JPS63199869A - Production of wear resistant article having tungsten carbide layer - Google Patents

Abstract

PURPOSE:To make it possible to easily remove a mask as well as to simply carry out effective masking when a WC layer is partially deposited on the surface of a metallic base material, by using fluororesin as a masking material. CONSTITUTION:The surface of a metallic base material 1 obtd. by forming a plated Ni-P layer 3 on a metallic base 2 of steel or the like is degreased and cleaned so as to improve the adhesion of fluororesin to the surface. A part of the base material 1 on which a WC layer is not formed by deposition is coated with polytetrafluoroethylene resin adjusted to proper viscosity by dilution with a solvent by an air spray method at ordinary temp. The resulting film is dried to evaporate the solvent and a fluororesin film 4 is formed by heating or baking the dried film. WC is then deposited on the base material 1 to form a WC layer 5. The fluororesin film 4 can be removed by scratching and scraping with an edged tool or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method of manufacturing a wear-resistant article having a tungsten carbide layer.

(Prior Art) A technique is known in which a tungsten carbide layer is deposited on the surface of a metal part by a CVD (chemical vapor deposition) method to provide wear resistance. For example, JP-A-52-8958
Publication No. 3 discloses that by forming a nickel phosphorus plating layer on the surface of a steel base material and depositing a tungsten carbide layer on the nickel plating layer, tungsten carbide and tungsten carbide are formed on the steel base material. There are descriptions of techniques for improving layer adhesion. In this case, tungsten
The carbide layer is formed using a gas phase reaction between WF6, hydrocarbon gas, and hydrogen.

(Problems to be Solved by the Invention) The present invention attempts to obtain a wear-resistant article in which a tungsten carbide layer is partially deposited on the surface of a metal base material. For this partial precipitation, the non-depositing portions of the metal base material may be masked and the tungsten carbide precipitation treatment may be performed, but in this case the following problem occurs.

That is, as the above-mentioned masking method, it is possible to partially wrap a copper plate or the like around the metal base material to prevent the CVD reaction gas from directly touching the non-deposited area.
Although it is possible to apply this method to a metal base material with a simple shape, the above-mentioned winding requires time and effort, and it is difficult to apply it to a material with a complex shape.

On the other hand, methods of applying metal plating to non-precipitated portions of the metal base material, methods of coating with water glass, methods of coating with ceramics, etc. can also be considered. However, with the plating method, it is difficult to perform partial plating processing itself, and tungsten carbide tends to precipitate on the surface of the plating layer, making it difficult to peel off the plating layer after CVD processing. By-product H
There is a problem that it is easily attacked by F, resulting in insufficient masking effect, and in the case of ceramics, there is a problem that it is difficult to peel off after CVD treatment. Furthermore, water glass and ceramics also have the problem of tungsten/carbide precipitation, and plating and ceramics also have problems with HF.
There is a problem of erosion due to

Furthermore, it is conceivable to coat resin as a masking material, but general resins are used at the CVD reaction temperature (3
00 to 1000°C) cannot be obtained, and
There are also problems of tungsten carbide precipitation and HF corrosion.

(Means for Solving the Problems) The present invention, as a means to solve the above-mentioned problems, forms a fluororesin coating on a portion of the surface of a metal base material where no tungsten carbide layer will be formed, and then The present invention provides a method for manufacturing a wear-resistant article having a tungsten carbide layer, which comprises subjecting a base material to a tungsten carbide precipitation treatment and then removing the fluororesin coating.

As the metal base material, articles made of stainless steel, other ferrous metals, and non-ferrous metals can be used, and the present invention can also be applied to articles in which a metal base material is plated with metal. .

As the fluororesin, PTFE (tetrafluoroethylene resin), PFA (tetrafluoroethylene-perfluoroalkoxyethylene copolymer), FEP (tetrafluoroethylene-hexafluoropropylene copolymer), etc. can be used. Can be done. The fluororesin film can be formed by coating the non-precipitated portions of the metal substrate with a fluororesin made into a liquid using a solvent by brushing, air spraying, or the like. In this case, after coating the metal base material, the fluororesin is dried and fired (180 to 400°C).

In depositing the tungsten carbide layer, CV
Method D can be used. That is, for the metal base material formed by coating the non-precipitated portion with fluororesin,
Temperature conditions of about 300 to 600℃, 10 to 200 torr
Supplying a mixed gas containing WF, (tungsten hexafluoride), hydrocarbon and hydrogen gas under reduced pressure conditions of about r,
A tungsten carbide layer is deposited by a gas phase reaction.

Next, the fluororesin coating can be removed by scratching and scraping the fluororesin coating using a knife or the like.

(Function) In the above manufacturing method, the firing temperature of the fluororesin film coated on the metal base material and the processing temperature of the metal base material during precipitation of the tungsten carbide layer overlap; In the tungsten carbide layer precipitation process, the temperature of the metal base material can be raised at the beginning to also serve as the firing of the fluororesin film.

Although the fluororesin coating acts as a mask against the precipitation of tungsten carbide, tungsten carbide itself is difficult to precipitate onto the fluororesin coating, which prevents waste of reaction gas for CVD. , the fluororesin coating becomes easier to peel off. Furthermore, since the fluororesin coating is not substantially corroded by HF, which is the exhaust gas during the deposition of the tungsten carbide layer, the masking function does not deteriorate during the deposition process.

(Effects of the Invention) Therefore, according to the present invention, by forming a fluororesin film, the effects of heat and exhaust gas (HF) during the tungsten carbide layer precipitation treatment can be reduced even on metal substrates with complex shapes. This makes it possible to easily perform effective masking and to easily remove this masking without being affected by the tungsten carbide layer. If it also serves as the firing of the film,
The number of processing steps and processing time in manufacturing wear-resistant articles using this tungsten carbide layer can be reduced.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

In this example, as shown in FIG.
A polyfluoroethylene resin (Polyflon TFE Tough Coat Enamel TC-7800 manufactured by Daikin Industries, Ltd.) was used as a masking material.

The nickel phosphorus plating layer 3 is formed by immersing the metal base material 2 in a palladium chloride aqueous solution to activate the surface of the base material, and then applying nickel chloride (30gffi-'), sodium hypophosphite (10gQ-1)-quench Sodium acid (100gΩ
-1), p containing ammonium chloride (5Ogu''''1)
It can be formed by immersing it in a H8-10 bath at a temperature of 40° C. for about 30 minutes.

Now, the manufacturing process of this example is as shown in FIG.

Pre-treatment step 6 - As a pre-treatment, the surface of the metal base material 1 is degreased and cleaned. This treatment is to improve the adhesion of the fluororesin.

Monofluororesin coating step 7 - The above-mentioned tetrafluoroethylene resin is diluted with a solvent (thinner) to adjust its viscosity, and then the non-precipitated portion of the metal base material 1 (which does not form a tungsten carbide layer) is applied using an air spray method. area) at room temperature.

Incidentally, in the above application, an electrostatic coating method or a brush coating may be employed.

Drying step 8 - Dry the coating film from the previous step at 90 to 100° C. for 20 to 30 minutes. This drying is done by evaporating the solvent.
This is to prevent defects such as peeling, cracking, and foaming from occurring in the coating film during subsequent baking.

-CVD process 9- This process consists of a temperature raising (firing) process 9a and a reaction precipitation process 9b.

1. Temperature raising (firing) step 9a- The object to be processed after the previous step is placed in a retort, the temperature of the object to be processed is raised to about 350° C., and held for 10 to 15 minutes. This temperature increase is to smoothly carry out the gas phase reaction in the next step, and the temperature is maintained at an elevated temperature to bake the coating film in the previous step. That is, in this step, the reaction temperature for tungsten carbide precipitation (300 to 60
(approximately 0°C) and the firing temperature of the coating film (180 to 400°C)
Since there is an overlap region between the two regions, the heating for the above reaction and the firing of the coating film are carried out at the same time.

Through the above steps, a fluororesin coating 4 having a thickness of approximately 20 to 30 μm as shown in FIG. 1 is formed on the non-precipitated portion of the surface of the nickel phosphorus plating layer 3.

Incidentally, the firing of the coating film may be performed in a separate step from the temperature raising for the gas phase reaction, that is, it may be performed before the temperature raising.

One reaction precipitation process First, the pressure inside the retort is reduced to about 100 torr,
A process in which a mixed gas of WF6, C6H6, H2, and Ar (argon) at a predetermined molar ratio is supplied little by little while the reaction temperature is maintained at about 350 DEG C. is continuously carried out for 2 hours. As a result, a tungsten carbide layer 5 having a thickness of approximately 3 μm is formed only on the surface of the metal base material 1, that is, the surface of the nickel phosphorus plating layer 3 on which the fluororesin coating 4 is not formed, as shown in FIG.

The gas phase reaction when the tungsten carbide layer 5 is formed is as follows, and the tungsten carbide layer 5 contains wc, W, and C.

Contains W3C.

6 WFe + CaHa + 15H246VC+
3611F12WF6+C,H,+3382-+ 6W
2G+72HF1811Fe + CeHe + 51
1 (2→611sC+ 108HF In the above reaction,
Although corrosive HF gas is generated, the fluororesin coating 4 has corrosion resistance against this HF gas, so there is no deterioration in the masking function.

Fluororesin coating removal step 10 - The fluororesin coating 4 is removed by scratching and scraping the fluororesin coating 4 using a knife. In this case, tungsten carbide is removed from the surface of the fluororesin coating 4. is not precipitated, so the fluororesin coating 4
It is possible to easily remove the chisel.

FIG. 3 shows an electron micrograph (100°
times). In the figure, the entire white part is the tungsten carbide layer 5, and the black part with a white line pattern is the fluororesin coating 4.
Since the boundary between the two is clearly visible, it can be seen that the fluororesin coating 4 is effective as a masking for preventing the precipitation of tungsten carbide.

FIG. 4 shows an optical micrograph (400x magnification) of the metal structure of the cross section of the part where the fluororesin coating 4 is formed, and shows that the nickel phosphorus plating layer 3 is formed on the lower metal base material 2. The overlapping gray area shown in the image is the fluororesin coating 4. No precipitation of tungsten carbide is observed on this fluororesin coating 4.

In addition, FIG. 5 shows an optical micrograph (4
The thin layer portion shown in white above the nickel phosphorus plating layer 3 is the tungsten carbide layer 5.

Therefore, the present invention is useful when imparting high wear resistance only to necessary parts such as the mold surface of press molds and extrusion dies, and the blades of various tools, or when a part of an article is to be processed later. This is an effective means for easily masking and removing the tungsten carbide layer when it is desired to prevent the precipitation of the tungsten carbide layer.

[Brief explanation of the drawing]

The drawings show embodiments of the present invention; FIG. 1 is a cross-sectional view showing the wear-resistant article with the fluororesin coating remaining; FIG. 2 is a block diagram showing the manufacturing process; and FIG. A microscopic photograph showing the metallographic structure of the surface of the wear-resistant article. Fig. 4 is a photomicrograph showing the metallographic structure of a cross section of the portion of the wear-resistant article where the fluororesin coating is formed. Fig. 5 is a photomicrograph showing the metallographic structure of the surface of the wear-resistant article. 1 is a micrograph showing the metal structure of a cross section of a portion of a sexual article in which a tungsten carbide layer is formed. 1...Metal base material, 2...Metal base material, 3
...Nickel phosphorus plating layer, 4...Fluororesin coating, 5...Tungsten carbide layer. Figure 1 Figure 2 Figure 3 Figure 4 Figure 561

Claims (1)

[Claims] (1) A method for producing a wear-resistant article in which a tungsten carbide layer is partially deposited on the surface of a metal base material, the method comprising forming a fluororesin coating on the non-deposited part of the surface of the metal base material. 1. A method for manufacturing a wear-resistant article having a tungsten carbide layer, which comprises subjecting the metal base material to a tungsten carbide precipitation treatment, and then removing the fluororesin coating.