Multistage composite metal ceramic, preparation method of multistage composite metal ceramic and shield cutter

[0050] The invention also provides a method for preparing the multi-stage composite cermet, which includes the following steps:

[0051] A) Coating n layers of transition phase on the outer layer of the wear-resistant phase to obtain agglomerates, n≥1;

[0052] The hardness of the n-layer transition phase gradually decreases, and the transition phase layer in contact with the wear-resistant phase has the highest hardness;

[0053] The wear-resistant phase includes AlMgB 14 -Ni 3 Al-SiC alloy;

[0054] B) Mixing the pellets with the matrix and sintering to obtain a multi-level composite cermet.

[0055] The present invention preferably includes n layers of transition phase in the outer layer of the wear-resistant spherical powder particles to obtain agglomerates, n≥1. The present invention preferably coats n layers of transition phase on the outer layer of the wear-resistant spherical powder particles to obtain the agglomerates. Yes, the wear-resistant phase spherical powder particles can be placed in the transition phase powder with the forming agent, mixed and granulated, and after pre-fired, spherical pellets with the wear-resistant phase inside and the outer layer coated with the transition phase are obtained . In the present invention, when the outer layer of the wear-resistant phase is coated with multiple transition phases, the coating can be carried out layer by layer, and the spherical powder particles of the wear-resistant phase are placed in the first layer of transition phase powder for mixing and granulation; Put the obtained particles in the second layer of transition phase powder for mixing and granulation; put the obtained particles in the third layer of transition phase powder for mixing and granulation, and so on, to obtain the wear-resistant phase inside and the outside The layer is coated with spherical particles of multiple transition phases.

[0056] In the present invention, the material, dosage and preparation method of the wear-resistant phase are consistent with the material, dosage and preparation method of the wear-resistant phase in the above technical solution, and will not be repeated here; the material and dosage of the transition phase are the same as those described above. The material and the amount of the transition phase in the technical solution are the same, and will not be repeated here; the type of the molding agent is the same as that in the above technical solution, and the details are not repeated here.

[0057] In the present invention, the mixing granulation process can be spray granulation or drum granulation well known to those skilled in the art. In the present invention, the particle size of the sintered wear-resistant phase obtained after the granulation is consistent with the particle size of the wear-resistant phase-transition phase aggregates described in the above technical solution, and can also be adjusted according to actual needs. The present invention does not Make special restrictions.

[0058] In the present invention, the obtained pellets are preferably pre-fired to obtain pre-fired pellets. In the present invention, the pre-sintering includes dewaxing and sintering. The dewaxing can be performed in hydrogen, argon, or nitrogen. Temperature 400-600℃, dewaxing time 0.5-2 hours, sintering can be carried out in hydrogen, argon, nitrogen, vacuum, sintering temperature 1100-1600℃. .

[0059] After the pre-sintering of the pellets is completed, the present invention mixes the pellets with the matrix and sinters to obtain a multi-level composite cermet. In the present invention, sintering methods such as hot pressing sintering, spark plasma sintering, microwave sintering or hot isostatic pressing sintering can be used, and spark plasma sintering (Spark Plasma Sintering, SPS) is preferred to prepare multi-level composite cermets. SPS technology uses discharge pulses to generate plasma between powder particles and at the same time generates Joule heat on the surface of the powder, which greatly accelerates powder purification, sintering neck growth, bulk diffusion, grain boundary diffusion, and evaporation-condensation and other sintering densification mechanisms. It can achieve rapid densification at a temperature several hundred degrees lower than conventional liquid phase sintering. With SPS technology, ultra-fine and nano-structured cermets with relatively uniform grain structure and high density can be prepared under low sintering temperature, short holding time, and controllable sintering pressure, and the mechanical properties produce strange "Double high (hardness and fracture toughness)" characteristics. Compared with the traditional liquid phase sintering process of cermets, spark plasma sintering has the advantages of rapid densification and prevention of grain growth, and is especially suitable for the preparation of non-uniform structure cermets such as multi-stage composites.

[0060] In the present invention, the sintering temperature is preferably 500 to 1600°C, more preferably 800 to 1400°C; the holding time during the sintering process is preferably 0.02 to 3 hours, more preferably 0.1 to 2 hours, most preferably For 0.5 to 1.5 hours.

[0061] The present invention also provides a shield cutter, including the multi-level composite cermet in the above technical scheme. The multi-level composite cermet in the present invention belongs to the non-uniform structure cermet, which is suitable for the excavation and cutting of soil and rock. The shield cutter made of the multi-level composite cermet in the present invention has comparable wear resistance and service life Cermet cutting tools are increased by more than 50%, and the hardness is greater than 85HRA.

[0062] The present invention provides a multi-level composite cermet, comprising a matrix phase and a number of aggregates distributed in the matrix phase, the aggregates comprising a wear-resistant phase and n layers of transition phases coated on the outside of the wear-resistant phase, n≥1; The hardness of the n-layer transition phase gradually decreases, and the transition phase layer that contacts the wear-resistant phase has the highest hardness; the wear-resistant phase includes AlMgB 14 -Ni 3 Al-SiC alloy. The present invention uses AlMgB 14 -Ni 3 Al-SiC alloy, as the super hard wear-resistant phase, is surrounded by the transition phase to form super hard composite cermet agglomerates. This kind of composite hard composite agglomerates with approximately spherical shape and coarser particle size are uniformly distributed in the continuous toughening In the matrix phase, a multi-level composite cermet with a special structure is obtained. The multi-level composite cermet of the present invention has both higher wear resistance and higher fracture toughness. The experimental results show that the multi-level composite cermet of the present invention The hardness of the cermet is 9-20GPa, and the fracture toughness is 8-20MPa·m 1/2.

[0063] The present invention tested the fracture toughness of the multi-level composite cermet of the present invention according to ASTM E399, and the results showed that the fracture toughness of the multi-level composite cermet of the present invention was as high as 20 MPa·m. 1/2.

[0064] The present invention tests the wear resistance of the multi-level composite cermet of the present invention according to ASTM B611, and the results show that the wear resistance of the multi-level composite cermet of the present invention is 15-30% higher than that of the conventional cermet with uniform structure. .

[0065] The present invention tests the Vickers hardness of the multi-level composite cermet of the present invention, and the result shows that the hardness of the multi-level composite cermet of the present invention is as high as 20 GPa.

[0066] The present invention tests the relevant life of the multi-level composite cermet excavated rock in the present invention, and the result shows that the relevant life of the excavated rock is as long as 300 min.

[0069] Example 1

[0070] Place the boron powder in 1×10 -3 In a Pa vacuum furnace, heat from room temperature to 1500°C and hold for 2 hours, then cool to room temperature with the furnace; mix aluminum powder, magnesium powder and boron powder by molar ratio Al:Mg:B=1:1:14 to obtain a mixture , Then heat the mixture to 1450°C under 20MPa and keep it for 90min. After cooling, prepare AlMgB 14 , The AlMgB 14 AlMgB is obtained after grinding 14 Pre-reaction powder.

[0071] In terms of mass fraction, mix 19% of Al, 9.0% of Cr, 0.65% of Zr, 0.6% of Y, 0.6% of V, 1% of B and the balance of Ni to obtain a mixed powder; Ball mill the mixed powder under inert atmosphere for 50h to obtain Ni 3 Al mixed powder.

[0072] In terms of mass fraction, 2% SiC whisker, 4% Ni 3 Al and 94% AlMgB 14 The pre-reacted powder is evenly mixed and passed through a 100-mesh sieve, and AlMgB is prepared after adding forming agent, wet milling, atomizing, drying, granulating, sieving, dewaxing, and sintering 14 -Ni 3 Al-SiC alloy spherical wear-resistant phase. The average particle size of the wear-resistant phase is 100 μm.

[0073] AlMgB 14 -Ni 3 The spherical wear-resistant phase of Al-SiC alloy is mixed and granulated in WC-Co powder containing 85% WC. The surface layer of the wear-resistant phase is covered with a layer of WC-Co powder as the transition phase to obtain cermet pellets. The average particle size of the ceramic pellets is 110 μm.

[0074] 55.7 g of cermet pellets and 44.3 g of WC-Co cermet are mixed (Co mass fraction is 70%), mixed uniformly, and pressed into molding, plasma sintered at 1200 DEG C, and heat preservation for 5 minutes to obtain a multi-level composite cermet. In the multi-stage composite cermet, in terms of volume fraction, the wear-resistant phase is 57.7%, the transition phase is 12.3%, and the matrix phase is 30%.

[0075] Example 2

[0076] Place the boron powder in 1×10 -3 In a Pa vacuum furnace, heat from room temperature to 1500°C and hold for 2 hours, then cool to room temperature with the furnace; mix aluminum powder, magnesium powder and boron powder by molar ratio Al:Mg:B=1:1:14 to obtain a mixture , Then heat the mixture to 1450°C under 20MPa and keep it for 90min. After cooling, prepare AlMgB 14 , The AlMgB 14 AlMgB is obtained after grinding 14 Pre-reaction powder.

[0077] In terms of mass fraction, mix 19% of Al, 9.0% of Cr, 0.65% of Zr, 0.6% of Y, 0.6% of V, 1% of B and the balance of Ni to obtain a mixed powder; Ball mill the mixed powder under inert atmosphere for 50h to obtain Ni 3 Al mixed powder.

[0078] In terms of mass fraction, 4% SiC whisker, 6% Ni 3 Al and 90% AlMgB 14 The pre-reacted powder is uniformly mixed with the forming agent and passed through a 100-mesh sieve, and is prepared after spray granulation, sieving, dewaxing, and pre-burning. The average particle size of the wear-resistant phase is 150 μm.

[0079] AlMgB 14 -Ni 3 The spherical wear-resistant phase of Al-SiC alloy is mixed and granulated in WC-Co powder containing 85% WC. The surface layer of the wear-resistant phase is covered with a layer of WC-Co powder as the transition phase to obtain cermet pellets. The average particle size of the ceramic pellets is 160 μm.

[0080] Mix 51.6g of cermet pellets with 48.4g of WC-Co (Co mass fraction is 70%), mix uniformly, and then press and shape, and then spark plasma sintering at 1200°C for 5 minutes to obtain a multi-level composite cermet. In the multi-stage composite cermet, in terms of volume fraction, the wear-resistant phase is 57.7%, the transition phase is 12.3%, and the matrix phase is 30%.