JPH06173009A - Coated cemented carbide excellent in wear resistance and its production - Google Patents

Abstract

(57) [Summary] [Purpose] Even if the coating layer is thickened, the toughness does not decrease and the adhesion with the cemented carbide base material is excellent, achieving a life far exceeding that of conventional coated cemented carbide. , Provides a new coated cemented carbide that can be used under severe conditions that could not be used with conventional coated cemented carbide. A WC film formed by a thermal CVD method using a fluoride of W on a surface of a cemented carbide base material obtained by sintering a hard phase containing WC as a main component with a binder phase containing Co as a main component, W
A coated cemented carbide, which comprises a ceramic coating formed on the C coating and in which cobalt has diffused and penetrated into the WC coating from the cemented carbide base material to a depth of 5 μm or more.

Description

Detailed Description of the Invention

[0001]

INDUSTRIAL APPLICABILITY The present invention is suitable for use as a wear resistant part and a structural material in addition to cutting tools and molds.
The present invention relates to a coated cemented carbide having a wear resistant ceramic coating on its surface, and a method for producing the same.

[0002]

Cemented carbide is tungsten carbide (α-W).
It is a composite alloy obtained by sintering a hard phase containing C) as a main component with a binder phase containing cobalt (Co) as a main component, and not only wear resistance of cutting tools and dies but also mechanical seals and dies. It is used in a wide range of fields as required jigs, mechanical parts, and structural materials.

In recent years, as the environment for use has become more and more severe, a CVD method (a chemical vapor deposition method or a chemical vapor method) such as a thermal CVD method, a plasma CVD method, or an MO-CVD method using an organic metal compound as a raw material. Phase-deposition method) or PVD method (physical vapor deposition method or physical vapor deposition method) such as vacuum deposition method, ion plating method, sputtering method, etc. to form a wear-resistant ceramic coating on the surface of the cemented carbide. The so-called coated cemented carbide formed is widely used.

Titanium carbide (TiC), titanium nitride (TiN), alumina (Al ₂ O ₃ ) and the like are mainly used as an example of such a ceramic coating. By providing these ceramic coatings in a single layer or multiple layers on the surface of the cemented carbide, not only is the wear resistance of the cemented carbide improved, but
It is well known that when used as a cutting tool, the reaction between the work material and the cemented carbide can be prevented, and as a result the tool life can be improved.

However, when the damage of an actual cutting tool, mold, etc. is examined in detail, the depth of wear scars almost always exceeds the thickness of the ceramic coating. In other words, the ceramic film exhibits the expected wear resistance only at the very beginning of wear, and after the wear depth exceeds the thickness of the ceramic film, the edge of the ceramic film shows the progress of wear. It's just holding back. Therefore, after the ceramic coating wears and the cemented carbide base material is exposed, the wear resistance of the cemented carbide itself determines the wear resistance of the coated cemented carbide tool.

From this point of view, it is expected that the wear resistance of the coated cemented carbide tool will be improved by increasing the thickness of the ceramic coating, but in reality, due to the brittleness of the ceramic, the coating of the ceramic coating is formed. It is known that when the thickness is 10 μm or more, the toughness is reduced and the life of the coated cemented carbide tool is shortened, and the coated cemented carbide having a ceramic coating with a thickness greater than this is not in practical use. . That is, Ti
Ceramics such as C, TiN and Al ₂ O ₃ have a larger coefficient of thermal expansion than the cemented carbide of the base material, so tensile stress remains in the ceramic film after film formation, which causes cracks in the ceramic film. It is believed to reduce toughness.

Therefore, instead of the conventionally used ceramics such as TiC, tungsten carbide (W which has a coefficient of thermal expansion approximately the same as or slightly lower than that of the cemented carbide as the base material).
When C) is used as the coating layer, residual stress due to thermal stress hardly occurs in the WC film after film formation, or only a small amount of compressive stress remains. Therefore, even if the WC film is formed on the surface of the cemented carbide, cracks do not occur, and it becomes possible to increase the film thickness without lowering the toughness of the WC film.
Since the C coating does not contain a binder phase and has a hardness higher than that of cemented carbide, improvement in wear resistance of the coated cemented carbide tool can be expected.

In accordance with this idea, Japanese Examined Patent Publication Sho 59-3924
No. 2 and Japanese Examined Patent Publication No. 61-46550 disclose tungsten (W) or tungsten carbide (C) having a crystal grain size of 1 μm or less by containing a predetermined amount of fluorine or chlorine as the outermost layer on the surface of a tool part. Surface-coated tool parts having a coating layer of WC) have been proposed. However, even if the grain size of the WC coating is 1 μm or less, it cannot surpass the cemented carbide in terms of toughness, and there is also a problem with the adhesion between the WC coating and the tool base material, so under particularly severe conditions. Has not yet reached a satisfactory tool life.

[0009]

SUMMARY OF THE INVENTION In view of such conventional circumstances, the present invention provides a coating layer which does not cause a decrease in toughness even if it is made thicker and has excellent adhesion to a cemented carbide base material, and has a conventional coating property. Not only can it achieve a life far beyond that of cemented carbide,
It is an object of the present invention to provide a new coated cemented carbide that can be used under severe conditions that could not be used with conventional coated cemented carbide.

[0010]

In order to achieve the above object, a coated cemented carbide provided by the present invention is a cemented carbide containing a hard phase composed mainly of tungsten carbide and a cemented phase composed of a binder phase composed mainly of cobalt. A hard metal base material, a tungsten carbide film formed on the surface of the hard metal base material, and a ceramic film excellent in wear resistance provided on the tungsten carbide film, and the binder phase cobalt is a tungsten carbide film from the cemented carbide base material. It is characterized in that it diffuses and penetrates into a depth of 5 μm or more.

In the above method for producing a coated cemented carbide,
Heat C using tungsten fluoride, hydrocarbon, and hydrogen as reaction gases at a base material temperature of cemented carbide of 500 to 900 ° C.
A tungsten carbide film is formed on the surface of the cemented carbide base material by the VD method, and then C such as a thermal CVD method, a plasma CVD method, or an MO-CVD method is formed on the tungsten carbide film.
A ceramic coating is formed at a base material temperature of 450 to 1200 ° C. by a VD method or a PVD method such as an ion plating method.

At that time, in order to obtain diffusion diffusion of cobalt having a depth of 5 μm or more from the cemented carbide base material into the tungsten carbide coating, the cemented carbide base material having the tungsten carbide coating at 950 to 1200 ° C. for 5 hours or more. It needs to be heated. In order to satisfy this heating condition, it is necessary to perform 95% before the formation of the ceramic film or after the formation of the ceramic film.
Perform diffusion annealing at 0 to 1200 ° C for 5 hours or more, or use the heat history at the time of forming the ceramic film to make the base material temperature 9
Film formation may be performed under conditions of 50 to 1200 ° C. and film formation time of 5 hours or longer, but a total of 950 to 1200 ° C. for 5 hours or longer is achieved by both diffusion annealing and heating at the time of forming the ceramic film. You may.

[0013]

In the present invention, a ceramic coating conventionally used for coated cemented carbide, such as TiC, TiN,
Ti (CN), HfN, HfC, Hf (CN), ZrN, Z
rC, Zr (CN), TiBN, Al ₂ O ₃ , HfO ₂ , Z
A thick film of tungsten carbide (WC), which is a type of ceramic, is used as an underlayer of rO ₂ etc., and cobalt, which is the binder phase of cemented carbide, is positively applied from the base material to a depth of 5 μm or more in the WC film. By making it diffuse and penetrate,
Despite the thickening of the coating layer, it was found that not only the toughness of the WC coating is improved and the hardness is hardly reduced, but also the adhesion to the base material is significantly improved. The wear resistance could be significantly improved.

The film thickness of the WC film is generally in the range of 5 to 100 μm, though it depends on the environment used as a cutting tool, mold, jig, etc., set life, dimensional accuracy and the like. It is preferable. If the film thickness is less than 5 μm, the effect of improving wear resistance due to the formation of WC film and diffusion of Co is hardly seen, and if it exceeds 100 μm, the WC film becomes relatively brittle and the toughness of the coated cemented carbide deteriorates. not only,
This is because it takes a long time to form the film, which increases the manufacturing cost.

As a method of forming such a WC film, a thermal CVD method using a chloride or carbonyl of tungsten, a PVD method such as an ion plating method or a sputtering method using metallic tungsten can be considered. However, in the present invention, it is economically advantageous to obtain a relatively thick WC film.
Although a film forming rate of 0 μm / hour or more is required, it is difficult to increase the supply rate of tungsten, which is a refractory metal, by the PVD method, so the film forming rate is extremely low at most 1 μm / hour. Further, in the conventional thermal CVD method, the vapor pressure of chloride or carbonyl of the raw material tungsten is low,
It is difficult to obtain a film forming rate of 5 μm / hour or more.

As a result of a study, it is possible to rapidly supply a fluoride gas by the thermal CVD method using a fluoride of tungsten (for example, WF ₆ ), which can be used as C ₃ H ₈ or C ₆
It has been found that a WC film can be formed at an extremely high speed by reacting with a hydrocarbon gas such as H ₆ and a hydrogen gas.
However, when the base metal temperature of the cemented carbide is less than 500 ° C, 10
In addition to not being able to achieve a film forming rate of μm / hour or more, the carbon content in the obtained WC film is low, and the film constituent phase is W ₃
Since it is a single phase of C, only an extremely brittle WC film can be obtained. On the other hand, when the base material temperature exceeds 900 ° C., the raw material gas reacts in the gas phase and only a powdery product is obtained.

Next, on this WC film, TiC, Ti
N, Ti (CN), HfN, HfC, Hf (CN), Zr
N, ZrC, Zr (CN), TiBN, Al ₂ O ₃ , HfO
₂ , a ceramic film such as ZrO ₂ is coated. The formation method thereof includes thermal CVD method, plasma CVD method, MO-C.
CVD method such as VD method or P such as ion plating method
The VD method can be used, but the base material temperature is 450 to 1200 ° C.
Need to The reason is that if the base material temperature is less than 450 ° C., the adhesion of the ceramic film is low, and there is a risk that the film will peel off without being able to withstand the heat history in the subsequent process.
This is because if the temperature exceeds 00 ° C, the structure of the cemented carbide as the base material changes, and the original performance of the cemented carbide is impaired.

Further, in the present invention, it is necessary that Co forming the binder phase of the cemented carbide is diffused and penetrated into the WC film from the base metal to a depth of 5 μm or more.
It was found that a heat treatment at 1200 ° C. for 5 hours or more is necessary. When the temperature is less than 950 ° C or the heating time is less than 5 hours, Co does not diffuse to a depth of 5 μm or more in the WC film, and when the temperature exceeds 1200 ° C, the structure of the cemented carbide as the base material changes. Occurs, and the original performance of the cemented carbide is impaired.

As a heating method for obtaining the diffusion and permeation of Co, a diffusion annealing is performed at 950 to 1200 ° C. for 5 hours or more before forming the ceramic film or after forming the ceramic film, or forming the ceramic film. There is a method of forming a film at a base material temperature of 950 to 1200 ° C. for 5 hours or more by utilizing the heat history during film formation.
You may make it satisfy | fill the heating conditions for 5 hours or more at 50-1200 degreeC.

The above steps of forming a WC film, diffusion annealing, and forming a ceramic film may be carried out in different film forming apparatuses or heat treatment furnaces, but if possible, they are exposed to the atmosphere in the same film forming apparatus. It is preferable to carry out the treatment continuously without any treatment. This is because if the object to be processed comes into contact with the atmosphere during movement, the surface may be contaminated by oxygen and moisture in the atmosphere, which may adversely affect the processing in the subsequent steps. Further, when a separate device is used for each process, extra setup time for moving from device to device is generated, which also causes an increase in manufacturing cost.

However, when the ceramic film is formed by the PVD method such as the ion plating method, since the WC film is formed by the CVD method, the same apparatus cannot always be used. Accordingly, it is preferable that the diffusion annealing is performed in the film forming apparatus of the CVD method, the base material is taken out into the atmosphere, washed, and then mounted in the film forming apparatus of the PVD method to form the ceramic film.

[0022]

Example 1 WC: 85% by weight, Co: 10% by weight, and TiC: 5
A cemented carbide tool having a composition of wt% is placed inside a heat-resistant alloy film-forming apparatus, and by the thermal CVD method under the following reaction conditions, (1) reaction gas conditions: WF ₆ 1 mol% C ₆ H ₆ 5 mol% H ₂ 10 mol% (2) reaction gas flow rate; 1.6 l / min (3) preform temperature; to form a WC coating 30 minutes surface; 800 ° C. (4) reaction time between.

The WC film obtained was subjected to X-ray diffraction to obtain α-
It was confirmed that it was composed of WC. It was also found that the film thickness of the WC film was 7 μm and the film forming rate was 14 μm / hour. When the cross-sectional hardness of this WC film was measured with a Knoop hardness meter (load: 50 g), a value of about 2400 kg / mm ² was obtained as the hardness of the WC film. Furthermore, W
When the adhesion strength of the C coating was evaluated using a scratch type adhesion strength measuring instrument, peeling of the coating occurred at 25 N (Newton).

This WC-coated cemented carbide tool was again installed inside the same film forming apparatus, and a TiC film was formed by a normal thermal CVD method under a base material temperature of 980 ° C. and a reaction time of 3 hours. Then, an Al ₂ O ₃ film was formed on the base material at a base material temperature of 1000 ° C. for a reaction time of 5 hours (Invention Example 1). A photograph of the obtained metallographic structure of the coated cemented carbide tool of Example 1 of the present invention is shown in FIG. By observing this cross section,
The total film thickness of the TiC film and the Al ₂ O ₃ film was 6 μm, and it was confirmed that Co diffused and penetrated into the WC film from the base material to a depth of approximately 7 μm.

When the adhesion strength of the coating was measured in the same manner as above, no peeling was observed at the interface between the WC coating and the TiC coating, and peeling occurred at 95 N at the interface between the WC coating and the base material. It was found that the adhesion strength was much improved as compared with the case of using only the WC film. Further, FIG. 2 shows the sectional hardness in the thickness direction of the coated cemented carbide tool measured by the same Knoop hardness meter as described above.

For comparison, the surface of the WC-coated cemented carbide tool on which the WC coating was formed in the same manner as above was coated with the TiC coating and A
The l ₂ O ₃ film is formed by plasma CVD at a base material temperature of 900
It was formed at 0 ° C. (Comparative Example 1). The cross section of the obtained coated cemented carbide tool of Comparative Example 1 was observed.
The total film thickness of the ₂ O ₃ film was 5 μm, and no Co diffusion was observed between the base material and the WC film. Further, when the adhesion strength of the film was measured in the same manner as above, the peeling at the interface between the base material and the WC film occurred at 30 N, and the adhesion strength was extremely lower than that of Example 1 of the present invention.

Example 2 A WC-coated cemented carbide tool having a WC coating (film thickness 7 μm) formed as in Example 1 above was annealed at 1050 ° C. for 5 hours, and then the following ceramic coating was formed on the WC coating. To obtain coated cemented carbide tools of Inventive Examples 2 to 5; Inventive Example 2: Ceramic film having a total film thickness of 6 μm obtained by laminating a TiC film, a TiBN film and an Al ₂ O ₃ film (plasma CVD method). ; Base material temperature 900 ° C.) Inventive Example 3: Ceramic film having a total film thickness of 7 μm in which HfO ₂ film and Al ₂ O ₃ film are laminated (MO-CVD method using metal alkoxide; base material temperature 700 ° C.) Example 4: Ceramic film having a total film thickness of 6 μm (ion plating method; laminated HfN film and HfC film)
Inventive Example 5: Ceramic film having a total film thickness of 7 μm in which a ZrN film, a Zr (CN) film and a ZrC film are laminated (ion plating method; base material temperature 600 ° C.)

When the cross sections of the coated cemented carbide tools of Examples 2 to 5 of the present invention were observed, in each case, W having a film thickness of 7 μm from the base material was observed.
Co diffused into the C film over a depth of 6 μm,
The adhesion strength of the WC film is 95 N in the invention example 2 and the invention example 3
93 N in the present invention, 92 N in the present invention example 4, and 94 in the present invention example 5.
N, and the adhesion strength of the WC film alone obtained in Example 1 was 25 N, which was significantly improved.

For comparison, the same WC film (film thickness 7 μ
m) formed WC-coated cemented carbide tool is annealed at 1000 ° C. for 2 hours, and then the WC-coated TiC film, T
Total film thickness of 6μ with iBN film and Al ₂ O ₃ film laminated
A ceramic film of m was formed at a base material temperature of 900 ° C. using a plasma CVD method (Comparative Example 2). When the cross section of the tool of Comparative Example 2 was observed, Co from the base material to the WC film was
The diffusion permeation of was only about 2 μm, and the adhesive strength of the WC film was 40N.

Example 3 Examples 1 to 5 of the present invention produced in Example 1 and Example 2 above
Then, for Comparative Examples 1 and 2, a cutting test was performed under the following conditions. In the same manner as in Example 1 except that the WC film was not formed, a TiC film having a total film thickness of 6 μm was formed on the surface of the cemented carbide tool.
For the coated cemented carbide tool having a coating and an Al ₂ O ₃ coating formed thereon (Comparative Example 3), a cutting test was conducted under the following conditions.

Cutting conditions: Work material SCM435 Cutting speed 250 m / min Feed 0.3 mm / rev. Cut 2 mm Cutting time 20 minutes

The flank wear and crater wear were measured by the above cutting test, and the results are shown together with the constitution of the laminated coating of each coated cemented carbide tool and the depth of Co diffusion and penetration into the WC coating.
Shown in Table 1 below;

[Table 1] Co diffusion depth Frank Crater tool sample Laminated coating composition (μm) Wear (mm) Wear (μm) Inventive Example 1 WC-TiC-Al ₂ O ₃ 7 0.09 11 Inventive Example 2 WC-TiC- TiBN-Al ₂ O ₃ 6 0.10 12 Inventive Example 3 WC-HfO ₂ -Al ₂ O ₃ 6 0.12 15 Inventive Example 4 WC-HfN-HfC 6 0.11 14 Inventive Example 5 WC-ZrN-Zr (CN)- ZrC 6 0.12 13 Comparative example 1 WC-TiC-Al ₂ O ₃ 0 Defective defect ratio Comparative example 2 WC-TiC-TiBN-Al ₂ O ₃ 2 0.32 (peeling) 20 Comparative example 3 TiC-Al ₂ O _3- 0.28 25 (Note) In Comparative Example 2, peeling occurred on part of the coating during cutting.

From the results of Table 1 above, Co in the WC film
In comparison with Comparative Examples 1 and 2 in which the diffusion and penetration of the alloy are small and Comparative Example 3 in which the WC coating is not included, the coated cemented carbide tools of the present invention examples all exhibit excellent wear resistance, and the Co-diffused WC coating is present. It is clear that the effect of improving the wear resistance of is remarkable. Further, regarding the diffusion of Co into the WC film, it is understood that the history of temperature and time during diffusion annealing or ceramic film formation, which controls the depth of diffusion, is important.

Example 4 WC: 90 wt% and Co: 10 wt% On the surface of the molded part of a cemented carbide die, in the same manner as in Example 1, except that the film formation time was changed to 3 hours, WC A film was formed. Next, a TiC film + a Ti (CN) film + a TiN film are sequentially laminated on this WC film in the same film forming apparatus under the conditions of a base material temperature of 1000 ° C and a film forming time of 7 hours by a thermal CVD method. To form a ceramic film.

Observation of the cross section of the obtained coated cemented carbide die of the present invention showed that the film thickness of the WC film was 55 μm and the total film thickness of the ceramic film was 6 μm. It was confirmed that a certain Co diffused and permeated into the WC film from the cemented carbide as the base material over a depth of 8 μm.

For comparison, a TiC film + Ti (CN) was formed on the surface of the same cemented carbide die without providing a WC film.
A mold was directly formed with a ceramic coating formed by laminating a coating and a TiN coating. Using the coated cemented carbide dies of the comparative example and the example of the present invention, cold forging of automobile parts was carried out, and the life of each die was evaluated. As a result, the mold of the example of the present invention reached the life after 300,000 shots, whereas the mold of the comparative example had a very short life of only 50,000 shots. Also, when observing the damaged mold, the mold of the present invention shows W at the corner portion of the mold tip where the damage is most severe.
While the C coating remained, the underlying cemented carbide was exposed in the mold of the comparative example.

Example 5 A WC film having a thickness of 80 μm was formed on the surface of a cemented carbide mechanical seal composed of 90% by weight of WC and 10% by weight of Co by the same method as in Example 1, and then 1200 ℃
Then, diffusion annealing was performed for 6 hours. Then, a TiN film having a film thickness of 5 μm was formed on the WC film in the same film forming apparatus at a base material temperature of 700 ° C. by the plasma CVD method.

Observation of the cross section of the coated cemented carbide mechanical seal of this invention revealed that Co, which is the binder phase of the cemented carbide, had a depth of 2 from the cemented carbide as the base material in the WC film.
It was diffused and permeated over 0 μm. WC for comparison
A mechanical seal was produced by directly forming a TiN film on the surface of the same cemented carbide mechanical seal without providing a film. These coated cemented carbide mechanical seals were assembled in a slurry pump of the same type, and a durability evaluation test was carried out.

As a result, in the example of the present invention, seizure and abrasion did not occur even after 20,000 hours had passed, and it could be used without any problem. In contrast, in the comparative example, the slurry leaked from the seal portion at 5000 hours and the life was shortened. Reached After the test, the mechanical seal was examined, and in the comparative example, not only was the TiN film worn away to expose the underlying cemented carbide, but corrosion of the cemented carbide was also observed, indicating a wear scar exceeding 100 μm in depth. However, in the case of the present invention example, the WC film was only worn to a depth of 5 μm, and no sign of corrosion was observed.

[0040]

According to the present invention, even if the coating layer is thickened, the toughness is not deteriorated, and the adhesion between the coating layer and the cemented carbide base material is excellent, and the cutting tool, the die, and the wear-resistant jig are excellent. , Machine parts,
When used as a structural material or the like, it is possible to provide a new coated cemented carbide that not only achieves a life far beyond the conventional one but also can be used under severe conditions that could not be conventionally used.

[Brief description of drawings]

FIG. 1 is a photograph showing a metallographic structure of a cross section in a coated cemented carbide tool of an example of the present invention produced in Example 1.

FIG. 2 is a graph showing the cross-sectional hardness in the thickness direction of the coated cemented carbide tool of the present invention produced in Example 1.

Front Page Continuation (72) Inventor Tsuyoshi Yoshioka 1-1-1 Kunyokita, Itami City, Hyogo Prefecture Sumitomo Electric Industries, Ltd. Itami Works

Claims (7)

[Claims] 1. A cemented carbide base material obtained by sintering a hard phase containing tungsten carbide as a main component with a binder phase containing cobalt as a main component, a tungsten carbide coating formed on the surface thereof, and a tungsten carbide coating provided on the tungsten carbide coating. It also has a ceramic film with excellent wear resistance, and cobalt, which is the binder phase, diffuses and permeates from the cemented carbide base material into the tungsten carbide film to a depth of 5 μm or more, and has excellent wear resistance. Coated cemented carbide. 2. The tungsten carbide coating has a thickness of 5-10.
The coated cemented carbide having excellent wear resistance according to claim 1, wherein the coated cemented carbide has a thickness of 0 μm. 3. The ceramic coating comprises TiC, TiN, T
i (CN), HfN, HfC, Hf (CN), ZrN, Zr
C, Zr (CN), TiBN, Al ₂ O ₃ , HfO ₂ or Z
It is composed of at least one layer of rO ₂ and has a film thickness of 1 to 15
The coated cemented carbide having excellent wear resistance according to claim 1 or 2, wherein the coated cemented carbide has excellent wear resistance. 4. A base metal temperature of the cemented carbide base material is 500 to 900 ° C. on the surface of the cemented carbide base material obtained by sintering a hard phase containing tungsten carbide as a main component with a binder phase containing cobalt as a main component.
, A tungsten carbide film is formed by a thermal CVD method using a fluoride of tungsten, hydrocarbons and hydrogen as a reaction gas, and then a ceramic film is formed on the base material at a temperature of 950 to 1
CVD method or PV at 200 ° C and film formation time of 5 hours or more
A method for producing a coated cemented carbide having excellent wear resistance, characterized by being formed by the D method. 5. The base material temperature of the cemented carbide base material is 500 to 900 ° C. on the surface of the cemented carbide base material obtained by sintering a hard phase containing tungsten carbide as a main component with a binder phase containing cobalt as a main component.
A tungsten carbide film is formed by a thermal CVD method using tungsten fluoride, hydrocarbon and hydrogen as a reaction gas, and a ceramic film is deposited on the tungsten carbide film at a base material temperature of 450 ° C or higher and lower than 950 ° C. Of a coated cemented carbide having excellent wear resistance, which is characterized by performing a diffusion anneal at 950 to 1200 ° C. for 5 hours or more prior to or after the formation of the ceramic coating. Method. 6. The base material temperature of the cemented carbide base material is 500 to 900 ° C. on the surface of the cemented carbide base material obtained by sintering a hard phase containing tungsten carbide as a main component with a binder phase containing cobalt as a main component.
At, a tungsten carbide film is formed by a thermal CVD method using a fluoride of tungsten, hydrocarbon and hydrogen as a reaction gas, and a ceramic film is formed on the tungsten carbide film at a base material temperature of 950 to 1200 ° C. Or, it is formed by a PVD method, and diffusion annealing is performed at 950 to 1200 ° C. for 5 hours or more before or after the formation of the ceramic film, and the total of the diffusion annealing time and the film forming time of the ceramic film is 5 hours or more. A method for producing a coated cemented carbide having excellent wear resistance, comprising: 7. The process according to claim 4, wherein all the steps from the formation of the tungsten carbide film to the formation of the ceramic film or the diffusion annealing are continuously carried out in the same film forming apparatus without exposing to the atmosphere. 7. The method for producing a coated cemented carbide having excellent wear resistance according to any one of items 1 to 6.