Self-lubricating composite material with cladding structure and preparation method thereof

Abstract

The present application belongs to the field of metal-based self-lubricating composite material, and particularly relates to a self-lubricating composite material with a coating structure and a preparation method thereof. The composite material comprises 70-90% of Ni, Co or Fe-based alloy powder, 5-15% of Ti3SiC2 or Ti3AlC2 powder and 5-15% of WS2 or MoS2 powder. Through component design and ball milling process control, the limited low-strength self-lubricating phase is coated on the surface of the protruding hard phase, the disadvantage of reducing the strength and toughness of the composite material caused by adding excessive self-lubricating phase in the traditional method is avoided, the material has the advantages of high strength, high toughness and high self-lubricating property, and is suitable for the production of sealing, bearing and other moving and transmission parts.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of metal-based self-lubricating composite materials, and particularly relates to a self-lubricating composite material with a coating structure and a preparation method thereof. BACKGROUND

[0002] With the rapid development of aviation, aerospace, marine and nuclear power industries, the operating conditions of some key parts of transmission or movement are becoming increasingly harsh. Under certain conditions, lubricating oil and grease will no longer meet the use requirements, and for sealed devices, the lubricity cannot be improved by adding lubricants. In view of this situation, a new type of self-lubricating material is the key to solving such problems.

[0003] Generally, researchers add self-lubricating phases such as graphite, Ag, WS2, MoS2 and BN into the metal matrix to reduce friction. However, due to the low hardness and shear strength of the lubricating phase, the wettability between the lubricating phase and the matrix is poor, and part of the lubricating phase is easy to decompose during sintering. When these lubricating phases are uniformly distributed in the matrix, the mechanical properties and wear resistance of the material will decrease, which brings challenges to the composite material as a mechanical component. Therefore, it is urgent to develop a self-lubricating composite material with excellent mechanical properties and good friction and wear resistance. Nickel-based alloy, cobalt-based alloy and stainless steel have high corrosion resistance, high strength and plasticity, and are often used as self-lubricating material matrix and applied to moving parts. However, when this kind of alloy is sintered with the lubricating phase, in-situ reaction easily occurs, which leads to the decomposition of the lubricating phase (WS2, MoS2, Ti3SiC2, etc.) or the generation of harmful phases, so that the friction and wear resistance requirements cannot be met, limiting its application in the self-lubricating direction.

[0004] Therefore, according to the requirements of industrial development for the mechanical properties and self-lubricating properties of materials, it is urgent to develop a new type of self-lubricating composite material with high strength and toughness and high self-lubricating property. SUMMARY

[0005] In view of the problems in the prior art, the present application provides a self-lubricating composite material with a coating structure and a preparation method thereof. The composite material is suitable for the production of moving and transmission parts such as seals and bearings, and solves the problems of easy decomposition of the lubricating phase of the self-lubricating material in the prior art, mismatch of strength and toughness, poor lubricating effect and the like.

[0006] The technical scheme of the present application is as follows:

[0007] A self-lubricating composite material with a coating structure, the composition of the composite material is as follows in terms of weight percentage:

[0008] Ni, Co or Fe-based alloy powder 70-90%;

[0009] Ti3SiC2 or Ti3AlC2 powder 5-15%;

[0010] WS2 or MoS2 powder 5-15%.

[0011] Further, the self-lubricating composite material with coating structure as described above, the Ni, Co or Fe-based alloy includes Ni, NiCr, NiCrAl, Co, CoCr and stainless steel, the original powder particle size is 30-100 μm; the Ti3SiC2 or Ti3AlC2 powder particle size is 30-80 μm; the WS2 or MoS2 powder particle size is less than 5 μm.

[0012] The preparation method of the self-lubricating composite material with coating structure as described above, the specific steps of the method are as follows:

[0013] (1) Powder mixing: first, the Ti3SiC2 or Ti3AlC2 powder and the WS2 or MoS2 powder are mixed by planetary ball milling, the rotation speed is 100-150 rpm, the ball milling time is 2-4 hours, at this time, the coating structure of the WS2 or MoS2 powder wrapping the Ti3SiC2 or Ti3AlC2 powder is obtained; then the coated powder and the Ni, Co or Fe-based alloy powder are mixed by planetary ball milling, the rotation speed is 100-150 rpm, the ball milling time is 2-4 hours, to obtain a uniformly mixed composite powder;

[0014] (2) Pre-pressing: the composite powder obtained in step (1) is loaded into a graphite mold, and then a cold press is used for pre-pressing;

[0015] (3) Spark plasma sintering: the graphite mold loaded with the composite powder in step (2) is placed in the furnace cavity of the spark plasma sintering equipment for sintering, and after sintering, the composite material is obtained by cooling with the furnace.

[0016] Further, the preparation method of the self-lubricating composite material with coating structure as described above, the ball milling tank and the mixing material used in the planetary ball mill in step (1) are stainless steel materials, and the ball-to-material ratio is 10:1.

[0017] Further, the preparation method of the self-lubricating composite material with coating structure as described above, in step (2), when pre-pressing with a cold press, the pre-pressing rate is 10 MPa / min to 20 MPa, and after maintaining for 10 min, the load is unloaded.

[0018] Further, the preparation method of the self-lubricating composite material with coating structure as described above, the process parameters of the spark plasma sintering are as follows:

[0019] The vacuum degree is less than 1×10 -2Pa, sintering temperature is 1000-1250 DEG C, temperature rising speed is 40-80 DEG C / min, sintering pressure is 30-50 MPa, and holding time is 10-30 min.

[0020] Further, the preparation method of the self-lubricating composite material with the coating structure has the following performance indexes of the self-lubricating composite material prepared by the method:

[0021] The density is greater than or equal to 99%, the hardness is greater than or equal to 350HV, the compressive strength is greater than or equal to 1400MPa, the compression rate is greater than or equal to 28%, the average friction coefficient is less than 0.28 in the air environment, the friction coefficient is less than 0.10 in the seawater corrosion environment, and the wear rate is less than 1.0*10 -5 mm 3 / (Nm).

[0022] The design idea of the application is:

[0023] The application is designed as follows: the lubricating phase WS2 (or MoS2) powder with small grain size is uniformly coated on the Ti3SiC2 (or Ti3AlC2) powder by using a low-energy ball milling process, and then the coated powder is mixed with the base alloy powder by low-energy ball milling. Although the lubricating phase will decompose during sintering, in-situ reaction will also occur, so that the hard phase is formed in the inside of the coating structure, and the MAX phase Ti2SC with excellent lubricity is formed on the outside. The coating structure concentrates and agglomerates the lubricating phase, not only avoids the uniform distribution of the lubricating phase with poor mechanical properties in the matrix, thereby improving the mechanical properties of the self-lubricating composite material, but also protrudes from the surface of the matrix, so that the coating structure with higher strength and better lubricity is preferentially subjected to the friction load, thereby providing lubrication and support, and achieving the effect of reducing friction and wear.

[0024] The application has the following advantages and beneficial effects:

[0025] (1) The application uses Ni, Co or Fe-based alloy as the matrix, has high strength and toughness, excellent corrosion resistance and other advantages, and after adding WS2 (or MoS2) powder and Ti3SiC2 (or Ti3AlC2) powder, new hard phase and lubricating phase are generated by in-situ reaction, so that the problem of self-lubricating failure caused by the decomposition of the lubricating phase can be avoided on the premise of ensuring excellent mechanical properties, which has great significance for ensuring the long-term safe and stable operation of mechanical equipment.

[0026] (2) The application adopts a secondary ball milling process to obtain a coating structure of lubricating phase wrapping hard phase in the Ni, Co or Fe-based alloy, and the coating structure protrudes from the surface of the matrix, so that the coating structure can preferentially provide lubrication and support when subjected to friction and load, thereby greatly reducing the friction coefficient and wear rate of the material.

[0027] (3) The process parameters in the material preparation process of the application are easy to control and have high feasibility, the experimental method is simple and novel, the metal powder used in the application has moderate price and is easy to obtain, the material performance can be adjusted through simple process adjustment, and the application has wide application in the fields of engineering machinery, nuclear power industry, aerospace, etc. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 Schematic diagram of ball milling process for obtaining coated structure;

[0029] Figure 2 Material microstructure after sintering of Example 1 using NiCr alloy powder as matrix and WS2 and Ti3SiC2 powders as additive phase through secondary coated ball milling;

[0030] Figure 3 Material microstructure after sintering of Comparative Example 1 using NiCr alloy powder as matrix and WS2 and Ti3SiC2 powders as additive phase through direct ball milling;

[0031] Figure 4 Enlarged view of the coated structure in Example 1 and the corresponding EDS spectrum. DETAILED DESCRIPTION

[0032] The specific embodiments of the application will be further described in detail below in conjunction with the drawings and examples of the specification. The following examples are used to illustrate the application, but cannot be used to limit the scope of the application. Example 1

[0033] In this embodiment, the preparation method of the self-lubricating composite material with coated structure uses NiCr high-temperature alloy as matrix with particle size of 30-50 μm, and WS2 powder and Ti3SiC2 particles as additive phase to prepare the composite material, WS2 powder particle size <5 μm, Ti3SiC2 particle size 30-60 μm, the composite material ratio is NiCr alloy 80 wt%, WS2 powder 10 wt%, Ti3SiC2 powder 10 wt%. The specific preparation process and parameters are as follows:

[0034] (1) Powder mixing: first mix Ti3SiC2 powder and WS2 powder by planetary ball milling, rotation speed 150 rpm, ball milling time 2 hours, at this time obtain the particle structure of WS2 powder coated Ti3SiC2 powder; then planetary ball mill the coated powder and NiCr alloy powder, rotation speed 150 rpm, ball milling time 2 hours, obtain uniformly mixed composite powder, such as Figure 1The schematic diagram of the ball milling process for obtaining the coated structure is shown, and the enlarged view of the coated structure and the corresponding EDS spectrum are shown in the figure.

[0035] (2) Pre-pressing: the composite powder obtained in step (1) was put into a graphite mold, and the composite powder was pre-pressed to 20 MPa at a rate of 10 MPa / min using a cold press, and unloaded after holding for 10 min.

[0036] (3) Spark plasma sintering: the graphite mold containing the composite powder was put into the furnace cavity, and spark plasma sintering was carried out:

[0037] The vacuum degree was less than 1×10 -2 Pa; the sintering temperature was 1100 ℃; the heating rate was 40 ℃ / min; the sintering pressure was 40 MPa; and the holding time was 15 min.

[0038] The microstructure of the sintered material is shown in the figure Figure 2 , the density of the composite material after sintering was 99.4%, the hardness was 425 HV, the yield strength was 856 MPa, the compressive strength was 1608 MPa, the compression rate was 32.1%, the average friction coefficient was 0.24 at room temperature with a parameter of 10N, 24mm / s and Si3N4 ball (diameter 9.5mm), and the wear rate was 7.5×10 -6 mm 3 / (Nm). Comparative Example 1

[0039] The difference between this comparative example and Example 1 is that the ball milling process of the composite material is direct ball milling.

[0040] The ball milling process was: the NiCr alloy powder, WS2 powder and Ti3SiC2 particles were simultaneously put into the ball milling tank for ball milling, the ball milling speed was 300 rpm, and the ball milling time was 4h.

[0041] The microstructure of the sintered material is shown in the figure Figure 3 , the density of the composite material after sintering was 99.5%, the hardness was 411 HV, the yield strength was 880 MPa, the compressive strength was 1433 MPa, the compression rate was 24.4%, the average friction coefficient at room temperature was 0.38, and the wear rate was 9.8×10 -6 mm 3 / (Nm). Comparative Example 2

[0042] The difference between this comparative example and Example 1 is that the composition ratio of the composite material is NiCr alloy 90 wt%, WS2 powder 5 wt%, and Ti3SiC2 powder 5 wt%.

[0043] The density of the sintered composite material was 99.7%, the hardness was 318HV, the yield strength was 670MPa, the compressive strength was 1682MPa, the compression rate was 38.9%, the average friction coefficient at room temperature was 0.35, and the wear rate was 4.6x10 -5 mm 3 / (Nm). Comparative Example 3

[0044] The difference between this comparative example and Example 1 was that the composition of the composite material was NiCr alloy 70 wt%, WS2 powder 15 wt%, and Ti3SiC2 powder 15 wt%.

[0045] The density of the sintered composite material was 99.3%, the hardness was 522HV, the yield strength was 1011MPa, the compressive strength was 1525MPa, the compression rate was 18.5%, the average friction coefficient at room temperature was 0.21, and the wear rate was 5.9x10 -6 mm 3 / (Nm). Comparative Example 4

[0046] The difference between this comparative example and Example 1 was that the composition of the composite material was NiCr alloy 80 wt%, MoS2 powder 10 wt%, and Ti3SiC2 powder 10 wt%.

[0047] The density of the sintered composite material was 99.4%, the hardness was 404HV, the yield strength was 815MPa, the compressive strength was 1586MPa, the compression rate was 30.5%, the average friction coefficient at room temperature was 0.26, and the wear rate was 8.4x10 -6 mm 3 / (Nm). Comparative Example 5

[0048] The difference between this comparative example and Example 1 was that the composition of the composite material was NiCr alloy 80 wt%, WS2 powder 10 wt%, and Ti3AlC2 powder 10 wt%.

[0049] The density of the sintered composite material was 99.5%, the hardness was 398HV, the yield strength was 768MPa, the compressive strength was 1541MPa, the compression rate was 31.2%, the average friction coefficient at room temperature was 0.29, and the wear rate was 9.2x10 -6 mm 3 / (Nm). Comparative Example 6

[0050] The difference between this comparative example and Example 1 was that the composition of the composite material was NiCr alloy 100 wt%.

[0051] The density of the sintered composite material is 99.1%; the hardness is 208 HV; the yield strength is 421 MPa; the average friction coefficient at room temperature is 0.55, and the wear rate is 9.8 x 10 -5 mm 3 / (Nm). Example 2

[0052] In this embodiment, the preparation method of the self-lubricating composite material with a coating structure is the same as that of Example 1, and a NiCr-based self-lubricating composite material with a coating structure is obtained. However, the friction environment of the material is different from that of Example 1, and the specific friction and wear parameters are as follows:

[0053] (1) The sample is subjected to friction and wear in 3.5% NaCl solution.

[0054] (2) In order to prevent liquid splashing, the experiment is carried out with a Si3N4 ball (diameter 9.5 mm) at a parameter of 10 N and 12 mm / s.

[0055] The friction and wear performance of the sample in 3.5% NaCl solution is as follows: the average friction coefficient is 0.08, and the wear rate is 3.2 x 10 -6 mm 3 / (Nm). Comparative Example 7

[0056] The difference between this comparative example and Example 2 is that the ball milling process of the composite material is direct ball milling.

[0057] The friction and wear performance of the sample in 3.5% NaCl solution is as follows: the average friction coefficient is 0.23, and the wear rate is 8.4 x 10 -6 mm 3 / (Nm). Comparative Example 8

[0058] The difference between this comparative example and Example 2 is that the mass fraction of NaCl solution is 5%.

[0059] The friction and wear performance of the sample in 5% NaCl solution is as follows: the average friction coefficient is 0.07, and the wear rate is 2.9 x 10 -6 mm 3 / (Nm). Example 3

[0060] In this embodiment, the preparation method of the self-lubricating composite material with a coating structure is used. Pure Ni is used as the matrix, the particle size is 50-90 μm, and the composite material is prepared by adding MoS2 powder and Ti3AlC2 particles. The particle size of the MoS2 powder is <5 μm, the particle size of the Ti3AlC2 particles is 40-80 μm, and the ratio of the composite material is 80 wt% of pure Ni powder, 10 wt% of MoS2 powder, and 10 wt% of Ti3AlC2 powder. The specific preparation process and parameters are as follows:

[0061] (1) Powder mixing: first, mix the Ti3AlC2 powder and the MoS2 powder by planetary ball milling at a speed of 150 rpm for 2 hours, at which time the MoS2 powder coated Ti3AlC2 powder particle structure is obtained; then mix the coated powder and the Ni powder by planetary ball milling at a speed of 150 rpm for 2 hours to obtain a uniformly mixed composite powder.

[0062] (2) Pre-pressing: place the composite powder obtained in step (1) into a graphite mold, and use a cold press to pre-press the composite powder at a rate of 10 MPa / min to 20 MPa, and then unload after 10 min.

[0063] (3) Spark plasma sintering: place the graphite mold containing the composite powder into the furnace cavity and perform spark plasma sintering:

[0064] The vacuum degree is less than 1×10 -2 Pa; the sintering temperature is 1100 ℃; the heating rate is 40 ℃ / min; the sintering pressure is 40 MPa; and the holding time is 15 min.

[0065] The density of the sintered composite material is 99.6%; the hardness is 393 HV; the yield strength is 818 MPa; the compressive strength is 1589 MPa; the compression rate is 31.4%; the average friction coefficient is 0.26 when the material is rubbed with Si3N4 balls (diameter 9.5 mm) at a parameter of 10 N and 24 mm / s at room temperature; and the wear rate is 7.9×10 -6 mm 3 / (Nm). Comparative Example 9

[0066] The difference between this comparative example and Example 3 is that the ball milling process of the composite material is direct ball milling.

[0067] The ball milling process is as follows: the pure Ni powder, the MoS2 powder and the Ti3AlC2 particles are placed into the ball milling tank at the same time, the ball milling speed is 300 rpm, and the ball milling time is 4 h.

[0068] The density of the sintered composite material is 99.6%, the hardness is 411 HV, the yield strength is 861 MPa, the compressive strength is 1538 MPa, the compression rate is 23.8%, the average friction coefficient at room temperature is 0.35, and the wear rate is 1.1 x 10 -5 mm 3 / (Nm). Example 4

[0069] In this embodiment, the preparation method of the self-lubricating composite material with a coating structure is used, the NiCrAl alloy is used as the matrix, the particle size is 50-80 μm, the MoS2 powder and Ti3SiC2 particles are used as the additive phase, the particle size of the MoS2 powder is <5 μm, the particle size of the Ti3SiC2 particles is 30-60 μm, the ratio of the composite material is 80 wt% of the NiCrAl alloy powder, 10 wt% of the MoS2 powder, and 10 wt% of the Ti3SiC2 powder, and the specific preparation process and parameters are as follows:

[0070] (1) Powder mixing: first, the Ti3SiC2 powder and the MoS2 powder are mixed by planetary ball milling at a speed of 150 rpm for 2 hours, at this time the particle structure of the MoS2 powder coated Ti3SiC2 powder is obtained; then the coated powder and the NiCrAl alloy powder are mixed by planetary ball milling at a speed of 150 rpm for 2 hours, to obtain a uniformly mixed composite powder.

[0071] (2) Pre-pressing: the composite powder obtained in step (1) is placed in a graphite mold, and a cold press is used to pre-press the composite powder at a rate of 10 MPa / min to 20 MPa, and then unloaded after 10 min.

[0072] (3) Spark plasma sintering: the graphite mold containing the composite powder is placed in the furnace cavity, and the spark plasma sintering is carried out:

[0073] The vacuum degree is less than 1 x 10 -2 Pa; the sintering temperature is 1150 ℃; the heating rate is 60 ℃ / min; the sintering pressure is 40 MPa; and the holding time is 15 min.

[0074] The density of the sintered composite material is 99.6%, the hardness is 431 HV, the yield strength is 896 MPa, the compressive strength is 1710 MPa, the compression rate is 26.5%, the average friction coefficient at room temperature is 0.27, and the wear rate is 6.8 x 10 -6 mm 3 / (Nm). Comparative Example 10

[0075] The difference between this comparative example and Example 4 is that the ball milling process of the composite material is direct ball milling.

[0076] The ball milling process is that the NiCrAl alloy powder, MoS2 powder and Ti3SiC2 particles are simultaneously put into a ball milling tank for ball milling at a rotation speed of 300 rpm for 4 h.

[0077] After sintering, the density of the composite material is 99.6 %, the hardness is 438 HV; the yield strength is 887 MPa; the compressive strength is 1735 MPa; the compression rate is 19.8 %; the average friction coefficient at room temperature is 0.37, and the wear rate is 1.6 x 10 -5 mm 3 / (Nm). Comparative Example 11

[0078] The difference between this comparative example and Example 4 is that the ball milling process of the composite material is direct ball milling.

[0079] After sintering, the density of the composite material is 99.7 %, the hardness is 339 HV; the yield strength is 689 MPa; the compressive strength is 1765 MPa; the compression rate is 36.7 %; the average friction coefficient at room temperature is 0.37, and the wear rate is 4.4 x 10 -5 mm 3 / (Nm) Example 5

[0080] In this example, the preparation method of the self-lubricating composite material with a coating structure is the same as that of Example 4, and a NiCrAl-based self-lubricating composite material with a coating structure is obtained. However, the friction environment of the material is different from that of Example 4, and the specific friction and wear parameters are as follows:

[0081] (1) The sample is subjected to friction and wear in a 3.5% NaCl solution.

[0082] (2) In order to prevent liquid splashing, the experiment is carried out with a 10N, 12mm / s parameter and a Si3N4 ball (diameter 9.5mm) for friction.

[0083] The friction and wear performance in the 3.5% NaCl solution is as follows: the average friction coefficient is 0.10, and the wear rate is 3.8 x 10 -6 mm 3 / (Nm). Comparative Example 12

[0084] The difference between this comparative example and Example 5 is that the ball milling process of the composite material is direct ball milling.

[0085] The friction and wear properties in 3.5% NaCl solution are as follows: the average friction coefficient is 0.26, and the wear rate is 7.9 x 10 -6 mm 3 / (Nm). Comparative Example 13

[0086] The difference between this comparative example and Example 5 is that the mass fraction of the NaCl solution is 5%.

[0087] The friction and wear properties in 5% NaCl solution are as follows: the average friction coefficient is 0.09, and the wear rate is 3.1 x 10 -6 mm 3 / (Nm). Example 6

[0088] In this example, the preparation method of the self-lubricating composite material with a coating structure is as follows: Co is used as the matrix, the particle size is 30-50 μm, WS2 powder and Ti3AlC2 particles are used as the additive phase to prepare the composite material, the particle size of the WS2 powder is <5 μm, the particle size of the Ti3AlC2 particles is 40-80 μm, and the ratio of the composite material is 80 wt% of pure Co powder, 10 wt% of WS2 powder, and 10 wt% of Ti3AlC2 powder. The specific preparation process and parameters are as follows:

[0089] (1) Powder mixing: first, mix the Ti3SiC2 powder and the WS2 powder by planetary ball milling at a speed of 150 rpm for 2 hours, at which time the particle structure of the WS2 powder coated Ti3AlC2 powder is obtained; then mix the coated powder and the pure Co powder by planetary ball milling at a speed of 150 rpm for 2 hours to obtain a uniformly mixed composite powder.

[0090] (2) Pre-pressing: place the composite powder obtained in step (1) into a graphite mold, and use a cold press machine to pre-press the composite powder at a rate of 10 MPa / min to 20 MPa, and keep for 10 min before unloading.

[0091] (3) Spark plasma sintering: place the graphite mold containing the composite powder into the furnace cavity, and perform spark plasma sintering as follows:

[0092] The vacuum degree is less than 1 x 10 -2 Pa; the sintering temperature is 1150 ℃; the heating speed is 60 ℃ / min; the sintering pressure is 40 MPa; and the holding time is 15 min.

[0093] The sintered composite material has a density of 99.5%, a hardness of 418HV, a yield strength of 968MPa, a compressive strength of 1824MPa, a compression rate of 27.3%, an average friction coefficient of 0.28 when rubbed with Si3N4 balls (diameter 9.5mm) at room temperature under the parameters of 10N and 24mm / s, and a wear rate of 8.1×10 -6 mm 3 / (Nm). Example 7

[0094] In this embodiment, the preparation method of the self-lubricating composite material with a coating structure is used to prepare the composite material with CoCr as the matrix and a particle size of about 50 μm, and WS2 powder and Ti3AlC2 particles as the additive phase. The particle size of the WS2 powder is <5 μm, the particle size of the Ti3AlC2 particles is 40-80 μm, and the composite material has a ratio of CoCr powder 80 wt%, WS2 powder 10 wt%, and Ti3AlC2 powder 10 wt%. The specific preparation process and parameters are as follows:

[0095] (1) Powder mixing: first, mix the Ti3SiC2 powder and the WS2 powder by planetary ball milling at a speed of 150 rpm for 2 hours to obtain a particle structure of WS2 powder coated Ti3AlC2 powder; then mix the coated powder and the CoCr powder by planetary ball milling at a speed of 150 rpm for 2 hours to obtain a uniformly mixed composite powder.

[0096] (2) Pre-pressing: place the composite powder obtained in step (1) into a graphite mold, and use a cold press to pre-press the composite powder at a rate of 10MPa / min to 20MPa, and keep for 10 min before unloading.

[0097] (3) Spark plasma sintering: place the graphite mold containing the composite powder into the furnace cavity, and perform spark plasma sintering:

[0098] The vacuum degree is less than 1×10 -2 Pa; the sintering temperature is 1150 ℃; the heating rate is 60 ℃ / min; the sintering pressure is 40MPa; and the holding time is 15 min.

[0099] The sintered composite material has a density of 99.5%, a hardness of 479HV, a yield strength of 951MPa, a compressive strength of 1921MPa, a compression rate of 28.7%, an average friction coefficient of 0.26 when rubbed with Si3N4 balls (diameter 9.5mm) at room temperature under the parameters of 10N and 24mm / s, and a wear rate of 7.4×10 -6 mm 3 / (Nm). Example 8

[0100] In this embodiment, the preparation method of self-lubricating composite material with coating structure, taking 316 stainless steel powder as matrix, particle size about 30 μm, taking MoS2 powder and Ti3AlC2 particles as additive phase to prepare the composite material, MoS2 powder particle size <5 μm and Ti3AlC2 particle size 40~80 μm, the composite material ratio is 316 stainless steel powder 80 wt%, MoS2 powder 10 wt%, Ti3AlC2 powder 10 wt%, the specific preparation process and parameters are as follows:

[0101] (1) Powder mixing: first, mix Ti3SiC2 powder and MoS2 powder by planetary ball milling, rotation speed 150 rpm, ball milling time 2 hours, at this time obtain MoS2 powder coated Ti3AlC2 powder particle structure; then mix the coated powder and 316 stainless steel powder by planetary ball milling, rotation speed 150 rpm, ball milling time 2 hours, obtain uniformly mixed composite powder.

[0102] (2) Pre-pressing: put the composite powder obtained in step (1) into graphite mold, use cold press to pre-press the composite powder to 20 MPa at a rate of 10 MPa / min, keep 10 min and unload.

[0103] (3) Spark plasma sintering: put the graphite mold containing the composite powder into the furnace cavity, and perform spark plasma sintering:

[0104] vacuum degree less than 1×10 -2 Pa; sintering temperature 1250 ℃; heating rate 50 ℃ / min; sintering pressure 40 MPa; holding time 15 min.

[0105] The density of the composite material after sintering is 99.4%; hardness 378 HV; yield strength 689 MPa; compressive strength 1320 MPa; compression rate 29.1%; at room temperature, friction with Si3N4 ball (diameter 9.5 mm) at parameters of 10 N and 24 mm / s, the average friction coefficient is 0.28; wear rate 8.3×10 -6 mm 3 / (Nm).

[0106] The results of the examples and comparative examples show that the present application is designed to firstly uniformly coat the lubricating phase WS2 (or MoS2) powder with small grain size on the Ti3SiC2 (or Ti3AlC2) powder by using a low-energy ball milling process, and then mix the coated powder with the Ni, Co or Fe-based alloy powder by using a low-energy ball milling process. The coated structure of the lubricating phase coated on the hard phase is formed during sintering. The coated structure not only improves the mechanical properties of the nickel-based self-lubricating material, but also plays a supporting and lubricating role when subjected to a friction load, so as to achieve the effect of reducing friction and wear resistance.

[0107] The above only describes the preferred embodiments of the present application, and the present application is not limited to the implementation depending on the above detailed composition and preparation method for those skilled in the art. Any improvement, product raw material replacement and addition of auxiliary ingredients of the present application are within the protection scope and disclosure scope of the present application.

Claims

1. A self-lubricating composite material having a clad structure, characterized by, The composite material is composed of the following components in percentage by weight: Ni, Co or Fe based alloy powder 70-90%; Ti3SiC2 or Ti3AlC2 powder 5-15%; WS2 or MoS2 powder 5-15%; The Ni, Co or Fe based alloy includes Ni, NiCr, NiCrAl, Co, CoCr and stainless steel, and the original powder particle size is 30-100 μm; the Ti3SiC2 or Ti3AlC2 powder particle size is 30-80 μm; and the WS2 or MoS2 powder particle size is less than 5 μm; The self-lubricating composite material with a coating structure is prepared by the following method: (1) Powder mixing: first, mix the Ti3SiC2 or Ti3AlC2 powder and the WS2 or MoS2 powder by planetary ball milling at a speed of 100-150 rpm for 2-4 hours to obtain a coating structure of the WS2 or MoS2 powder wrapping the Ti3SiC2 or Ti3AlC2 powder; then mix the coated powder and the Ni, Co or Fe based alloy powder by planetary ball milling at a speed of 100-150 rpm for 2-4 hours to obtain a mixed and uniform composite powder; (2) Pre-pressing: load the composite powder obtained in step (1) into a graphite mold, and then pre-press using a cold press; (3) Discharge plasma sintering: place the graphite mold with the composite powder in step (2) into a discharge plasma sintering device furnace cavity for sintering, and obtain the composite material after cooling in the furnace after sintering.

2. The self-lubricating composite material with a clad structure according to claim 1, characterized by The ball milling tank and the mixing material used in the planetary ball mill in step (1) are stainless steel materials, and the ball-to-material ratio is 10:

1.

3. The self-lubricating composite material with a cladding structure according to claim 1, characterized in that, In step (2), the cold press is pre-pressed at a rate of 10 MPa / min to 20 MPa, and unloaded after 10 min of holding.

4. The self-lubricating composite material with a cladding structure according to claim 1, characterized by, The process parameters of the discharge plasma sintering are as follows: a vacuum of less than 1 x 10 -2 a sintering temperature of 1000-1250 °C; a temperature rising speed of 40-80 °C / min; a sintering pressure of 30-50 MPa; and a holding time of 10-30 min.

5. The self-lubricating composite material with a cladding structure according to claim 1, characterized in that, The performance indicators of the self-lubricating composite material are as follows: Density ≥ 99%; hardness ≥ 350 HV; compressive strength ≥ 1400 MPa; compressibility ≥ 28%; average friction coefficient less than 0.28 in air and less than 0.10 in seawater corrosion environment, and wear rate less than 1.0 x 10 -5 mm 3 / (Nm) when rubbing against Si3N4 material at room temperature with parameters of 10 N and 24 mm / s.

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