MoAlB ceramic particle reinforced copper / graphite composite material and preparation method thereof

Abstract

The invention discloses a MoAlB ceramic particle reinforced copper / graphite composite material and a preparation method thereof. The composite material comprises the following raw materials in percentage by mass: 1-20% of copper-plated graphite powder, 1-20% of MoAlB powder and the balance of pure copper powder and less than 0.01% of inevitable impurities. The preparation process of the composite material comprises the following steps: grinding and mixing the raw materials including the copper-plated graphite powder, the MoAlB powder and the pure copper powder, putting into a mold, sintering, cooling along with a furnace after sintering, discharging, and demolding to obtain the composite material. According to the composite material, on the basis of the synergistic effect among the components of the raw materials, especially the good interface bonding effect between MoB derived from MoAlB and a matrix, the hardness, bending strength, wear resistance and other performance of the composite material are remarkably improved, and the technical problem that ceramic is prone to being separated from the matrix in the material wear process in the prior art is effectively solved.

Description

Technical Field

[0001] The invention relates to a ceramic particle reinforced copper / graphite composite material, in particular to a MoAlB ceramic particle reinforced copper / graphite composite material and a preparation method thereof, belonging to the technical field of copper-based composite materials. Background Art

[0002] Copper / graphite composites are often used as sliding bearing materials, electrical contact materials, brake pads, etc. due to their combination of copper's excellent electrical conductivity and thermal conductivity, and graphite's excellent lubrication performance and thermal stability. With the continuous development of the economy and society, there is a higher demand for the performance of copper-based self-lubricating materials, requiring them to have better mechanical properties and friction and wear properties. However, the introduction of softer graphite will reduce the mechanical properties of the composite material, and graphite and copper can only be combined mechanically, and there are many structural defects in the composite material. For this reason, there are a lot of studies on improving the interface between graphite and copper by plating a metal layer (such as copper, nickel, etc.) on the surface of graphite particles. However, graphite surface modification has limited effect on improving the performance of copper-based composites, and it cannot make the material achieve the expected higher mechanical and friction properties. For this reason, another feasible method to improve the mechanical and tribological properties of copper-based composites is to simultaneously add chemically stable hard ceramic particles. For example, the addition of traditional ceramics such as Al2O3, TiC, TiB2, SiC and B4C into the copper matrix can effectively enhance the performance of copper-based composites. However, these ceramics have poor interface bonding with the metal matrix, which results in these hard particles being easily separated from the matrix during the wear process, causing severe abrasive wear. Summary of the invention

[0003] In view of the problems existing in the prior art, the first object of the present invention is to provide a MoAlB ceramic particle reinforced copper / graphite composite material. The composite material is based on the synergistic effect between the components of the raw materials, especially the good interface bonding effect between MoB derived from MoAlB and the matrix, which significantly improves the hardness, bending strength and wear resistance of the composite material, and effectively solves the technical problem of the prior art that the ceramic is easily separated from the matrix during the wear process.

[0004] The second object of the present invention is to provide a method for preparing a MoAlB ceramic particle reinforced copper / graphite composite material. The method controls the decomposition degree of MoAlB by strictly controlling the ratio of each component of the raw material, the pressure and the sintering temperature, so as to promote the decomposition of MoAlB to form a Cu(Al) solid solution and a MoB phase, thereby greatly improving the wear resistance and mechanical strength of the composite material; the method has the advantages of simple process, fast molding and low cost, and is convenient for large-scale and continuous industrial implementation.

[0005] In order to achieve the above technical purpose, the present invention provides a MoAlB ceramic particle reinforced copper / graphite composite material, which includes the following raw materials in mass percentage: 1-20% copper-plated graphite powder, 1-20% MoAlB powder, and the balance is pure copper powder and less than 0.01% of inevitable impurities.

[0006] As a preferred solution, the composite material comprises the following raw materials in mass percentage: 5-15% copper-plated graphite powder, 1-15% MoAlB powder, and the remainder is pure copper powder and less than 0.01% of inevitable impurities.

[0007] The addition amount of each component in the present invention must be strictly implemented in accordance with the above requirements. The hardness and flexural strength of the composite material increase with the increase of the addition amount of MoAlB, and the wear resistance is also enhanced. However, when the addition amount of MoAlB exceeds 15%, the density of the composite material decreases. This is because the addition amount of MoAlB is too high, which will cause the copper content to be relatively reduced and fail to form good sintering.

[0008] As a preferred solution, the purity of the copper-plated graphite powder, MoAlB powder and pure copper powder is ≥99.9%.

[0009] As a preferred solution, the particle size of the copper-plated graphite powder, MoAlB powder and pure copper powder is 300-500 mesh.

[0010] As a preferred solution, the copper content of the copper-coated graphite is 30-60%, more preferably, the copper content of the copper-coated graphite is 40-50%, and most preferably, the copper content of the copper-coated graphite is 50%.

[0011] The invention also provides a preparation method of MoAlB ceramic particle reinforced copper / graphite composite material, comprising grinding and mixing raw materials including copper-plated graphite powder, MoAlB powder and pure copper powder, and then putting them into a mold for sintering, cooling them with the furnace after sintering, and removing them from the furnace to obtain the composite material.

[0012] As a preferred solution, the grinding method is dry ball milling, the grinding balls are zirconia balls, the ball-to-material mass ratio is 2 to 5:1, the ball mill speed is 150 to 200 r / min, and the ball milling time is 6 to 10 hours.

[0013] As a preferred solution, before the hot pressing sintering, the ball-milled powder needs to be pre-pressed in a mold at 20 to 40 MPa.

[0014] As a preferred solution, the sintering process is carried out under vacuum or protective atmosphere.

[0015] As a preferred solution, when the sintering process is carried out under vacuum, the vacuum degree is ≤40Pa.

[0016] As a preferred solution, the protective atmosphere is high-purity nitrogen and / or high-purity argon.

[0017] As a preferred solution, the sintering process is vacuum hot pressing sintering, and the process is: at 40-60MPa, the temperature is raised to 750-1000°C at 50-100°C / min, and kept warm for 5-15min. Further preferably, the sintering temperature is 850-950°C. The decomposition degree of MoAlB is greatly affected by the sintering temperature. The higher the sintering temperature, the higher the decomposition degree of MoAlB. The decomposition of MoAlB to form Cu(Al) solid solution and MoB phase is beneficial to improving the mechanical properties and wear resistance of the composite material, but too high a sintering temperature will result in a coarse matrix grain structure. Therefore, controlling the sintering temperature at 850-950°C can enable the composite material to maintain good strength and wear resistance.

[0018] Compared with the prior art solutions, the beneficial technical effects of the technical solution of the present invention are:

[0019] 1) The copper / graphite composite material provided by the present invention is based on the synergistic effect between the components of the raw materials, especially the good interface bonding effect between MoB derived from MoAlB and the matrix, which significantly improves the hardness, flexural strength and wear resistance of the composite material, and effectively solves the technical problem of the ceramic being easily separated from the matrix during the wear process in the prior art.

[0020] 2) The preparation method provided by the present invention controls the decomposition degree of MoAlB by strictly controlling the ratio of each component of the raw material, pressure and sintering temperature, thereby promoting the decomposition of MoAlB to form Cu(Al) solid solution and MoB phase, thereby greatly improving the wear resistance and strength of the composite material; the method has the advantages of simple process, fast molding and low cost, and is convenient for large-scale and continuous industrial implementation. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a SEM image of the composite material provided in Example 1 of the present invention;

[0022] Figure 2 This is a SEM image of the composite material provided in Example 3 of the present invention;

[0023] Figure 3 This is a SEM image of the composite material provided in Example 4 of the present invention;

[0024] Figure 4 The friction performance and mechanical performance images of Example 4, Example 7 and the comparative example of the present invention are shown;

[0025] in, Figure 4 (a) is the friction coefficient test diagram of the composite material. Figure 4(b) is the three-point bending stress-strain diagram of the composite material. DETAILED DESCRIPTION

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other relevant drawings can also be obtained based on these drawings without creative work. Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0027] Example 1

[0028] A method for preparing a MoAlB particle reinforced copper / graphite composite material comprises the following steps:

[0029] Step S1, pure copper powder, copper-plated graphite powder, and MoAlB powder are mixed according to mass percentage, and the ratio is as follows: MoAlB: 5%, copper-plated graphite: 10% (copper content 50%), Cu: 85%, wherein the particle size of copper-plated graphite and MoAlB is 300 mesh, and the particle size of copper powder is 500 mesh.

[0030] Step S2, putting the powder prepared in step S1 and the zirconium oxide balls into a ball mill and introducing argon gas, and then mixing the materials in a planetary ball mill, with a ball-to-material mass ratio of 2:1, a ball mill speed of 180 r / min, and a ball milling time of 6 h.

[0031] Step S3, loading the mixed powder obtained in step S2 into a graphite mold, sending it into a rapid hot pressing sintering furnace for pre-pressing (40MPa), and then performing vacuum sintering, setting the gas pressure to less than 30MPa, the heating rate of the rapid hot pressing sintering is 60℃ / min, the sintering temperature is 750℃, the sintering pressure is 50MPa, the insulation time is 10min, and the mixture is taken out of the furnace after cooling. After final demolding, the sample is obtained.

[0032] Please refer to Figure 1 , Figure 1 This is a scanning electron microscope photo of the composite material of Example 1 of the present invention. The gray phase is the copper matrix, the black phase is graphite, and the white phase is MoAlB. Figure 1 It can also be seen that the Al of MoAlB in the prepared composite material hardly diffuses into the copper matrix, indicating that MoAlB is almost not decomposed when sintered at 750 °C.

[0033] Example 2

[0034] On the basis of Example 1, the sintering temperature was adjusted to 800° C., and other parameters were the same as those in Example 1.

[0035] Example 3

[0036] On the basis of Example 1, the sintering temperature was adjusted to 850° C., and other parameters were the same as those in Example 1.

[0037] Please refer to Figure 2 , Figure 2 This is a scanning electron microscope photo of the composite material of Example 3 of the present invention. The gray phase is the copper matrix, the black phase is graphite, and the white phase is MoAlB or MoB. Figure 2 It can also be seen that part of the Al in MoAlB in the prepared composite material diffuses into the copper matrix, indicating that when sintered at 850 °C, part of the MoAlB decomposes to form a Cu(Al) solid solution and a MoB phase with good interface bonding with the copper matrix.

[0038] Example 4

[0039] On the basis of Example 1, the sintering temperature was adjusted to 900° C., and other parameters were the same as those in Example 1.

[0040] Please refer to Figure 3 , Figure 3 : is a scanning electron microscope photo of the composite material of Example 4 of the present invention. Figure 3 It can be seen that the Al element in MoAlB is almost completely diffused into the copper matrix, forming a Cu(Al) solid solution and a MoB phase with good interface bonding with the copper matrix.

[0041] Example 5

[0042] On the basis of Example 1, the sintering temperature was adjusted to 950° C., and other parameters were the same as those in Example 1.

[0043] Example 6

[0044] On the basis of Example 1, the sintering temperature was adjusted to 1000° C., and other parameters were the same as those in Example 1.

[0045] Example 7

[0046] On the basis of Example 4, the ratio of the raw material components was adjusted, and other parameters were the same as those of Example 4. In this example, the ratio of each component in the raw material by mass percentage was as follows: MoAlB: 10%, copper-plated graphite: 10% (copper content 50%), Cu: 80%.

[0047] Example 8

[0048] On the basis of Example 4, the ratio of the raw material components was adjusted, and other parameters were the same as those of Example 1. In this example, the ratio of each component in the raw material by mass percentage was as follows: MoAlB: 15%, copper-plated graphite: 10% (copper content 50%), Cu: 75%.

[0049] Comparative Example 1

[0050] This comparative example refers to the preparation method of Example 4, and the difference from Example 4 is that no MoAlB powder is added to the mixed powder, that is, only pure copper powder and copper-plated graphite powder are mixed according to mass percentage, and the proportion is as follows: copper-plated graphite: 10% (copper content 50%), Cu: 90%.

[0051] The mechanical and tribological properties of the composite materials of Examples 1 to 8 and the comparative examples were tested, and the test results are shown in Table 1. Among them, the friction coefficient of the composite materials of Example 4, Example 7 and the comparative example (GCr15 steel against grinding ball, load 10N, rotation speed 0.65 m / s) changes with distance, and the three-point bending stress-strain curve is shown in Table 1. Figure 4 shown.

[0052] Table 1 shows the properties of the composite materials obtained in Examples 1 to 8 of the present invention and the comparative examples.

[0053]

[0054]

[0055] As can be seen from Table 1, compared with the copper / graphite composite material prepared by sintering without adding MoAlB (Comparative Example 1), the mechanical properties of the composite material obtained in the embodiment are significantly improved, and the wear resistance is also significantly improved. The decomposition degree of MoAlB is greatly affected by the sintering temperature. The higher the sintering temperature, the higher the decomposition degree of MoAlB. The decomposition of MoAlB to form Cu(Al) solid solution and MoB phase is beneficial to improving the mechanical properties and wear resistance of the composite material, but too high a sintering temperature will result in a coarse matrix grain structure. Therefore, controlling the sintering temperature at 850-950°C can enable the composite material to maintain good strength and wear resistance.

[0056] The hardness and flexural strength of the composite material increase with the increase of MoAlB addition, and the wear resistance also increases. When the addition amount of MoAlB is 15%, the density of the composite material decreases significantly. This may be because the addition amount of MoAlB is too high, which will cause the copper content to decrease relatively and fail to form a good sintering. Figure 4 It can be seen that, compared with the composite material with a lower MoAlB content, the composite material with a higher MoAlB content has poor plasticity and a larger friction coefficient. Therefore, in the composite material of the present invention, the addition amount of MoAlB should not exceed 15%.

Claims

1. A MoAlB ceramic particle reinforced copper / graphite composite material, characterized in that: The invention comprises the following raw materials in percentage by mass: 1-20% of copper-plated graphite powder, 1-20% of MoAlB powder, and the balance of pure copper powder and unavoidable impurities less than 0.01%.

2. The MoAlB ceramic particle reinforced copper / graphite composite material according to claim 1, characterized in that: The invention comprises the following raw materials in percentage by mass: 5-15% of copper-plated graphite powder, 1-15% of MoAlB powder, and the balance of pure copper powder and unavoidable impurities less than 0.01%.

3. The MoAlB ceramic particle reinforced copper / graphite composite material according to claim 1, characterized in that: The purity of the copper-plated graphite powder, MoAlB powder and pure copper powder is ≥99.9%; the particle size of the copper-plated graphite powder, MoAlB powder and pure copper powder is 300-500 meshes.

4. The MoAlB ceramic particle reinforced copper / graphite composite material according to claim 1, characterized in that: The copper content of the copper-plated graphite is 30-60%.

5. The method for preparing a MoAlB ceramic particle reinforced copper / graphite composite material according to any one of claims 1 to 4, characterized in that: The copper-plated graphite powder, MoAlB powder and pure copper powder are ground and mixed, and then loaded into a mold for sintering. After the sintering is completed, the powder is cooled and taken out of the furnace, and then demolded to obtain the powder.

6. The method for preparing a MoAlB ceramic particle reinforced copper / graphite composite material according to claim 5, characterized in that: The grinding method is dry ball milling, the grinding balls are zirconia balls, the ball-to-material mass ratio is 2-5:1, the ball mill speed is 150-200 r / min, and the ball milling time is 6-10 hours.

7. The method for preparing a MoAlB ceramic particle reinforced copper / graphite composite material according to claim 5, characterized in that: Before the hot pressing and sintering, the ball-milled powder needs to be pre-pressed in a mold at 20 to 40 MPa.

8. The method for preparing a MoAlB ceramic particle reinforced copper / graphite composite material according to claim 5, characterized in that: The sintering process is carried out under vacuum or protective atmosphere; when the sintering process is carried out under vacuum, the vacuum degree is ≤40Pa.

9. The method for preparing a MoAlB ceramic particle reinforced copper / graphite composite material according to claim 8, characterized in that: The protective atmosphere is high-purity nitrogen and / or high-purity argon.

10. The method for preparing a MoAlB ceramic particle reinforced copper / graphite composite material according to claim 8, characterized in that: The sintering process is vacuum hot pressing sintering, and the process is: at 40-60 MPa, the temperature is raised to 750-1000° C. at 50-100° C. / min, and the temperature is kept for 5-15 minutes.

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