Rare earth gradient doped WC particle reinforced iron-based surface composite material and preparation method

Abstract

The invention discloses a rare earth gradient-doped WC particle-reinforced iron-based surface composite material and a preparation method thereof, belonging to the technical field of preparation of wear-resistant and corrosion-resistant composite materials. First, the invention prepares a mixture A, a mixture B, a mixture C, and a mixture D in which one rare earth element, two rare earth elements, three rare earth elements, and four rare earth elements are attached to WC particles; after drying, they are respectively pressed into preforms A, preforms B, preforms C, and preforms D, and then WC-reinforced steel-based preform wafers, preform A, preform B, preform C, preform D, and cast steel preforms are arranged from top to bottom, and the composite material is obtained after sintering. By adding WC particles with gradient doping of various rare earth elements between the cast steel preform and the WC-reinforced steel-based preform wafer, and through sintering, the invention promotes the metallurgical bonding of the macroscopic interface of the rare earth gradient-doped WC particle-reinforced iron-based surface composite material, regulates the interface of the composite material, improves its mechanical properties, and increases the density of the composite material.

Description

Technical Field

[0001] The present invention belongs to the technical field of preparation of wear-resistant and corrosion-resistant composite materials, and particularly relates to a rare-earth gradient-doped WC particle-reinforced iron-based surface composite material and a preparation method thereof. Background Art

[0002] With the development of the equipment manufacturing industry, the impact and wear on materials under harsh working conditions are becoming higher and higher. Therefore, general steel materials are difficult to withstand and frequently suffer from wear failure, which brings a heavy burden to enterprises. During service, it is necessary to take into account both the high plasticity and high toughness of the material, and also consider its wear resistance and hardness. Therefore, tungsten carbide-reinforced steel-based composite materials are increasingly widely used in metallurgy, mining, mechanical wear-resistant components and other conditions. However, the interfacial bonding strength of the composite material determines its service life. Under high-load and high-impact working conditions, the composite material is prone to cracking due to weak interfacial bonding, resulting in material failure. Therefore, the control of the bonding degree of the macroscopic interface between ceramic particles and the steel matrix should be widely studied.

[0003] Our country is rich in rare-earth element resources. Utilizing the active nature and low electronegativity of rare-earth elements, doping them into the macroscopic interface of the composite material, adsorbing at the grain boundaries of the matrix and the reinforcement, improving the wettability between the matrix and the reinforcement, purifying the grain boundaries, and enhancing the interfacial bonding strength of the composite material. If a new substance with low interfacial energy is formed by reacting with the reinforcement phase, the interfacial energy will be reduced, further making the interfacial bonding closer.

[0004] Chinese Patent Application CN113106313A discloses a rare-earth-doped WC particle-reinforced steel-based composite material and a preparation method thereof. The rare-earth types are one of Y, La, Ce, Nd, Pr, Sc, etc., the addition amount is 1-1.5%, ball milling is carried out and then tablet pressing is carried out with a tablet press, and finally sintering is carried out using a vacuum tube furnace. This method has a single rare-earth element type and no type gradient is set. The ability of a single rare-earth element to purify the grain boundaries is insufficient, and the strengthening effect is not obvious. Summary of the Invention

[0005] Aiming at the above-mentioned shortcomings of the prior art, the present invention provides a rare-earth gradient-doped WC particle-reinforced iron-based surface composite material and a preparation method thereof. The present invention improves the wettability of macroscopic interface particles by controlling the content and type gradient of rare-earth elements, enables better metallurgical bonding at the interface, improves the density of powder metallurgy samples, improves defects such as pores, and enhances the wear resistance of the composite material to a certain extent.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A preparation method of a rare-earth gradient-doped WC particle-reinforced iron-based surface composite material, comprising the following steps:

[0008] (1) Using paraffin wax as the binder, a rare earth element, two rare earth elements, three rare earth elements, and four rare earth elements were respectively attached to WC particles by ball milling to obtain mixtures A, B, C, and D;

[0009] (2) The four mixtures were dried and then the dried mixtures were respectively pressed into preforms A, B, C, and D;

[0010] (3) WC particles and cast steel powder were ball milled and then pressed into a WC-reinforced steel matrix preform wafer;

[0011] (4) They were placed in the order from top to bottom as the WC-reinforced steel matrix preform wafer, preform A, preform B, preform C, preform D, and cast steel preform, and then sintered to obtain a rare earth gradient doped WC particle-reinforced iron-based surface composite material;

[0012] The one rare earth element, two rare earth elements, three rare earth elements, and four rare earth elements are respectively one, two, three, and four of La, Ce, Y, and Nd.

[0013] As a preferred embodiment of the present invention, in step (1), paraffin wax and WC particles were heated in a water bath, stirred to make paraffin wax adhere to the surface of WC particles, and then one rare earth element, two rare earth elements, three rare earth elements, or four rare earth elements were respectively mixed with the WC particles adhered with paraffin wax, and then ethanol was added for ball milling to obtain mixtures A, B, C, and D.

[0014] As a preferred embodiment of the present invention, the mass ratio of paraffin wax to WC particles is 1:50, and the volume of ethanol covers the WC particles.

[0015] As a preferred embodiment of the present invention, the process of ball milling is: first rotate forward for 50 - 60 min and then stop for 15 - 20 min, and then rotate backward for 50 - 60 min and then stop for 15 - 20 min, and the ball milling speed is 280 - 300 r / min.

[0016] As a preferred embodiment of the present invention, in step (1), the mass fraction of rare earth elements in mixture A is 1.0%; the mass fraction of each rare earth element in mixture B is 0.5% - 1.0%; the mass fraction of each rare earth element in mixture C is 0.3% - 0.7%; the mass fraction of each rare earth element in mixture D is 0.25% - 0.5%.

[0017] As a preferred embodiment of the present invention, in the step (2), the drying process includes: drying under vacuum conditions, first drying at 70 - 75 °C for 5 - 6 h, and then drying at 200 °C for 11 - 12 h; the vacuum degree is 6.0×10 -1 Pa.

[0018] As a preferred embodiment of the present invention, in the steps (2) and (3), the pressing process includes: raising the pressure to 500 - 600 MPa, holding the pressure for 3 - 5 min; then releasing the pressure and raising the pressure again to 600 - 700 MPa, holding the pressure for 8 - 10 min.

[0019] As a preferred embodiment of the present invention, in the step (2), the thicknesses of the preforms A, B, C, and D are all 1 - 2 mm, the thickness of the WC - enhanced steel - based preform wafer is 0.5 - 0.6 cm, and the thickness of the cast - steel preform is 0.5 - 0.6 cm.

[0020] As a preferred embodiment of the present invention, in the step (3), the mass ratio of WC particles to cast - steel powder is 2:3.

[0021] As a preferred embodiment of the present invention, in the step (3), the ball - milling process is: first rotate forward for 60 - 90 min and then stop for 10 - 15 min during ball - milling, and then rotate backward for 60 - 90 min, and the ball - milling speed is 180 - 200 r / min.

[0022] As a preferred embodiment of the present invention, in the step (1), the number of ball - milling times is more than three times to make the ball - milling more sufficient and the material mixing more uniform.

[0023] As a preferred embodiment of the present invention, in the step (4), the sintering temperature is 1350 °C and the sintering time is 90 min.

[0024] As a preferred embodiment of the present invention, in the step (4), the sintering process specifically includes: rising from room temperature to 500 °C at a rate not exceeding 5 °C / min; rising from 500 °C to 800 °C at a rate not exceeding 10 °C / min; rising from 800 °C to 1000 °C at a rate not exceeding 5 °C / min; rising from 1000 °C to 1350 °C at a rate not exceeding 3 °C / min.

[0025] As a preferred embodiment of the present invention, the cast - steel preform is obtained by pressing cast - steel powder, and the pressing process is the same as that of the WC - enhanced steel - based preform wafer. The cast - steel powder is 45 - steel powder.

[0026] The present invention also claims the rare earth gradient doped WC particle reinforced iron-based surface composite material prepared by the preparation method of the rare earth gradient doped WC particle reinforced iron-based surface composite material. The composite material includes a wear-resistant layer, a first interface layer, a second interface layer, a third interface layer, a fourth interface layer, and a matrix layer from top to bottom. The first interface layer, the second interface layer, the third interface layer, and the fourth interface layer contain one, two, three, and four rare earth elements respectively.

[0027] The wear-resistant layer is obtained by sintering a WC-reinforced steel-based preform wafer. The first interface layer is obtained by sintering preform A. The second interface layer is obtained by sintering preform B. The third interface layer is obtained by sintering preform C. The fourth interface layer is obtained by sintering preform D. The matrix layer is obtained by sintering a cast steel preform.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] (1) By adding WC particles with gradient doping of various rare earth elements between the cast steel preform and the WC-reinforced steel-based preform wafer, and through sintering, the present invention promotes the metallurgical bonding of the macroscopic interface of the rare earth gradient doped WC particle reinforced iron-based surface composite material, regulates the interface of the composite material, improves its mechanical properties, and increases the density of the composite material.

[0030] (2) Compared with sintering with a single rare earth element mixed powder, successively preparing tungsten carbide particle preforms with one, two, three, and four rare earth elements dispersed and attached, and adding them between the cast steel matrix and the WC-reinforced steel-based composite material can give full play to the synergistic and coupling effects between the rare earth elements and the tungsten carbide particles. By regulating the types of rare earth elements, four layers of rare earth element and WC mixtures with different types of gradients are formed. Rare earth elements are chemically active and can react with impurity elements such as O, S, and P at the interface to form compounds with lower free energy and then float up and be removed. A variety of multi-level rare earth elements exist at the grain boundaries of the interface phase, comprehensively hindering ion migration, inhibiting grain growth, and refining grains. The effects of these gradient rare earth elements are coordinated with each other, showing their respective action mechanisms, reducing the pores and impurities at the interface, and thus improving and optimizing the overall performance of the material to maximize the mechanical properties of the composite material. Description of the Drawings

[0031] Figure 1 It is a structural diagram of a rare earth gradient doped WC particle reinforced iron-based surface composite material.

[0032] In the figure, (a) is the wear-resistant layer, which is formed after sintering of the WC-reinforced steel-based preform disc; (b) is the first interface layer, which is formed after sintering of preform A; (c) is the second interface layer, which is formed after sintering of preform B; (d) is the third interface layer, which is formed after sintering of preform C; (e) is the fourth interface layer, which is formed after sintering of preform D; (f) is the matrix layer, which is formed after sintering of the cast steel preform. Detailed implementation mode

[0033] To better illustrate the purpose, technical solution and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0034] Embodiment 1

[0035] A preparation method of a rare earth gradient-doped WC particle-reinforced iron-based surface composite material includes the following steps:

[0036] (1) Prepare WC particles with rare earth element dispersion and attachment treatment: Heat 50 g of WC particles and 1 g of paraffin in a water bath at 60 °C, slowly stir to make the paraffin attach to the surface of WC, then add 1.0% by mass of rare earth element Y to the ball mill tank containing WC particles with attached paraffin, and add ethanol for ball milling to obtain mixture A.

[0037] Prepare WC particles with two rare earth element dispersion and attachment treatments: Heat 50 g of WC particles and 1 g of paraffin in a water bath at 60 °C, slowly stir to make the paraffin attach to the surface of WC, then successively add 0.5%-1.0% by mass of two rare earth elements Nd and La to the ball mill tank containing WC particles with attached paraffin, and add ethanol for ball milling to obtain mixture B.

[0038] Prepare WC particles with three rare earth element dispersion and attachment treatments: Heat 50 g of WC particles and 1 g of paraffin in a water bath at 60 °C, slowly stir to make the paraffin attach to the surface of WC, then successively add 0.3%-0.7% by mass of three rare earth elements Ce, Y, and La to the ball mill tank containing WC particles with attached paraffin, and add ethanol for ball milling to obtain mixture C.

[0039] Prepare WC particles with four rare earth element dispersion and attachment treatments: Heat 50 g of WC particles and 1 g of paraffin in a water bath at 60 °C, slowly stir to make the paraffin attach to the surface of WC, then successively add 0.25%-0.5% by mass of four rare earth elements Ce, Y, La, and Nd to the ball mill tank containing WC particles with attached paraffin, and add ethanol for ball milling to obtain mixture D.

[0040] The process of ball milling is as follows: During ball milling, it rotates forward for 60 minutes first and then stops for 20 minutes, then rotates backward for 60 minutes and finally stops for 20 minutes again. The rotation speed is 300 r / min, and the above process is repeated 3 times.

[0041] (2) Take out the mixture A - D and put it into a vacuum drying oven. Dry it at 70 °C for 6 hours to remove ethanol, and then dry it at 200 °C for 11 hours to remove paraffin.

[0042] (3) Press the obtained four portions of mixed powder into four preforms using a tablet press: preform A, preform B, preform C, and preform D, with a thickness of 1 - 2 mm. The pressing process is as follows: Raise the pressure to 500 MPa and hold the pressure for 5 minutes; then release the pressure and raise the pressure again to 600 MPa and hold the pressure for 8 minutes.

[0043] (4) Put WC particles with a mass fraction of 40% and cast steel powder with a mass fraction of 60% into a ball milling tank. Rotate forward for 60 minutes first and then stop for 15 minutes, and then rotate backward for 60 minutes. The ball milling speed is 180 r / min. Then put it into a tablet press, raise the pressure to 600 MPa and hold the pressure for 3 minutes; then release the pressure and raise the pressure again to 600 MPa and hold the pressure for 10 minutes to obtain a WC - reinforced steel - based preform wafer.

[0044] (5) Put the cast steel powder into a tablet press, raise the pressure to 600 MPa and hold the pressure for 3 minutes; then release the pressure and raise the pressure again to 600 MPa and hold the pressure for 10 minutes to obtain a cast steel preform.

[0045] (6) Place the preform wafers in the order of a WC - reinforced steel - based preform wafer with a thickness of 0.5 cm from top to bottom, preform A with a thickness of 1 mm, preform B with a thickness of 1 mm, preform C with a thickness of 1 mm, preform D with a thickness of 1 mm, and a cast steel preform with a thickness of 0.6 cm.

[0046] (7) Put the obtained sample into a vacuum tube furnace for sintering. Heat it from room temperature to 500 °C at a rate of 5 °C / min; heat it from 500 °C to 800 °C at a rate of 10 °C / min; heat it from 800 °C to 1000 °C at a rate of 5 °C / min; heat it from 1000 °C to 1350 °C at a rate of 3 °C / min, and hold it at 1350 °C for 90 minutes.

[0047] Example 2

[0048] A preparation method of a rare - earth gradient - doped WC - particle - reinforced iron - based surface composite material, comprising the following steps:

[0049] (1) Preparation of WC particles with rare earth elements dispersed and adhered: 50 g of WC particles and 1 g of paraffin were heated in a water bath at 65 °C, and slowly stirred to make the paraffin adhere to the surface of WC. Then, 1.0% by mass of rare earth element La was added to the ball mill tank containing WC particles with paraffin adhered, and ethanol was added for ball milling to obtain mixture A.

[0050] Preparation of WC particles with two rare earth elements dispersed and adhered: 50 g of WC particles and 1 g of paraffin were heated in a water bath at 65 °C, and slowly stirred to make the paraffin adhere to the surface of WC. Then, two rare earth elements Y and Nd with a mass fraction of 0.5% - 1.0% were successively added to the ball mill tank containing WC particles with paraffin adhered, and ethanol was added for ball milling to obtain mixture B.

[0051] Preparation of WC particles with three rare earth elements dispersed and adhered: 50 g of WC particles and 1 g of paraffin were heated in a water bath at 65 °C, and slowly stirred to make the paraffin adhere to the surface of WC. Then, three rare earth elements Ce, Nd, and La with a mass fraction of 0.3% - 0.7% were successively added to the ball mill tank containing WC particles with paraffin adhered, and ethanol was added for ball milling to obtain mixture C.

[0052] Preparation of WC particles with four rare earth elements dispersed and adhered: 50 g of WC particles and 1 g of paraffin were heated in a water bath at 65 °C, and slowly stirred to make the paraffin adhere to the surface of WC. Then, four rare earth elements Ce, Y, La, and Nd with a mass fraction of 0.25% - 0.5% were successively added to the ball mill tank containing WC particles with paraffin adhered, and ethanol was added for ball milling to obtain mixture D.

[0053] The ball milling process was as follows: During ball milling, it rotated forward for 60 min and then stopped for 20 min, then rotated backward for 60 min and finally stopped for 20 min, with a rotation speed of 300 r / min. The above process was repeated 3 times.

[0054] (2) Mixtures A - D were taken out and placed in a vacuum drying oven, dried at 70 °C for 6 h to remove ethanol, and then dried at 200 °C for 11 h to remove paraffin.

[0055] (3) The four obtained mixed powders were pressed into four preforms with a thickness of 1 - 2 mm by a tablet press: preform A, preform B, preform C, and preform D. The pressing process was as follows: The pressure was increased to 500 MPa and held for 5 min; then the pressure was released, and the pressure was increased again to 600 MPa and held for 8 min.

[0056] (4) Put WC particles with a mass fraction of 40% and cast steel powder with a mass fraction of 60% into a ball milling tank. First, rotate forward for 60 min and then stop for 15 min, and then rotate backward for 60 min. The ball milling speed is 180 r / min. Then put it into a tablet press, raise the pressure to 600 MPa, and keep the pressure for 3 min; then release the pressure, and raise the pressure to 600 MPa again and keep the pressure for 10 min to obtain a WC-reinforced steel-based preform wafer.

[0057] (5) Put the cast steel powder into a tablet press, raise the pressure to 600 MPa, and keep the pressure for 3 min; then release the pressure, and raise the pressure to 600 MPa again and keep the pressure for 10 min to obtain a cast steel preform.

[0058] (6) Place the preform wafers in the order of a WC-reinforced steel-based preform wafer with a thickness of 0.6 cm from top to bottom, a preform A with a thickness of 2 mm, a preform B with a thickness of 2 mm, a preform C with a thickness of 2 mm, a preform D with a thickness of 2 mm, and a cast steel preform with a thickness of 0.5 cm.

[0059] (7) Put the obtained sample into a vacuum tube furnace for sintering. Heat it from room temperature to 500 °C at a rate of 5 °C / min; heat it from 500 °C to 800 °C at a rate of 10 °C / min; heat it from 800 °C to 1000 °C at a rate of 5 °C / min; heat it from 1000 °C to 1350 °C at a rate of 3 °C / min, and keep it at 1350 °C for 90 min.

[0060] Example 3

[0061] A preparation method of a rare earth gradient doped WC particle-reinforced iron-based surface composite material, comprising the following steps:

[0062] (1) Prepare WC particles with rare earth element dispersion and attachment treatment: Put 50 g of WC particles and 1 g of paraffin into a water bath at 60 °C, stir slowly to make the paraffin adhere to the WC surface, and then add rare earth element Nd with a mass fraction of 1.0% to the ball milling tank containing the WC particles with paraffin attachment, and add ethanol for ball milling to obtain mixture A.

[0063] Prepare WC particles with two rare earth element dispersion and attachment treatments: Put 50 g of WC particles and 1 g of paraffin into a water bath at 60 °C, stir slowly to make the paraffin adhere to the WC surface, and then add two rare earth elements Ce and Y with a mass fraction of 0.5%-1.0% successively to the ball milling tank containing the WC particles with paraffin attachment, and add ethanol for ball milling to obtain mixture B.

[0064] Prepare WC particles with three rare earth elements dispersed and attached: Heat 50 g of WC particles and 1 g of paraffin in a water bath at 60 °C, and slowly stir to make the paraffin attach to the surface of WC. Then, successively add three rare earth elements Y, Nd, and Ce with a mass fraction of 0.3% - 0.7% to the ball mill tank containing WC particles attached with paraffin, and add ethanol for ball milling to obtain mixture C.

[0065] Prepare WC particles with four rare earth elements dispersed and attached: Heat 50 g of WC particles and 1 g of paraffin in a water bath at 60 °C, and slowly stir to make the paraffin attach to the surface of WC. Then, successively add four rare earth elements Ce, Y, La, and Nd with a mass fraction of 0.25% - 0.5% to the ball mill tank containing WC particles attached with paraffin, and add ethanol for ball milling to obtain mixture D.

[0066] The ball milling process is as follows: First, rotate forward for 60 min and then stop for 20 min during ball milling, then rotate backward for 60 min and finally stop for 20 min. The rotation speed is 300 r / min, and the above process is repeated 3 times.

[0067] (2) Take out mixtures A - D and put them into a vacuum drying oven. Dry at 70 °C for 6 h to remove ethanol, and then dry at 200 °C for 11 h to remove paraffin.

[0068] (3) Press the four obtained mixed powders into four preforms with a thickness of 1 - 2 mm using a tablet press: preform A, preform B, preform C, and preform D. The pressing process is as follows: Raise the pressure to 500 MPa and hold the pressure for 5 min; then release the pressure, and raise the pressure to 600 MPa again and hold the pressure for 8 min.

[0069] (4) Put 40% by mass of WC particles and 60% by mass of cast steel powder into the ball mill tank. First, rotate forward for 60 min and then stop for 15 min, then rotate backward for 60 min. The ball milling speed is 180 r / min. Then put it into the tablet press, raise the pressure to 600 MPa and hold the pressure for 3 min; then release the pressure, and raise the pressure to 600 MPa again and hold the pressure for 10 min to obtain a WC - reinforced steel - based preform wafer.

[0070] (5) Put the cast steel powder into the tablet press, raise the pressure to 600 MPa and hold the pressure for 3 min; then release the pressure, and raise the pressure to 600 MPa again and hold the pressure for 10 min to obtain a cast steel preform.

[0071] (6) Place the preform wafers in the following order from top to bottom: a 0.5 - cm - thick WC - reinforced steel - based preform wafer, a 1.5 - mm - thick preform A, a 1.5 - mm - thick preform B, a 1.5 - mm - thick preform C, a 1.5 - mm - thick preform D, and a 0.6 - cm - thick cast steel preform.

[0072] (7) Place the obtained sample into a vacuum tube furnace for sintering. Heat it from room temperature to 500 °C at a rate of 5 °C / min; from 500 °C to 800 °C at a rate of 10 °C / min; from 800 °C to 1000 °C at a rate of 5 °C / min; from 1000 °C to 1350 °C at a rate of 3 °C / min, and hold at 1350 °C for 90 min.

[0073] Example 4

[0074] A preparation method of a rare earth gradient doped WC particle reinforced iron-based surface composite material, comprising the following steps:

[0075] (1) Prepare WC particles with rare earth element dispersion and attachment treatment: Heat 50 g of WC particles and 1 g of paraffin in a water bath at 65 °C, slowly stir to make the paraffin attach to the surface of WC, then add 1.0% by mass of rare earth element Ce into the ball milling tank containing WC particles with attached paraffin, and add ethanol for ball milling to obtain mixture A.

[0076] Prepare WC particles with two rare earth element dispersion and attachment treatment: Heat 50 g of WC particles and 1 g of paraffin in a water bath at 65 °C, slowly stir to make the paraffin attach to the surface of WC, then successively add 0.5%-1.0% by mass of two rare earth elements Ce and La into the ball milling tank containing WC particles with attached paraffin, and add ethanol for ball milling to obtain mixture B.

[0077] Prepare WC particles with three rare earth element dispersion and attachment treatment: Heat 50 g of WC particles and 1 g of paraffin in a water bath at 65 °C, slowly stir to make the paraffin attach to the surface of WC, then successively add 0.3%-0.7% by mass of three rare earth elements Y, Nd, and La into the ball milling tank containing WC particles with attached paraffin, and add ethanol for ball milling to obtain mixture C.

[0078] Prepare WC particles with four rare earth element dispersion and attachment treatment: Heat 50 g of WC particles and 1 g of paraffin in a water bath at 65 °C, slowly stir to make the paraffin attach to the surface of WC, then successively add 0.25%-0.5% by mass of four rare earth elements Ce, Y, La, and Nd into the ball milling tank containing WC particles with attached paraffin, and add ethanol for ball milling to obtain mixture D.

[0079] The ball milling process is as follows: First rotate forward for 60 min and then stop for 20 min during ball milling, then rotate backward for 60 min and finally stop for 20 min, with a rotation speed of 300 r / min, and the above process is repeated 3 times.

[0080] (2) Take out the mixtures A - D and place them in a vacuum drying oven. Dry at 70 °C for 6 h to remove ethanol, and then dry at 200 °C for 11 h to remove paraffin.

[0081] (3) Press the four obtained mixed powders into four preforms using a tablet press: preform A, preform B, preform C, and preform D, with a thickness of 1 - 2 mm. The pressing process is as follows: Raise the pressure to 500 MPa and hold for 5 min; then release the pressure and raise the pressure again to 600 MPa and hold for 8 min.

[0082] (4) Put WC particles with a mass fraction of 40% and cast steel powder with a mass fraction of 60% into a ball - milling tank. First, rotate forward for 60 min and then stop for 15 min, and then rotate backward for 60 min. The ball - milling speed is 180 r / min. Then put it into a tablet press, raise the pressure to 600 MPa and hold for 3 min; then release the pressure and raise the pressure again to 600 MPa and hold for 10 min to obtain a WC - reinforced steel - based preform wafer.

[0083] (5) Put the cast steel powder into a tablet press, raise the pressure to 600 MPa and hold for 3 min; then release the pressure and raise the pressure again to 600 MPa and hold for 10 min to obtain a cast steel preform.

[0084] (6) Place the preform wafers in the order of a WC - reinforced steel - based preform wafer with a thickness of 0.5 cm from top to bottom, preform A with a thickness of 1 mm, preform B with a thickness of 1 mm, preform C with a thickness of 1 mm, preform D with a thickness of 1 mm, and a cast steel preform with a thickness of 0.6 cm.

[0085] (7) Put the obtained sample into a vacuum tube furnace for sintering. Heat from room temperature to 500 °C at a rate of 5 °C / min; from 500 °C to 800 °C at a rate of 10 °C / min; from 800 °C to 1000 °C at a rate of 5 °C / min; from 1000 °C to 1350 °C at a rate of 3 °C / min, and hold at 1350 °C for 90 min.

[0086] Comparative Example 1

[0087] A preparation method of a rare - earth gradient - doped WC - particle - reinforced iron - based surface composite material, comprising the following steps:

[0088] (1) Prepare WC particles with rare - earth element dispersion and attachment treatment: Heat 50 g of WC particles and 1 g of paraffin in a water bath at 60 °C, slowly stir to make the paraffin attach to the WC surface, and then add 1.0% by mass of rare - earth element Nd to the ball - milling tank containing the WC particles with attached paraffin, and add ethanol for ball - milling to obtain mixture A.

[0089] The process of ball milling is as follows: During ball milling, it rotates forward for 60 minutes first and then stops for 20 minutes, then rotates backward for 60 minutes and finally stops for 20 minutes again. The rotation speed is 300 r / min, and the above process is repeated 3 times.

[0090] (2) Take out the mixture A and put it into a vacuum drying oven. Dry it at 70 °C for 6 hours to remove ethanol, and then dry it at 200 °C for 11 hours to remove paraffin.

[0091] (3) Press the dried mixed powder into a preform A with a tablet press; the pressing process is as follows: Raise the pressure to 500 MPa and keep the pressure for 5 minutes; then release the pressure and raise the pressure to 600 MPa again and keep the pressure for 8 minutes.

[0092] (4) Put WC particles with a mass fraction of 40% and cast steel powder with a mass fraction of 60% into a ball mill tank. Rotate forward for 60 minutes first and then stop for 15 minutes, and then rotate backward for 60 minutes. The ball milling speed is 180 r / min. Then put it into a tablet press, raise the pressure to 600 MPa and keep the pressure for 3 minutes; then release the pressure and raise the pressure to 600 MPa again and keep the pressure for 10 minutes to obtain a WC-reinforced steel matrix preform wafer.

[0093] (5) Put the cast steel powder into a tablet press, raise the pressure to 600 MPa and keep the pressure for 3 minutes; then release the pressure and raise the pressure to 600 MPa again and keep the pressure for 10 minutes to obtain a cast steel preform.

[0094] (6) Place the preform wafers in the order of a WC-reinforced steel matrix preform wafer with a thickness of 0.5 cm from top to bottom, a preform A with a thickness of 1 mm, and a cast steel preform with a thickness of 0.6 cm.

[0095] (7) Put the obtained sample into a vacuum tube furnace for sintering. Heat it from room temperature to 500 °C at a rate of 5 °C / min; heat it from 500 °C to 800 °C at a rate of 10 °C / min; heat it from 800 °C to 1000 °C at a rate of 5 °C / min; heat it from 1000 °C to 1350 °C at a rate of 3 °C / min, and keep it at 1350 °C for 90 minutes.

[0096] Comparative Example 2

[0097] A preparation method of a rare earth gradient-doped WC particle-reinforced iron-based surface composite material, comprising the following steps:

[0098] (1) Prepare WC particles with two rare earth elements dispersed and attached: Heat 50 g of WC particles and 1 g of paraffin in a water bath at 60 °C, slowly stir to make the paraffin attach to the surface of the WC, and then sequentially add two rare earth elements Ce and Y with a mass fraction of 0.5% - 1.0% to the ball mill tank containing the WC particles with paraffin attached, and add ethanol for ball milling to obtain a mixture B.

[0099] The process of ball milling is as follows: During ball milling, it rotates forward for 60 minutes first and then stops for 20 minutes, then rotates backward for 60 minutes and finally stops for 20 minutes again. The rotation speed is 300 r / min, and the above process is repeated 3 times.

[0100] (2) Take out the mixture B and put it into a vacuum drying oven. Dry it at 70 °C for 6 hours to remove ethanol, and then dry it at 200 °C for 11 hours to remove paraffin.

[0101] (3) Press the dried mixed powder into a preform B with a tablet press; the pressing process is: raise the pressure to 500 MPa and keep the pressure for 5 minutes; then release the pressure and raise the pressure to 600 MPa again and keep the pressure for 8 minutes.

[0102] (4) Put WC particles with a mass fraction of 40% and cast steel powder with a mass fraction of 60% into a ball milling tank. Rotate forward for 60 minutes first and then stop for 15 minutes, then rotate backward for 60 minutes. The ball milling speed is 180 r / min, and then put it into a tablet press. Raise the pressure to 600 MPa and keep the pressure for 3 minutes; then release the pressure and raise the pressure to 600 MPa again and keep the pressure for 10 minutes to obtain a WC-reinforced steel matrix preform wafer.

[0103] (5) Put the cast steel powder into a tablet press. Raise the pressure to 600 MPa and keep the pressure for 3 minutes; then release the pressure and raise the pressure to 600 MPa again and keep the pressure for 10 minutes to obtain a cast steel preform.

[0104] (6) Place the preform wafers in the order of a WC-reinforced steel matrix preform wafer with a thickness of 0.5 cm from top to bottom, a preform B with a thickness of 1 mm, and a cast steel preform with a thickness of 0.6 cm.

[0105] (7) Put the obtained sample into a vacuum tube furnace for sintering. Heat it from room temperature to 500 °C at a rate of 5 °C / min; heat it from 500 °C to 800 °C at a rate of 10 °C / min; heat it from 800 °C to 1000 °C at a rate of 5 °C / min; heat it from 1000 °C to 1350 °C at a rate of 3 °C / min, and keep it at 1350 °C for 90 minutes.

[0106] Comparative Example 3

[0107] A preparation method of a rare earth gradient-doped WC particle-reinforced iron-based surface composite material, comprising the following steps:

[0108] (1) Prepare WC particles with three rare earth elements dispersed and adhered: Heat 50 g of WC particles and 1 g of paraffin in a water bath at 60 °C, and slowly stir to make the paraffin adhere to the surface of WC. Then, successively add three rare earth elements Y, Nd, and Ce with a mass fraction of 0.3%-0.7% to the ball milling tank containing WC particles with adhered paraffin, and add ethanol for ball milling to obtain mixture C.

[0109] The process of ball milling is as follows: First, rotate forward for 60 min and then stop for 20 min, then rotate backward for 60 min and finally stop for 20 min. The rotation speed is 300 r / min, and the above process is repeated 3 times.

[0110] (2) Take out mixture C and put it into a vacuum drying oven. Dry it at 70 °C for 6 h to remove ethanol, and then dry it at 200 °C for 11 h to remove paraffin.

[0111] (3) Press the dried mixed powder into preform C with a tablet press; the pressing process is as follows: Raise the pressure to 500 MPa and keep the pressure for 5 min; then release the pressure, and raise the pressure to 600 MPa again and keep the pressure for 8 min.

[0112] (4) Put WC particles with a mass fraction of 40% and cast steel powder with a mass fraction of 60% into the ball milling tank. First, rotate forward for 60 min and then stop for 15 min, then rotate backward for 60 min. The ball milling speed is 180 r / min, and then put it into the tablet press. Raise the pressure to 600 MPa and keep the pressure for 3 min; then release the pressure, and raise the pressure to 600 MPa again and keep the pressure for 10 min to obtain a WC-reinforced steel matrix preform wafer.

[0113] (5) Put the cast steel powder into the tablet press. Raise the pressure to 600 MPa and keep the pressure for 3 min; then release the pressure, and raise the pressure to 600 MPa again and keep the pressure for 10 min to obtain a cast steel preform.

[0114] (6) Place the preform wafers in the order of a WC-reinforced steel matrix preform wafer with a thickness of 0.5 cm from top to bottom, preform C with a thickness of 1 mm, and a cast steel preform with a thickness of 0.6 cm.

[0115] (7) Put the obtained sample into a vacuum tube furnace for sintering. Heat from room temperature to 500 °C at a rate of 5 °C / min; heat from 500 °C to 800 °C at a rate of 10 °C / min; heat from 800 °C to 1000 °C at a rate of 5 °C / min; heat from 1000 °C to 1350 °C at a rate of 3 °C / min, and keep the temperature at 1350 °C for 90 min.

[0116] Comparative Example 4

[0117] A preparation method of a rare earth gradient-doped WC particle-reinforced iron-based surface composite material, comprising the following steps:

[0118] (1) Preparation of WC particles with four rare earth elements dispersed and attached: 50 g of WC particles and 1 g of paraffin were heated in a water bath at 60 °C, and the paraffin was slowly stirred to adhere to the surface of WC. Then, four rare earth elements Ce, Y, La, and Nd with a mass fraction of 0.25%-0.5% were successively added to the ball milling tank containing WC particles with paraffin attached, and ethanol was added for ball milling to obtain mixture D.

[0119] The ball milling process was as follows: First, it rotated forward for 60 min and then stopped for 20 min, then rotated backward for 60 min and finally stopped for 20 min. The rotation speed was 300 r / min, and the above process was repeated 3 times.

[0120] (2) Mixture D was taken out and placed in a vacuum drying oven. It was dried at 70 °C for 6 h to remove ethanol, and then dried at 200 °C for 11 h to remove paraffin.

[0121] (3) The dried mixed powder was pressed into preform D with a tablet press; the pressing process was as follows: The pressure was increased to 500 MPa and held for 5 min; then the pressure was released, and the pressure was increased to 600 MPa again and held for 8 min.

[0122] (4) 40% by mass of WC particles and 60% by mass of cast steel powder were put into the ball milling tank. It rotated forward for 60 min and then stopped for 15 min, then rotated backward for 60 min. The ball milling speed was 180 r / min, and then it was put into a tablet press. The pressure was increased to 600 MPa and held for 3 min; then the pressure was released, and the pressure was increased to 600 MPa again and held for 10 min to obtain a WC-reinforced steel matrix preform wafer.

[0123] (5) The cast steel powder was put into a tablet press. The pressure was increased to 600 MPa and held for 3 min; then the pressure was released, and the pressure was increased to 600 MPa again and held for 10 min to obtain a cast steel preform.

[0124] (6) The preform wafers were placed in the order of a WC-reinforced steel matrix preform wafer with a thickness of 0.5 cm from top to bottom, preform D with a thickness of 1 mm, and a cast steel preform with a thickness of 0.6 cm.

[0125] (7) The obtained sample was put into a vacuum tube furnace for sintering. It was heated from room temperature to 500 °C at a rate of 5 °C / min; from 500 °C to 800 °C at a rate of 10 °C / min; from 800 °C to 1000 °C at a rate of 5 °C / min; from 1000 °C to 1350 °C at a rate of 3 °C / min, and held at 1350 °C for 90 min.

[0126] Comparative Example 5

[0127] A preparation method of a rare earth gradient doped WC particle reinforced iron-based surface composite material, comprising the following steps:

[0128] (1) Prepare WC particles with rare earth element dispersion and attachment treatment: Heat 50 g of WC particles and 1 g of paraffin in a water bath at 60 °C, slowly stir to make the paraffin adhere to the WC surface, then add 1.0% by mass of rare earth element Nd to the ball milling tank containing the WC particles with paraffin attached, and add ethanol for ball milling to obtain mixture A.

[0129] Prepare WC particles with two rare earth element dispersion and attachment treatment: Heat 50 g of WC particles and 1 g of paraffin in a water bath at 60 °C, slowly stir to make the paraffin adhere to the WC surface, then successively add 0.5%-1.0% by mass of two rare earth elements Ce and Y to the ball milling tank containing the WC particles with paraffin attached, and add ethanol for ball milling to obtain mixture B.

[0130] Prepare WC particles with three rare earth element dispersion and attachment treatment: Heat 50 g of WC particles and 1 g of paraffin in a water bath at 60 °C, slowly stir to make the paraffin adhere to the WC surface, then successively add 0.3%-0.7% by mass of three rare earth elements Y, Nd, and Ce to the ball milling tank containing the WC particles with paraffin attached, and add ethanol for ball milling to obtain mixture C.

[0131] The ball milling process is as follows: First rotate forward for 60 min and then stop for 20 min during ball milling, then rotate backward for 60 min and finally stop for 20 min, the rotation speed is 300 r / min, and the above process is repeated 3 times.

[0132] (2) Take out mixtures A-C, put them into a vacuum drying oven, dry at 70 °C for 6 h to remove ethanol, and then dry at 200 °C for 11 h to remove paraffin.

[0133] (3) Press the obtained three portions of mixed powder into three preforms: preform A, preform B, and preform C, with a thickness of 1-2 mm; the pressing process is as follows: Raise the pressure to 500 MPa and hold the pressure for 5 min; then release the pressure, and raise the pressure to 600 MPa again and hold the pressure for 8 min.

[0134] (4) Put 40% by mass of WC particles and 60% by mass of cast steel powder into the ball milling tank, first rotate forward for 60 min and then stop for 15 min, then rotate backward for 60 min, the ball milling rotation speed is 180 r / min, then put it into a press, raise the pressure to 600 MPa and hold the pressure for 3 min; then release the pressure, and raise the pressure to 600 MPa again and hold the pressure for 10 min to obtain a WC reinforced steel-based preform wafer.

[0135] (5) Put the cast steel powder into a tablet press, raise the pressure to 600 MPa, and hold the pressure for 3 min; then release the pressure and raise the pressure to 600 MPa again, and hold the pressure for 10 min to obtain a cast steel preform.

[0136] (6) Place the prefabricated circular wafers in the order of a WC-reinforced steel matrix preform wafer with a thickness of 0.5 cm from top to bottom, a preform A with a thickness of 1 mm, a preform B, a preform C, and a cast steel preform with a thickness of 0.6 cm.

[0137] (7) Put the obtained sample into a vacuum tube furnace for sintering. Heat it from room temperature to 500 °C at a rate of 5 °C / min; heat it from 500 °C to 800 °C at a rate of 10 °C / min; heat it from 800 °C to 1000 °C at a rate of 5 °C / min; heat it from 1000 °C to 1350 °C at a rate of 3 °C / min, and hold the temperature at 1350 °C for 90 min.

[0138] Comparative Example 6

[0139] A preparation method of a rare earth gradient-doped WC particle-reinforced iron-based surface composite material includes the following steps:

[0140] (1) Prepare WC particles with rare earth element dispersion and attachment treatment: Heat 50 g of WC particles and 1 g of paraffin in a water bath at 60 °C, slowly stir to make the paraffin attach to the surface of WC, and then add 1.0% by mass of rare earth element Nd to the ball mill tank containing the WC particles with paraffin attached, and add ethanol for ball milling to obtain mixture A.

[0141] Prepare WC particles with two rare earth element dispersion and attachment treatments: Heat 50 g of WC particles and 1 g of paraffin in a water bath at 60 °C, slowly stir to make the paraffin attach to the surface of WC, and then successively add 0.5%-1.0% by mass of two rare earth elements Ce and Y to the ball mill tank containing the WC particles with paraffin attached, and add ethanol for ball milling to obtain mixture B.

[0142] The ball milling process is as follows: First, rotate forward for 60 min and then stop for 20 min during ball milling, then rotate backward for 60 min and finally stop for 20 min, with a rotation speed of 300 r / min, and the above process is repeated 3 times.

[0143] (2) Take out mixtures A and B, put them into a vacuum drying oven, dry them at 70 °C for 6 h to remove ethanol, and then dry them at 200 °C for 11 h to remove paraffin.

[0144] (3) Press the obtained two portions of mixed powder into two preforms: preform A and preform B, with a thickness of 1-2 mm; the pressing process is as follows: Raise the pressure to 500 MPa and hold the pressure for 5 min; then release the pressure and raise the pressure to 600 MPa again, and hold the pressure for 8 min.

[0145] (4) Put WC particles with a mass fraction of 40% and cast steel powder with a mass fraction of 60% into a ball milling tank. First, rotate forward for 60 min and then stop for 15 min, and then rotate backward for 60 min. The ball milling speed is 180 r / min. Then put it into a tablet press, raise the pressure to 600 MPa, and keep the pressure for 3 min; then release the pressure, raise the pressure to 600 MPa again, and keep the pressure for 10 min to obtain a WC-reinforced steel matrix preform wafer.

[0146] (5) Put the cast steel powder into a tablet press, raise the pressure to 600 MPa, and keep the pressure for 3 min; then release the pressure, raise the pressure to 600 MPa again, and keep the pressure for 10 min to obtain a cast steel preform.

[0147] (6) Place the preform wafers in the order of a WC-reinforced steel matrix preform wafer with a thickness of 0.5 cm from top to bottom, preform A with a thickness of 1 mm, preform B, and a cast steel preform with a thickness of 0.6 cm.

[0148] (7) Put the obtained sample into a vacuum tube furnace for sintering. Heat it from room temperature to 500 °C at a rate of 5 °C / min; heat it from 500 °C to 800 °C at a rate of 10 °C / min; heat it from 800 °C to 1000 °C at a rate of 5 °C / min; heat it from 1000 °C to 1350 °C at a rate of 3 °C / min, and keep it at 1350 °C for 90 min.

[0149] Comparative Example 7

[0150] A preparation method of a rare earth gradient doped WC particle-reinforced iron-based surface composite material, comprising the following steps:

[0151] (1) Prepare WC particles with rare earth element dispersion and attachment treatment: Heat 50 g of WC particles and 1 g of paraffin in a water bath at 60 °C, slowly stir to make the paraffin attach to the WC surface, and then add 1.0% by mass of rare earth element Nd to the ball milling tank containing the WC particles with paraffin attachment, and add ethanol for ball milling to obtain mixture A.

[0152] Prepare WC particles with two rare earth element dispersion and attachment treatments: Heat 50 g of WC particles and 1 g of paraffin in a water bath at 60 °C, slowly stir to make the paraffin attach to the WC surface, and then add two rare earth elements Ce and Y with a mass fraction of 0.5%-1.0% successively to the ball milling tank containing the WC particles with paraffin attachment, and add ethanol for ball milling to obtain mixture B.

[0153] The ball milling process is as follows: First, rotate forward for 60 min and then stop for 20 min during ball milling, then rotate backward for 60 min and finally stop for 20 min, and the rotation speed is 300 r / min. The above process is repeated 3 times.

[0154] (2) Take out the mixtures A and B, put them into a vacuum drying oven, dry at 70 °C for 6 h to remove ethanol, and then dry at 200 °C for 11 h to remove paraffin.

[0155] (3) Press the two obtained mixed powders into two preforms: preform A and preform B with a thickness of 1 - 2 mm using a tablet press. The pressing process is as follows: raise the pressure to 500 MPa and hold for 5 min; then release the pressure and raise the pressure again to 600 MPa and hold for 8 min.

[0156] (4) Put WC particles with a mass fraction of 40% and cast steel powder with a mass fraction of 60% into a ball - milling tank. First, rotate forward for 60 min and then stop for 15 min, and then rotate backward for 60 min. The ball - milling speed is 180 r / min. Then put it into a tablet press, raise the pressure to 600 MPa and hold for 3 min; then release the pressure and raise the pressure again to 600 MPa and hold for 10 min to obtain a WC - reinforced steel - based preform wafer.

[0157] (5) Put the cast steel powder into a tablet press, raise the pressure to 600 MPa and hold for 3 min; then release the pressure and raise the pressure again to 600 MPa and hold for 10 min to obtain a cast steel preform.

[0158] (6) Place the preform wafers in the order of a WC - reinforced steel - based preform wafer with a thickness of 0.5 cm from top to bottom, preform A with a thickness of 2 mm, preform B with a thickness of 2 mm, and a cast steel preform with a thickness of 0.6 cm.

[0159] (7) Put the obtained sample into a vacuum tube furnace for sintering. Heat from room temperature to 500 °C at a rate of 5 °C / min; heat from 500 °C to 800 °C at a rate of 10 °C / min; heat from 800 °C to 1000 °C at a rate of 5 °C / min; heat from 1000 °C to 1350 °C at a rate of 3 °C / min, and hold at 1350 °C for 90 min.

[0160] Effect Example 1

[0161] Test the hardness and compressive properties of the materials prepared in the examples and comparative examples, and the results are shown in Table 1.

[0162] Table 1

[0163]

[0164]

[0165] As can be seen from Table 1, compared with the comparative examples and the examples, the preparation methods of the macro-interfaces of the Fe-based surface composites reinforced by WC particles with four-layer multi-type rare earth element gradient doping were not used in Comparative Examples 1-7. The hardness of the overall interface reaction zone, the matrix hardness, and the compressive strength of the obtained samples were lower than those of Examples 1-4. When the samples of Examples 1-4 were in friction service, due to their high hardness, scratches were not easily generated on the surface. Under the action of pressure, the higher the compressive strength, the stronger the load-bearing capacity, and it was not easily deformed or even broken and failed. The samples prepared with only one or several rare earth element single interface layers in Comparative Examples 1-7 could not well exert the synergistic and coupling effects between multi-type rare earth elements and tungsten carbide particles, and could not form a multi-layer rare earth element and WC mixture with different types of gradients. The reaction between rare earth elements and impurity elements such as O, S, and P at the interface was not sufficient, and the single-layer rare earth elements could not fully inhibit grain growth and refine grains at the grain boundaries. The pore impurities at the interface could not be sufficiently reduced, and the overall performance improvement and optimization of the material were less.

[0166] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A preparation method of a rare earth gradient doped WC particle reinforced iron-based surface composite material, characterized in that, It includes the following steps: (1) Using paraffin as the binder, a rare earth element, two rare earth elements, three rare earth elements, and four rare earth elements are respectively attached to WC particles by the ball milling method to obtain mixture A, mixture B, mixture C, and mixture D; (2) The four mixtures are dried and then the dried mixtures are respectively pressed into preforms A, B, C, and D; (3) WC particles and cast steel powder are ball milled and then pressed into a WC-reinforced steel matrix preform wafer; (4) They are placed in the order of WC-reinforced steel matrix preform wafer, preform A, preform B, preform C, preform D, and cast steel preform from top to bottom, and then sintered to obtain a rare earth gradient doped WC particle reinforced iron-based surface composite material; The one rare earth element, two rare earth elements, three rare earth elements, and four rare earth elements are respectively one, two, three, and four of La, Ce, Y, and Nd.

2. The preparation method of the rare earth gradient doped WC particle reinforced iron-based surface composite material according to claim 1, characterized in that, In the step (1), paraffin and WC particles are heated in a water bath, stirred to make paraffin adhere to the surface of WC particles, and then a rare earth element, two rare earth elements, three rare earth elements, and four rare earth elements are respectively mixed with the WC particles adhered with paraffin, and then ethanol is added for ball milling to obtain mixture A, mixture B, mixture C, and mixture D respectively.

3. The preparation method of the rare earth gradient doped WC particle reinforced iron-based surface composite material according to claim 1, characterized in that, In the step (1), the ball milling process is: first rotate forward for 50 - 60 min and then stop for 15 - 20 min, then rotate backward for 50 - 60 min and then stop for 15 - 20 min, and the ball milling speed is 280 - 300 r / min; in the step (3), the ball milling process is: first rotate forward for 60 - 90 min and then stop for 10 - 15 min, then rotate backward for 60 - 90 min, and the ball milling speed is 180 - 200 r / min.

4. The preparation method of the rare earth gradient doped WC particle reinforced iron-based surface composite material according to claim 1, characterized in that, In the step (1), the mass fraction of the rare earth element in mixture A is 1.0%; the mass fraction of each rare earth element in mixture B is 0.5% - 1.0%; the mass fraction of each rare earth element in mixture C is 0.3% - 0.7%; the mass fraction of each rare earth element in mixture D is 0.25% - 0.5%.

5. The preparation method of the rare earth gradient doped WC particle reinforced iron-based surface composite material according to claim 1, characterized in that, In the step (2), the drying process includes: drying under vacuum conditions, first drying at 70 - 75 °C for 5 - 6 h, and then drying at 200 °C for 11 - 12 h; the degree of vacuum is 6.0×10 -1 Pa.

6. The preparation method of the rare earth gradient doped WC particle reinforced iron-based surface composite material according to claim 1, characterized in that In the steps (2) and (3), the pressing process includes: raising the pressure to 500 - 600 MPa, holding the pressure for 3 - 5 min; then releasing the pressure and raising the pressure again to 600 - 700 MPa, holding the pressure for 8 - 10 min.

7. The preparation method of the rare earth gradient doped WC particle reinforced iron-based surface composite material according to claim 1, characterized in that, In the step (2), the thicknesses of preforms A, B, C, and D are all 1 - 2 mm, the thickness of the WC-reinforced steel matrix preform wafer is 0.5 - 0.6 cm, and the thickness of the cast steel preform is 0.5 - 0.6 cm.

8. The preparation method of the rare earth gradient doped WC particle reinforced iron-based surface composite material according to claim 1, characterized in that, In the step (3), the mass ratio of WC particles to cast steel powder is 2:

3.

9. The preparation method of the rare earth gradient doped WC particle reinforced iron-based surface composite material according to claim 1, characterized in that, In the step (4), the sintering temperature is 1350 °C, the sintering time is 90 min. When sintering, it is heated from room temperature to 500 °C at a rate not exceeding 5 °C / min; from 500 °C to 800 °C at a rate not exceeding 10 °C / min; from 800 °C to 1000 °C at a rate not exceeding 5 °C / min; from 1000 °C to 1350 °C at a rate not exceeding 3 °C / min.

10. A rare earth gradient doped WC particle reinforced iron-based surface composite material prepared by the method for preparing a rare earth gradient doped WC particle reinforced iron-based surface composite material according to claim 1, wherein the composite material comprises a wear-resistant layer, a first interface layer, a second interface layer, a third interface layer, a fourth interface layer, and a matrix layer from top to bottom; the first interface layer, the second interface layer, the third interface layer, and the fourth interface layer contain one, two, three, and four rare earth elements respectively.

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