JPH0213028B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to high melting point inorganic compounds, such as carbides, borides, The present invention relates to a method for applying thick coatings of silicides, phosphides, sulfides, nitrides, oxides, and composite compounds thereof to the surfaces of various metal or ceramic molded bodies.

BACKGROUND TECHNOLOGY Conventionally, thermal spraying, CVD, and PVD methods have been used to coat the surface of a metal or ceramic molded body with a high-melting point inorganic compound. Although these methods are effective for coating thin films because it takes time to form a coating layer, they are not suitable from the viewpoint of work efficiency as techniques for coating thicker layers of 1 mm or more. Further, as a method for forming thick ceramics on the surface of a metal or ceramic molded body, there is a method of bonding preformed ceramics. These methods include inserting a bonding insert material between ceramic molded bodies and bonding by heat treatment, or brazing, but it is necessary to manufacture the ceramics to be bonded in advance. This method is not necessarily satisfactory when the joint surface has a complicated shape.

By igniting a small portion of the surface layer of the metal-nonmetal mixture to a temperature sufficient to initiate the combustion process, in which case the propagation of the combustion zone from one layer to the other occurs as a result of the reaction between the starting components. Methods are known to initiate reactions between metals and non-metals (based on released heat and heat transfer) to synthesize high melting point inorganic compounds. (Special Publication No. 56-27441) The reaction proceeds in a thin layer of the mixture known as the combustion zone, where the temperature is 2000
The temperature is as high as ~4000K. The combustion zone spreads through the mixture at a speed of 1-15 cm/s. A method has been proposed in which a high-density molded body is obtained by compressing such a high-melting-point inorganic compound using centrifugal force, static gas pressure, or hydrostatic pressure during synthesis. (For example, patent application 1973-
5212, Patent Application No. 57-500289) Problems to be Solved by the Invention The purpose of the present invention is to provide a method for synthesizing a high melting point inorganic compound as the combustion zone progresses by starting a reaction by locally igniting a metal-nonmetal mixture. An object of the present invention is to provide a method for producing a thick coating of a high melting point inorganic compound at a low cost using a device with a simple structure, by simultaneously synthesizing the high melting point inorganic compound and bonding it to the surface of a metal or ceramic molded body. .

Means for Solving the Problems According to the present invention, at least one metal or metal compound selected from the second, third, fourth, fifth, sixth and seventh periods of the periodic table, a nonmetallic element C,
At least one of B, Si, P, S, or azide is thoroughly mixed, and the mixture is pressurized and compressed onto the surface of a metal or ceramic molded object to be coated, and the mixture is heated under vacuum or an inert atmosphere of 0.1 to 200 atm. The end of the mixture is ignited by ignition to initiate an exothermic reaction, and under conditions where the reaction is further propagated by heat transfer to the next layer of the mixture, the synthesis reaction proceeds in a self-propagating manner approximately in the direction of pressure. develop in parallel directions,
This purpose can be achieved by bonding to the surface of a metal or ceramic molded body at the same time as synthesis by utilizing the stretching force of a compression spring.

The joining in the method of the present invention utilizes a joining method whose main factor is a mechanical action called an anchoring effect. The high melting point inorganic compound to be coated is one that generates high heat during the synthesis reaction (e.g. titanium diboride _TiB2 or zirconium diboride).
ZrB ₂ ), and if the metal or ceramic molded object to be coated has low thermal conductivity or has a low melting point, and the surface layer will partially melt due to high heat, the high melting point to be coated is particularly important. There is no need to provide a separate layer of a high exothermic mixture between the inorganic compound and the metal or ceramic molded body to be coated. However, there are conditions in which the surface layer partially melts because the high melting point inorganic compound to be coated generates little heat during the synthesis reaction, or the metal or ceramic molded object to be coated has good thermal conductivity or has a high melting point. If the layer does not exist, it should be provided in advance between the high melting point inorganic compound to be coated with the high exothermic mixture layer and the metal or ceramic molded object to be coated, and a layer formed as a result of the reaction of the high exothermic mixture layer during the synthesis reaction. It is necessary to use high heat for bonding. Further, by processing the surface of the metal or ceramic to be coated in advance to have an uneven surface instead of a flat surface, it is possible to effectively coat the surface with high bonding strength.

The feature of the method of the present invention is that the metal or ceramic molded object to be coated has a metal layer on the surface thereof.
Non-metallic mixtures are compressed under pressure, vacuum or 0.1~
In a container purged with 200 atm inert gas,
The end of the mixture is ignited with high heat to start an exothermic reaction, and a self-propagating synthesis reaction progresses in a direction almost parallel to the direction of pressure, and the reaction reaches the surface of the metal or ceramic molded object to be coated. The point is that the pressure necessary for bonding is continuously applied by the tension force of the compression spring so that the composite and the metal or ceramics are firmly bonded when the composite is bonded to the metal or ceramic. Therefore, the role of the compression spring is to enable the joining of the powder mixture and the composite, and the compression spring must have a spring constant, compressive strength, and extension length that meet this purpose. . The optimum conditions for these conditions can be determined depending on the shrinkage distance of the high melting point inorganic compound to be coated, the compressed cross-sectional area, the material of the metal or ceramic to be coated, etc.

The ignition method in the method of the present invention is such that two parts are placed in contact with the end of the mixture in order to ensure ignition and to allow the reaction to progress in a direction substantially parallel to the direction of pressurization and compression.
An ignition jig is used in which conductive wires made of tungsten or an equivalent high-melting point metal are arranged, and a platinum wire with a diameter of 0.2 mm, for example, is connected between the two conductors. By passing an electric current through the tungsten wire, the platinum wire is heated by electricity, or by passing an electric current, the platinum that evaporates and scatters becomes a path for the subsequent current, which gives the mixture intense heat and ensures reliable ignition. lead to. Instead of connecting a thin wire between the two conductive wires, it is also possible to pass a high-frequency current through the ionized gas and apply intense heat to the mixture using the ionized gas as the current path. By providing such a reliable ignition method, the method of the present invention becomes extremely practical as a thick coating method for high-melting point inorganic compounds.

Effects of the Invention According to the method of the present invention, carbides, borides, silicides, phosphides, sulfides of metals selected from the second, third, fourth, fifth, sixth and seventh periods of the periodic table, The method of the present invention is highly practical, as it is possible to coat the surface of metal or ceramics with nitrides, oxides, and their composite compounds in a short time using extremely simple equipment and operations. . Furthermore, according to the method of the present invention, it is possible to coat almost any metal or ceramic surface. The thickness of the coating layer can be 1 mm or more, and there is virtually no limit to the maximum thickness. The area that can be coated at one time is 1 mm ² or more, and by devising the equipment, there is virtually no limit to the area. By appropriately considering the optimum method, it is possible to cope with cases where the coating surface has a complicated shape. Next, the present invention will be explained in more detail with reference to Examples.

Example 1 As shown in Figure 1, a mold made of chromium-molybdenum steel heat-insulated with graphite was placed in a container that could be evacuated, and titanium and boron powders were placed in the mold at a molar ratio of 1.
A well-mixed mixture in a 2:2 ratio is filled, and a titanium rod to be coated is placed on top of the mixture. The coating area was 1 cm ² and the mixed powder was 2 g. A pressure of 500Kg/cm ² is applied from above and below to compress the spring and at the same time compact the powder. Vacuum the inside of the container to remove excess gas. A current is instantaneously passed through a pre-installed ignition jig (a platinum wire with a diameter of 0.2 mm is welded to the ends of two tungsten wires) to initiate a reaction from the outside of the coating layer toward the joint surface. As the reaction progresses from the edge of the compact, densification progresses simultaneously with the synthesis reaction of titanium diboride (TiB ₂ ) in the combustion zone heated to 3000℃, and the distance contracted by the reaction is This is successively compensated for by the expansion of the spring. When the combustion zone reaches the end face of the titanium rod, the surface layer of the titanium rod is melted by high heat and is firmly bonded to the thick coating layer of titanium diboride. After the reaction is complete, the cooled sample is removed from the mold and the titanium surface is coated with titanium diboride to complete the production of a joined body. The resulting coating layer had a density of 4.4 g/cm ³ , a thickness of 4.5 mm, and a bonding strength of 400 Kg/cm ² .

Example 2 Titanium boride (TiB) is coated onto a brass surface in the same manner as described in Example 1, except that the reactants are compressed in a mold under a pressure of 200 Kg/cm ² . As for the titanium and boron powders to be filled into the mold, 2 g of a mixture sufficiently mixed at a molar ratio of 1:1 is used. The resulting coating layer has a density
The weight was 4.5g/cm ³ , the thickness was 4.4mm, and the bonding strength was 400Kg/cm ² .

Example 3 The reactant was compressed in a mold under a pressure of 200 kg/ ^cm2 , and 0.2 g of a high exothermic mixture of titanium and boron powders mixed at a molar ratio of 1:2 was added to the coating layer in advance. Titanium boride (TiB) is coated on the titanium surface in the same manner as described in Example 1 except that it is filled between the titanium rods to be coated. As the powders of titanium and boron to be filled into the mold, 2 g of a mixture sufficiently mixed at a molar ratio of 1:1 is used. The resulting coating layer had a density of 4.5 g/cm ³ and a thickness of 5 mm.
The bonding strength was 400Kg/cm ² .

Example 4 The reactant is compressed in a mold under a pressure of 500 Kg/cm ² , and 0.2 g of a high exothermic mixture of titanium and boron powders mixed at a molar ratio of 1:2 is coated with the coating layer in advance. Zirconium carbide (ZrC) is coated on the surface of stainless steel in the same manner as described in Example 1 except that it is filled between the stainless steel (SUS304) to be coated. The zirconium and carbon powders to be filled into the mold are 2 g of a mixture sufficiently mixed at a molar ratio of 1:1. The resulting coating layer had a density of 6.1 g/cm ³ , a thickness of 3.6 mm, and a bonding strength of 300 Kg/cm ² .

Example 5 Titanium nitride (TiN) was deposited on the surface of aluminum metal in the same manner as described in Example 1, except that the reactants were compressed in a mold under a pressure of 200 Kg/ ^cm2 .
is coated. The powder of titanium and sodium azide (NaN ₃ ) to be filled into the mold is 2 g of a mixture sufficiently mixed at a molar ratio of 3:1. The reaction between titanium and sodium azide produces titanium nitride and sodium, and the sodium is discharged out of the mold as a gas, forming a coating layer of titanium nitride on the aluminum surface.
The resulting coating layer has a density of 5.3 g/cm ³ and a thickness of
3.4 mm, and the bonding strength was 200 Kg/cm ² .

[Brief explanation of drawings]

FIG. 1 is an elevational view showing an example of an apparatus for applying a thick coating of a high melting point inorganic compound according to the method of the present invention, and an example of loading a metal-nonmetal mixture and a metal to be coated. 1 is a part of the compression device, 2 is a vacuum container, 3 is a vacuum outlet, 4 is an argon gas inlet, 5 is a current application device for ignition, 6 is a compression spring, and 7 is a mold made of chrome-molybdenum steel. , 8 is a thermal insulation material made of graphite, 9 is a tungsten wire, 10 is a metal-nonmetal mixture, 11
is the metal to be coated.

Claims (1)

[Claims] 1. At least one metal or metal compound selected from periods 2, 3, 4, 5, 6, and 7 of the periodic table, nonmetallic elements C, B, Si, P, S
or sufficiently mixed with at least one azide,
The above mixture is pressurized and compressed onto the surface of the metal or ceramic molded object to be coated, and the end of the mixture is ignited with high heat in a vacuum or an inert atmosphere of 0.1 to 200 atm to start an exothermic reaction. Furthermore, under conditions propagated by heat transfer to the next layer of the mixture, the synthesis reaction progresses in a self-propagating manner in a direction approximately parallel to the direction of pressure, and synthesis is performed by utilizing the tension force of the compression spring. At the same time, a method in which a thick coating of a high melting point inorganic compound is applied to the surface of a metal or ceramic molded body. 2 At least one metal or metal compound selected from the 2nd, 3rd, 4th, 5th, 6th and 7th periods of the periodic table, non-metallic elements C, B, Si, P, S
or sufficiently mixed with at least one azide;
When the above-mentioned mixture is pressurized and compressed on the surface of the metal or ceramic molded body to be coated, a layer of the high exothermic mixture is further provided between the thick coating layer synthesized by reaction and the metal or ceramic molded body. , under vacuum or an inert atmosphere of 0.1 to 200 atm, under conditions where the end of the mixture is ignited to initiate an exothermic reaction, which is further propagated by heat transfer to the next layer of the mixture. By allowing the synthesis reaction to progress in a self-propagating manner in a direction almost parallel to the direction of pressure, and by utilizing the tension of a compression spring, a thick coating of a high-melting point inorganic compound can be applied to the surface of a metal or ceramic molded body at the same time as synthesis. How to do it.