A method for preparing at13 plasma spray feedstock by direct granulation of a precursor sol

Abstract

The application provides a method for preparing AT13 plasma spraying feedstock by directly granulating precursor sol, and the method comprises the following steps: S1, preparing Al2O3 precursor sol concentrate; S2, preparing TiO2 precursor sol concentrate; S3, mixing the two kinds of precursor sol concentrates to prepare AT13 precursor sol; S4, spray granulating the AT13 precursor sol to prepare AT13 precursor granulated powder; and S5, heat treating the AT13 precursor granulated powder to prepare AT13 plasma spraying feedstock. By the method for preparing AT13 plasma spraying feedstock by directly granulating precursor sol, AT13 plasma spraying layers with more superior comprehensive performance, at least higher film layer bonding strength and stronger crack propagation resistance can be sprayed.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of preparation of thermal spraying ceramic powder, in particular, it relates to a method for preparing AT13 plasma spraying feedstock by directly granulating precursor sol. BACKGROUND

[0002] The ceramic coating prepared on the metal substrate can combine the characteristics of ceramic materials and metal materials organically, and obtain products with various composite structures, which has become the most active and most effective field of contemporary thermal spraying technology, especially in the high-tech field. The melting point of ceramic material is high, and the powder flame spraying is limited by the flame temperature. When the melting point of ceramic material is higher than 2300 DEG C, powder flame spraying is not suitable, so the preparation of ceramic coating usually adopts plasma spraying technology.

[0003] Alumina ceramic belongs to neutral oxide, has high reflectivity to light and high temperature radiation, and low thermal radiation, and is often used for heat preservation coating of artificial satellite under sunlight and backlight. However, the toughness of pure alumina coating is poor, and the porosity is high, so in order to improve the quality of the coating, other oxides are added to the alumina material to obtain a series of composite materials based on Al2O3. The alumina composite material used for thermal spraying mainly includes Al2O3-TiO2, Al2O3-SiO2, Al2O3-Cr2O3, Al2O3-MgO and the like. Using them can obtain a coating with higher bonding strength and higher density, and significantly improve the corrosion resistance, heat insulation, fracture toughness and electrical insulation of the Al2O3 ceramic coating.

[0004] AT13 (i.e. Al2O3-13% TiO2) is usually used to prepare wear-resistant particle wear, hard surface wear, micro-vibration wear, chemical fiber and yarn wear coating, and anti-erosion, wear corrosion and particle erosion coating. The current AT13 spraying powder preparation technology is mainly through physical mixing of Al2O3 and 13% TiO2, then granulating, loose sintering, or further plasma spheroidizing treatment after loose sintering. In order to ensure that the spraying material reaches a high loose density, high temperature treatment is usually required, which inevitably increases the average size of the primary particles of the spraying powder, leading to the difficulty in obtaining nanocrystalline film layer (and the cost of plasma spheroidizing treatment is relatively high), so the comprehensive performance of the nanoscale AT13 feedstock after spraying is not very significant (the bonding strength of the coating is generally only increased to 10-20% of the ordinary coating, and the crack propagation resistance is generally only increased by 10-13%). SUMMARY

[0005] Therefore, the present application aims to solve the technical problem of providing a method for preparing AT13 plasma spraying feedstock by directly granulating precursor sol, which can be used to spray AT13 plasma spraying layer with superior comprehensive performance, at least higher film layer bonding strength and stronger crack propagation resistance.

[0006] To solve the above technical problem, the present application provides a method for preparing AT13 plasma spraying feedstock by directly granulating precursor sol, comprising the following steps:

[0007] S1: preparing Al2O3 precursor sol concentrate;

[0008] S2: preparing TiO2 precursor sol concentrate;

[0009] S3: mixing the two kinds of precursor sol concentrates to prepare AT13 precursor sol;

[0010] S4: spray granulating the AT13 precursor sol to prepare AT13 precursor granulated powder;

[0011] S5: heat treating the AT13 precursor granulated powder to prepare AT13 plasma spraying feedstock.

[0012] Preferably, step S1 comprises the following specific steps:

[0013] S11: selecting aluminum sulfate octadecahydrate as the first raw material, adding deionized water according to a mass fraction of 1:(12-13), and dispersing at a high speed of 30-35 Hz for 10-20 min with a homogenizer to make the solution clear and transparent;

[0014] S12: adding ammonia water with a concentration of 25-28% at a pump speed of 20-30 r / min with a peristaltic pump, and continuing to disperse at a high speed of 30-35 Hz for 5-10 min with the homogenizer after the addition is completed to become Al2O3 precursor sol with a pH value of 7-8;

[0015] S13: standing for more than 20 h to obtain Al2O3 precursor sol concentrate with a solid content of 7.0-7.5%.

[0016] Preferably, in step S12, the ammonia water is added in a mass ratio of (0.62-0.65):1 to the first raw material.

[0017] Preferably, step S2 comprises the following specific steps:

[0018] S21: selecting titanium sulfate oxide dihydrate as the second raw material, adding deionized water according to a mass fraction of 1:(69-70), and dispersing at a high speed of 30-35 Hz for 10-20 min with a homogenizer to make the solution clear and transparent;

[0019] S22: The ammonia water with a concentration of 25-28% is added dropwise by a peristaltic pump at a pump speed of 20-30 r / min, and after the dropwise addition is completed, the homogenizer is used for high-speed dispersion for 5-10 min under the condition of 30-35 Hz, so as to become a TiO2 precursor sol with a pH value of 7-8;

[0020] S23: After standing for more than 20 h, the supernatant is pumped and discharged, so as to obtain a TiO2 precursor sol concentrate with a solid content of 2.53%.

[0021] Preferably, in step S21, the second raw material is selected according to the proportion of TiO2 in AT13, and the first raw material is selected according to a mass ratio of 0.05633:1.

[0022] Preferably, in step S22, the ammonia water is added dropwise according to a mass ratio of (0.95-0.99):1 with the second raw material.

[0023] Preferably, step S3 comprises the following specific steps:

[0024] S31: The Al2O3 precursor sol concentrate prepared in step S1 and the TiO2 precursor sol concentrate prepared in step S2 are placed in the same dispersion barrel, and the homogenizer is used for high-speed dispersion for 60-80 min under the condition of 35-40 Hz, so as to become a uniform and stable AT13 precursor sol.

[0025] Preferably, step S4 comprises the following specific steps:

[0026] S41: The uniformly mixed AT13 precursor sol in step S3 is pumped into a granulation tower for spray granulation, wherein the pump speed is set to 40-60 r / min, the inlet air temperature is controlled to 200-220°C, and the outlet air temperature is controlled to 80-90°C, so as to form an AT13 precursor granulation powder with a particle size of 15-50 μm.

[0027] Preferably, during the execution of step S41, the homogenizer is kept rotating to make the granulation process uniform.

[0028] Preferably, step S5 comprises the following specific steps:

[0029] S51: After the AT13 precursor granulation powder prepared in step S4 is heat treated at 1050-1150°C for 2-3 h, an AT13 plasma spray feedstock with a particle size of 5-20 μm, a flowability of 45-51 s (50 g, 2.5 mm aperture), and a loose bulk density of 1.43-1.58 g / cm 3 is obtained.

[0030] Compared with the prior art, the method for preparing AT13 plasma spraying feedstock by directly granulating a precursor sol has the following beneficial effects:

[0031] The AT13 plasma sprayed layer obtained by spraying has superior comprehensive performance, at least higher bonding strength and stronger crack propagation resistance. DETAILED DESCRIPTION

[0032] In order to make the above-mentioned objects, technical solutions and advantages of the present application more clear and easy to understand, the present application will be further described in detail. It should be understood that the specific embodiments of the present application described herein are only part of the embodiments of the present application, which are only used to explain the present application and do not constitute a limitation on the present application. In the case of no conflict, the embodiments in the present application and the features in the embodiments can be combined with each other.

[0033] The central idea of the present application is to provide a method for preparing AT13 plasma spraying feedstock by directly granulating a precursor sol. Al2O3 and TiO2 precursor sols are prepared respectively, and the sol concentrates are obtained after settling. After uniform mixing, spray granulation is performed, and finally loose sintering is performed at a lower temperature. The AT13 plasma sprayed layer obtained by spraying the prepared AT13 plasma spraying feedstock on a substrate has ultra-fine grains, higher bonding strength and stronger crack propagation resistance. The specific preparation process of the AT13 plasma spraying feedstock is as follows:

[0034] Step S1: preparation of Al2O3 precursor sol concentrate, which can specifically include the following steps:

[0035] S11: select aluminum sulfate octadecahydrate as the first raw material, add deionized water according to a mass fraction of 1:(12-13), and disperse at a high speed of 30-35 Hz for 10-20 min with a homogenizer to make the solution clear and transparent;

[0036] S12: add ammonia water with a concentration of 25-28% at a pump speed of 20-30 r / min with a peristaltic pump, and continue to disperse at a high speed of 30-35 Hz for 5-10 min with a homogenizer after the addition is completed to obtain an Al2O3 precursor sol with a pH value of 7-8, wherein the addition amount of ammonia water and the first raw material is controlled according to a mass ratio of (0.62-0.65):1;

[0037] S13: obtain an Al2O3 precursor sol concentrate with a solid content of 7.0-7.5% by standing for more than 20 h.

[0038] Specifically, in step S13, the Al2O3 precursor sol is allowed to stand for more than 20 hours, and no sedimentation occurs basically except for a thin supernatant on the top. At this time, the solid content (concentration) of the Al2O3 precursor sol concentrate obtained is 7.0-7.5%.

[0039] Step S2: preparation of the TiO2 precursor sol concentrate, which specifically can include the following steps:

[0040] S21: selecting dihydrate titanyl sulfate as the second raw material, adding deionized water according to a mass fraction of 1:(69-70), and dispersing the solution at a high speed for 10-20 minutes under the condition of 30-35 Hz using a homogenizer, so that the solution is clear and transparent. Herein, the second raw material is selected according to the proportion of TiO2 in AT13, and the first raw material is selected according to a mass ratio of 0.05633:1.

[0041] S22: adding ammonia water with a concentration of 25-28% at a pump speed of 20-30 r / min using a peristaltic pump, and continuing to disperse the solution at a high speed for 5-10 minutes under the condition of 30-35 Hz using the homogenizer after the addition is completed, so that the TiO2 precursor sol with a pH value of 7-8 is obtained. Herein, the ammonia water is added and controlled according to a mass ratio of (0.95-0.99):1 with respect to the second raw material.

[0042] S23: after standing for more than 20 hours, the supernatant is pumped out, so that the TiO2 precursor sol concentrate with a solid content of 2.53% is obtained.

[0043] Specifically, in step S23, the TiO2 precursor sol is allowed to stand for more than 20 hours, and the sedimentation is obvious and basically reaches the limit. The supernatant is pumped out, so that the solid content of the sol can be increased from 1.41% before standing to 2.53%, that is, the TiO2 precursor sol concentrate with a solid content of 2.53% is obtained.

[0044] Step S3: mixing the two precursor sol concentrates to prepare the AT13 precursor sol, which specifically can include the following steps:

[0045] S31: placing the Al2O3 precursor sol concentrate prepared in step S1 and the TiO2 precursor sol concentrate prepared in step S2 in the same dispersion barrel, and dispersing the solution at a high speed for 60-80 minutes under the condition of 35-40 Hz using the homogenizer, so that the AT13 precursor sol is obtained, which is uniform and stable.

[0046] Specifically, when TiO2 powder and α-Al2O3 powder are mixed using a conventional process, the particle density, particle size distribution and the like are quite different, and it is difficult to mix them uniformly. However, through the molecular-level mixing of steps S1-S3, the raw material uniformity is better. More specifically, after the precursor sols are respectively prepared, the particle size is reduced by an order of magnitude, the sol has better suspension stability, and therefore, after high-speed dispersion, a feedstock with more uniform micro-distribution can be obtained, which is also conducive to the uniformity of the film layer after plasma spraying and the improvement of other comprehensive physical properties.

[0047] Step S4: The AT13 precursor sol is spray granulated to prepare AT13 precursor granulated powder, which can specifically include the following steps:

[0048] S41: The uniformly mixed AT13 precursor sol in step S3 is pumped into a granulation tower for spray granulation, wherein the pump speed is set to 40-60 r / min, the inlet air temperature is controlled at 200-220°C, and the outlet air temperature is controlled at 80-90°C, so as to form AT13 precursor granulated powder with a particle size of 15-50 μm.

[0049] Specifically, since the precursor sol dry powder after granulation has a very small primary particle size and a high surface energy, it will have higher sintering activity. Of course, during the execution of step S41, the homogenizer can still be kept rotating to make the granulation process uniform.

[0050] Step S5: The AT13 precursor granulated powder is heat treated to prepare AT13 plasma sprayed feedstock, which can specifically include the following steps:

[0051] S51: The AT13 precursor granulated powder prepared in step S4 is heat treated at 1050-1150°C for 2-3 h to obtain AT13 plasma sprayed feedstock with a particle size of 5-20 μm, a flowability of 45-51 s (50 g, 2.5 mm aperture), and a loose bulk density of 1.43-1.58 g / cm 3 .

[0052] Specifically, the loose sintering temperature of conventional nanoscale TiO2 and α-Al2O3 powder generally exceeds 1200°C, while the AT13 precursor granulated powder has higher sintering activity, and therefore, the ideal loose bulk density and flowability can be achieved at 1050-1150°C. After testing the densified feedstock, the particle size is about 5-20 μm, the flowability is 45-51 s (50 g, 2.5 mm aperture), and the loose bulk density is 1.43-1.58 g / cm 3, all meet the requirements, thus not only reducing the energy consumption and cost, and effectively avoiding the prior art for spraying powder once the passive increase in the average size of the grain, and the use of this feed spray coating, the average grain size can be reduced to 0.3 μm or less.

[0053] That is, the AT13 plasma sprayed feed formed after the AT13 nanocrystalline film layer performance will be significantly improved, with brass as an example, the film layer bonding strength is 35.6-38.5 MPa, about 63-71% higher than the ordinary coating; crack propagation resistance is 8.7-9.4 (1 / μ·m) x·10 -3 , about 50-60% higher than the ordinary coating.

[0054] Example 1

[0055] First select aluminum sulfate octadecahydrate as raw material, add 12.5 times (calculated as mass fraction) of deionized water, using homogenizer at 33 Hz conditions, high speed dispersion 10 min, make the solution clear and transparent, then use peristaltic pump at 30 r / min pump rate drop 63% of the mass fraction of ammonia (concentration 25-28%) of the raw material, after the drop is completed, continue to high speed dispersion 10 min, become the pH value of 8 of Al2O3 precursor sol. The sol is placed for 22 h, and basically no settlement occurs, at this time the solid content is about 7.5%.

[0056] According to the proportion of TiO2 in AT13, select about 5.633% of titanium sulfate oxide dihydrate of aluminum sulfate octadecahydrate raw material, add 70 times of deionized water, use homogenizer at 33 Hz conditions, high speed dispersion 10 min, make the solution clear and transparent, then use peristaltic pump at 30 r / min pump rate drop 98% of the mass fraction of ammonia (concentration 25-28%) of titanium sulfate oxide dihydrate, after the drop is completed, continue to high speed dispersion 10 min, become the pH value of 7.5 of TiO2 precursor sol. The sol is placed for 28 h, and basically settled to the limit, after the upper clear liquid is pumped, the sol solid content is increased from 1.41% (solute is titanium sulfate oxide dihydrate) to 2.53%.

[0057] Then the prepared two sols are placed in the same dispersion barrel, using homogenizer at 35 Hz conditions, high speed dispersion 80 min, become uniform, stable AT13 precursor sol.

[0058] Then the mixed uniform AT13 precursor sol is pumped into the granulation tower for granulation (the homogenizer is still rotating during the period to make the pump liquid uniform), wherein the pump speed is set to 50 r / min, the inlet air temperature is controlled at 220℃, and the outlet air temperature is controlled at about 85℃, forming AT13 precursor granulation powder, the size is about 15-50 μm.

[0059] Finally, the prepared AT13 precursor granulated powder is heat treated at 1000℃ for 3h to obtain AT13 feedstock.

[0060] Specifically, the AT13 plasma spraying feedstock prepared in this embodiment has a particle size of about 5-20μm, a fluidity of 48.2s (50g, 2.5mm aperture), and a loose bulk density of 1.50g / cm 3 . Still taking brass as the substrate as an example, the coating layer after spraying has a bonding strength of 37.7MPa, which is about 69% higher than that of the ordinary coating layer, and is much higher than the 10-20% increase in the prior art; the crack propagation resistance is 9.3(1 / μ·m)×·10 -3 , which is about 58% higher than that of the ordinary coating layer, and is much higher than the 10-13% increase in the prior art.

[0061] Although the present application has been disclosed with reference to the above embodiments, the present application is not limited to the above. Any person skilled in the art can make various modifications and changes without departing from the spirit and scope of the present application, and the scope of protection of the present application should be defined by the scope of claims.

Claims

1. A method for preparing AT13 plasma spraying feedstock by direct granulation of precursor sol, characterized in that, Includes the following steps: S1: Preparation of Al2O3 precursor sol concentrate; S2: Preparation of TiO2 precursor sol concentrate; S3: Mix the two precursor sol concentrates to prepare AT13 precursor sol; S4: Spray granulation of AT13 precursor sol to prepare AT13 precursor granulated powder. S5: Heat-treat the AT13 precursor granulated powder to prepare AT13 plasma spraying feed. Step S1 includes the following specific steps: S11: Select aluminum sulfate octadechydrate as the first raw material, add deionized water at a mass fraction of 1:(12~13), and disperse at high speed for 10~20 min using a homogenizer at 30~35 Hz to make the solution clear and transparent; S12: Add 25-28% ammonia solution dropwise using a peristaltic pump at a pump speed of 20-30 r / min. After the addition is complete, continue to disperse at high speed for 5-10 min using a homogenizer at 30-35 Hz to obtain an Al2O3 precursor sol with a pH value of 7-8. S13: After standing for more than 20 hours, an Al2O3 precursor sol concentrate with a sol solid content of 7.0~7.5% is obtained; Step S2 includes the following specific steps: S21: Titanium sulfate dihydrate is selected as the second raw material. Deionized water is added at a mass fraction of 1: (69~70). The solution is dispersed at high speed for 10~20 min at 30~35 Hz using a homogenizer to make the solution clear and transparent. S22: Add ammonia water with a concentration of 25-28% by dripping at a pumping speed of 20-30 r / min using a peristaltic pump. After the dripping is completed, continue to disperse at high speed for 5-10 min using a homogenizer under 30-35 Hz conditions to obtain a TiO2 precursor sol with a pH value of 7-8. S23: After standing for more than 20 hours, use a pump to remove the supernatant to obtain a TiO2 precursor sol concentrate with a sol solid content of 2.53%. Step S3 includes the following specific steps: S31: Place the Al2O3 precursor sol concentrate prepared in step S1 and the TiO2 precursor sol concentrate prepared in step S2 into the same dispersion tank, and disperse them at high speed for 60-80 min at 35-40 Hz using a homogenizer to obtain a uniform and stable AT13 precursor sol. Step S5 includes the following specific steps: S51: The AT13 precursor granulated powder prepared in step S4 is heat-treated at 1050~1150℃ for 2~3h to obtain a particle size of 5~20μm, a flowability of 45~51s, and a bulk density of 1.43~1.58g / cm³. 3 The flowability test conditions for the AT13 plasma spraying feedstock were: 50g, 2.5mm pore size.

2. The method for preparing AT13 plasma spraying feedstock by direct granulation of precursor sol according to claim 1, characterized in that, In step S12, the amount of ammonia added is controlled by the mass ratio of (0.62~0.65):1 to the first raw material.

3. The method for preparing AT13 plasma spraying feedstock by direct granulation of precursor sol according to claim 1, characterized in that, In step S21, the second raw material is selected according to the proportion of TiO2 in AT13, and its mass ratio with the first raw material is 0.05633:

1.

4. The method for preparing AT13 plasma spraying feedstock by direct granulation of precursor sol according to claim 1, characterized in that, In step S22, the amount of ammonia added is controlled by the mass ratio of (0.95~0.99):1 to the mass ratio of the second raw material.

5. The method for preparing AT13 plasma spraying feedstock by direct granulation of precursor sol according to claim 1, characterized in that, Step S4 includes the following specific steps: S41: The AT13 precursor sol mixed evenly in step S3 is pumped into the granulation tower for spray granulation. The pump speed is set to 40~60 r / min, the inlet air temperature is controlled at 200~220℃, and the outlet air temperature is controlled at 80~90℃ to form AT13 precursor granulated powder with a particle size of 15~50μm.

6. The method for preparing AT13 plasma spraying feedstock by direct granulation of precursor sol according to claim 5, characterized in that, During step S41, the homogenizer is kept rotating to ensure uniform feeding during the granulation process.