The sintering temperature was 700-900 °C, the sintering pressure was 20-30 MPa, and the holding time was 20-50 min to obtain a density of 5.8-6.4 g / cm 3 Copper-based graphite sealing material.

4. The method for preparing the copper-based graphite sealing material for an aero-engine according to claim 3, wherein: In step 1.1, the irregular electrolytic copper powder and the porous sponge iron powder are placed in a reduction furnace for reduction treatment; Among them, the temperature for reduction of irregular electrolytic copper powder is 350-450 ℃, the atmosphere is H2, the heating rate is 100-120 ℃ / h, the reduction reaction holding time is 1-3 hours, and it is cooled with the furnace; the temperature for progressive reduction of porous sponge iron powder is 600-700 ℃, the atmosphere is H2, the heating rate is 120-150 ℃ / h, the reduction reaction holding time is 1-2 hours, and it is cooled with the furnace; Place natural lamellar graphite, silicon dioxide, aluminum oxide, and tungsten disulfide powder in an oven for drying. Raise the oven temperature to 150-200°C and keep it warm for 1-2 hours.

5. The method for preparing the copper-based graphite sealing material for an aero-engine according to claim 4, wherein: In step 2.2, ball milling was performed for 5 h.

6. A sealing bushing for an aircraft engine, characterized in that: The material is the copper-based graphite sealing material for aircraft engines as described in any one of claims 1-2.

7. The method for preparing the sealing bushing for an aircraft engine according to claim 6, characterized in that: Based on the method for preparing the copper-based graphite sealing material for aircraft engines described in claim 3, step 4 is added: The copper-based graphite sealing material for the aircraft engine is mechanically processed according to the design drawings to obtain a finished sealing bushing for the aircraft engine.

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