Nanometer rare earth oxide and its doped wc-co cr spraying powder, coating and preparation method

Abstract

The application belongs to the technical field of materials and coating thereof, and particularly relates to a nano-rare earth oxide and a doped WC-CoCr spraying powder, a coating and a preparation method. x O y The precursor composite powder is sintered to obtain the WC-CoCr-RE with the uniform distribution of rare earth x O y The thermal spraying powder is prepared by the WC-CoCr-RE through the supersonic flame spraying process x O y The surface and subsurface microhardness and the bonding strength with the substrate of the coating are higher than those of the WC-CoCr coating without the addition of rare earth, the subsurface microhardness of the coating is greater than or equal to 1380HV, the bonding strength with the substrate is greater than or equal to 68MPa, and the high-quality coating is obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of materials and coating technology, in particular to a kind of nano rare earth oxide and its doped WC-CoCr spraying powder, coating, preparation method. BACKGROUND

[0002] WC-Co coating is widely used, especially in wear-resistant field is widely used, if a certain amount of Cr is introduced therein, the coating has high hardness and high wear resistance, and has excellent corrosion resistance. In the actual industrialization process, how to improve the performance of WC-CoCr coating has been the focus of the industry.

[0003] Rare earth elements have a unique 4f electron structure, the outer 5s and 5p electrons are shielded by the completely filled 4f electrons, and the inner f layer orbit is filled with electrons as the atomic number increases. This unique electronic structure makes it have unique catalytic activity and doping modification effect. For example, a small amount of rare earth can make the strength, toughness and wear resistance of traditional WC-Co cemented carbide more superior. In-situ high melting point rare earth oxysulfide can be formed on the surface of the WC-Co hard alloy thermal spraying powder, which can improve the wear resistance of the coating and strengthen the bonding between the coating and the substrate. Doping rare earth oxides can also make thermal barrier coatings have excellent anti-sintering properties, improve their high-temperature phase stability and oxidation resistance, and reduce the porosity and cracks of the coating.

[0004] The addition of rare earth in WC-Co coating can improve its performance, but the practical application of rare earth in WC-CoCr coating is less. On the one hand, the mechanism of rare earth in WC-CoCr is not clear, which brings a lot of blindness to the research and application of rare earth doped WC-CoCr. On the other hand, it is not easy to obtain uniform distribution of rare earth in WC-CoCr. Non-uniform distribution of rare earth may reduce the performance of the coating. SUMMARY

[0005] To solve the problems in the prior art, the main purpose of the present application is to provide a kind of nano rare earth oxide and its doped WC-CoCr spraying powder, coating, preparation method.

[0006] To solve the above technical problems, according to one aspect of the present application, the present application provides the following technical scheme:

[0007] A preparation method of nano rare earth oxide, according to the ratio of 300-350 mL zirconium oxide grinding ball and 180-230 mL polyethylene glycol per 100 g micron rare earth oxide, micron rare earth oxide powder is wet ground, the ball milling speed is 320-360 r / min, and the ball milling time is 55-70 min. The particle size D90 of the nano rare earth oxide is less than 0.1 μm.

[0008] As a preferred embodiment of the preparation method of the nanometer rare earth oxide, in the application, the nanometer rare earth oxide is Pr6O 11 .

[0009] To solve the above technical problems, according to another aspect of the application, the application provides the following technical solutions:

[0010] The nanometer rare earth oxide doped WC-CoCr spraying powder comprises the following components in percentage by mass:

[0011] Co powder 9-12wt%, Cr powder 3-5wt%, nanometer rare earth oxide powder prepared by the above preparation method 0.02-0.30wt%, and the balance of WC powder; wherein the mass of the nanometer rare earth oxide powder cannot exceed 3% of the mass of the Co powder;

[0012] The particle size of the WC powder is 0.5-1.0μm, and the purity is ≥99.99%;

[0013] The particle size of the Co powder is 0.6-0.8μm, and the purity is ≥99.9%;

[0014] The particle size of the Cr powder is 2.0-3.0μm, and the purity is ≥99.9%.

[0015] As a preferred embodiment of the nanometer rare earth oxide doped WC-CoCr spraying powder, in the application, the particle size of the spraying powder is 200-600 mesh.

[0016] To solve the above technical problems, according to another aspect of the application, the application provides the following technical solutions:

[0017] The preparation method of the nanometer rare earth oxide doped WC-CoCr spraying powder comprises the following steps:

[0018] S1. Mixing

[0019] The nanometer rare earth oxide powder is added into anhydrous ethanol to form a paste-like slurry, heated to 65-70℃, 0.2-2vol% of paraffin is added, the paraffin is uniformly melted into the slurry by stirring, the slurry is continuously and slowly added with Co powder at a flow rate of 5-20g / h, and the mechanical stirring is stopped when the slurry is thick and not easy to stir; the slurry is dried in a vacuum drying oven at a temperature of 75-80℃ for 2-8h; the dried slurry is taken out, the caked powder is crushed in a corundum mortar jar, and the Co-RE x O y composite powder is screened out by a 2000 mesh screen, wherein the particle size of the Co-RE x O yThe composite powder is mixed with WC powder and Cr powder to obtain a mixed powder; and the mixed powder is stirred with distilled water to obtain a mixed slurry;

[0020] S2. Granulation

[0021] After 0.5-2 wt% of a binder PE3000 is added to the mixed slurry, the slurry is continuously stirred in a heated reaction kettle, and deionized water is continuously added to maintain good fluidity of the slurry. The slurry is pumped into a spray dryer for spray drying and granulation to obtain granules.

[0022] S3. Sintering

[0023] The granules obtained by spray granulation are placed in a sintering furnace in a hydrogen reducing atmosphere for sintering.

[0024] S4. Crushing and screening

[0025] After sintering, the sintered product is crushed by a crusher and screened by a 200-600 mesh vibrating screen to obtain a spray powder.

[0026] As a preferred scheme of the method for preparing the nano-rare earth oxide doped WC-CoCr spray powder, in step S1, the paddle is continuously stirred in the same direction to fully and uniformly mix the slurry, and the stirring paddle rotates at a speed of 10-60 r / min.

[0027] As a preferred scheme of the method for preparing the nano-rare earth oxide doped WC-CoCr spray powder, in step S2, the process parameters for the spray drying and granulation are as follows:

[0028] The evaporation amount is 4.8-5.0 kg / h, the air inlet temperature is 245-255°C, the outlet temperature is 120-125°C, and the pump flow rate is 4.2-4.5 L / min.

[0029] As a preferred scheme of the method for preparing the nano-rare earth oxide doped WC-CoCr spray powder, in step S3, the sintering temperature is 1400-1480°C.

[0030] To solve the above technical problems, according to another aspect of the present application, the present application provides the following technical scheme:

[0031] A nano-rare earth oxide doped WC-CoCr spray coating, wherein the raw material of the spray coating is the above-mentioned nano-rare earth oxide doped WC-CoCr spray powder.

[0032] As a preferred scheme of the nano-rare earth oxide doped WC-CoCr spray coating, the thickness of the coating is 130-160 μm.

[0033] As a preferred scheme of the nano-rare earth oxide doped WC-CoCr sprayed coating according to the present application, the subsurface microhardness of the coating is greater than or equal to 1380HV, and the bonding strength with the substrate is greater than or equal to 68MPa.

[0034] To solve the above technical problems, according to another aspect of the present application, the present application provides the following technical solutions:

[0035] A preparation method of a nano-rare earth oxide doped WC-CoCr sprayed coating, comprising the following steps:

[0036] B1. substrate treatment;

[0037] B2. spraying the nano-rare earth oxide doped WC-CoCr sprayed powder on the surface of the substrate to obtain a coating;

[0038] The spraying process parameters are as follows: the oxygen flow is 1900-2000SCFH (standard cubic feet per minute), the fuel consumption is 6.0-6.5GPH (gallons per hour), the powder feeding carrier gas flow is 21-25SCFH (standard cubic feet per minute), the powder feeding rate is 32-36g / min, the spraying distance is 370-400mm, and the gun moving speed is 450-520mm / s.

[0039] As a preferred scheme of the preparation method of the nano-rare earth oxide doped WC-CoCr sprayed coating according to the present application, in the step B2, the spraying is realized by using a supersonic flame spraying device.

[0040] The present application has the following beneficial effects:

[0041] The present application proposes a nano-rare earth oxide and a WC-CoCr sprayed powder, a coating and a preparation method doped with the same. The nano-rare earth oxide with a particle size of less than 100 nanometers is prepared by using an optimized preparation method, and is doped into the Co phase to form a Co-RE x O y The precursor composite powder is sintered to obtain a WC-CoCr-RE x O y The thermal spraying powder is prepared by a supersonic flame spraying process. x O y The microhardness of the coating surface and the subsurface, and the bonding strength with the substrate are all higher than those of the WC-CoCr coating without adding rare earth. The microhardness of the subsurface of the coating according to the present application is greater than or equal to 1380HV, and the bonding strength with the substrate is greater than or equal to 68MPa, so that a high-quality coating is obtained. BRIEF DESCRIPTION OF DRAWINGS

[0042] In order to make the technical solutions in the embodiments of the present application or the prior art clearer, the accompanying drawings needed in the embodiments or prior art description will be briefly introduced. Obviously, the accompanying drawings in the following description only represent some embodiments of the present application, and all other drawings obtained by those of ordinary skill in the art without any creative effort based on these drawings also belong to the protection scope of the present application.

[0043] Figure 1 SEM micrographs of the powders prepared by spray granulation for the present application comparative example 1 and example 1;

[0044] Figure 2 SEM micrographs of the powders obtained by sintering and crushing sieving for the present application comparative example 1 and example 1;

[0045] Figure 3 SEM micrographs of the coating cross sections prepared by deposition for the present application comparative example 1 and example 1.

[0046] The implementation, functional features and advantages of the present application will be further described with reference to the embodiments and the accompanying drawings. DETAILED DESCRIPTION

[0047] The technical solutions in the embodiments will be described clearly and completely below. Obviously, the described embodiments only represent some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without any creative effort belong to the protection scope of the present application.

[0048] According to one aspect of the present application, the present application provides the following technical solutions:

[0049] A method for preparing nanometer rare earth oxide, micron rare earth oxide powder is wet ground according to the ratio of 300-350 mL zirconium oxide grinding ball per 100 g micron rare earth oxide, 180-230 mL polyethylene glycol, the ball milling speed is 320-360 r / min, and the ball milling time is 55-70 min; the particle size D90 of the nanometer rare earth oxide is less than 0.1 mu m. Preferably, the ball milling is intermittent, and the ball milling is stopped for 5-10 min every 20-30 min. Specifically, the amount of zirconium oxide grinding ball can be, for example but not limited to, any one of 300 mL, 310 mL, 320 mL, 330 mL, 340 mL, 350 mL or a range between any two of them, the amount of polyethylene glycol can be, for example but not limited to, any one of 180 mL, 190 mL, 200 mL, 210 mL, 220 mL, 230 mL or a range between any two of them, the ball milling speed can be, for example but not limited to, any one of 320 r / min, 330 r / min, 340 r / min, 350 r / min, 360 r / min or a range between any two of them, and the ball milling time can be, for example but not limited to, any one of 55 min, 60 min, 65 min, 70 min or a range between any two of them.

[0050] The particle size distribution of the original powder, the powder after ball milling for 60 min and the powder after ball milling for 90 min of Eu2O3, Nd2O3 and Pr6O 11 is tested and analyzed by using a laser particle size analyzer, and the results are shown in Tables 1-3.

[0051] Table 1 Particle size cumulative distribution of Eu2O3 powder before and after ball milling

[0052]

[0053] The particle size of the original europium oxide Eu2O3 powder is counted, and the particle size distribution is in the range of 0.4-25 μm; after 60 min of ball milling, the minimum particle size is reduced to 0.14 μm, and the maximum particle size is reduced to 2 μm; after 90 min of ball milling, the minimum particle size is increased from 0.14 μm when ball milling for 60 min to 0.18 μm, and the maximum particle size is increased from 2 μm when ball milling for 60 min to 3 μm. Meanwhile, in Table 1, D50 is the median particle size, representing that the particles with a volume content of 50% are greater than or less than this particle size; D90 is the particle size at which the cumulative distribution of particles is 90%, representing that the particles with a volume content of 90% are less than this particle size; D10 is the particle size at which the cumulative distribution of particles is 10%, representing that the particles with a volume content of 10% are less than this particle size. As can be seen from Table 1, 90% of the original europium oxide powder particles have a particle size of 1.247-9.411 μm, and the median particle size is 4.157 μm; after ball milling, most of the micron-level europium oxide particles can be significantly refined to below 1 μm, reaching the nanometer level. As can be seen from Table 1, with the increase of the ball milling time, the cumulative particle size distribution D90, D50 and D10 of europium oxide all first decrease and then increase. When the ball milling time is 60 min, D90, D50 and D10 all reach the minimum value, the median particle size D50 is refined from 4.157 μm of the original particles to 0.433 μm, which is refined by 9.6 times; when the ball milling time is increased to 90 min, the median particle size D50 is increased from 0.433 μm when ball milling for 60 min to 0.605 μm, which is increased by 39.7%, and D90 and D10 are also increased compared with those when ball milling for 60 min.

[0054] The particle size of the original neodymium oxide Nd2O3 powder is counted, and the particle size distribution is in a large range of 0.2 μm to 18 μm; after 60 min of ball milling, the upper limit of the maximum particle size is reduced to 1 μm, and the minimum particle size is refined to 0.1 μm, and the lower limit of the minimum particle size is less than 0.1 μm detected by the Mastersizer 3000E laser particle size analyzer used in the application; after 90 min of ball milling, the minimum particle size is also refined to 0.1 μm, and the lower limit of the particle size is less than 0.1 μm, and the upper limit of the maximum particle size is increased to 1.4 μm from 1 μm when the ball milling time is 60 min; the D90 and D10 of the original particles are 5.636 μm and 0.519 μm respectively, as shown in Table 2, 90% of the particle size of the original neodymium oxide powder is between 0.519 μm and 5.636 μm, and the median particle size D50 is 1.7 μm. After ball milling, the cumulative particle size distribution values D90, D50 and D10 are all less than 1 μm, which indicates that the neodymium oxide particles can be significantly refined to less than 1 μm by ball milling, reaching the nanometer level. As can be seen from Table 2, with the increase of the ball milling time, the powder particle size of neodymium oxide, like europium oxide, also shows a trend of first decreasing and then increasing. When the ball milling time is 60 min, D90, D50 and D10 all reach the minimum value, the median particle size D50 is reduced from 1.7 μm of the original particle to 0.324 μm, which is refined by 5.3 times; when the ball milling time is increased to 90 min, the median particle size D50 is increased by 15.7% from 0.324 μm when the ball milling time is 60 min to 0.375 μm, and D90 and D10 are also increased compared with those when the ball milling time is 60 min.

[0055] Table 2 Cumulative particle size distribution of Nd2O3 powder before and after ball milling and comparison

[0056]

[0057] Table 3 Pr6O 11 Cumulative particle size distribution of powder before and after ball milling and comparison

[0058]

[0059] Pr6O 11The original powder particle size is counted, and the particle size distribution is in a large range of 0.1 μm-30 μm. Since the lower limit of the instrument detection is 0.1 μm, most of the praseodymium oxide particles have a particle size less than 0.1 μm after 60 min of ball milling, so that the instrument cannot detect the particle size distribution. According to the similar trend of the particle size of the europium oxide and neodymium oxide powder with the ball milling time, the micron-sized rare earth oxide can be refined to the nanometer level after 60 min of ball milling. When the ball milling time continues to increase to 90 min, the particle size of the powder particles will increase because the powder particles will be re-agglomerated due to the long milling time. The praseodymium oxide powder after 60 min of ball milling is taken and continues to be ball milled for 30 min, so that the total ball milling time is 90 min. The particle size of the praseodymium oxide powder with a total ball milling time of 90 min is tested by the laser particle size analyzer, and the particle size is concentrated in a narrow range of 0.1-0.6 μm. Since the lower limit of the Mastersizer 3000E laser particle size analyzer used in the present application is 0.1 μm, it is speculated that the actual lower limit of the particle size should be lower than 0.1 μm. It can be seen that the particle size of the rare earth oxide changes with the ball milling time, and the smallest oxide nanoparticles can be obtained by 60 min of ball milling. As shown in Table 3, the D90 and D10 of the original particle size are 10.673 μm and 1.077 μm, respectively, indicating that 90% of the particles in the original praseodymium oxide powder have a particle size in a wide range of 1.077-10.673 μm, and the median particle size D50 is 4.600 μm. When the ball milling time reaches 60 min, the particle size of the praseodymium oxide powder is less than the lower limit 0.1 μm of the Mastersizer 3000E laser particle size analyzer, so that the particle size distribution cannot be obtained. When the ball milling time continues to increase to 90 min, the particle size distribution of the powder can be detected by the Mastersizer 3000E laser particle size analyzer, the median particle size D50 is 0.213 μm, the D90 value and the D10 value are 0.326 μm and 0.139 μm, respectively, and the particle size is very fine and the distribution is very concentrated.

[0060] In summary, the praseodymium oxide powder prepared by the process of the present application has the smallest particle size and the most concentrated particle size distribution, D90<0.1 μm, and deep nanometer (100 nanometers or less) rare earth oxide can be obtained. The prepared neodymium oxide powder and europium oxide powder cannot meet the requirements of nanometer rare earth oxide, and cannot meet D90<0.1 μm. The praseodymium oxide powder prepared by the process of the present application is used to prepare a WC-CoCr spraying powder.

[0061] According to another aspect of the present application, the present application provides the following technical solutions:

[0062] A nanometer rare earth doped WC-CoCr spraying powder, which comprises the following components in mass percentage:

[0063] Co powder 9-12wt%, Cr powder 3-5wt%, nanometer rare earth oxide powder prepared by the above preparation method 0.02-0.30wt%, and the balance being WC powder; wherein the mass of the nanometer rare earth oxide powder cannot exceed 3% of the mass of the Co powder;

[0064] The particle size of the WC powder is 0.5-1.0μm, and the purity is ≥99.99%;

[0065] The particle size of the Co powder is 0.6-0.8μm, and the purity is ≥99.9%;

[0066] The particle size of the Cr powder is 2.0-3.0μm, and the purity is ≥99.9%.

[0067] Specifically, the mass percentage of the Co powder in the spraying powder can be, for example but not limited to, any one of 9wt%, 9.5wt%, 10wt%, 10.5wt%, 11wt%, 11.5wt%, 12wt% or a range between any two of them; the mass percentage of the Cr powder in the spraying powder can be, for example but not limited to, any one of 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt% or a range between any two of them; and the mass percentage of the nanometer rare earth oxide powder in the spraying powder can be, for example but not limited to, any one of 0.02wt%, 0.05wt%, 0.08wt%, 0.1wt%, 0.15wt%, 0.2wt%, 0.25wt%, 0.3wt% or a range between any two of them.

[0068] Preferably, the particle size of the spraying powder is 200-600 mesh. Specifically, the particle size of the spraying powder can be, for example but not limited to, any one of 200 mesh, 300 mesh, 400 mesh, 500 mesh, 600 mesh or a range between any two of them.

[0069] According to another aspect of the present application, the present application provides the following technical solutions:

[0070] A preparation method of a nanometer rare earth doped WC-CoCr spraying powder, comprising the following steps:

[0071] S1. Mixing

[0072] Nano-rare earth oxide powder is mixed with anhydrous ethanol to form a paste. The paste is heated to 65–70°C, and 0.2–2 vol% (v / v) of paraffin wax is added. The mixture is stirred until the paraffin wax is uniformly melted into the paste. While maintaining continuous stirring, Co powder is slowly and continuously added at a flow rate of 5–20 g / h. The mechanical stirring blades are continuously stirred in the same direction to ensure thorough and uniform mixing. The stirring speed is 10–60 r / min. The mixture is stopped when it becomes too viscous to stir. It is then placed in a vacuum drying oven and dried at 75–80°C for 2–8 hours. After drying, the agglomerated powder is crushed using an agate mortar and pestle. The Co-RE particles smaller than 2000 mesh are sieved through a 2000-mesh sieve. x O y Composite powder, with Co-RE x O y The composite powder is mixed with WC powder and Cr powder to obtain a mixed powder; the mixed powder is stirred with distilled water to make a mixed slurry; the inventors have found that, under the same rare earth oxide content, the deep nano rare earth oxide powder with a particle size of less than 100 nm described in this invention is more likely to achieve uniform distribution in the matrix, avoiding the adverse effects of uneven distribution. On the other hand, the deep nano rare earth oxide powder can play a better modifying role than micron and micron rare earth oxide powders, thereby achieving a better modification effect.

[0073] S2. Granulation

[0074] After adding 0.5-2wt% of the binder PE3000 into the mixed slurry, the slurry is loaded into a heated reaction kettle for continuous stirring and mixing, during which deionized water is constantly supplemented to maintain good fluidity of the slurry. The slurry is pumped into a spray dryer for spray drying and granulation to obtain granules. The process parameters for the spray drying and granulation are as follows: evaporation capacity of 4.8-5.0 kg / h, air inlet temperature of 245-255°C, outlet temperature of 120-125°C, and pump flow rate of 4.2-4.5 L / min. Specifically, the evaporation capacity can be, for example but not limited to, any one of 4.8 kg / h, 4.85 kg / h, 4.9 kg / h, 4.95 kg / h, 5.0 kg / h, or a range between any two of them; the air inlet temperature can be, for example but not limited to, any one of 245°C, 246°C, 247°C, 248°C, 249°C, 250°C, 251°C, 252°C, 253°C, 254°C, 255°C, or a range between any two of them; the outlet temperature can be, for example but not limited to, any one of 120°C, 121°C, 122°C, 123°C, 124°C, 125°C, or a range between any two of them; and the pump flow rate can be, for example but not limited to, any one of 4.2 L / min, 4.25 L / min, 4.3 L / min, 4.35 L / min, 4.4 L / min, 4.45 L / min, 4.5 L / min, or a range between any two of them.

[0075] S3. Sintering

[0076] The spray granulated granules are placed into a sintering furnace in a hydrogen reducing atmosphere for sintering. The sintering temperature is 1400-1480°C. Specifically, the sintering temperature can be, for example but not limited to, any one of 1400°C, 1410°C, 1420°C, 1430°C, 1440°C, 1450°C, 1460°C, 1470°C, 1480°C, or a range between any two of them.

[0077] S4. Crushing and sieving

[0078] After sintering, the sintered product is crushed by a crusher and sieved by a 200-600 mesh vibrating screen machine to obtain a spray powder. The particle size of the spray powder is 200-600 mesh. The particle size of the spray powder can be, for example but not limited to, any one of 200 mesh, 300 mesh, 400 mesh, 500 mesh, 600 mesh, or a range between any two of them.

[0079] According to another aspect of the present application, the present application provides the following technical solutions:

[0080] A nano-rare earth doped WC-CoCr sprayed coating, wherein the raw material of the sprayed coating is the nano-rare earth doped WC-CoCr sprayed powder as described above. The thickness of the coating is 130-160 μm. The subsurface microhardness of the coating is ≥1380 HV, and the bonding strength with the substrate is ≥68 MPa.

[0081] According to another aspect of the present application, the present application provides the following technical solutions:

[0082] A preparation method of a nano-rare earth doped WC-CoCr sprayed coating, comprising the following steps:

[0083] B1. substrate treatment;

[0084] B2. spraying the nano-rare earth doped WC-CoCr sprayed powder on the surface of the substrate to obtain a coating.

[0085] The spraying is realized by using a high velocity oxygen fuel spraying device, and the spraying process parameters are as follows: the oxygen flow rate is 1900-2000 SCFH (standard cubic feet per minute), the fuel consumption is 6.0-6.5 GPH (gallons per hour), the powder feeding carrier gas flow rate is 21-25 SCFH, the powder feeding rate is 32-36 g / min, the spraying distance is 370-400 mm, and the spraying gun moving speed is 450-520 mm / s. Specifically, the oxygen flow rate can be, for example but not limited to, any one of 1900 SCFH, 1910 SCFH, 1920 SCFH, 1930 SCFH, 1940 SCFH, 1950 SCFH, 1960 SCFH, 1970 SCFH, 1980 SCFH, 1990 SCFH, 2000 SCFH or a range between any two of them, the fuel consumption can be, for example but not limited to, any one of 6.0 GPH, 6.1 GPH, 6.2 GPH, 6.3 GPH, 6.4 GPH, 6.5 GPH or a range between any two of them, the powder feeding carrier gas flow rate can be, for example but not limited to, any one of 21 SCFH, 22 SCFH, 23 SCFH, 24 SCFH, 25 SCFH or a range between any two of them, the powder feeding rate can be, for example but not limited to, any one of 32 g / min, 33 g / min, 34 g / min, 35 g / min, 36 g / min or a range between any two of them, the spraying distance can be, for example but not limited to, any one of 370 mm, 375 mm, 380 mm, 385 mm, 390 mm, 395 mm, 400 mm or a range between any two of them, and the spraying gun moving speed is any one of 450 mm / s, 460 mm / s, 470 mm / s, 480 mm / s, 490 mm / s, 500 mm / s, 510 mm / s, 520 mm / s or a range between any two of them.

[0086] The technical solutions of the present application are further described below in combination with specific examples.

[0087] The nano-rare earth oxide in the embodiments 1-2 of the present application is nano-Pr6O 11 powder with a particle size of D90 < 0.1 μm, which is prepared by the following method:

[0088] According to 100 g of the micron-grade Pr6O 11 , 320 mL of zirconium oxide grinding balls and 200 mL of polyethylene glycol are added in a ratio of 1:1.5:1 to wet mill the micron-grade Pr6O 11 to obtain nano-Pr6O 11 powder. The ball milling speed is 350 r / min, the ball milling time is 60 min, and the ball milling is intermittently reversed every 30 min of operation for 10 min of stoppage.

[0089] The coating powder used in the embodiment 1 of the present application has the following composition in terms of mass percentage: 10 wt% of Co powder, 4 wt% of Cr powder, 0.2 wt% of the nano-Pr6O 11 powder prepared in the present embodiment, and the balance of WC powder.

[0090] The coating powder used in the embodiment 2 of the present application has the following composition in terms of mass percentage: 10 wt% of Co powder, 4 wt% of Cr powder, 0.07 wt% of the nano-Pr6O 11 powder prepared in the present embodiment, and the balance of WC powder.

[0091] The coating powder used in the comparative example 1 of the present application has the following composition in terms of mass percentage: 10 wt% of Co powder, 4 wt% of Cr powder, and the balance of WC powder.

[0092] The spraying powders of the embodiments 1-2 and the comparative example 1 of the present application are prepared by the following process (the comparative example 1 does not contain the following related content concerning the nano-Pr6O 11 powder) :

[0093] S1. Mixing

[0094] The ball-milled nano-Pr6O 11 powder is added into anhydrous ethanol to form a paste-like slurry, heated to 65 °C, 2 vol% of paraffin is added, and the paraffin is uniformly melted into the slurry by stirring. The slurry is continuously and slowly added with Co powder at a flow rate of 10 g / h, and the mechanical stirring blades are continuously stirred in the same direction to fully and uniformly mix the slurry. The stirring blade speed is 50 r / min, and the stirring is stopped when the slurry is thick and not easy to stir. The slurry is placed in a vacuum drying oven, the temperature is 75 °C, and the time is 2 h. The clumped powder is crushed with a garnet mortar tank, and the Co-Pr6O 11Composite powder, containing Co-Pr6O 11 The composite powder is mixed with WC powder and Cr powder to form WC-10Co-4Cr-0.2Pr6O 11 (Example 1) or WC-10Co-4Cr-0.07Pr6O 11 (Example 2) Mixed powder; The mixed powder and distilled water were mixed in a mass ratio of 3:2 to prepare a slurry, and stirred evenly for 24 hours to obtain a mixed slurry;

[0095] S2. Granulation

[0096] Add 1 wt% binder PE3000 to the mixed slurry, then load the mixture into a heated reactor. Heat to 400°C and continue stirring thoroughly, continuously adding deionized water to maintain good slurry flowability. Pump the thoroughly mixed slurry into a YC018 spray dryer for spray granulation. The spray drying granulation process parameters are: evaporation rate of 5.0 kg / h, inlet air temperature of 245°C, outlet temperature of 125°C, pump flow rate of 4.5 L / min, and powder yield of 85%. The SEM microstructure images of the powders obtained by spray granulation in Comparative Example 1 and Example 1 are shown below. Figure 1 As shown in (a) and (b). From Figure 1 It can be seen that most of the powder particles exhibit complete secondary agglomerated spherical particles. During the spray drying granulation process, the particles consist of WC primary single particles, Co primary single particles, Cr primary single particles, and Pr6O. 11 A primary powder slurry droplet composed of a single nanoparticle and water undergoes microscopic processes such as atomization, shrinkage, droplet / particle aggregation and breakup, ultimately forming secondary aggregated particles. For example... Figure 1 As shown, most of the secondary particles obtained after spray granulation are complete spheres with a loose and porous surface, and very few are broken. This indicates that under the process conditions of this study, the powder slurry mainly undergoes two microscopic processes: atomization and shrinkage. The agglomeration and breakage of droplets / particles are not obvious, thus the obtained powder exhibits a complete spherical shape. The particle size of the secondary agglomerated particles in Comparative Example 1 and Example 1 is also mainly determined by the two microscopic processes of droplet atomization and shrinkage. The atomization and shrinkage of slurry droplets are significantly affected by slurry concentration, slurry flow rate, atomizing gas flow rate, and drying gas temperature. Therefore, the particle size and distribution of the secondary agglomerated powder can be controlled by adjusting the slurry concentration, slurry flow rate, atomizing gas flow rate, and drying gas temperature, thereby controlling the particle size and distribution of the final secondary agglomerated particles for thermal spraying.

[0097] S3. Sintering

[0098] The powder obtained by spray granulation was placed in a hydrogen reducing atmosphere sintering furnace and sintered at a temperature of 1450℃.

[0099] S4. Breaking and sieving

[0100] The sintered powder was broken by a breaker and sieved by a 600 mesh vibrating screen to obtain the spraying powder. The SEM micrographs of the powders obtained by sintering, breaking and sieving of Comparative Example 1 and Example 1 are shown in Figs. (a) and (b) of Figure 2 the drawings, respectively. After sintering, most of the powder particles remained intact and spherical, and almost no breaking occurred, indicating that the sintering process was reasonable and no obvious breaking and agglomeration occurred during the sintering process.

[0101] The coatings of Examples 1-2 and Comparative Example 1 were prepared by the following process (Comparative Example 1 does not contain the following content related to nano-Pr6O 11 11 powder) :

[0102] B1. Substrate treatment; the substrate was selected as 45# steel, and the surface was pretreated: to ensure good bonding between the coating and the substrate, the surface of the 45# steel substrate was sandblasted to remove rust and dirt, and to achieve a certain roughness;

[0103] B2. The nano-rare earth doped WC-CoCr spraying powder was sprayed on the surface of the 45# steel substrate by using a JP8000 supersonic flame spraying device to obtain a coating. The spraying parameters were as follows: oxygen flow rate was 2000 SCFH (standard cubic feet per minute), fuel consumption was 6.2 GPH (gallons per hour), powder feeding carrier gas flow rate was 23 SCFH, powder feeding rate was 35 g / min, spraying distance was 380 mm, and the moving speed of the spraying gun was 500 mm / s.

[0104] Compared with the plasma spraying method, the decomposition of WC during the spraying process can be greatly reduced by using the supersonic flame spraying technology. The JP8000 supersonic flame spraying device was used in Examples 1-2 and Comparative Example 1 to deposit the coating layers of Comparative Example 1 and Example 1, respectively. The SEM micrographs of the cross-sectional microstructures of the coating layers are shown in Figs. (a) and (b) of the drawings, respectively. The average thickness of the coating layers obtained by depositing the spraying powders of Comparative Example 1 and Example 1 was about 150 μm, and the coating layers of Comparative Example 1 and Example 1 were both well combined with the substrate. By comparing the pore size, distribution and coating density between the two, it can be found that the coating layer of Example 1 had fewer and smaller pores, and had higher density, while the coating layer of Comparative Example 1 had more and larger pores, and the pores were more densely distributed from the bonding part with the substrate to the surface, and the coating density was not as high as that of Example 1. It can be seen that the coating layer of Example 1 with the addition of nano-rare earth Pr6O Figure 3 11 powder had higher density, lower porosity and better quality than the coating layer of Comparative Example 1 without the addition of nano-rare earth Pr6O

[0105] The coating performance of the coating obtained in Example 1-2 and Comparative Example 1 was tested:

[0106] (1) Microhardness

[0107] The coating cross section of Comparative Example 1 and Example 1-2 was tested by longitudinal hardness dot testing using a micro Vickers hardness tester, and points were taken at 10, 30, 50, 70 and 90 μm from the coating surface and at the substrate under the conditions of room temperature 25℃, load 300g and loading time 15s, and the microhardness (HV) test results of the coating of Comparative Example 1 and Example 1-2 at different thicknesses are shown in Table 2.

[0108] Table 2 Hardness of coating cross section at different thicknesses

[0109]

[0110]

[0111] As shown in Table 2, the microhardness of the coating surface and subsurface of Example 1-2 is higher than the hardness of the coating interior, and reaches a maximum at 30 μm from the coating surface, and the microhardness of all test points of the coating is higher than HV1100; the microhardness of the coating surface of Comparative Example 1 is the lowest, only HV982, which is much lower than the microhardness of Example 1-2 at the corresponding position, and the microhardness of the subsurface of Comparative Example 1 is also lower than the microhardness of Example 1-2 at the corresponding position, and the microhardness of Comparative Example 1 reaches a maximum at 90 μm from the coating surface, which is obviously not conducive to the wear resistance of the coating. The reason for the optimized hardness of the coating of the present application is that the optimized ball milling process of the present application produces nano Pr6O11 particles with a particle size of less than 100 nanometers. 11 After doping, the tendency of decarburization of WC in the spraying process is reduced, thereby reducing the precipitation of η phase such as Co6W6C and Co3W3C which is not conducive to performance.

[0112] (2) Coating bonding strength

[0113] The coating bonding strength is tested according to GB / T8642-2002 test method, using a Ф25*5mm cylindrical couple sample, the coating bonding strength tension test result shows that the coating of the sample of the comparative example 1 and the example 1-2 is not peeled off from the base body, but is separated at the bonding position of the high-temperature adhesive and the base body, the strength of the sample of the comparative example 1 and the example 1-2 is 65.45MPa and 68.33MPa, 68.25MPa respectively, all in the bonding strength range of the high-temperature adhesive and the base body used in the experiment, which shows that the bonding strength of the coating and the base body is higher than the bonding strength between the high-temperature adhesive and the base body used in the experiment. It is inferred that the bonding strength of the coating and the base body of the comparative example 1 and the example 1-2 is higher than 65.45MPa, 68.23MPa respectively, and it can be seen that the bonding strength between the coating and the base body of the example 1-2 is higher than that of the comparative example 1.

[0114] The embodiment of the application adopts an optimized ball milling process to prepare nanometer rare earth oxides with a particle size of less than 100 nanometers, and the nanometer rare earth oxides are doped into Co to form Co-RE x O y The precursor composite powder is sintered to obtain WC-CoCr-RE with uniform distribution of rare earth elements x O y The thermal spraying powder is prepared by a high-velocity oxygen fuel (HVOF) process to obtain WC-CoCr-RE with high quality x O y The coating has a subsurface microhardness of ≥1380HV and a bonding strength with the base body of ≥68MPa.

[0115] The above description is only the preferred embodiments of the application, and does not limit the patent scope of the application, and any equivalent structural transformation or direct / indirect application in other related technical fields based on the inventive concept of the application and the content of the specification of the application is included in the patent protection scope of the application.

Claims

1. A nanosized rare earth oxide doped WC-CoCr sprayed coating, characterized in that, The coating has a thickness of 130-160 microns, a subsurface microhardness of greater than or equal to 1380 HV, and a bonding strength with the substrate of greater than or equal to 68 MPa. The raw material of the sprayed coating is a nano-rare earth oxide doped WC-CoCr sprayed powder, the composition of the nano-rare earth oxide doped WC-CoCr sprayed powder is, in mass percentage: Co powder 9~12 wt%, Cr powder 3~5 wt%, nano-rare earth oxide powder 0.02~0.30 wt%, and the balance is WC powder; wherein the mass of the nano-rare earth oxide powder cannot exceed 3% of the mass of the Co powder, the particle size of the WC powder is 0.5~1.0 µm, and the purity is ≥99.99%; the particle size of the Co powder is 0.6~0.8 µm, and the purity is ≥99.9%; the particle size of the Cr powder is 2.0~3.0 µm, and the purity is ≥99.9%; the particle size of the sprayed powder is 200~600 mesh; the nano-rare earth oxide powder is nano-Pr6O 11 The preparation method of the nano-rare earth oxide powder is: according to the ratio of 100 g of micron-grade rare earth oxide to 300~350 mL of zirconium oxide grinding balls and 180~230 mL of polyethylene glycol, wet grinding the micron-grade rare earth oxide powder, the ball milling speed is 320~360 r / min, and the ball milling time is 55~70 min. The preparation method of the nanometer rare earth oxide doped WC-CoCr sprayed coating comprises the following steps: B1. substrate treatment; B2. spraying nanometer rare earth oxide doped WC-CoCr sprayed powder on the surface of the substrate to obtain a coating; The spraying process parameters are as follows: oxygen flow rate is 1900-2000 SCFH, fuel consumption is 6.0-6.5 GPH, powder feeding carrier gas flow rate is 21-25 SCFH, powder feeding rate is 32-36 g / min, spraying distance is 370-400 mm, and spraying gun moving speed is 450-520 mm / s.

2. The nanosized rare earth oxide-doped WC-CoCr sprayed coating according to claim 1, characterized in that, The preparation method of the nanometer rare earth oxide doped WC-CoCr sprayed powder comprises the following steps: S1. mixing The nano-rare earth oxide powder is added into anhydrous ethanol to make a paste slurry, heated to 65-70℃, 0.2-2vol% paraffin is added, stirred to make the paraffin melt into the slurry, keep the slurry stirring, Co powder is continuously added at a flow rate of 5-20g / h, mechanical stirring is stopped when the slurry is thick and not easy to stir; put into a vacuum drying oven, temperature is 75-80℃, time is 2-8h; take out, use a jade mortar pot to crush the agglomerated powder, use a 2000 mesh screen to screen out Co-RE x O y composite powder, the Co-RE x O y composite powder is mixed with WC powder and Cr powder to obtain a mixed powder; the mixed powder is stirred with distilled water to prepare a mixed slurry; S2. granulation After adding 0.5-2 wt% adhesive PE3000 into the mixed slurry, the slurry is loaded into a heating reaction kettle for continuous stirring and mixing, and deionized water is continuously supplemented to maintain good fluidity of the slurry, and the slurry is pumped into a spray dryer for spray drying and granulation to obtain granules; S3. sintering The spray granulated granules are placed into a hydrogen reducing atmosphere sintering furnace for sintering; S4. crushing and screening After sintering, the granules are crushed by a crusher and then screened by a 200-600 mesh vibrating screen machine to obtain the sprayed powder.

3. The nanosized rare earth oxide-doped WC-CoCr sprayed coating according to claim 2, characterized in that, In step S1, the blades continuously stir the slurry in the same direction to fully and uniformly mix the slurry, and the stirring blade speed is 10-60 r / min.

4. The nanosized rare earth oxide-doped WC-CoCr sprayed coating according to claim 2, characterized in that, In step S2, the process parameters for the spray drying and granulation are as follows: Evaporation capacity is 4.8-5.0 kg / h, air inlet temperature is 245-255℃, outlet temperature is 120-125℃, and pump flow rate is 4.2-4.5 L / min.

5. The nanosized rare earth oxide-doped WC-CoCr sprayed coating according to claim 2, characterized in that, In step S3, the sintering temperature is 1400-1480℃.

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