A multiphase boride-based cermet and a method for producing the same

Abstract

The application discloses a kind of multiphase boride-based cermet and its preparation method, the metal ceramic includes three kinds of hard phase particles and Fe-based binder phase.Three kinds of hard phase particles are respectively: the hard phase particle with core-ring structure, the core is Mo2FeB2 Particle, the ring phase of coating core is (Mo, W)2(Fe, Co)B2 Complex solid solution;Near equiaxed W2CoB2 Particle;Near equiaxed TiC Particle.The metal ceramic preparation method includes the following steps: with Mo powder, FeB powder, Fe powder as raw material, by ball milling, vacuum pre-sintering to prepare intermediate reaction product;Then with intermediate reaction product powder, Fe powder, WC powder, Co powder, TiB2 Powder and graphite powder as raw material preparation mixed material, by ball milling, forming, vacuum sintering, to obtain multiphase boride-based cermet.The metal ceramic not only has higher hardness and wear resistance, also has higher strength and toughness.

Description

Technical Field

[0001] This invention belongs to the field of powder metallurgy technology, specifically a multiphase boride-based metal ceramic and its preparation method. Background Technology

[0002] Ternary boride-based Mo2FeB2 cermets not only possess high hardness, wear resistance, red hardness, corrosion resistance, electrical conductivity, and a thermal expansion coefficient similar to steel, but also have low manufacturing costs. Therefore, they have begun to find applications in some wear-resistant and corrosion-resistant fields, such as injection molding equipment parts, wire drawing dies, and non-ferrous metal extrusion dies, and have become a hard material with great development potential.

[0003] However, because the intrinsic hardness of the Mo2FeB2 hard phase is significantly lower than that of conventional hard phases such as WC, TiC, and Ti(C,N), the currently prepared Mo2FeB2-based cermets have relatively lower hardness compared to other hard materials, such as cemented carbides and Ti(C,N)-based cermets, affecting the material's service life. This insufficient hardness directly leads to relatively poor wear resistance. Under working conditions subjected to abrasive wear, erosive wear, or high-stress wear, the material surface is more prone to wear spalling and scratches, severely limiting the material's service life and application range in scenarios requiring higher wear resistance.

[0004] To further improve the hardness of Mo2FeB2-based cermets while maintaining their high strength and toughness, researchers have conducted relevant studies. Patent CN 110735076 B discloses "A high-entropy cermet and its preparation method and application," which involves using high-entropy boride ceramic powder (A... 0.2 B 0.2 C 0.2 D 0.2 E 0.2 High-entropy cermets were prepared by ball milling and mixing boron compound B2 with binders Ni, Co, and Mo, where A, B, C, D, and E are distinct elements selected from Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, or W. The mixture was then dried, pressed, and sintered in an argon atmosphere. This boride-based cermet exhibited significantly improved hardness, but its strength and toughness were noticeably reduced due to the relatively low wettability between the hard phase and the binder phase.

[0005] Patent CN 111979464 B discloses "A Mo2FeB2-based cermet with dual-scale, dual-morphology hard phase grains and its preparation method." The method first prepares a mixed powder using Mo powder, FeB powder, and Fe powder as raw materials, and obtains an intermediate reaction product through pre-sintering. Then, the intermediate reaction product powder, Fe powder, WC powder, Cr powder, Ni powder, and graphite powder are used as raw materials to prepare a cermet mixture. This mixture is then ball-milled, shaped, and vacuum-sintered to obtain a Mo2FeB2-based cermet with a microstructure consisting of two different scales and morphologies of hard phase particles (fine near-equiaxed and coarse plate-like) and an Fe-based binder phase. This method mainly utilizes the characteristics of fine near-equiaxed Mo2FeB2 to improve the material's hardness and coarse plate-like Fe3(W,Mo)3C to improve its toughness, resulting in a certain degree of improvement in hardness and toughness compared to conventional Mo2FeB2-based cermets. However, since the two hard phases of different scales and morphologies mentioned above are Mo2FeB2 and Fe3(W,Mo)3C solid solutions, their intrinsic hardness is significantly lower than that of hard phases such as WC, TiC, and Ti(C,N). Therefore, the hardness of the prepared cermets is still difficult to match that of other cermets and hard alloys, and their service life is greatly affected.

[0006] In summary, the existing Mo2FeB2-based cermets have the following technical defects: (1) The intrinsic hardness of the Mo2FeB2 hard phase is low, resulting in insufficient overall hardness and wear resistance of the material, making it difficult to meet the requirements of high wear conditions; (2) Although the high-entropy boride scheme can improve hardness and wear resistance, the wettability between the hard phase and the binder phase is poor, which seriously sacrifices the strength and toughness of the material; (3) In the dual-scale dual-morphology scheme, the intrinsic hardness of Mo2FeB2 and Fe3(W,Mo)3C solid solutions is still low, and the improvement in hardness and wear resistance is limited.

[0007] In view of the above, in order to enable Mo2FeB2-based cermets to be better applied in more fields, it is necessary to develop a Mo2FeB2-based cermet with comprehensive mechanical properties, which can significantly improve hardness and wear resistance while maintaining high strength and toughness. Summary of the Invention

[0008] The purpose of this invention is to provide a multiphase boride-based metal ceramic and its preparation method, which solves the problems of low hardness and relatively insufficient wear resistance of existing ternary boride-based metal ceramics, while maintaining high strength and toughness.

[0009] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows:

[0010] A multiphase boride-based cermet, the cermet comprising three hard phase particles and an Fe-based binder phase;

[0011] The three types of hard phase particles are as follows:

[0012] (1) Hard phase particles with core-ring structure, the core is Mo2FeB2 particles, and the ring phase covering the core is (Mo,W)2(Fe,Co)B2 complex solid solution;

[0013] (2) Nearly equiaxed W2CoB2 particles;

[0014] (3) Nearly equiaxed TiC particles;

[0015] The mass fractions of the multiphase boride-based cermet are as follows: Mo: 22.10~38.68, B: 6.03~6.94, Fe: 15.65~27.39, W: 12.04~24.08, Ti: 5.43~10.87, Co: 9.29~18.59, C: 1.14~1.77.

[0016] As a further improved technical solution of the present invention, the particle size of the hard phase particles with core-ring structure is 1~5.5μm, the particle size of the nearly equiaxed W2CoB2 particles is 0.5~3.5μm, and the particle size of the nearly equiaxed TiC particles is 0.2~5μm.

[0017] In the composition of the multiphase boride-based cermet material, Mo is introduced from Mo powder, Fe from FeB powder and Fe powder, B from FeB and TiB2, C from graphite and WC powder, W from WC powder, Ti from TiB2 powder, and Co from Co powder. The particle size of Mo powder is 3.5~4.0 μm, FeB powder is 45.0~50.0 μm, Fe powder is 3.0~3.5 μm, Co powder is 1.2~2.0 μm, TiB2 powder is 3.0~4.0 μm, WC powder is 0.5~1.5 μm, and graphite powder is 3.0~4.0 μm.

[0018] Secondly, to achieve the above-mentioned technical objectives, another technical solution adopted by the present invention is as follows:

[0019] A method for preparing multiphase boride-based metal ceramics includes the following steps:

[0020] (1) A pre-sintered mixture is prepared using Mo powder, FeB powder, and Fe powder as raw materials. The mass ratio of Mo, Fe, and B in the pre-sintered mixture is such that the pre-sintering reaction generates an intermediate reaction product mainly composed of the hard phase of Mo2FeB2. The specific mass fractions of the mixture are: Mo: 52.25~57.34, Fe: 37.33~42.86, B: 4.89~5.33.

[0021] (2) The above pre-sintered mixture is ball-milled, dried, sieved and then pre-sintered under vacuum to obtain an intermediate reaction product with Mo2FeB2 hard phase as the main component.

[0022] (3) The intermediate reaction product obtained in step (2) is crushed to obtain intermediate reaction product powder;

[0023] (4) The intermediate reaction product powder obtained in step (3), Fe powder, WC powder, Co powder, TiB2 powder and graphite powder are mixed to obtain a metal-ceramic mixed powder. The elemental composition of the metal-ceramic mixed powder is as follows in parts by mass: Mo: 22.10~38.68, B: 6.03~6.94, Fe: 15.65~27.39, W: 12.04~24.08, Ti: 5.43~10.87, Co: 9.29~18.59, C: 1.14~1.77;

[0024] (5) The above-mentioned metal-ceramic mixed powder is ball-milled, pressed and sintered under vacuum to obtain a multiphase boride-based metal-ceramic material;

[0025] The vacuum sintering process is as follows: the compact is heated to a first temperature and held, then heated to a second temperature and held, then heated to a third temperature and held, and finally cooled to 1000℃ at a cooling rate of 15~20℃ / min, and cooled in the furnace; the first temperature is 1020~1060℃, the second temperature is 1220~1260℃, and the third temperature is 1380~1440℃; the sintering process is carried out under a vacuum degree higher than 1.0×10⁻¹Pa.

[0026] As a further improvement of the present invention, in step (2), the ball milling and mixing is carried out in a planetary ball mill with a ball-to-material ratio of 5:1, a ball mill speed of 200~300 rpm, and a ball milling time of 18~24 h.

[0027] As a further improvement of the present invention, in step (2), the pre-sintering is carried out at a vacuum degree higher than 1.0 × 10⁻⁶. -1 The sintering process is carried out in a vacuum sintering furnace at a temperature of 1050~1100℃ and a holding time of 0.5~1h.

[0028] As a further improvement of the present invention, the crushing in step (3) is carried out in a vibrating mill with a vibration frequency of 20.0~24.0Hz, an amplitude of 10.0~15.0mm, and a crushing time of 2~4min.

[0029] As a further improvement of the present invention, the ball milling and mixing in step (5) is carried out in a planetary ball mill with a ball-to-material ratio of 5:1 to 7:1, a ball mill speed of 200 to 300 rpm, and a ball milling time of 24 to 30 hours.

[0030] As a further improvement of the present invention, the pressing and molding in step (5) is completed by a mechanical powder metallurgy press with a pressure of 160~200MPa.

[0031] As a further improvement of the present invention, in the vacuum sintering process of step (5), the holding time of the first temperature is 1~2h, the holding time of the second temperature is 1~2h, and the holding time of the third temperature is 40~80min.

[0032] As a further improvement of the present invention, the drying in step (2) is done at 80°C and the sieving is done at 60 mesh.

[0033] To achieve the objective of this invention, in step (2) above, a mixture prepared from Mo powder, FeB powder, and Fe powder is pre-sintered. During the pre-sintering stage, the following solid-state reactions occur sequentially: Fe + FeB → Fe2B; 2Mo + 2FeB → Mo2FeB2; 2Mo + 2Fe2B → Mo2FeB2 + 3Fe, etc., generating an intermediate reaction product mainly composed of the hard phase Mo2FeB2. Subsequently, in step (3), the intermediate reaction product is pulverized to obtain intermediate reaction product powder.

[0034] To achieve the purpose of this invention, in step (4) above, intermediate reaction product powder with Mo2FeB2 hard phase as the main component, Fe powder, WC powder, Co powder, TiB2 powder and graphite powder are mixed to obtain a metal-ceramic mixed powder. In the high-temperature sintering stage of step (5), the following reactions occur sequentially: WC + Co + TiB2 → WCoB + TiC; WCoB + WC → Co6W6C + W2CoB2; WCoB → W2CoB2 + Co; Co6W6C → WC + Co; WC + Co + WCoB → W2CoB2, forming a nearly equiaxed W2CoB2 hard phase with a significantly higher intrinsic hardness than the Mo2FeB2 hard phase. A small amount of TiC hard phase particles are also generated. On the other hand, through a dissolution-precipitation mechanism, a layer of (Mo,W)2(Fe,Co)B2 annular phase precipitates on the surface of the undissolved Mo2FeB2 particles, forming hard phase particles with a core-ring structure. The intrinsic hardness of the (Mo,W)2(Fe,Co)B2 annular phase is significantly higher than that of Mo2FeB2, and it also exhibits better wettability with the metal binder phase. Therefore, compared to Mo2FeB2-based cermets, the prepared multiphase boride-based cermet shows a significant improvement in hardness and better overall performance.

[0035] To achieve the purpose of this invention, the vacuum sintering in step (5) above is divided into four stages. First, the compact is heated to 1020~1060℃ and held for 1~2h; then heated to 1220~1260℃ and held for 1~2h; then heated to 1380~1440℃ and held for 40~80min; finally, the temperature is rapidly reduced to 1000℃ at a cooling rate of 15~20℃ / min and cooled with the furnace to obtain multiphase boride-based metal ceramics. Holding at 1020~1060℃ for 1~2h is to allow TiB2 to fully react with WC and Co as follows: WC+Co+TiB2→WCoB+TiC; then heating to 1220~1260℃ and holding for 1~2h is to allow the following reaction to proceed fully: CoB+WC→Co6W6C+W2CoB2; WCoB→W2CoB2+ Co; Co6W6C → WC + Co; WC + Co + WCoB → W2CoB2; This also promotes the initial densification of the material; Then, the temperature is raised to 1380~1440℃ and held for 40~80min to allow the dissolution and precipitation process in the liquid phase sintering stage to proceed fully. On the surface of the undissolved Mo2FeB2 particles, a complex solid solution of (Mo,W)2(Fe,Co)B2 is precipitated, forming hard phase particles with a core-ring structure, while simultaneously completing the densification and homogenization of the sintered body; Finally, the temperature is rapidly reduced to 1000℃ at a cooling rate of 15~20℃ / min and cooled with the furnace. Cooling to 1000℃ at a moderate cooling rate can prevent the hard phase particles from growing excessively and can also reduce internal stress. Cooling with the furnace below 1000℃ can further release internal stress and reduce defects.

[0036] The beneficial effects of this invention are as follows:

[0037] (1) The multiphase boride-based metal ceramic provided by the present invention includes three types of hard phases: hard phase particles with core-ring structure, nearly equiaxed W2CoB2 particles, and nearly equiaxed TiC particles. Among them, the in-situ formation of near-equiaxed W2CoB2 particles directly solves the problem of insufficient hardness and wear resistance in existing Mo2FeB2-based cermets due to the low intrinsic hardness of the Mo2FeB2 hard phase. The intrinsic hardness of W2CoB2 (approximately 2200~2400 HV) is significantly higher than that of Mo2FeB2 (approximately 1600~1800 HV). Its in-situ formation significantly improves the overall hardness and abrasive wear resistance of the material, making the surface less prone to wear and spalling under abrasive and erosive wear conditions. The formation of core-ring structure hard phase particles with Mo2FeB2 particles as the core and (Mo,W)2(Fe,Co)B2 solid solution as the ring phase provides an effective way to solve the defects of poor wettability and reduced strength and toughness in existing high-entropy boride schemes. The (Mo,W)2(Fe,Co)B2 ring phase not only has an intrinsic hardness of approximately 1900~2100 HV, but also... The hard phase (HV) is higher than that of Mo2FeB2, and it has good wettability with the Fe-based binder phase. While improving the hardness and wear resistance of the hard phase, it also improves the interfacial bonding between the ceramic and metallic binder phases, enhancing the interfacial bonding strength and increasing the hardness of the hard phase. This prevents hard phase particles from detaching during wear due to poor interfacial bonding, thus further improving the wear resistance and reliability of the material. The formation of a small amount of near-equiaxed TiC particles (intrinsic hardness approximately 2800~3200 HV) further increases the material's hardness. The synergistic effect of the three hard phases makes the material prepared by this invention significantly higher in hardness, wear resistance, and toughness than ternary boride-based metal ceramics prepared by traditional methods.

[0038] (2) The multiphase boride-based cermet provided by this invention has excellent comprehensive mechanical properties. While significantly improving hardness and wear resistance, it maintains high strength and toughness. Furthermore, by adjusting the composition and process, the hardness, flexural strength, fracture toughness, and wear resistance of this cermet can be controlled within a certain range. Specifically, the product of this invention has a hardness of 91.7~92.6 HRA, a flexural strength of 1907~2207 MPa, and a fracture toughness of 19.6~24.5 MN·m⁻³ / ², exhibiting excellent comprehensive mechanical properties. The high hardness endows the material with excellent wear resistance, enabling it to have a longer service life in wear-resistant and corrosion-resistant applications such as injection molding equipment parts, wire drawing dies, and non-ferrous metal extrusion dies. Simultaneously, the high strength and fracture toughness ensure that the material can resist impact loads during service, avoiding brittle failure.

[0039] (3) This invention only requires conventional equipment (planetary ball mill, vibratory mill, mechanical powder metallurgy press, vacuum sintering furnace, etc.), the preparation process is simple and controllable, which is conducive to industrial promotion and application, and the production cost is relatively low, which has good economic performance and market competitiveness. Attached Figure Description

[0040] Figure 1 SEM microstructure of the multiphase boride-based cermet prepared in Example 1.

[0041] In the figure, 1. Hard phase particles with core-ring structure; 2. Near-equiaxed W2CoB2 particles; 3. Near-equiaxed TiC particles; 4. Fe-based binder phase. Detailed Implementation

[0042] The technical effects of the present invention will be further illustrated below with examples.

[0043] The raw materials used in the following examples are: Mo powder, FeB powder, Fe powder, WC powder, Co powder, TiB2 powder, and graphite powder. The particle size of Mo powder is 3.5–4.0 μm, FeB powder is 45.0–50.0 μm, Fe powder is 3.0–3.5 μm, WC powder is 0.5–1.5 μm, Co powder is 1.2–2.0 μm, TiB2 powder is 3.0–4.0 μm, and graphite powder is 3.0–4.0 μm.

[0044] In the following embodiments, the vibratory mill used is a GJ-1 vibratory mill manufactured by Changsha Tianchuang Powder Technology Co., Ltd.; the planetary ball mill is a QM-3SP planetary ball mill manufactured by Nanjing Nanda Instrument Co., Ltd.; the mechanical powder metallurgy press used for pressing and molding is an HPP-60F powder forming machine manufactured by Yangzhou Haili Precision Machinery Manufacturing Co., Ltd.; and the vacuum sintering furnace is a ZY-40-20Y vacuum hot press furnace manufactured by Shanghai Chenhua Electric Furnace Co., Ltd.

[0045] Table 1 shows the composition of the pre-sintered mixtures with four different formulations, and Table 2 shows the composition of the cermet mixtures with four different formulations. Cermets were prepared using three different process parameters as described in Examples 1-3, and the Rockwell hardness, flexural strength, and Palmqvist fracture toughness of the samples were measured. Rockwell hardness was measured according to GB / T 3849.1-2015, room temperature flexural strength was measured according to GB / T 3851-2015, and fracture toughness was measured according to GB / T 33819-2017.

[0046] Table 1. Composition of four pre-sintered mixtures:

[0047] Element Mo Fe B <![CDATA[1 # ]]> 52.25 42.86 4.89 <![CDATA[2 # ]]> 54.11 40.85 5.04 <![CDATA[3 # ]]> 55.76 39.06 5.18 <![CDATA[4 # ]]> 57.34 37.33 5.33

[0048] Table 2. Composition of four metal-ceramic mixtures:

[0049] Element Mo Fe B Ti Co W C <![CDATA[1 # ]]> 22.10 15.65 6.94 10.87 18.59 24.08 1.77 <![CDATA[2 # ]]> 26.54 18.80 6.70 9.44 16.14 20.88 1.50 <![CDATA[3 # ]]> 34.24 24.27 6.27 6.88 11.77 15.26 1.31 <![CDATA[4 # ]]> 38.68 27.39 6.03 5.43 9.29 12.04 1.14

[0050] Example 1:

[0051] The preparation steps of the metal-ceramic in this embodiment are as follows:

[0052] (1) Using Mo powder, FeB powder and Fe powder as raw materials, four kinds of pre-sintered mixed powders were prepared according to the composition formula shown in Table 1.

[0053] (2) The mixed powder was placed in a planetary ball mill for ball milling and mixing. The ball-to-material ratio was 5:1, the ball mill speed was 200 rpm, and the ball milling time was 24 h.

[0054] (3) After drying at 80℃ and sieving through a 60-mesh sieve, the product is then subjected to a vacuum degree higher than 1.0×10⁻⁶. -1 Pre-sintering was carried out in a vacuum sintering furnace of Pa at a sintering temperature of 1050℃ and a holding time of 1h to obtain an intermediate reaction product mainly composed of Mo2FeB2 hard phase.

[0055] (4) The intermediate reaction product obtained in step (3) is placed in a vibrating mill for crushing. The vibration frequency is 20.0 Hz, the amplitude is 15.0 mm, and the crushing time is 4 min to obtain intermediate reaction product powder with Mo2FeB2 hard phase as the main component.

[0056] (5) Using the intermediate reaction product obtained in step (4), Fe powder, WC powder, Cr powder, Ni powder and graphite powder as raw materials, prepare four kinds of metal-ceramic mixed powders according to Table 2 respectively;

[0057] (6) Place the mixed powder in a planetary ball mill for ball milling and mixing. The ball-to-material ratio is 5:1, the ball mill speed is 300 rpm, and the ball milling time is 24 h.

[0058] (7) It is formed by mechanical powder metallurgy press with a pressure of 160 MPa;

[0059] (8) The final sintering is carried out in a vacuum sintering furnace with a vacuum degree higher than 1.0 × 10⁻⁶. -1 Pa. Vacuum sintering is divided into four stages: first, the temperature is raised to 1020℃ and held for 2 hours; then the temperature is raised to 1260℃ and held for 1 hour; then the temperature is raised to 1380℃ and held for 80 minutes; finally, the furnace temperature is reduced to below 1000℃ at a cooling rate of 15℃ / min, thus obtaining multiphase boride-based metal ceramics.

[0060] The metal-ceramic SEM microstructure obtained in this embodiment is as follows: Figure 1 As shown, Figure 1 In the diagram, 1 represents a hard phase particle with a core-ring structure, wherein the core is a Mo2FeB2 particle and the ring phase covering the core is a complex solid solution of (Mo,W)2(Fe,Co)B2; 2 represents a nearly equiaxed W2CoB2 particle; 3 represents a nearly equiaxed TiC particle; and 4 represents an Fe-based binder phase.

[0061] The material obtained in this embodiment was subjected to performance testing, and the test results are shown in Table 3.

[0062] Table 3. Mechanical properties of different metal ceramics prepared using Example 1:

[0063] Element <![CDATA[1 ＃ ]]> <![CDATA[2 ＃ ]]> <![CDATA[3 ＃ ]]> <![CDATA[4 ＃ ]]> <![CDATA[Flexural strength σ b (MPa)]]> 1937 2069 2142 2114 Hardness (HRA) 92.4 92.2 91.8 91.7 <![CDATA[Fracture toughness (MN·m -3 / 2 )]]> 19.9 21.1 22.8 23.5

[0064] Example 2:

[0065] The preparation steps of the metal-ceramic in this embodiment are as follows:

[0066] (1) Using Mo powder, FeB powder and Fe powder as raw materials, prepare four kinds of pre-sintered mixed powders according to the composition formula shown in Table 1;

[0067] (2) The mixed powder was placed in a planetary ball mill for ball milling and mixing. The ball-to-material ratio was 5:1, the ball mill speed was 250 rpm, and the ball milling time was 20 h.

[0068] (3) After drying at 80℃ and sieving through a 60-mesh sieve, the product is then subjected to a vacuum degree higher than 1.0×10⁻⁶. -1 Pre-sintering was carried out in a vacuum sintering furnace of Pa at a sintering temperature of 1100℃ and a holding time of 0.5h to obtain an intermediate reaction product mainly composed of Mo2FeB2 hard phase.

[0069] (4) The intermediate reaction product obtained in step (3) is placed in a vibrating mill for crushing. The vibration frequency is 22.0 Hz, the amplitude is 12.0 mm, and the crushing time is 3 min to obtain intermediate reaction product powder with Mo2FeB2 hard phase as the main component.

[0070] (5) Using the intermediate reaction product obtained in step (4), Fe powder, WC powder, Cr powder, Ni powder and graphite powder as raw materials, prepare four kinds of metal-ceramic mixed powders according to Table 2;

[0071] (6) Place the mixed powder in a planetary ball mill for ball milling and mixing. The ball-to-material ratio is 6:1, the ball mill speed is 250 rpm, and the ball milling time is 28 h.

[0072] (7) It is formed by mechanical powder metallurgy press with a pressure of 180 MPa;

[0073] (8) The final sintering is carried out in a vacuum sintering furnace with a vacuum degree higher than 1.0 × 10⁻⁶. -1 Pa. Vacuum sintering is divided into four stages: first, the compact is heated to 1040℃ and held for 1.5h; then it is heated to 1220℃ and held for 2h; then it is heated to 1410℃ and held for 60min; finally, the furnace temperature is rapidly reduced to below 1000℃ at a cooling rate of 18℃ / min, thus obtaining multiphase boride-based metal ceramics.

[0074] The material obtained in this embodiment was subjected to performance testing, and the test results are shown in Table 4.

[0075] Table 4. Mechanical properties of different metal ceramics prepared using Example 2:

[0076] Element <![CDATA[1 ＃ ]]> <![CDATA[2 ＃ ]]> <![CDATA[3 ＃ ]]> <![CDATA[4 ＃ ]]> <![CDATA[Flexural strength σ b (MPa)]]> 1946 2166 2123 2207 Hardness (HRA) 92.6 92.5 92.1 92.1 <![CDATA[Fracture toughness (MN·m -3 / 2 )]]> 19.6 20.5 22.3 22.1

[0077] Example 3:

[0078] The preparation steps of the metal-ceramic in this embodiment are as follows:

[0079] (1) Using Mo powder, FeB powder and Fe powder as raw materials, prepare four kinds of pre-sintered mixed powders according to the composition formula shown in Table 1;

[0080] (2) The mixed powder was placed in a planetary ball mill for ball milling and mixing. The ball-to-material ratio was 5:1, the ball mill speed was 300 rpm, and the ball milling time was 18 h.

[0081] (3) After drying at 80℃ and sieving through a 60-mesh sieve, the product is then subjected to a vacuum degree higher than 1.0×10⁻⁶. -1 The product was pre-sintered in a vacuum furnace of Pa at a sintering temperature of 1080℃ and a holding time of 0.7h to obtain an intermediate reaction product mainly composed of Mo2FeB2 hard phase.

[0082] (4) The intermediate reaction product obtained in step (3) is placed in a vibrating mill for crushing. The vibration frequency is 24.0 Hz, the amplitude is 10.0 mm, and the crushing time is 2 min to obtain intermediate reaction product powder with Mo2FeB2 hard phase as the main component.

[0083] (5) Using the intermediate reaction product obtained in step (4), Fe powder, WC powder, Cr powder, Ni powder and graphite powder as raw materials, prepare four kinds of metal-ceramic mixed powders according to Table 2;

[0084] (6) Place the mixed powder in a planetary ball mill for ball milling and mixing. The ball-to-material ratio is 7:1, the ball mill speed is 200 rpm, and the ball milling time is 30 h.

[0085] (7) It is formed by pressing with a mechanical powder metallurgy press at a pressure of 200 MPa;

[0086] (8) The final sintering is carried out in a vacuum sintering furnace with a vacuum degree higher than 1.0 × 10⁻⁶. -1 Pa. Vacuum sintering is divided into four stages: first, the compact is heated to 1060℃ and held for 1 hour; then it is heated to 1240℃ and held for 1.5 hours; then it is heated to 1440℃ and held for 40 minutes; finally, the furnace temperature is rapidly reduced to below 1000℃ at a cooling rate of 20℃ / min, thus obtaining multiphase boride-based metal ceramics.

[0087] The material obtained in this embodiment was subjected to performance testing, and the test results are shown in Table 5.

[0088] Table 5. Mechanical properties of different metal ceramics prepared using Example 3:

[0089] Element <![CDATA[1 ＃ ]]> <![CDATA[2 ＃ ]]> <![CDATA[3 ＃ ]]> <![CDATA[4 ＃ ]]> <![CDATA[Flexural strength σ b (MPa)]]> 1907 1974 2089 2104 Hardness (HRA) 92.2 92.0 91.9 91.7 <![CDATA[Fracture toughness (MN·m -3 / 2 )]]> 22.6 21.4 23.2 24.5

[0090] In summary, the multiphase boride-based cermet provided by this invention possesses excellent comprehensive mechanical properties. While significantly improving hardness and wear resistance, it maintains high strength and toughness. Furthermore, by adjusting the composition and process, the hardness, flexural strength, fracture toughness, and wear resistance of this cermet can be controlled within a certain range. Specifically, the product of this invention achieves a hardness of 91.7~92.6 HRA, a flexural strength of 1907~2207 MPa, and a fracture toughness of 19.6~24.5 MN·m⁻³ / ², exhibiting excellent comprehensive mechanical properties. The high hardness endows the material with excellent wear resistance, enabling it to have a longer service life in wear- and corrosion-resistant applications such as injection molding equipment parts, wire drawing dies, and non-ferrous metal extrusion dies. Simultaneously, the high strength and fracture toughness ensure that the material can withstand impact loads during service, avoiding brittle failure.

[0091] Within the scope of this patent, the final firing process parameters have a relatively significant impact on the properties of cermets. When the process parameters at each stage of final firing are appropriately matched, the relevant phase reactions and microstructure evolution processes can be better completed, and the cermets with the above-mentioned component formulations can obtain relatively good comprehensive mechanical properties. In summary, within the scope of this patent, the above-mentioned process factors have a limited impact on the properties of the prepared cermets.

[0092] The above embodiments are merely for illustrating the content of the present invention and are not intended to limit it. Therefore, any changes that fall within the meaning and scope equivalent to the claims of the present invention should be considered as included within the scope of the claims.

[0093] This invention has many specific applications. The above description is only a preferred embodiment of this invention. It should be noted that for those skilled in the art, several improvements can be made without departing from the principle of this invention, and these improvements should also be considered within the scope of protection of this invention.

Claims

1. A multiphase boride-based metal ceramic, characterized in that: The cermet comprises three hard phase particles and an Fe-based binder phase; The three types of hard phase particles are as follows: (1) Hard phase particles with core-ring structure, the core is Mo2FeB2 particles, and the ring phase covering the core is (Mo,W)2(Fe,Co)B2 complex solid solution; (2) Nearly equiaxed W2CoB2 particles; (3) Nearly equiaxed TiC particles; The mass fractions of the multiphase boride-based cermet are as follows: Mo: 22.10~38.68, B: 6.03~6.94, Fe: 15.65~27.39, W: 12.04~24.08, Ti: 5.43~10.87, Co: 9.29~18.59, C: 1.14~1.

77.

2. The multiphase boride-based metal ceramic according to claim 1, characterized in that: The hard phase particles with the core-ring structure have a particle size of 1~5.5μm, the near-equiaxed W2CoB2 particles have a particle size of 0.5~3.5μm, and the near-equiaxed TiC particles have a particle size of 0.2~5μm.

3. A method for preparing multiphase boride-based cermets as described in claim 1 or 2, characterized in that, Includes the following steps: (1) A pre-sintered mixture is prepared using Mo powder, FeB powder and Fe powder as raw materials. The mass ratio of Mo, Fe and B in the pre-sintered mixture is such that the pre-sintering reaction generates an intermediate reaction product mainly composed of Mo2FeB2 hard phase. (2) The above pre-sintered mixture is ball-milled, dried, sieved and then pre-sintered under vacuum to obtain an intermediate reaction product with Mo2FeB2 hard phase as the main component. (3) The intermediate reaction product obtained in step (2) is crushed to obtain intermediate reaction product powder; (4) The intermediate reaction product powder, Fe powder, WC powder, Co powder, TiB2 powder and graphite powder obtained in step (3) are mixed to obtain a metal-ceramic mixed powder, wherein the elemental composition of the metal-ceramic mixed powder conforms to the mass part number of the claim 1. (5) The above-mentioned metal-ceramic mixed powder is ball-milled, pressed and sintered under vacuum to obtain a multiphase boride-based metal-ceramic material; The vacuum sintering process is as follows: the compact is heated to a first temperature and held, then heated to a second temperature and held, then heated to a third temperature and held, and finally cooled to 1000℃ at a cooling rate of 15~20℃ / min, and cooled in the furnace; the first temperature is 1020~1060℃, the second temperature is 1220~1260℃, and the third temperature is 1380~1440℃; the sintering process is carried out under a vacuum degree higher than 1.0×10⁻¹Pa.

4. The preparation method according to claim 3, characterized in that: In step (2), the ball milling and mixing are carried out in a planetary ball mill with a ball-to-material ratio of 5:1, a ball mill speed of 200~300 rpm, and a ball milling time of 18~24 h.

5. The preparation method according to claim 3, characterized in that: In step (2), the pre-sintering is carried out under a vacuum degree higher than 1.0 × 10⁻⁶. -1 The sintering process is carried out in a vacuum sintering furnace at a temperature of 1050~1100℃ and a holding time of 0.5~1h.

6. The preparation method according to claim 3, characterized in that: The crushing in step (3) is carried out in a vibratory mill with a vibration frequency of 20.0~24.0Hz, an amplitude of 10.0~15.0mm, and a crushing time of 2~4min.

7. The preparation method according to claim 3, characterized in that: The ball milling and mixing in step (5) is carried out in a planetary ball mill with a ball-to-material ratio of 5:1 to 7:1, a ball mill speed of 200 to 300 rpm, and a ball milling time of 24 to 30 hours.

8. The preparation method according to claim 3, characterized in that: In step (5), the pressing and molding is completed by a mechanical powder metallurgy press with a pressure of 160~200MPa.

9. The preparation method according to claim 3, characterized in that: In the vacuum sintering process of step (5), the holding time at the first temperature is 1-2 hours, the holding time at the second temperature is 1-2 hours, and the holding time at the third temperature is 40-80 minutes.

10. The preparation method according to claim 3, characterized in that: The drying in step (2) is done at 80°C, and the sieving is done at 60 mesh.

Images