JP3127582B2 - Zirconia granulated dry powder for thermal spraying - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to zirconia granulation for thermal spraying.
It concerns dry powder.

[0002]

2. Description of the Related Art Generally, when spraying powder, the inner diameter is 2 m.
m or less through the powder tube to the spray gun. Therefore, fluidity at the time of powder supply is regarded as important for the thermal spraying powder. In recent years, in order to obtain more excellent film properties such as heat resistance, hardness, abrasion resistance, corrosion resistance, etc., the use of zirconia powder of 1 μm or less is increasing, and this fine powder is spray-dried and tumbled granulated. Granulated by flow granulation, stirring granulation, etc., and classified and adjusted to a particle size that can be supplied stably.

[0003]

By the way, the finer the zirconia powder, the greater the generation of static electricity due to friction between the powders or between the powders and the wall of the container. Since the powder that has just been granulated and classified as described above is soft, it is broken by the carrier gas in the supply tube, and the fine powder is generated and charged, whereby the fine powder adheres to the surface of the granulated powder. In addition, the liquid is accumulated in the tube, causing a clogging phenomenon and a defective supply. If this supply is not carried out smoothly, the lamination composed of grain boundaries, crystal grains and pores in the sprayed layer will be non-uniform, and the coating thickness per operation will be non-uniform. When such a phenomenon occurs, the heat resistance of the product,
Hardness, abrasion resistance, strength, corrosion resistance, etc. are adversely affected.

Further, the sprayed coating of partially stabilized zirconia is inferior to that of alumina in corrosion resistance in an acidic liquid or gas atmosphere. For example, 30 wt% H ₂ SO ₄
When a zirconia sprayed coating partially stabilized with Y ₂ O ₃ is immersed in a solution, monoclinic crystals increase due to phase transition, and strength and the like decrease. On the other hand, the thermal spray coating of stabilized zirconia does not cause phase transition and has excellent electrical properties such as conductivity, but has low mechanical strength.

[0005] These problems cannot be solved simply by using a fine powder having a high purity and classifying and heat-treating the powder in the conventional manner to form a thermal spray coating. That is,
It is difficult to obtain a zirconia sprayed coating excellent in all aspects such as heat resistance, hardness, abrasion resistance and corrosion resistance.

The present invention has solved these problems, that is, it is hard to be broken by a carrier gas during thermal spraying, has good fluidity, does not cause a clogging phenomenon or a defective supply in a tube, and has heat resistance, hardness and resistance. Zirconia for thermal spraying that can form a thermal spray coating with excellent wear resistance, corrosion resistance, conductivity, etc.
It is intended to provide a granulated dry powder.

[0007]

The present invention mainly comprises zirconium oxide, yttrium oxide and Al ₂ O _{3 having a} crystallite diameter of 1200 A or less, and the molar ratio of Y ₂ O ₃ / ZrO ₂ is 1.5 / 98.5. 212/88, and Al _{2 with} respect to the sum of zirconium oxide and yttrium oxide.
The amount of O ₃ is 0.05 wt% or more and less than 1.0 wt%, the amount of SiO ₂ is 0.01 wt% or less based on the total of zirconium oxide and yttrium oxide, and
A zirconia granulated dry powder for thermal spraying having an average granule crushing strength of 0.10 kgf / mm ² or more.

The molar ratio of Y ₂ O ₃ / ZrO ₂ is 1.5 /
It must be in the range of 98.5 to 12/88, and particularly preferably in the range of 2.5 / 97.5 to 10/90. If this ratio is less than 1.5 / 98.5, the phase transition between tetragonal and monoclinic at high temperature or under stress tends to occur, and the toughness and mechanical strength of the sprayed coating are reduced. On the other hand, there is a peak in the conductivity when the amount of Y ₂ O ₃ added is in the range of 8/92 to 12/88, and when it exceeds 12/88, the conductivity is too low.

[0009] The content of Al ₂ O ₃ is ZrO ₂ and Y ₂ O
Or 0.05 wt% less than 1.0 wt% relative to the sum of the ₃ (the value of the content of _Al 2 _{O 3} is assumed to the total of ZrO ₂ and _Y 2 _{O 3)} should be. If this is less than 0.05 wt%, the effect of improving the wear resistance and the like of the film by Al ₂ O ₃ is not sufficient.
If it is 0 wt% or more, the conductivity of the film will be too low.

Regarding the corrosion resistance, in the partially stabilized region,
If the content of Al ₂ O ₃ is less than 0.05 wt%, 30 wt% of H
_The effect of suppressing the transition of the tetragonal crystal of the film to monoclinic in ₂ SO ₄ or the like is insufficient, and Al ₂ O ₃ 0.05 wt.
% Or more to provide sufficient corrosion resistance. on the other hand,
Even if Al ₂ O ₃ exceeds 1.0 wt%, the corrosion resistance is not so much improved as compared with the case where it is less than 1.0 wt%. However, in the stabilized region, there is no problem of phase transition regardless of the content of Al ₂ O ₃ .

[0011] SiO ₂ forms a glass layer at the grain boundary and inhibits the movement of oxygen ions, but if it is 0.01 wt% or less, the coexistence of Al ₂ O ₃ suppresses the formation of the glass layer.

The zirconia powder has a crystallite size of 1200 A
Must be: When the crystallite diameter exceeds 1200A, neck sintering may occur between powder particles,
This is because the fluidity at the time of thermal spraying deteriorates and causes troubles such as unevenness in the lamination and thickness of the film.

The average granule crushing strength is 0.10 kgf / m
must m ² or more. It is 0.10kgf /
If the particle size is less than mm ² , the granules will break in the carrier gas when used for thermal spraying, causing obstacles such as the above-mentioned blockage.

Zirconia granulation satisfying such conditions
The dry powder can be produced by a spray drying method, a tumbling granulation method, a fluidized granulation method, a stirring granulation method, or the like. For example,
Neutralizing or hydrolyzing the zirconium salt containing the yttrium compound to obtain a zirconia hydrated sol, spray-drying this to a granular gel, and calcining at 600 to 1200 ° C. to form a zirconia in which Y 2 O 3 is dissolved To obtain Al ₂
O ₃ was added and wet pulverized to an average particle diameter of 1 μm or less,
It can be manufactured by adjusting the viscosity to 00 to 3000 cp, granulating in the air and then drying or drying and granulating, and firing or drying at 1500 ° C. or lower.

The above-mentioned zirconium salt may be any water-soluble zirconium salt, for example, zirconium oxychloride, zirconium chloride, zirconium nitrate, zirconium sulfate and the like. The time when the yttrium compound is added to the aqueous solution of the zirconium salt is preferably before neutralization in the case of the neutralization method and may be before or after in the case of the hydrolysis method, but preferably before the hydrolysis. As a form to be added,
There is an oxide or a salt, a hydrated oxide, a hydroxide or a mixture thereof, which becomes an oxide upon firing. Before the hydrolysis, if hydrated zirconia, zirconium oxide particles and the like are added to the water-soluble zirconium salt aqueous solution,
Hydrolysis time can be reduced. After the completion of the hydrolysis, the hydrolysis-completed solution may be concentrated in order to improve the productivity in the subsequent step. Although it is possible to produce a spray zirconia granulated and dried powder of the present invention by the addition of Al ₂ O ₃ to zirconia Y ₂ O ₃ in a solid solution as described above, timing of addition of Al ₂ O ₃ source You don't have to.
For example, in the case of the neutralization method, it is better before neutralization, and in the case of the hydrolysis method, there is no particular difference between before and after, but it is better before hydrolysis. The Al ₂ O ₃ source is, similarly to the above Y ₂ O ₃ source, an oxide, a salt, a hydrated oxide,
A hydroxide or a mixture thereof may be used. When added as an oxide, the powder particle size is preferably 1 μm or less.

When the hydrated zirconia sol is dried to obtain a gel powder, it may be dried immediately after completion of the hydrolysis or dried after concentration, and further dried after completion of the hydrolysis or after pH adjustment after concentration. May be. As a method for drying the hydrated zirconia sol to obtain a granulated gel powder, a spray drying method is preferably used, and among them, a rotating disk method is particularly preferable for improving fluidity. Hot air temperature during spray drying is preferably 50 to 300 ° C, and 95 to 200 ° C.
Is more preferred.

Regarding the method of calcining the granulated gel powder, regardless of the continuous or batch method, an electric furnace or a gas furnace is generally used in many cases, but the hydrated zirconia sol is sprayed by a rotating disk. Meanwhile, a method of simultaneously performing drying and calcination may be used.

The calcination of the granulated gel powder is preferably carried out under the conditions of 500 to 1200 ° C. and a holding time of about 15 minutes to 10 hours, regardless of the neutralization method or the hydrolysis method.
The calcining temperature can be changed according to the required properties of the coating, and a sprayed powder suitable for the purpose can be obtained.

Al ₂ O ₃ is added to zirconia powder,
As a pulverizer used for wet pulverization and mixing, a wet pulverizer such as a ball mill, a vibrating ball mill, and an attrition mill is preferable, and a pulverizing medium at that time is preferably made of zirconia or alumina. Slurry after grinding
The concentration is preferably 25% by weight or more in view of economy.

As a method for adjusting the viscosity of the zirconia slurry to a viscosity of 500 to 3000 cp using a thickener, and granulating and drying to obtain a granulated dry powder, a spray drying method is preferable. For improvement, the rotating disk method is particularly preferable. In order to maintain the granule strength after the spray drying, an organic binder may be added before and after the viscosity adjustment, and then the spray drying may be performed. The hot air temperature during spray drying is 50
The temperature is preferably from 300 to 300 ° C. In the case of an aqueous system, the temperature is more preferably from 150 to 230 ° C. The average particle size of the powder obtained by spray drying is preferably 100 μm or less.

A solution in which a binder such as polyvinyl alcohol, polyvinyl butyral, an acrylic monomer or a polymer is dissolved in water or a solvent is sprayed onto the zirconia granulated dry powder obtained as described above, and the powder is applied by spraying. By doing so, a zirconia granulated dry powder for thermal spraying of the present invention having an average granule crushing strength of 0.10 kgf / mm ² or more can be obtained. The addition of this binder
It may be carried out at the stage of the zirconia slurry after the above wet pulverization. Also, alcohols such as glycerin and sorbitol having a property of preventing the zirconia powder from being charged with the binder, such as glycerin and sorbitol; esters such as glycerin fatty acid ester and polyethylene glycol fatty acid ester; Anionic surfactants; nonionic surfactants such as polyoxyethylene fatty acid alcohol ether and polyoxyethylene stearamide; amphoteric surfactants such as alkyl imidazolium betaine and β-alkylaminopropionate; dimethyldialkylammonium chloride; If a cationic surfactant such as alkyltrimethylammonium chloride; a quaternary ammonium compound; an amine is used in combination, the charging of the zirconia powder can be prevented. Can be cormorants fluidity good thermal spray zirconia granulated and dried powder.

The above zirconia granulated dry powder is prepared by
A zirconia granulated and dried powder for thermal spraying having a high average granule crushing strength can also be produced by a method of baking at a temperature of 800 to 1500 ° C, preferably 1000 to 1300 ° C with a gas or the like. This heat treatment temperature is 800
If the temperature is lower than 0 ° C, the average granular crushing strength of the obtained powder is insufficient. On the other hand, if the temperature exceeds 1500 ° C, the crystallite diameter of the obtained powder exceeds 1200A, and in any case, the zirconia granules for thermal spraying of the present invention are used. Dry powder cannot be obtained. Also, when the heat treatment temperature is too high as in the latter, there is a place where sintering occurs partially in the granulated particles, and when the thermal spraying temperature is low, the unmelted portion remains and the adhesion effect of the thermal spray coating is reduced. As the porosity increases, the heat resistance and hardness of the film decrease.

[0023]

As described above, zirconia for thermal spraying according to the present invention.
The granulated dry powder has excellent fluidity as compared with conventional ones, and does not block even a powder tube having an inner diameter of 2 mm or less, and the supply amount per unit time is stable.
Therefore, it is possible to obtain a sprayed coating that is homogeneous, has high adhesion efficiency, and is excellent in wear resistance, corrosion resistance, conductivity, and the like.

By spraying this powder on a place requiring abrasion resistance, corrosion resistance or the like or a place requiring oxygen ion conductivity to form a coating, a sprayed coating having a longer life than that obtained by the conventional method can be obtained. It is expected to be obtained.

[0025]

EXAMPLE 1 Y in aqueous solution of zirconium oxychloride in terms of ZrO ₂ concentration 50 g / l of Y ₂ O ₃ to the total of ZrO ₂ and Y ₂ O _{3 2}
O ₃ was added so that the terms of 3 mol%, degree of hydrolysis is hydrolyzed until 90% under reflux, further A in aqueous solution
l ₂ O ₃ (AKP-30 manufactured by Sumitomo Chemical Co., Ltd .; the same applies hereinafter)
Was added to ZrO ₂ at 0.5 wt%, and then concentrated until the concentration in terms of ZrO ₂ became 300 g / l to obtain a hydrated zirconia sol. This sol was spray-dried at a hot air temperature of 150 ° C. using a rotary disk type spray-drying apparatus to obtain a spherical granulated gel powder. This gel powder was further heat-treated in an electric furnace under the conditions of 1300 ° C. and 2 hours in the atmosphere to obtain a partially stabilized zirconia granulated dry powder for thermal spraying.

Example 2 YCl ₃ was added to an aqueous solution of zirconium oxychloride having a concentration of 50 g / l in terms of ZrO ₂ by adding YCl ₃ to the sum of ZrO ₂ and Y ₂ O _3.
The solution was added so as to be 3 mol% in terms of ₂ O _3, and was hydrolyzed under reflux until the hydrolysis rate became 89%.
It was concentrated until the concentration in terms of rO ₂ became 310 g / l to obtain a hydrated zirconia sol. The sol was subjected to spray drying under the same conditions as in Example 1, to obtain a gel powder, 850 ° C. in an electric furnace under air atmosphere, and calcined under the conditions of 2 hours to obtain a zirconia powder, a Al ₂ O ₃ The amount of the zirconia powder is 0.
After adding 95 wt%, wet milling and mixing are performed by a ball mill for 24 hours to form a slurry having an average particle diameter of 0.7 μm, the viscosity is adjusted to 2,000 cp with 2 wt% aqueous ammonia, and spray-dried in 190 ° C. hot air to be partially stable. A spherical granulated powder made of zirconia was obtained. The powder was further heat-treated in an electric furnace under the conditions of 1200 ° C. and 2 hours in the atmosphere to obtain a partially stabilized zirconia granulated dry powder for thermal spraying.

Example 3 The amount of Al ₂ O ₃ added was 0.05 w with respect to the zirconia powder.
A partially stabilized zirconia granulated dry powder for thermal spraying was obtained under the same conditions as in Example 2 except that the content was changed to t%.

Example 4 YCl ₃ was added to an aqueous solution of zirconium oxychloride having a concentration of 50 g / l in terms of ZrO ₂ by adding YCl ₃ to the sum of ZrO ₂ and Y ₂ O _3.
It was added so as to be 3 mol% in terms of ₂ O ₃ and hydrolyzed under reflux until the hydrolysis rate became 90%. Further, a sodium hydroxide solution was added to the aqueous solution to obtain a hydrated zirconia sol. This sol was spray-dried under the same conditions as in Example 1,
A gel powder was obtained and 850 ° C. in an electric furnace under air atmosphere.
The zirconia powder was calcined under the condition of holding for 2 hours to obtain Al powder.
After 0.5 wt% of ₂ O ₃ was added to the zirconia powder, the mixture was wet-pulverized and mixed by a ball mill for 24 hours to form a slurry having an average particle diameter of 0.7 μm, and polyvinyl alcohol (a degree of saponification of 88 and a degree of polymerization of 500) was added to the slurry. 5% by weight based on the zirconia powder, a thickener (A-81 manufactured by San Nopco)
8) to adjust the viscosity to 1500 cp, and as an antistatic agent, an anionic surfactant (San Nopco's Nopco Santo R)
FA) was added to the above zirconia powder in an amount of 0.5% by weight and spray-dried in hot air at 180 ° C. to obtain a partially stabilized zirconia granulated dry powder for thermal spraying.

Example 5 Y ₂ O ₃ was used as a yttria source, and the added amount was Zr.
A stabilized zirconia granulated dry powder for thermal spraying was obtained under the same conditions as in Example 3 except that the content was 8 mol% with respect to the total amount of O ₂ .

Example 6 A stabilized zirconia powder (TZ-8Y manufactured by Tosoh Corporation) was added with A
l ₂ O ₃ was added to the stabilized zirconia powder in an amount of 0.05 wt.
%, And then pulverized and mixed for 8 hours with a vibration ball mill, and thereafter, under the same conditions as in Example 2, stabilized zirconia for thermal spraying
A granulated dry powder was obtained.

Example 7 The addition amount of Al ₂ O ₃ was set to 0.1 with respect to the stabilized zirconia powder.
A stabilized zirconia granulated dry powder for thermal spraying was obtained under the same conditions as in Example 6 except that the content was 9 wt%.

COMPARATIVE EXAMPLE 1 The spray-dried spherical granulated powder of partially stabilized zirconia obtained in Example 2 was directly used as a partially stabilized zirconia granulated dry powder for thermal spraying.

In the thermal spraying test, a waving phenomenon occurred within 2 to 3 minutes after the start of thermal spraying, the powder was not supplied stably, and a film having a uniform thickness could not be obtained.

Comparative Example 2 A partially stabilized zirconia granulated dry powder for thermal spraying was obtained in the same manner as in Example 2 except that Al ₂ O ₃ was not added.

Comparative Example 3 The amount of Al ₂ O ₃ added was 5 w
A stabilized zirconia granulated dry powder for thermal spraying was obtained under the same conditions as in Example 6 except that the content was changed to t%.

Comparative Example 4 A stabilized zirconia granulated dry powder for thermal spraying was prepared under the same conditions as in Example 6 except that the addition amount of Al ₂ O ₃ was 0.03 wt% and SiO ₂ was added together with Al ₂ O _3. Obtained.

Comparative Example 5 A partially stabilized zirconia granulated dry powder for thermal spraying was obtained under the same conditions as in Example 6 except that the heat treatment temperature was changed to 1400 ° C.

In the thermal spray test, a waving phenomenon occurred, the amount of powder supplied became unstable, and a film having a uniform thickness could not be obtained.

Table 1 shows the characteristics of the thermal spraying powders obtained in the above examples, and Table 2 shows the results of the thermal spraying test.

The average granule crushing strength is an average value measured by using a smile compression tester manufactured by Shimadzu Corporation for 10 granules close to the average particle size.

The thermal spraying is performed by plasma spraying at 50 mm × 6.
A blasted SUS304 specimen of 0 mm × 5 mm was subjected to a coating thickness of 200 μm (sprayer M
ETCO Inc., plasma gas Ar _{/ H} 2). Evaluation of the coating is based on microscopic observation of the cross section of the sprayed coating. The hardness of the film was measured with a micro Vickers hardness tester at a test load of 20
The measurement was performed under the conditions of 0 g and a load time of 10 seconds. Furthermore, JI
Ceramic spray test method for SH 8666 and JI
The thermal shock resistance was measured by repeating the operation of heating the test piece to 900 ° C., throwing it into water and cooling it ten times by a thermal shock test according to the quality standard of SH 8304.

The corrosion resistance test was performed using a coating obtained by spraying zirconia on the entire surface of SUS304. As a test method,
Performed under static immersion conditions for 20 days in a 30 wt% H ₂ SO ₄ solution at 100 ° C., measurement of the phase transition rate (monoclinic amount) of the film surface by X-ray diffraction method, and observation of the film surface by a scanning electron microscope Was done. The monoclinic amount was calculated using the following equation.

Monoclinic amount (%) = [{I _m (11-1) + I _m (111)} / {I _m (11-1) + I _m (111) + It _{, c} (111)}] × 100 _here, I m (11-1) X-ray intensity of 11 - side of the _monoclinic, I m (111) X-ray intensity of the 111 plane of monoclinic,
It _{, c} (111) is the X-ray intensity of the tetragonal and cubic 111 planes.

The conductivity was measured at 600 ° C. in the atmosphere for the partially stabilized region and 1000 ° C. in the atmosphere for the stabilized region.
The temperature was measured by a cold-coil plot method using complex impedance at ℃.

[0045] Table _{1 Y 2 O 3 SiO 2 Al} 2 O 3 crystallite size average grain average grain / ZrO ₂ diameter crushing strength molar ratio wt% wt% A μm Example 13 3 0.007 0.5 520 46 0.25 23 3 0.005 0.95 440 50 0.20 33 0.008 0.05 430 50 0.15 43 0.004 0.05 275 57 0.10 5 8 0.005 0.05 540 50 0.14 6 8 0.006 0.5 520 52 0.16 7 8 0.005 0.9 530 50 0.20 Comparative Example 13 0.005 0.01 270 58 0.04 23 0.005 0.01 450 50 0.14 38 0.0065 5 440 52 0.22 48 0.025 0.03 500 52 0.16 58 0.007 0.05 1500 45 0.20 Note) Unit of average granule crushing strength: kgf / mm ²

Table 2 Amount of Monoclinic Crystal Corrosion Resistance Hardness of Film Heat Resistant Conductivity % Evaluation Hv impact S / cm Example 120 ○ 780 ○ 0.08 230 ◎ 850 ○ 0.05 330 740 ○ 0.001 425 ○ 760 ０．００ 0.002 50 ◎ ８００ 800 ０．０ 0.096 ○ 820 ○ 0.047 ○ ◎ 870 ０．９ 0.9 Comparative Example 175 × 470 ０．００ 0.002 270 720 ０．００ 0.002 30 820 006 40 × ７００ 700 ９ 0.0095 ○ △ 750 不可能 Unavailable Note) Corrosion resistance test ：: No change in film ：: There is film corrosion 評 価: Evaluation of film ◎: Uniform thickness and extremely small pores ：: Thickness Uniform and few pores Δ: Non-uniform thickness but few pores Thermal shock test ○: No peeling at all △: Peeled in 5 to 10 times

Claims (1)

(57) [Claims] The present invention mainly comprises zirconium oxide, yttrium oxide and Al ₂ O _{3 having a} crystallite diameter of 1200 A or less, and has a molar ratio of Y ₂ O ₃ / ZrO ₂ of from 1.5 / 98.
/ 88, wherein the amount of Al ₂ O ₃ with respect to the total of zirconium oxide and yttrium oxide is 0.05 wt% or more and less than 1.0 wt%, and the amount of SiO ₂ with respect to the total of zirconium oxide and yttrium oxide is 0.01w
t% or less, and the average granule crushing strength is 0.10 k
A zirconia granulated dry powder for thermal spraying, having a gf / mm ² or more.