JPH0318487Y2 - - Google Patents

Description

[Detailed explanation of the idea]

[Industrial Application Field] The present invention relates to a member having a ceramic coating, and particularly to a member in which the coating has outstanding properties such as strength and corrosion resistance. [Prior Art] Ceramics have properties such as high temperature resistance, high corrosion resistance, and high hardness that are not found in conventional metal materials or synthetic resin materials. However, as is well known, it has low bending strength, low tensile strength, and brittleness, which limits its use as an independent member. Therefore, using ceramics as a coating material,
BACKGROUND ART Conventionally, it has been carried out to impart excellent properties such as high temperature resistance, high corrosion resistance, and high hardness to the surface of a member. As coating methods for forming such ceramic coatings, vapor deposition methods such as CVD as well as thermal spraying are known. [Problems to be solved by the invention] Since thermal spraying is simple and highly practical, it is used for ceramic coating of turbine blades, etc., but there is a problem that it is difficult to obtain a dense ceramic layer. The CVD method has the advantage of being able to obtain a highly pure film, but on the other hand, when the film thickness is large, the precipitates tend to form columnar crystals that grow perpendicular to the film surface. There is a problem that the value decreases. In other words, if the film produced by CVD treatment contains many columnar crystals grown perpendicular to the film surface,
Grain boundaries also become oriented in a direction perpendicular to the film surface. Then, when stress in a direction parallel to the film surface is applied to the film, the stress concentrates on the grain boundaries of the columnar crystals in the film, making it easier for fracture to start from these grain boundaries. Therefore, in ceramic films formed by conventional CVD methods, it has been difficult to form large film thicknesses with excellent mechanical properties. [Means for Solving the Problems] The present invention provides that when the surface of a member is coated with one or more layers of ceramic coating, whiskers grow into the layer from the lower interface of the layer. It is characterized by [Function] In the member having the ceramic coating of the present invention, the coating can be reinforced by the whiskers growing from the layer interface. In addition, the whiskers exert a mechanical or thermal buffering effect. Furthermore, the growth of columnar crystals can be suppressed by the formation of whiskers, and in combination with the above-mentioned effects, even more excellent mechanical properties are exhibited. [Examples] Examples will be described below with reference to the drawings. FIG. 1 is a sectional view of a member having a ceramic coating according to an embodiment of the present invention. Reference numeral 1 denotes a member (base material), which is made of a material such as metal or ceramics. The surface of this member 1 has one or two layers.
A ceramic coating 2 of more than one layer is formed. In this example, three layers of ceramic coating 3,
4 and 5 are provided. The ceramic coatings 3 to 5 have lower interfaces 3a, 4a, and
It includes whiskers 6 growing from 5a toward the inside of the layer (inside the matrix 7). To form the coatings 3 to 5 including such whiskers 6, for example, the following procedure is performed. First, as shown in FIG. 2, CVD treatment is performed on the surface of the member under whisker precipitation conditions to grow whiskers 6. Next, a coating is formed
After changing to CVD conditions, CVD treatment is performed to remove the ceramic coating matrix 7 from the surface of member 1.
grow. (See FIG. 3) After the matrix 7 has grown to fill the whiskers 6, the CVD conditions are returned to the whisker growth conditions again, and the whiskers 6 are grown on the formed ceramic film 3. (See Figure 4) After the whiskers 6 have grown on the ceramic film 3, the CVD conditions are changed to film forming conditions, and the matrix 7 is grown on the ceramic film 3, and the whiskers formed on it are Try to fill in the . By repeating this process of whisker growth→matrix formation, multiple layers of ceramic coatings can be easily formed. In addition, in order to control the CVD conditions to whisker growth conditions or film formation conditions, the concentration of CVD gas and
The CVD reaction temperature conditions may be changed appropriately. In general, increasing the temperature or decreasing the supersaturation degree of CVD gas strengthens the whisker growth tendency, and vice versa.
By increasing the degree of supersaturation of the CVD gas, the tendency to generate polycrystalline particles, that is, to form a film, increases.
Therefore, by appropriately setting and changing the CVD gas concentration and CVD reaction temperature, it is possible to alternately grow whiskers and form a film. Ceramic coating 2 formed in this way
As mentioned above, the mechanical properties of the member having the above-described structure are extremely excellent due to the reinforcing effect of the whiskers 6 on the coatings 3 to 5 and the mechanical and thermal buffering effects of the whiskers 6. Furthermore, when forming ceramic coatings according to the process described above, there is little formation of katinate crystals. That is, when a film is generally formed by CVD processing, Katsura crystals tend to grow in the latter half of the CVD process when the film thickness gradually increases. In the above process, the formation of the matrix 7 is temporarily interrupted when the whiskers 6 are buried, and after the whiskers 6 are grown thereon, the formation of the film (matrix 7) is restarted. In this way, the formation of matrix 7 is
It is not continuous, but intermittent, so
At the time of interruption, the growth of the Katsura crystal is stopped, and the layer interface 3a,
Above 4a and 5a, almost no katinate crystals grow. In addition, when the whiskers 6 grow randomly in three-dimensional directions, the crystal growth of the matrix 7 in one direction is restricted, and it is presumed that this also suppresses the development of Katsura crystals. Further, due to the crystal grain growth suppressing effect of the whiskers 6, the obtained matrix 7 becomes finely crystalline, and its properties such as mechanical strength and corrosion resistance are further improved. In the illustrated embodiment, three layers of ceramic coating are formed, but in the present invention, one layer of ceramic coating is formed.
A ceramic coating may be formed in one layer, two layers, or four or more layers. In the present invention, in order to suppress the growth of Katsura crystals, when forming a thick coating, it is preferable to form a plurality of layers of ceramic coating. In the present invention, the material of the ceramic coating is not particularly limited, and various ceramics such as oxides, nitrides, and silicides can be used for both the whiskers 6 and the matrix 7.
Furthermore, the whiskers 6 are not limited to ceramics, and heat-resistant metals having heat-resistant and corrosion-resistant properties can also be used. In the present invention, the whiskers 6 and the matrix 7 may be made of the same material or may be made of different materials. However, when using different materials, it is preferable to use materials that are compatible with each other or materials that have similar coefficients of thermal expansion. Next, specific examples will be described. Example 1 2 mm x 3 mm x 40 mm SiC obtained by pressureless sintering
After growing whiskers on the base material under the following SiC whisker growth conditions, a SiC film was subsequently grown under the following SiC film forming conditions, and this process was repeated three times. SiC whisker growth conditions CVD gas: SiCl ₄ = 8 c.c./min H ₂ = 2000 c.c./min C ₃ H ₈ = 2 c.c./min Temperature: 1500°C Total pressure: 300 torr Time: 40 minutes SiC coating Formation conditions CVD gas SiCl ₄ = 200c.c./min H ₂ = 1200c.c./min C ₃ H ₈ = 60c.c./min Temperature: 1500℃ Total pressure: 150torr Time: 30 minutes As a result, the first As shown in the figure, SiC whiskers grow from the lower interface in each layer, and the gaps between the whiskers are filled with SiC microcrystals, forming a dense 3-layer structure.
A component with a layered SiC coating (thickness 800 μm) was obtained. Regarding the 10 members obtained in this way,
A four-point bending test was conducted at room temperature in accordance with JIS R 1601, the average value was determined, and the results are shown in Table 1. Comparative Example 1 The SiC film formation conditions of Example 1 were applied to the same SiC substrate as used in Example 1 (however, the time was 90 days continuously).
It was a minute. ) on which a SiC film (thickness: 800 μm) was formed, the average value of the four-point bending strength was determined in the same manner as in Example 1, and the results are shown in Table 1.

[Table] From Table 1, it is clear that according to the present invention, a member having a high-strength SiC coating is provided despite the thickness of 800 μm. [Effects] As detailed above, the member provided by the present invention has extremely excellent properties such as high mechanical strength and thermal shock resistance, in addition to the inherent properties of ceramics such as heat resistance, high hardness, and corrosion resistance. Covered with a ceramic coating. By providing a plurality of layers of this coating, a thick film coating with these excellent properties can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a portion near the surface of a member according to an embodiment of the present invention, and FIGS. 2, 3, and 4 are sectional views each illustrating a method of forming a ceramic coating. 1... Member (base material), 3, 4, 5... Ceramic coating, 6... Whisker, 7... Matrix.

Claims (1)

[Scope of utility model registration request] A member having one or more layers of ceramic coating on the surface of the member, which has a ceramic coating characterized by the presence of whiskers growing from the lower interface in the ceramic layer. Element.