JPH05117857A - Coating member - Google Patents

Abstract

PURPOSE:To prevent from peeling and destruction of a coating material by making a surface part of a substrate porous and by forming a dense layer made by impregnating the coating material into the pore of the surface of the porous layer to make a coating layer. CONSTITUTION:The porous layer 2 is formed on the substrate 1. The porous layer 2 is easily formed by machining or chemical dissolution. The coating material is impregnated into the pore of the porous layer 2 to form the dense layer 3 and furthermore the coating layer 4 is formed from the coating material. Adhesive strength of the substrate 1 with the coating material is excellent and stripping, destruction or the like are prevented and excellent durability and dimensional accuracy is attained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a covering member having a base material and a layer of a covering material laminated on at least one surface thereof, and particularly suitable for use in a portion to which a mechanical external force is applied,
More specifically, the present invention relates to a covering member in which peeling, breakage and the like of the coating substance is reduced by improving the adhesion between the base material and the coating substance, and durability and dimensional accuracy are improved.

[0002]

2. Description of the Related Art In order to protect a base material from external physical and chemical effects, a cover member having a base material coated with a substance capable of withstanding these functions is conventionally known. Widely used from. However, in such a covering member, if the adhesion between the base material and the coating layer is poor, peeling of the coating layer from the base material and destruction of the coating layer occur,
Therefore, the base material may not be sufficiently protected.

Therefore, as a method for improving the adhesion between the base material and the coating layer, for example, in Japanese Unexamined Patent Publication No. 2-129366, a carbon-based base material used as a structural material for the outer wall portion of the body of an aircraft or space shuttle is used. S to improve acid resistance
When forming a coating layer made of iC or Si ₃ N _4, there has been proposed a method of forming an intermediate layer made of TiC or Ti (C · N) between the coating layer and the substrate. However, in such an improvement method, the process is complicated because the intermediate layer is formed, and the thickness of the entire coating layer (the coating layer and the intermediate layer) is increased, resulting in cost and labor.

In JP-A-48-26597, there is disclosed a covering member in which the distortion of the covering layer is relaxed by reacting the surface of a graphite substrate with Si and then forming a SiC layer having no pinhole by chemical vapor deposition. Proposed. However, in this case, since the coating layer is a compound of the base material and another substance,
The coating material is limited, and the formation of the coating layer becomes very difficult when the substrate does not react easily.

Further, Japanese Patent Application Laid-Open No. 2-164873 proposes a method for improving the adhesion between the base material and the coating layer by processing the surface of the graphite base material to provide irregularities. When the method is applied to high hardness substrates,
The surface processing requires cost and labor.

The present invention has been made in view of the above circumstances.
An object of the present invention is to provide a covering member having excellent adhesion and excellent dimensional accuracy.

[0007]

Means for Solving the Problems and Actions The inventors of the present invention have conducted extensive studies to achieve the above object, and as a result, have a coating having a base material and a layer of a coating material laminated on at least one surface of the base material. In the member, the base material has a porous layer in which at least the surface portion of the surface to be coated of the base material is made porous, and the coating substance is infiltrated into the pores of the surface of the porous layer or the entire porous layer. By forming a densified layer and forming a coating layer consisting only of the coating substance on the surface of the densified layer,
The obtained covering member has a base material and a porous layer skeleton, a densified layer and a coating layer which are continuous bodies, and when the base material is coated with the coating material, the coating material penetrates into the pores of the porous layer. By doing so, the formed densified layer provides excellent adhesion between the coating layer and the base material, and the combination of the base material and the coating material can be freely selected in consideration of the difference in thermal expansion. It was also found that by making the surface of the base material porous, the outer shape of the base material finished to the specified dimensions is maintained as it is, so that the dimensional accuracy does not decrease, and the base material can be easily manufactured. The present invention has been completed.

The present invention will be described in more detail below. The coated member of the present invention is a coated member having a base material and a layer of the coating material laminated on at least one surface of the base material.
A porous layer is formed by making at least the surface portion of the target surface of the base material porous, and forming a densified layer by infiltrating the coating substance into the pores or the entire porous layer of the porous layer surface, The densified layer has a coating layer formed on the surface of the densified layer.

FIG. 1 illustrates an embodiment of such a covering member of the present invention, showing a cross section of the covering member in which a densified layer is formed by infiltrating a covering substance into the surface of a porous layer,
In the figure, 1 is a substrate, 2 is a porous layer, 3 is a densified layer, and 4 is a coating layer.

Here, the base material is not particularly limited as long as the surface can be made porous.

The method for making the surface of the base material porous to form the porosity is either machining, for example, a method of removing one of the constituents of the composite material, a method of dissolving or decomposing with an acid or alkali, etc. Can also be used. For example, when a reaction-bonded silicon carbide product or a silicon-impregnated recrystallized silicon carbide product is used as a base material, a porous silicon layer can be easily formed by removing the metallic silicon portion of the surface layer by acid treatment. it can.

The thickness of the porous layer is selected depending on the base material and the coating material. For example, the base material is SiC-Si and the coating material is S.
If it is iC, it is preferably 500 μm or less, and particularly preferably 100 to 10 μm. The proportion of pores in the porous layer is preferably 5 to 50% by volume of the entire porous layer. When the proportion of pores exceeds 50% by volume, thermal stress is generated due to the resistance of the porous layer pores to the heat conduction of the pores, and the porous layer is easily broken, and
Destruction may occur easily due to mechanical shock.

As the coating substance, a substance having a small difference in coefficient of thermal expansion from the base material is preferable. For example, when a silicon carbide material having free silicon is used as the base material, silicon carbide can be used.

The thickness of the densified layer formed by infiltrating the coating substance into the pores of the porous layer is preferably 10 μm or more. When the thickness of the densified layer is less than 10 μm, improvement in adhesion between the base material and the coating layer may not be recognized in some cases.

The coating method is not particularly limited, but it may be a chemical vapor deposition method (CVD method), a method of immersing in a coating material melt, or a method of immersing in a liquid precursor that easily chemically changes to the coating material. In the case of silicon carbide, for example, in the case of silicon carbide, a method of diffusing and precipitating a gas species by a CVD method on a substrate placed in a sufficiently depressurized reaction furnace to perform a SiC coating treatment, and SiO ₂ For the coating, a method of immersing in tetraethyl orthosilicate (TEOS) and performing a SiO ₂ coating treatment by a sol-gel reaction can be adopted.

[0016]

EXAMPLES The present invention will be specifically described below by showing Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[Examples, Comparative Examples 1 and 2] Three reaction-bonded silicon carbide substrates having a diameter of 30 mm and a thickness of 10 mm whose surfaces were ground were prepared, and two of them were dipped in an HF / HNO ₃ solution. Adjust the reaction time, temperature and solution concentration to obtain a thickness of 50μ
m and 650 μm, respectively, were formed (Sample 1: Example, Sample 2: Comparative Example 1).

Each of these three substrates was coated with silicon carbide by the CVD method under general conditions. The thickness of each coating layer was 100 μm.

As described above, the porous layer 50 μm (the portion where the coating substance has not entered is 40 μm), the densified layer 1
Sample having a structure of 0 μm, coating layer 100 μm (Sample 1), porous layer 650 μm (640 μm in a portion where the coating substance has not entered), densification layer 10 μm, coating layer 100
A sample having a structure of μm (Sample 2) and a sample in which the surface-ground substrate was directly coated (Sample 3, Comparative Example 2) were obtained.

A thermal shock test was performed on these three samples.
In the test, after holding Samples 1 to 30 in an electric furnace kept at 270 ° C. for 30 minutes, the samples were put into water at 20 ° C., and cracks, peeling, etc. in the film were visually observed. If there was no abnormality, the water content was sufficiently removed, and the sample was again placed in an electric furnace to repeatedly undergo thermal shock. When a thermal shock of ΔT = 250 ° C. was applied to each sample, the coating layer of sample 2 was broken. Then, when the same thermal shock was repeatedly applied to each of Samples 1 and 3, the coating layer of Sample 3 was destroyed by 20 impacts, but the coating layer was not damaged in Sample 1, and the adhesion was good. Met.

[0021]

EFFECT OF THE INVENTION The coated member of the present invention has good adhesion between the base material and the coating substance, is free from peeling and destruction of the coating substance, and is excellent in durability and dimensional accuracy.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of a covering member according to the present invention.

[Explanation of symbols]

 1 base material 2 porous layer 3 densification layer 4 coating layer

Claims (1)

[Claims] 1. A covering member comprising a base material and a layer of a coating substance laminated on at least one surface of the base material, wherein the base material makes at least a surface portion of a surface to be coated of the base material porous. A porous layer is provided, and a densified layer in which the coating substance is infiltrated into the pores or the entire porous layer on the surface of the porous layer is formed, and a coating layer consisting of the coating substance alone is formed on the surface of the densified layer. A covering member characterized by being formed.