JP2988983B2 - Ceramic cured film and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention relates to a ceramic which has a low heating temperature, can reduce the number of repetitive treatments, and can be formed by firmly applying a reinforced ceramic coating to a metal surface. The present invention relates to a cured film and a method for producing the same.

(Prior Art) There are various methods for coating a metal surface with a ceramic, and a method of forming a ceramic slurry by applying a heating and firing treatment is one of the methods. A method in which powder is mixed and applied as a slurry is used as an effective means for forming a ceramic film. However, in this method, the heating and sintering temperature is 316 ° C. or higher, and the heating and sintering temperature in consideration of workability is relatively high as 450 to 550 ° C., and a high temperature is required. In order to obtain the desired hardness and denseness, there is a problem that ten or more repetitive treatments are required. As a method for improving these, for example, a method of using trivalent organic chromium (for example, chromium acetate), a method of reducing hexavalent chromic acid with formic acid, tartaric acid, sodium sulfite, sodium hydrogen sulfite, phosphoric acid, etc. Is used alone to increase the effect of reducing the number of times of impregnation.

(Problems to be Solved by the Invention) However, since trivalent organic chromic acid does not have an oxidation-reduction action, it only fills the pores of the ceramic film and cannot improve the hardness. In the method using formic acid or tartaric acid, the reducing action (reaction of CrO ₃ → Cr ₂ O ₃ )
Occurs at a low temperature, but does not contribute to improving the properties of the ceramic coating due to the decomposition component of the organic acid. Furthermore, in the method using phosphoric acid alone, a phosphoric acid product is formed first in order to perform the treatment multiple times, and it is not suitable for performing a subsequent densification treatment. There are problems with each method.

An object of the present invention is to provide a method capable of reducing the number of treatments, lowering the heating and firing temperature, strengthening the film, and firmly applying the film.

(Means for Solving the Problems) As a result of repeated studies to solve the above-mentioned problems and achieve the above-mentioned object, the present inventors have found that when a ceramic slurry is prepared, a mixture of chromic acid and phosphoric acid is concentrated. The inventors have found that the object can be achieved by using a liquid and repeating the impregnation-firing treatment of the obtained ceramic film with a mixed concentrated liquid of chromic acid and phosphoric acid, thereby solving the present invention.

That is, the first embodiment of the present invention relates to a ceramic in which at least one of ceramic particles and metal particles is dispersed in a matrix in which the ratio of the molecular weights of phosphorus oxide and chromium oxide is 1: 0.48 to 2.7. It is characterized by a cured film.

In a second embodiment of the present invention, a mixed concentrated solution comprising a concentrated solution of chromic acid and phosphoric acid is added to a metal surface with ZrO ₂ , Al ₂ O
_{3, Cr 2 O 3, TiO} 2 or oxide such as SiO _2, nitrides such as Si ₃ N ₄ or ZnN, carbides and Co, such as SiC or Cr ₃ C _2, Zr or
A ceramic slurry formed by mixing at least one kind of metal powder such as Mo is applied to form a film, and a heat treatment is performed on the ceramic film forming step. And a film hardening treatment step of repeating heat treatment at least once by impregnating with an impregnating liquid consisting of a concentrated liquid mixture of phosphoric acid, 0.48 to molecular weight ratio
It is characterized by the method for producing a ceramic cured film described in 2.7.

(Operation) The metal materials used in the present invention include iron, steel,
Aluminum or a material having a porous surface on which thermal spraying or chromium plating has been applied or an anodic oxide film has been formed.

Chromic acid is obtained by dissolving chromium trioxide in water,
Used as a concentrated aqueous solution adjusted to 1.65, phosphoric acid is 75
Commercial products with a concentration of ~ 88% can be used.

As raw materials for slurry, ZrO ₂ , Al ₂ O ₃ , Cr ₂ O ₃ ,
Oxides such as TiO ₂ and SiO ₂ , nitrides such as Si ₃ N ₄ and ZnN, Si
Uses ceramic powder consisting of carbides such as C and Cr ₃ C ₂ or metal powders such as Zr, Co and Mo. Each has a purity of about 95% and a maximum particle size of 20 μm
Hereinafter, those having an average particle size of 1.4 μm are preferable, and at least one of them is selected and used.

As the mixed concentrated solution of chromic acid and phosphoric acid, a mixture of the above chromic acid aqueous solution at a ratio of 0.48 to 2.7 molecular weight with respect to one molecular weight of the phosphoric acid is used, and the above ratio is further
It is preferably 0.96 to 1.36. In this case, if the ratio of the molecular weight of chromic acid is less than 0.48 in the mixed concentrated liquid, the viscosity becomes high, and the impregnation of fine pores formed in the film is not performed smoothly. However, further increase in hardness cannot be expected.On the other hand, when the ratio of the molecular weight of chromic acid exceeds 2.7, the catalytic effect of phosphoric acid decreases, and a higher temperature than the calcination temperature is required. Unless the number of treatments is increased in such a case, it is difficult to form a film having desired characteristics.

By the way, phosphoric acid itself is a polymer from dehydration condensation and blending with metal ions It forms a structure and has the effect of reducing chromic acid. It has a structure and forms a strong cured film.

In the ceramic film forming step, the ceramic raw material is added to the mixed concentrated liquid thus adjusted at a rate of 1.5 kg to 2.5 kg / and stirred sufficiently to form a ceramic slurry, as has been conventionally performed. The order is not limited), and this is applied to the surface of the material on the metal surface by brushing, spraying, or dipping the work in a slurry, and then baked at 200 to 300 ° C. for 30 to 120 minutes to form a ceramic. Form a film. Next, in the film hardening treatment step, on the ceramic film, the mixed concentrated liquid is impregnated with a brush, sprayed or impregnated by dipping the work in the liquid, and baked at 200 to 300 ° C. for 30 to 150 minutes. . This impregnation-firing treatment is repeated at least once, and is preferably repeated 3 to 5 times, and it is usually sufficient to repeat the treatment 5 times.

According to the method of the present invention, as described above, the baking temperature in the film hardening treatment step can be as low as 200 to 300 ° C., and the number of times of impregnation can be increased by increasing the number of components remaining in one pore. Is sufficient to suppress the generation of a mixed gas of a water component and CrO ₃ , but such an effect is attributable to the effect of phosphoric acid as a catalyst for the low-temperature reduction of chromic acid and the effect of CrO 3 _This is because when ₃ is converted to Cr ₂ O ₃ , a chemical change occurs with phosphoric acid and an organic oxidative bond, and it is an effective means for obtaining a hardening and filling effect of the ceramic film because it remains as a film. it is conceivable that.

When the ratio of the molecular weight of chromium oxide to the molecular weight of phosphorus oxide was examined for the film obtained after the film hardening treatment, the ratio of the molecular weight of chromic acid to phosphoric acid in the above-mentioned concentrated mixture remained almost unchanged. Was.

(Example) Next, an example of the present invention will be described.

Example 1 215 g of aluminum oxide (purity 98%), 510 g of silicon dioxide (purity 92.5%), 455 g of chromium oxide (purity 99.3%),
A ceramic slurry was prepared by stirring 55 ml of chromic acid (specific gravity 1.64) and 45 ml of 88% H ₃ PO ₄ for 30 minutes using a stirrer. This slurry was degreased and blasted S25C
On the disk surface, spray-coated to a thickness of 150 to 200 μm, baked at 280 ° C. for 60 minutes to form a ceramic film, and then polished to a film pressure of 85 μm, and then a chromic acid having a specific gravity of 1.6 272 ml of concentrated liquid and commercially available 85% H ₃ PO
Suction impregnation using the mixed concentrate with ₄ 256 ml as impregnating liquid, followed by baking at 280 ° C. for 60 minutes. This impregnation-firing treatment was repeated 5 times to obtain a ceramic cured film in which particles of aluminum oxide, silicon dioxide, and chromium oxide were dispersed in a matrix having a molecular weight ratio of chromium oxide to phosphorus oxide of 1: 0.86. .

The hardness of the obtained ceramic coating is such that the surface hardness is the average Hv
1214.

Example 2 A ceramic slurry comprising 420 g of stabilized zirconium oxide (purity 94.0%), 70 g of silicon dioxide (purity 99.3%), 250 ml of ZnO 35 g chromic acid concentrate (specific gravity 1.65) and 250 ml of H ₃ PO ₄ was prepared. A 5 μm thick nickel-plated aluminum material is coated by dipping in a slurry and baked at 250 ° C. for 90 minutes to form a ceramic film, and then mixed with 200 ml of a chromic acid concentrated solution having a specific gravity of 1.62. The solution was applied as an impregnating solution and baked at 250 ° C for 90 minutes twice.
1.62) 600 ml and Similarly impregnation as impregnation liquid mixture concentrate consisting of 85% H ₃ PO ₄ 500ml - underwent three burning treatment, a total of 5 times impregnation - performs firing process, chromium oxide and phosphorus oxide A ceramic cured film was obtained in which particles of stabilized zirconium oxide, silicon dioxide, and ZnO were dispersed in a matrix having a molecular weight ratio of 1.33: 1 to the product.

The hardness of the obtained ceramic coating is such that the surface hardness is the average Hv
It was 1008. This film was heated at 300 ° C for 30 minutes and dropped into water, but no peeling of the film was observed.
Excellent adhesion was exhibited.

(Effect of the Invention) In the present invention, since the ceramic effect film is formed by dispersing ceramic particles and / or metal particles in a matrix in which chromium oxide and phosphorus oxide are mixed, the hardness of the film is high and the film is dense. Extremely excellent in heat and corrosion resistance.

Further, a ceramic film is formed by using a ceramic slurry obtained by mixing a ceramic raw material with a mixed solution of chromic acid and phosphoric acid, and a mixed solution of chromic acid and phosphoric acid is further impregnated on this film. Since the impregnation-sintering process is performed repeatedly using the conventional method, the sintering temperature is 450 to 550 ° C in the conventional method, but the process can be performed at a low temperature of 200 to 300 ° C. The number of times is also 10 in the conventional method
Although several treatments were necessary, about five treatments could be sufficient. Therefore, deterioration and deformation of the base material were reduced, and deposition on a low-melting base material such as aluminum became possible. Ingredients
A remarkable effect is observed such that generation of a mixed gas with CrO ₃ is suppressed, the working environment can be improved, and a film that is firmly bonded can be formed.

Claims (3)

(57) [Claims] 1. A hardened ceramic coating, wherein at least one of ceramic particles and metal particles is dispersed in a matrix in which the ratio of the molecular weights of phosphorus oxide and chromium oxide is 1: 0.48 to 2.7. 2. A mixed concentrated solution comprising a concentrated solution of chromic acid and phosphoric acid on a metal surface, wherein ZrO ₂ , Al ₂ O ₃ , Cr ₂ O ₃ , TiO ₂ or Si
Oxides such as O _2, nitrides such as Si ₃ N ₄ or ZnN, SiC or C
A ceramic film forming step of applying a ceramic slurry formed by mixing at least one of carbides such as r ₃ C ₂ and metal powders such as Co, Zr or Mo to form a film, and performing a heat treatment, A ceramic hardening film, wherein the ceramic hardening film formed in the preceding step is impregnated with an impregnating liquid comprising a concentrated solution of chromic acid and phosphoric acid, and heat-treated at least once. Manufacturing method. 3. The method for producing a cured ceramic film according to claim 2, wherein the ratio of the molecular weight of the aqueous solution of chromic acid to one molecular weight of phosphoric acid in the concentrated concentrate is 0.48 to 2.7.