JPS6242996B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for coating the surface of cutting tools, high-speed tools, and other objects that require wear resistance and adhesion resistance. Conventionally, for example, the manufacturing method of HfC film was made using methane,
Attempts have been made to form hydrogen and hafnium tetrachloride (HfCl ₄ ) by a chemical vapor deposition method (CVD method). However, such coatings are performed at substrate temperatures of 1500°C or higher. Therefore, such coatings often have a negative effect on the substrate, and also have a problem in that the range of application is limited. In addition, hafnium halides such as HfCl ₄ , which are raw materials for decomposition, have the disadvantage of being extremely easy to hydrolyze.
There is a problem with poor workability. Therefore, as a method for coating hafnium compounds at low temperatures (Japanese Unexamined Patent Publication No. 52-36585), for example, hafnium is reacted with hydrogen chloride and hydrochloric acid gas to form lower hafnium halides (HfCl ₃ ,
HfCl ₂ , HfCl), which is diffused into hydrocarbons, nitrogen gas, and at least one gas selected from the group consisting of hydrogen, helium, and argon, and thermally decomposed at a temperature of 900 to 1300°C. This produces a hafnium compound. however,
In this method, for example, using iodine as the halogen,
When forming hafnium carbide, it is difficult not only to form lower-grade hafnium iodide but also to form stoichiometric hafnium carbide, which has the disadvantage that a film exhibiting sufficient hardness cannot be obtained. Another disadvantage is that a hafnium carbide film having a uniform composition or a film coated uniformly throughout the reaction region cannot be obtained. On the other hand, the present inventors have discovered that it is possible to produce a dense hafnium carbide film with close stoichiometry at sufficiently low temperatures and by introducing only hydrocarbon gas without using lower halides.
Furthermore, the present inventors have discovered that by performing this coating under reduced pressure, uniform coating can be achieved over the entire surface. The object of the invention is to avoid the above-mentioned disadvantages, e.g.
In the production of HfC, iodine and hafnium metal are reacted to preform hafnium tetraiodide, which is a higher hafnium iodide, and hydrocarbons are introduced into it to form a material that spreads and adheres well on the substrate at low temperatures. , a method for producing a wear-resistant coating is provided. In order to achieve the above object, the present invention provides a method for producing a hafnium compound film, in which iodine and hafnium metal are reacted in the same reaction system to produce hafnium tetraiodide, which contains hydrocarbons, nitrogen,
By introducing one or two types of ammonia gas,
In this method, the mixture of gases is passed over a coating base and pyrolyzed under reduced pressure at a temperature in the range of 800 to 1250°C. The apparatus used in the present invention is shown in FIG. The reaction system has a two-stage structure, so there are also two heating elements.
It has a structure in several places. In the first stage, hafnium metal and iodine react to form hafnium tetraiodide, and in the second stage, hafnium iodide reacts with a hydrocarbon (e.g., butane, C ₄ H ₁₀ ) to produce HfC. It is generation. The first stage heating is 200-600
°C, the second stage is 800-1250 °C. The heating method is
Either resistance heating or high frequency heating may be used. Preferably, the first stage heating is performed using a resistance, and the second stage heating is performed using a high frequency method. The path of the generated hafnium tetraiodide and the C ₄ H ₁₀ path are separate, forming a double structure in which iodine vapor and C ₄ H ₁₀ do not react. Furthermore, the hafnium tetraiodide produced is kept in a gaseous state at a temperature at which it will not be decomposed, and the structure is such that it can be heated so that it flows into the second stage reaction system. Furthermore, hafnium tetraiodide is produced by pouring iodine vapor into hafnium heated to 200-600°C. The hafnium metal used may be in any shape such as sponge, chip, or granule, but preferably sponge. The iodine supply system is structured to control its vapor pressure by controlling the temperature. As shown in FIG. 2, the iodine container must have an orifice-type outlet for the iodine vapor so that the amount of iodine supplied is always constant. Also,
As shown in Figure 3, the iodine container is kept at a constant temperature (vapor pressure), argon gas is poured into it, and the flow rate of the argon gas is controlled.
There are also ways to control the amount of iodine. The iodine vapor controlled in this way is heated to a constant temperature using a ribbon heater or the like, and is blown into the hafnium container through a path. This is an apparatus for producing a hafnium compound film having the structure described above. Therefore, we will show examples of the conditions for generating HfC using this device and the resulting HfC generation rate.

[Table] As is clear from this, the production rate is controlled by the temperature (vapor pressure) of iodine. Next, the change in formation temperature is shown.

[Table] As is clear from the table, when the temperature of iodine is kept constant, the production rate varies depending on the reaction temperature. Therefore, the iodine temperature was set at 30, 35℃.
Figure 4 shows the results of plotting the relationship between HfC production rate and production temperature. As is clear from this, there is a direct relationship between the HfC production rate and the production temperature, and it can be seen that the HfC production rate can be controlled by the iodine temperature. Furthermore, the film obtained under these conditions is
When observed with SEM, it is dense and has a lattice constant of 4.643Å, so the composition is
It was confirmed that HfC close to _1.0 was obtained _. HfC film is formed at a reaction temperature of 800℃ or higher;
It will not be generated in the following cases. In addition, the reaction temperature is 1250℃
In the above case, the properties of the cemented carbide (WC-Co alloy) that is the base material change. This is because the liquidus temperature of WC-Co is 1270℃, so if the temperature exceeds 1270℃, a WC-Co reaction will occur, changing the physical properties of the substrate itself and making it brittle. Therefore, the reaction temperature needs to be 1250°C or lower. When the reaction is carried out at atmospheric pressure, the film formation rate is fast, but the resulting film tends to be porous and lacks adhesion and abrasion resistance. Furthermore, there is a problem that the entire surface of the substrate cannot be coated, resulting in poor coverage.
However, the above problem can be solved by conducting the reaction under reduced pressure. The method for producing an HfC film, which is an example of the present invention, does not use a carrier gas such as H ₂ or Ar, so when increasing the pressure in the reaction system,
The amount of butane introduced must be increased. In this way, the pressure can be increased to 10 Torr depending on the amount of butane introduced.
In the above case _, the composition of the film obtained deviates from the stoichiometric composition (HfC _1.0 ), and a composition of HfC+C is obtained, resulting in an HfC film with poor wear resistance. Furthermore, as a method of increasing the pressure within the reaction system while keeping the amount of butane introduced constant, there is a method of reducing the capacity of the oil rotary pump. When produced using this method at a pressure of 10 Torr or more in the reaction system, the production rate becomes faster, but the resulting film tends to be porous. Therefore, in the present invention, it is necessary to carry out the reaction under reduced pressure of 10 Torr or less. Next, coat the carbide chips with the coating conditions shown below.

[Table] As a result of coating for 5 hours, the variation in film thickness within the carbide chip (including the front and back surfaces) was within ±10%, confirming that uniform coating was possible. In addition, using the aforementioned carbide tip and using nitrogen gas as the introduced gas, coating conditions were applied as shown below.

[Table] As a result of coating for 7 hours, a pale golden HfN
It was confirmed that the material could be coated uniformly on carbide chips. Similarly, a mixed gas of methane gas and nitrogen gas was used as the introduced gas, and the coating conditions were as shown below.

[Table] As a result of coating for 4 hours, it was confirmed that hafnium carbonitride (HfCN) could be coated uniformly. As described above, according to the manufacturing method of the present invention, even at low reaction temperatures of 800 to 1250°C, a sufficiently wear-resistant hafnium compound film with good adhesion and close to stoichiometric composition can be applied to the reaction area. can be manufactured uniformly over the entire area. This makes industrial large-scale production possible, and it becomes possible to provide products with uniform quality and excellent characteristics at a relatively low cost.

[Brief explanation of the drawing]

Fig. 1 is a float diagram of an apparatus to which the method of the present invention is applied, Figs. 2 and 3 are schematic diagrams of an iodine vapor control apparatus, and Fig. 4 is a diagram showing the relationship between HfC production rate and production temperature. . 1: Stop valve, 2: Vacuum gauge, 4: Mass flow controller, 8: Water bath, 9: Iodine, 10: Iodine container, 11: Electronic thermostat, 1
4: Electric furnace, 15: Hafnium, 19: Sample, 2
0: Orifice type iodine container.

Claims (1)

[Claims] 1. In a method for producing a hafnium compound film, iodine and hafnium metal are reacted in the same reaction system to produce hafnium tetraiodide (HfI ₄ ), which is a higher hafnium iodide, and a hydrocarbon, introducing at least one of nitrogen or ammonia and passing said gas mixture over the substrate to be coated;
hafnium compound coatings of hafnium carbide (HfC), hafnium nitride (HfN) and hafnium carbonitride (HfCN) in the temperature range of 800-1250℃, and the pressure in the reaction system.
A method for producing a hafnium compound film, characterized in that the film is produced by reaction under reduced pressure of 10 Torr or less. 2. The method for producing a hafnium compound film according to claim 1, characterized in that the amount of iodine supplied is controlled by its vapor pressure to control the production rate of the hafnium compound film. 3. In paragraph 1 or 2 of the claims, the hafnium tetraiodide reaction path is heated to 200°C.
A method for producing a hafnium compound film, characterized in that the film is passed over a substrate to be coated in a state where the film is heated to a temperature below its thermal decomposition temperature. 4. A method for producing a hafnium compound film according to any one of claims 1 to 3, characterized in that coating is carried out under reduced pressure within the reaction system of 1 Torr or less in order to obtain a dense film. .