JP2772494B2 - Super hard film coated member and method of manufacturing the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a superhard film-coated member used as a cutting / polishing tool, a polishing component, an optical component, or an electronic material, and a chemical vapor deposition method on a surface of a cemented carbide. To form a diamond and / or diamond-like carbon film.

BACKGROUND ART When diamond is coated on the surface of a cemented carbide by a chemical vapor synthesis method, amorphous carbon is easily formed on cobalt in a binder phase, and diamond formation is inhibited. As a solution, etching treatment with an acid or treatment to remove the binder metal at a certain depth from the substrate surface can produce a diamond film and significantly improve the adhesion strength between the diamond film and the substrate. Things are disclosed,
A representative example is JP-B-63-20911.

Further, Japanese Unexamined Patent Publication (Kokai) No. 63-100182 discloses that a cemented carbide in which the amount of cobalt serving as a binder phase is reduced to 1 to 4% by weight is suitable as a diamond-coated base material. It is necessary to remove cobalt by etching with an acid even in an alloy.

As a method for removing the binder phase, other than the acid method, a dry etching method in carbon fluoride plasma, hydrogen,
A method of performing sputter etching with an argon gas or the like is disclosed in Japanese Patent Application Laid-Open No. 62-67174.

On the other hand, a method of forming an intermediate layer has been proposed as a method for increasing the adhesion strength without removing the binder phase as described above. As an example, the surface of a substrate such as cemented carbide
Japanese Patent Publication No. Sho 63-1280 discloses a method of forming a layer composed of carbides, nitrides, borides and the like of elements a, Va and VIa, or a compound or a mixture thereof, and providing a diamond film thereon.

Further, the thickness of the ultra-hard film is 20 in JP-A-1-242491.
It is described that if the thickness exceeds μm, the film is peeled off due to thermal stress in the film, which is not preferable.

As mentioned above, many proposals have been made for improving the adhesion strength of the diamond film, but still have sufficient quality,
No method suitable for industrial production has been found, and its establishment is required.

That is, in the cemented carbide etched with acid, the binder phase at the surface layer of the cemented carbide is removed, so that the WC particles present at the interface between the base material and the diamond film are not necessarily held firmly. . The adhesion strength of the diamond film formed on such a surface is not sufficient, and its use as a cutting tool is low (less than 12%) for silicon-aluminum alloys, graphite, carbon fiber reinforced plastics, green compacts, etc. It is limited and cannot withstand heavy cutting such as intermittent cutting of 18-20% Si-Al alloy and long-time high feed and deep cutting.

Further, when a diamond film close to 15 μm is coated on a cemented carbide etched with an acid, the film spontaneously peels off. Therefore, since the thickness of the film in the conventional method can be set to only 0.1 to 5 μm in view of the peeling measure, the flank wear (Vb) amount for judging the tool life even when the diamond film does not come off before reaching the predetermined amount. The base material is exposed to the surface, which naturally limits the tool life.

The present invention provides a super-hard film-coated cemented carbide having a high adhesive force and provides a super-hard film-coated cemented carbide having a longer life by coating with a thick film and a method for producing the same. Is to solve.

DISCLOSURE OF THE INVENTION The present inventors have made it possible to coat a super hard film by performing a heat treatment without performing a pre-process of removing a binder phase of a cemented carbide by etching, and to reduce a thermal expansion coefficient of a substrate surface portion. A study was conducted to coat a cemented carbide with a thick super-hard film with a strong adhesive force by approaching that of diamond. 1) When the cemented carbide substrate was heat-treated or repeated, the binder phase metal was mainly deposited on the substrate surface. A hemispherical precipitate as a component is formed.

2) If a super-hard film is coated after performing the pre-treatment one or more times by repeating the above-mentioned heat treatment step, a super-hard film-coated super-hard alloy exceeding 20 μm having excellent adhesion is obtained.

3) When heat treatment is performed in an atmosphere containing carbon atoms, hemispherical precipitates and deposits mainly composed of carbon are formed on the surface of the base material. If the film is formed after the heat treatment and the removal of the deposit are repeated one or more times, a thick ultra-hard film having a strong adhesive force can be obtained.

4) The cemented carbide base material having the heat treatment of the above 2 and 3 has a portion where the content of the binder phase is reduced within a range of 30 μm from the surface, but the interval between the hard phase particles is the same as that of the base material. It has a strength that can withstand heavy cutting such as intermittent cutting, high feed, and deep cutting because the strength of the base material has not been reduced since it is smaller than that of.
Also, the coefficient of thermal expansion of the surface of the base material is thereby reduced and approaches that of diamond.

5) As the super-hard film-coated member, the adhesive force is improved by the structure of the above-mentioned substrate surface portion and the precipitate existing at the interface between the super-hard film and the substrate surface.

By obtaining the findings described in (1) to (5) above, the present invention described in the following examples has been completed.

The above-described means of the present invention and the following examples all show a case where a base material is a commercially available general-purpose cemented carbide represented by a WC-Co system by comparison with the prior art, but contains free carbon. Needless to say, the present invention can be applied to a material having a sintered surface, a material having a sintered surface, and a material having a base material of another cemented carbide using a binder metal other than cobalt. In addition, in the implementation process shown in the embodiment, a known or new process may be added, for example, a process of scratching the surface of the base material before film formation described in 5 described later. In particular, when the surface roughness of the cemented carbide is 0.2 μmRa or less, the damage treatment prior to the heat treatment is indispensable.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic sectional view of a hot filament CVD apparatus used for heat treatment and film formation in an embodiment of the present invention.

FIG. 2 is a secondary electron image of the surface showing the particle structure of the cemented carbide substrate heat-treated in an atmosphere containing carbon atoms.

 FIG. 3 is a schematic diagram for explaining FIG.

FIG. 4 is a photograph of an initial structure in which diamond formed on the surface of FIG. 2 is formed.

FIG. 5 is a structural photograph showing a state in which diamond generation has progressed further than in FIG.

6a, 6b, and 6c are micrographs showing the composition of the interface between the cemented carbide substrate and the diamond film.

FIG. 7 is a secondary electron image of a cross section of the surface showing the particle structure of the surface of the cemented carbide substrate in comparison.

FIG. 8 is a table showing the heat treatment temperature and the state of formation of precipitates.

FIG. 9 is a table showing the heat treatment time and the number and size of precipitates generated.

FIG. 10 is a backscattered electron image of the surface of the heat-treated cemented carbide substrate.

 11a, 11b and 11c are images obtained by enlarging and analyzing FIG.

FIGS. 12 and 13 are secondary electron images of the cutting edge of the commercially available tool and the cutting tool of the present invention after the cutting test, respectively.

FIGS. 14, 15, 16 and 17 are tables showing the results of cutting tests in the comparative example and the example of the present invention.

FIG. 18 is a table showing the thickness of the formed film in the comparative example and the example of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION As the cemented carbide substrate, a first group of commercially available WC-4% Co cemented carbide chips and a second group of WC-25% Co cemented carbide chips are used. Implementation steps were performed.

1. Heat treatment → 2. Solvent removal → 3. Heat treatment → 4. Soot removal → 5. Film formation → 6. Polishing The details of each execution step will be described later, but the main conditions of each step are as follows.

2,4. Soot removal (common) Use a cotton swab to wipe off soot (sediment) generated on the substrate surface.

5. Film forming (common) Equipment used Hot filament CVD apparatus shown in Fig. 1 Atmosphere H ₂ -1% CH ₄ pressure 100 Torr Base material temperature 900 ° C Reaction time 15 hours 7. Polishing (common) # 800 (30 μm) resin bonded diamond Polishing with a wheel Details of each process 1,3 Heat treatment The equipment used is a CVD apparatus with the configuration shown in Fig. 1, 1 is a reaction vessel, 2 is an atmosphere gas introduction valve, 3 is a dangsten filament, and 4 is a substrate support. A cooling stand, 5 is a cemented carbide substrate, and 6 is a gas discharge valve.

AC120v × 120A was applied to the tungsten filament, and the temperature was set to 2150 to 2200 ° C.

The distance between the filament and the substrate is 10 mm and the substrate temperature is 900 ° C. as described above.

FIG. 2 shows a secondary electron image of a cross section of the surface of the base material obtained by subjecting the base material of the first group to the heat treatment of Group A. FIG. 3 is a schematic diagram thereof.

Although cobalt of the binder phase 11 precipitates on the surface of the base material by the heat treatment, it does not spread over the entire surface of the base material but rises as a hemispherical precipitate 12. Conversely, a portion 13 having a low content of the binder phase metal is generated in the base material by precipitation.

This low content portion is observed within about 30 μm from the substrate surface. In this portion, the WC particles, which are the hard particles 15, undergo rearrangement, and the interval between the WC particles is narrower than the inside.

The state of formation of the precipitate 12 is as follows.
In more than a minute, a precipitate of cobalt can be observed. Here, 14 is soot deposited on the surface of the base material, and 16 is generated diamond.

2.4 Soot removal Almost all of the sediment is removed by soot removal. At this time, precipitate 12
Most remain as is.

Precipitates are mainly composed of cobalt, a binder phase metal, which contains trace amounts of tungsten, carbon, etc.
Since the growth of the precipitate stops when the deposit adheres to the surface of the precipitate, it is preferable to remove the soot by removing the deposit. For the formation of precipitates, heat treatment of Group A for 90 minutes and soot removal twice are sufficient. The heat treatment temperature is appropriately selected from the range of 500 to 1300 ° C. in consideration of the holding time of the heat treatment. However, it is preferable that the heat treatment temperature is higher than the film formation temperature in the next step.

5 Film formation As can be understood from FIG. 4, the generation of diamond nuclei starts around the precipitate and on the surface of the base material in a portion where no precipitate exists.
Thereafter, as shown in FIG. 5, the diamond film wraps around the precipitate and covers the substrate surface.

6a, b, and c are cross-sectional photographs of the interface between the substrate and the diamond film, where a is a secondary electron image, b is an X-ray image of Kal of Co, and c is an X-ray image of Lal of W. It is an image image.

The X-ray image is received by the same LiF crystal. The boundary between the substrate and the diamond film can be specified from the secondary electron image. It can be seen that tungsten has a clear boundary with diamond, whereas cobalt exists on the diamond side from the boundary. The cobalt detected on the diamond side is considered to be a trace of the precipitate.

6. Film formation The surface roughness after film formation is 2 μmRa, and can be finished to 5 nmRa by polishing. Further, even a film having a thickness of 30 μm can be formed without peeling and can be polished. In the conventional method, polishing of a film having a thickness of more than 20 μm was impossible even to produce a film having good adhesive force.

As a result of further trial production of a third substrate other than the first and second groups, which was obtained by changing the process of the embodiment, an excellent film was obtained. The third one will be described below.

The cemented carbide substrate used in the third one is a commercially available WC-
6% Co cemented carbide tip 1/2 ".

Process 0. Pre-processing of base material → 1. Heat treatment → 2. Removal of soot → 3. Heat treatment → 4. Removal of soot → 5. Deposition → 6. Polishing → 7. Cutting test Machining Damage Blasting # 80 SiC particles Degreasing Ultrasonic cleaning in acetone solution 1,3.Heat treatment conditions Equipment Hot filament CVD equipment Atmosphere H ₂ -0.6% CH ₄ (Atmospheric gas is introduced after exhausting the atmosphere with a rotary pump) Pressure 100 Torr temperature Filament temperature 2180 ° C Base material temperature 950 ° C Holding time 90 minutes x 3 times 2,4. Soot removal Soot generated on the base material surface with a cotton swab (sediment)
Towel.

5. Deposition equipment Hot filament CVD equipment Atmosphere H ₂ -1% CH ₄ Pressure 100 Torr Temperature Filament temperature 2180 ° C Base material temperature 850 ° C Reaction time 15 hours 6. Polishing (Common) # 800 (30μm) Polishing with resin bond diamond wheel 7. Cutting test Machine used Lathe made by Mori Seiki Work material Al-18% Si Cutting conditions Cutting speed 800m / min Depth of cut 0.5mm Feed 0.1mm / rotation Wet / continuous cutting Contents of each process 1.3 Heat treatment Figure 7 shows the same heat treated The cross-section of the base material with and without the precipitate was observed up and down 2
This is the next electron image.

Even if the upper side (where no precipitate is present) is heat-treated, the space between the WC particles is filled with the binder phase metal and there is no space.

On the lower side (white protrusions from the upper side to the lower side), migration (precipitation) of the binder phase metal to the surface and rearrangement of WC particles occur, and the thickness of the binder phase metal is reduced. In addition, small voids that could not be filled during the rearrangement of the WC particles exist near the precipitates. In other words, at least in the range of a depth of 30 μm from the surface of the substrate surface, the content of the binder phase metal is small, the gap between the hard crystal grains of WC is narrow, and the coefficient of thermal expansion of the substrate is diamond. It is considered that the gradient function is formed close to the coefficient of thermal expansion.

FIG. 8 shows the number of precipitates generated when heat treatment is performed at various substrate temperatures by a hot filament CVD apparatus. Filament temperature: 2200 ° C, atmosphere gas: H ₂ -1% CH ₄ (flow rate H ₂ : 500
ccm, CH ₄ : 5 ccm), and the distance between the filament and the base material is 10 mm. When heat-treated for 1 hour, precipitates appear remarkably, and drastically decrease when the temperature exceeds 1000 ° C.

FIG. 9 shows the relationship between the change in the particle size and quantity of the precipitate and the heat treatment time.

The device used is a hot filament CVD device, and the substrate is JIS K10
Grade cemented carbide (WC-6% Co), atmosphere gas: H ₂ -1% CH
₄ (flow rate H ₂ : 500 ccm, CH ₄ : 5 ccm, pressure: 100 Torr), substrate temperature: 950 ° C., filament temperature: 2200 ° C., distance between filament and substrate: 10 mm.

The number of precipitates reaches several tens per hour in an area of 50 μm × 50 μm. If the treatment time is lengthened, the number decreases but the particle size increases.

FIG. 10 is a backscattered electron image of the substrate surface heat-treated at 950 ° C. in FIG. In the backscattered electron image, an element having a larger atomic number is observed whiter, and an element having a smaller atomic number is observed blacker. The black dots in the photo are the precipitates, which are enlarged and analyzed.
Although 11 is a, b, and c, the precipitate is observed as black because Co is the main component, and is observed as white because the substrate surface is WC. a is a secondary electron image, b is an X-ray image of Kal of cobalt, and c is an X-ray image of Lal of tungsten.

From now on, the optimal conditions for heat treatment at a methane concentration of 1%
If the heat treatment time is 1 hour, a precipitate can be obtained.

In the heat treatment with flowing methane, the deposition of amorphous carbon starts on the binder phase metal, and the formation of precipitates starts at this location. If the heat treatment is further continued, the precipitate will be covered with amorphous carbon. In this state, since the growth of the precipitates stops, the steps of heat treatment and soot removal are repeated. As this process is repeated, the accumulation of soot is reduced, and the generation of diamond on the surface of the base material becomes remarkable.

A heat treatment was performed for 2 hours in an atmosphere gas containing only hydrogen without flowing methane under the same conditions as in FIG. 9, and the precipitate was observed with a scanning electron microscope.

From this, it is considered necessary to supply carbon atoms in order to efficiently generate precipitates.

When the precipitate is covered with amorphous carbon, the growth of the precipitate stops, and when the soot is removed, the growth starts again.Therefore, the precipitate is exposed to excitons such as thermionic electrons emitted from the hot filament. Is determined to be necessary for growth.

Indirectly heated vacuum furnace (5 × 10 ^-3 To
In rr), a precipitate was observed by heating to 1300 ° C.

For this reason, in the presence of excitons, movement of the binder phase metal to the surface is likely to occur in combination with the presence of carbon. At this time, it is presumed that the substrate surface and the precipitates are contaminated by the carbon atmosphere and the residual gas in the atmosphere, and the transferred binder phase metal becomes hemispherical precipitates.

Exposure to thermoelectrons and easy to generate plasma at 100 Torr
When heat treatment was performed under the conditions, precipitates were formed at 900 ° C., but in a heating furnace with few excitons, the temperature at which precipitates are generated becomes higher. Therefore, in order to efficiently generate precipitates, the heat treatment apparatus is preferably a hot filament CVD apparatus, but a heating method using high energy such as microwave, electron beam, laser beam, or other heating methods may be used. Needless to say.

7. Cutting equipment Fig. 12 is a secondary electron image of the cutting edge of a 500mm aluminum alloy (Al-18% Si) machined with a commercially available diamond film coated tool. The coating film has been peeled off after processing 500m. The film thickness is also as thin as 10 μm or less, and grinding streaks on the substrate surface are observed as irregularities on the diamond film.

FIG. 13 shows the cutting edge of 3500 m when a heat treatment of 1.5 hours was repeated three times in FIG. 9 and the film was formed with H ₂ -1% CH _{4 at} a substrate temperature of 850 ° C. for 15 hours. It is a secondary electron image. No delamination and slight wear on flank. Further, since the film thickness is large, irregularities on the surface of the base material cannot be recognized from the surface of the film.

FIG. 14 shows the results of a cutting test performed by polishing the rake face and flank face of the tool shown in FIG. Here, the thickness of the flank was 25 μm, and the thickness was reduced to 15 μm by polishing. In the figure, the commercial product shows the cutting performance of the tool shown in FIG. 12, and the cemented carbide shows the cutting performance of the third substrate, which is a tool using the cemented carbide as it is without coating diamond.

FIG. 15 is a table showing a comparison of the cutting performance between the polished product and the unpolished product in FIG. 14, and the flank wear is significantly reduced by polishing.

FIG. 16 is a table showing a performance comparison between the drill manufactured using the ultra-hard film-coated member of the embodiment of the present invention in FIG. 15 and a commercially available diamond coated drill.

FIG. 17 is a table showing a comparison of the cutting performance between the unpolished product of FIG. 15, that is, a film formed by leaving a precipitate after heat treatment and a film formed by removing a precipitate and performing film formation by 10 μm after heat treatment. It is.

FIG. 18 is a table showing a comparison of the film thicknesses that can be formed by the conventional method and the comparative example and the conventional method.

In the case where the precipitate is left, cobalt is contained on the interface side of the base material of the diamond film as described above, and the effect of suppressing peeling due to a difference in thermal expansion coefficient from the base material is further remarkable. Removing the precipitate does not have this additional effect, but is far superior to conventional commercial products.

In the figure, the commercially available product is obtained by measuring the thickness of a commercially available diamond coating chip. In the boric acid treatment, a diamond film is formed after immersing a cemented carbide base material, which has been successfully manufactured by the inventors, in boric acid.

In the precipitates remaining in the examples, the precipitates are present at the time of diamond film formation, the nucleation of diamond is not on the precipitates, and the generation of diamond-like carbon or the like is presumed on the precipitates. It is considered that the substrate and the substrate were not firmly attached. Conversely, this is considered to contribute to the relaxation of the thermal stress between the diamond film and the substrate. This has both an effect that remains as a trace in the diamond film and a function of inclining the thermal expansion coefficient by reducing the movement of the binder phase metal on the surface of the cemented carbide base material due to the formation of precipitates. Thick film is now possible.

The method of removing the precipitate has only the effect of reducing the movement of the binder phase metal on the surface of the medium base material, and is superior to the commercially available conventional method and the comparative example of the boric acid treatment.

INDUSTRIAL APPLICABILITY As described above, the super-hard film-coated member of the present invention can form a diamond film on a cemented carbide base material, which has been almost impossible in the past, by a chemical vapor deposition method with a strong adhesion and a thick diamond film. It can be used for various applications such as cutting wear-resistant tools and wear-resistant parts. In addition, the heat treatment and the film formation can be performed by the same CVD apparatus in the production, so that it is suitable for industrial production and economical.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Akio Hara 2-80, Hokita-cho, Sakai-shi, Osaka Inside Osaka Diamond Diamond Industry Co., Ltd. (56) References JP-A-3-219079 (JP, A) JP-A-Hei 1-246361 (JP, A) JP-A-1-103996 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C23C 16/02 C23C 16/26 C30B 29/04 B23P 15 / 28

Claims (7)

(57) [Claims] 1. The method according to claim 1, wherein the surface of the cemented carbide substrate has diamond and / or diamond.
Or in a member formed by forming an ultra-hard film made of diamond-like carbon, the substrate is within 30 μm from the substrate surface, the spacing between the hard phase particles is smaller than that of the original substrate,
An ultra-hard film covering member having a portion having a low binder phase metal content. 2. The member according to claim 1, wherein the surface of the ultra-hard film is polished. 3. A step of subjecting a surface of a cemented carbide substrate to a heat treatment to form a hemispherical precipitate mainly composed of a binder phase metal on the surface of the substrate, and then to form a chemical vapor on the surface. A method for producing an ultra-hard film-coated member, wherein diamond and / or diamond-like carbon is produced by a phase synthesis method. 4. A heat treatment is performed on the surface of a cemented carbide substrate in an atmosphere in which carbon atoms are present, and a hemispherical precipitate containing a binder phase metal as a main component and a deposit containing carbon as a main component are formed on the surface. After removing the deposits formed on the surface or further removing part or all of the precipitates, diamond and / or diamond-like carbon is deposited on the surface by chemical vapor synthesis. A method for producing an ultra-hard film-coated member, characterized in that the member is formed. 5. The method according to claim 4, wherein the heat treatment and the removal of the deposit or the deposit and the precipitate are performed twice or more. 6. A step of subjecting a cemented carbide base material to a heat treatment in an atmosphere in which hydrogen atoms are present or in a low vacuum to form a hemispherical precipitate containing a binder phase metal as a main component on the surface of the base material. And producing diamond and / or diamond-like carbon on the same surface by a chemical vapor synthesis method. 7. The method for producing a superhard film-coated member according to claim 3, wherein the heat treatment of the superhard alloy is performed by a hot filament CVD apparatus.