JPH04348823A - Cutting tool made of rigid layer-covered cemented carbide - Google Patents

Abstract

PURPOSE:To provide a cutting tool made of rigid layer-covered cemented carbide and manufacture thereof, which provide excellent cutting performance when it is used for intermittent cutting, such as milling, and middle and low speed and high speed continuous cutting, by providing a concentration gradient on a rigid covering layer. CONSTITUTION:(x) of a carbon titanium nitride single rigid layer formed on the surface of a cemented carbide base substance and having a composition represented by Ti(CxNy), where in x+y is equal to 1, takes at least one maximal value between the innermost surface and the outermost surface of the carbon titanium nitride single rigid layer. simultaneously, density of C and N is changed so that (y) takes at least one minimum value between the innermost surface and the outermost surface of the carbon titanium nitride single rigid layer. To form the carbon titanium nitride single rigid layer wherein density of C and N is changed as described above, physical deposition is carried out, as shown in Fig 2, as hydrocarbon and nitrogen gas are fed.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] This invention relates to a hard layer-coated cemented carbide cutting tool coated with a single hard layer of titanium carbonitride with finer grains than conventional ones, and a method for manufacturing the same. The hard layer-coated cemented carbide cutting tool produced by the above method exhibits excellent cutting performance not only for medium-low and high-speed continuous cutting, but also for interrupted cutting such as milling.

0002

[Prior Art] Generally, one or more iron group metals are contained as a binder phase forming component, and if necessary, carbides and nitrides of metals of groups 4a, 5a, and 6a of the periodic table are contained. , TiCN on the surface of a cemented carbide substrate (hereinafter referred to as the cemented carbide substrate) containing 0.5 to 30% by weight of carbonitrides, with the remainder consisting of tungsten carbide (hereinafter referred to as WC) and unavoidable impurities. Hard layer-coated cemented carbide cutting tools are known, which are coated with a layer by physical vapor deposition (
(See Japanese Unexamined Patent Publication No. 10871/1983).

0003

[Problems to be Solved by the Invention] However, the TiCN layer formed by the above-mentioned conventional physical vapor deposition method has a coarse crystal grain size, so it lacks toughness and easily cracks and peels off. (1) When a hard layer-coated cemented carbide cutting tool with a TiCN layer formed by the conventional physical vapor deposition method is used for interrupted cutting such as milling, the TiCN hard layer will peel off and break off from that part. (2) Furthermore, when using the above-mentioned conventional hard layer-coated cemented carbide cutting tool, continuous cutting at medium to low speeds causes severe flank wear, and continuous cutting at high speeds causes severe crater wear. Therefore, a satisfactory service life cannot be obtained unless a hard layer-coated cemented carbide cutting tool is used depending on the continuous cutting speed. There have been issues such as not using them properly, and as a result, sufficient cutting life has not been achieved.

0004

[Means for solving the problem] Therefore, the present inventors
In order to solve the above-mentioned problems and to obtain a hard layer-coated cemented carbide cutting tool that has a longer service life not only for medium-low and high-speed continuous cutting but also for interrupted cutting such as milling. As a result of our research, we found that in hard layer-coated cemented carbide cutting tools in which the surface of a cemented carbide base is coated with a single hard layer of titanium carbonitride, the composition of the single hard layer of titanium carbonitride is Ti(CxNy) [where x+y=1
], x of the titanium carbonitride Ti (CxNy) single hard layer takes at least one maximum value or minimum value between the innermost surface and the outermost surface of the titanium carbonitride single hard layer, Correspondingly, when the concentrations of C and N are respectively changed so that y takes at least one local minimum value or maximum value between the innermost and outermost surfaces of the titanium carbonitride single hard layer, It was discovered that the crystal grains of the entire Ti(CxNy) single hard layer were refined, and a hard layer-coated cemented carbide cutting tool that was tough and had excellent peeling resistance could be obtained.

[0005] The present invention was made based on this knowledge, and it is possible to apply Ti(Cx
In a cutting tool coated with a single hard layer of titanium carbonitride having a composition represented by Ny) [where x+y=1], the single hard layer of titanium carbonitride Ti (CxNy)
x takes at least one local maximum or minimum value between the innermost and outermost surfaces of the single hard titanium carbonitride layer, and correspondingly, y takes at least one local maximum or minimum value between the innermost and outermost surfaces of the single hard titanium carbonitride layer. It is characterized by a hard layer-coated cemented carbide cutting tool in which the concentration of C and N changes so as to take at least one minimum value or maximum value between the inner surface and the outermost surface, and a method for manufacturing the same. be.

FIG.
A physical vapor deposition apparatus shown in is used. In FIG. 1, 1 is a reactor, 2 is a reaction gas inlet, 3 is a substrate, 4 is a crucible,
5 is a discharge electrode, 6 is titanium metal, 7 is an electron beam, 8
is a heater, 9 is a mass flow controller, 10 is a vacuum gauge, and 11 is a pressure controller.

After inserting the substrate 3 into the reactor 1, heating the inside of the reactor 1 to a predetermined temperature, and filling the crucible 4 installed in the reactor 1 with metal titanium 6, the reactor 1 is heated to a predetermined temperature. The interior of the reactor 1 is kept in vacuum, and Ar gas is introduced from the mass flow controller 9 through the reaction gas inlet 2.
The substrate 3 is bombarded while being maintained in an Ar gas atmosphere, and then the Ar gas is discharged from the reactor 1, nitrogen gas and hydrocarbon gas are introduced, and the metal titanium 6 is irradiated with an electron beam 7 to melt it. A positive voltage is applied to the discharge electrode 5, and the electron beam 7 collides with the molten titanium 6 between the discharge electrode 5 and the molten titanium 6 to generate secondary electrons and molten titanium. Electric discharge is caused by metal vapor evaporated from the surface of 6. The mass flow controller 9 that introduces the nitrogen gas and hydrocarbon gas is a pressure controller 1 connected to a vacuum gauge 10.
1.

The mass flow controller 9 is controlled by the pressure controller 11, and the reaction mixture gas consisting of nitrogen gas and hydrocarbon gas introduced into the reactor 1 is controlled, for example, as shown in the graph of FIG. Accordingly, the amount of nitrogen gas introduced is continuously reduced to reach the minimum value Qmin, and then the amount of nitrogen gas introduced is continuously increased from the minimum value Qmin, and the hydrocarbon gas is inversely proportional to this. It is supplied so as to increase continuously to reach the maximum value Qmax, and then it is supplied so as to continuously decrease from the maximum value Qmax.

The above-mentioned minimum value Qmin is the value at the point where the amount of introduced reactant gas changes from decreasing to increasing. The curve shows the bottom of the valley between the innermost surface and the outermost surface of the titanium carbonitride single hard layer. Maximum value Qm
ax indicates the value at which the amount of introduced reactant gas changes from increasing to decreasing, and is the value at which the component concentration curve reaches the peak between the innermost and outermost surfaces of the titanium carbonitride single hard layer. be.

The amount of nitrogen gas introduced and the amount of hydrocarbon gas introduced may be changed intermittently, but it is preferable to change them continuously. In the graph of FIG. 2, the amount of nitrogen gas introduced and the amount of hydrocarbon gas introduced are Although it is continuously changed in a curved manner, it is not limited to this, and may be changed continuously in a straight line as shown in FIG.

As shown in FIG. 4, as the physical vapor deposition progresses, the amount of nitrogen gas introduced is continuously increased to reach the maximum value Qmax, and then the maximum value Qm is increased.
ax is supplied so as to continuously decrease, and in inverse proportion to this, hydrocarbon gas is supplied so as to continuously decrease to reach the minimum value Qmin, and then the above minimum value Q
The supply may be continuously increased from min.

Furthermore, as shown in FIGS. 5 and 6, the minimum value Qmin and the maximum value Qma of the amount of nitrogen gas introduced are
It may be supplied continuously so that one or more of each of x exists, and at the same time, one or more of each of maximum value Qmax and minimum value Qmin of hydrocarbon gas exists.

The single hard layer of titanium carbonitride obtained by introducing the reaction mixture gas into the reactor 1 in this way while changing the amounts of nitrogen gas and hydrocarbon gas introduced is made of Ti (CxNy
) [where x+y=1], the values of x and y are respectively 0.005≦x≦0.99 due to the relationship that a mixed gas of nitrogen gas and hydrocarbon gas is introduced as the reaction gas.
5 and 0.005≦y≦0.995, the C and N concentration distributions are similar to the supply patterns of the reaction mixture gas shown in FIGS. 2 to 6 above.

[0014] As shown in the method of the present invention, when nitrogen gas and hydrocarbon gas are introduced as a reactive gas mixture while changing their supply amounts, the formed titanium carbonitride single hard layer is particularly sensitive to crystal grains. The titanium carbonitride single hard layer, which contains TiN as the largest component on the innermost surface in contact with the cemented carbide substrate, has even better adhesion to the cemented carbide substrate. Become something. Therefore, the hard layer-coated cemented carbide cutting tool of the present invention is not only applicable to continuous cutting with a wide range of cutting speeds from medium to low speeds to high speeds, but also has excellent effects in interrupted cutting such as milling. be.

The thickness of this single hard layer of titanium carbonitride is 2
It is preferably 0 μm or less. If it exceeds 20 μm, the difference in thermal expansion between the material and the substrate during cutting will become large, causing cracks to occur and peeling to occur easily. On the other hand, the single hard layer is 0.
If the thickness is less than 5 μm, the effect of suppressing peeling of the hard layer will not be sufficient, so the thickness is preferably 0.5 μm or more.

[0016]

[Embodiments] Next, embodiments of the hard layer-coated cemented carbide cutting tool and the method for manufacturing the same according to the present invention will be described in detail with reference to the drawings.

Example 1 As the raw material powder, Co with an average particle size of 1.2 μm was used.
Prepare powder, TiC powder, TaC powder, and WC powder, and blend these powders so that Co powder: 9% by weight, TiC powder: 1% by weight, TaC powder: 2% by weight, and the remainder: WC powder, After mixing, it is molded into a green compact, the green compact is sintered under normal conditions to produce a sintered body, and this sintered body is ground to have the shape of ISO standard TNGA160408. A WC-based cemented carbide chip having a material equivalent to P30 was produced.

Next, this WC-based cemented carbide chip was used as a base and mounted above the reaction furnace 1 in the ordinary ion plating apparatus shown in FIG. A crucible 4 placed below was filled with Ti metal 6. In this state, the inside of the reactor 1 of the ion plating apparatus was maintained at a vacuum of 1×10 −5 Torr, and the temperature was increased at a rate of 6° C./min. The temperature was raised to 700°C.

While maintaining this temperature, Ar gas was supplied from the mass flow controller 9 through the reaction gas inlet 2 to maintain an Ar gas atmosphere of 5×10 −2 Torr for bombardment cleaning.

Next, the Ti metal 6 is heated and evaporated by the electron beam 7, and the mass flow controller 9 is switched to supply nitrogen gas (99.95%) from the reaction gas inlet 2.
Start by introducing a mixed gas of 0.05% acetylene gas by volume, and reduce the pressure inside the reactor 1 of the ion plating device to vacuum while exhausting the used reaction mixed gas from the exhaust port. Total 10 gives 2.0×10-
The temperature was maintained at 4 Torr, and the nitrogen gas was supplied as shown by the solid line in FIG. 7, and at the same time, acetylene gas was supplied as shown by the dotted line in FIG.

In FIG. 7, the reaction mixture gas starts at a mixing ratio of 99.5% by volume of nitrogen gas and 0.5% by volume of acetylene gas, and the amount of nitrogen gas supplied is linearly reduced. was increased linearly, and at the end of 50 minutes, the mixing ratio was 0.5% by volume for nitrogen gas and 99.5% by volume for acetylene gas.
At the time when 0 minutes have elapsed, it is shown that the mixing ratio of nitrogen gas is 99.5% by volume and acetylene gas is 0.5% by volume, which is linearly changed and supplied.

As described above, physical vapor deposition is performed while continuously changing the amounts of nitrogen gas and acetylene gas in inverse proportion to each other, so that the surface of the WC-based cemented carbide chip has a thickness of:
Ten chips 1 made of hard metal coated with a hard layer of the present invention each coated with a single hard layer of titanium carbonitride having a thickness of 5 μm were manufactured.

[0023] Any one of the ten hard layer coated cemented carbide chips 1 of the present invention was taken out, and a single hard layer of titanium carbonitride with a thickness of 5 μm formed on its surface was analyzed by Auger analysis. The spectral intensities of TiN and TiC were determined by point analysis in the depth direction, and the factor analysis of TiN/TiC was performed based on the spectral intensities. As a result, the concentrations of C and N in the depth direction of the layer thickness shown in Fig. distribution was obtained.

Furthermore, the single hard layer of titanium carbonitride is
Scherr
The average grain size was calculated using the formula er, and the results are shown in Table 1.
It was shown to.

Example 2 The WC-based cemented carbide tip produced in Example 1 was used in Example 1.
Bombard cleaning is performed in the ion plating apparatus in the same manner as above, and then the Ti metal 6 is heated and evaporated by the electron beam 7, and the mass flow controller 9 is switched to inject nitrogen gas from the reaction gas inlet 2: 0% by volume,
Acetylene gas: Start by introducing a 100% mixed gas, and the used reaction mixed gas is exhausted from the exhaust port while being pumped into the reactor 1 of the ion plating equipment.
The pressure inside was set to 2.0 x 10-4 Torr by the vacuum gauge 10.
The nitrogen gas was supplied as shown by the solid line in FIG. 9, and at the same time, the acetylene gas was supplied as shown by the dotted line in FIG.

In FIG. 9, the reaction mixture gas starts at a mixing ratio of 0.5% by volume of nitrogen gas and 99.5% by volume of acetylene gas, and the amount of nitrogen gas supplied is increased linearly. was reduced linearly, and at the end of 40 minutes, the mixing ratio was 99.5% by volume for nitrogen gas and 0.5% by volume for acetylene gas, and 10% by volume for acetylene gas.
At the time when 0 minutes have elapsed, it is shown that the mixing ratio of nitrogen gas is 0.5% by volume and that of acetylene gas is 99.5% by volume, which is linearly changed and supplied.

As described above, physical vapor deposition is performed while continuously changing the amounts of nitrogen gas and acetylene gas in inverse proportion to the surface of the WC-based cemented carbide chip to a thickness of:
Ten hard layer-coated cemented carbide chips 2 of the present invention each coated with a single hard layer of titanium carbonitride having a thickness of 5 μm were manufactured.

[0028] Any one of the ten hard layer-coated cemented carbide chips 2 of the present invention was taken out, and a single hard layer of titanium carbonitride with a thickness of 5 μm formed on its surface was analyzed by Auger analysis. The spectral intensities of TiN and TiC were determined by point analysis in the depth direction, and the factor analysis of TiN/TiC based on these spectral intensities was performed. As a result, the concentration of C and N in the depth direction of the layer thickness shown in Fig. 10 was distribution was obtained.

Furthermore, the single hard layer of titanium carbonitride is
Scherr
The average grain size was calculated using the formula er, and the results are shown in Table 1.
It was shown to.

Conventional Example 1 On the other hand, for comparison, a WC-based cemented carbide chip was subjected to bombardment cleaning in the same manner as in Example 1, and then a mixed gas of nitrogen gas and acetylene gas was mixed with nitrogen gas:acetylene gas=1: By physical vapor deposition while flowing at a constant ratio of 1 for 100 minutes, ten conventional hard layer-coated cemented carbide chips 1 made of a titanium carbonitride layer with a thickness of 5 μm were deposited on the surface of the WC-based cemented carbide chips. Manufactured. These 10
Any one of the conventional hard layer coated cemented carbide tips 1
As a result of measuring the composition of a single hard layer of titanium carbonitride with a thickness of 5 μm formed on its surface using EPMA, it was found that Ti (C0.5
N0.5) It was confirmed that a coating layer with a uniform composition was formed. Further, X-ray diffraction was performed, and the average crystal grain size was calculated using the Scherrer equation using the half width of the (200) plane, and the results are shown in Table 1.

Ten hard layer coated cemented carbide chips 1 of the present invention produced in Example 1, ten hard layer coated cemented carbide chips 2 of the present invention produced in Example 2, and conventional example 1. An interrupted cutting test, a medium-low speed continuous cutting test, and a high-speed continuous cutting test were conducted on the 10 conventional hard layer-coated cemented carbide tips 1 under the following conditions, and the cutting test results are also shown in Table 1.

Intermittent dry cutting test Work material: Cylindrical body made of SCM440 (Brinell hardness: 300) with four grooves on the axial outer circumference, cutting speed: 100 m/min, feed: 0.21 mm/rev. , Depth of cut: 1.0mm, Cutting time: 2min. Intermittent dry cutting was carried out under these conditions, and the number of cutting edges in which breakage occurred among the 10 test cutting edges was measured.

Medium and low speed continuous cutting test Work material: SNCM439 (Brinell hardness: 250), cutting speed: 150 m/min, feed: 0.3 mm/rev. , Depth of cut: 1.5 mm, 10 chips were each continuously cut under the following conditions.
The time (minutes) required for the flank wear width VB, which wears most severely in medium and low speed continuous cutting, to reach 0.3 mm was measured, and the average value thereof was determined.

High-speed continuous cutting test Work material: SNCM439 (Brinell hardness: 250), cutting speed: 210 m/min, feed: 0.25 mm/rev. , Depth of cut: 1.5mm, Cutting time: 20min. Dry high-speed continuous cutting was performed on each of 10 chips under the following conditions, and the average value of the depth of crater wear, which is the most severe wear during high-speed continuous cutting, was determined.

[0035]

[Table 1]

From the results shown in Table 1, the hard layer coated cemented carbide tips 1 and 2 of the present invention have fine crystal grain sizes in the coated hard layer, do not cause any breakage in intermittent dry cutting, and While it exhibits excellent cutting performance over a long period of time in continuous cutting at medium to low speeds and high speeds,
In the conventional hard layer coated cemented carbide tip 1, the crystal grain size of the coated hard layer is coarse, there are many defects in intermittent dry cutting, and the flank wear width is 0 in medium to low speed continuous cutting.
．． It is clear that the cutting performance is poor because it takes a short time to reach 3 mm, and cutting edge breakage occurs in a short period of time during high-speed continuous cutting, and the life of the tip is therefore short.

Examples 3 to 9 As in Example 1, the gas supply time was adjusted while continuously changing nitrogen gas and acetylene gas so that the nitrogen gas had a minimum value Qmin and the acetylene gas had a maximum value Qmax. A single hard layer of titanium carbonitride with various thicknesses shown in Table 2 was formed on the surface of the WC-based cemented carbide chip prepared in Example 1, and the hard layer coated cemented carbide chip 3 of the present invention was prepared.
-9 were produced in 10 pieces each.

Regarding these hard layer-coated cemented carbide chips 3 to 9 of the present invention, the average crystallization was determined by X-ray diffraction of a single hard layer of titanium carbonitride using the half-width of the (200) plane according to Scherrer's formula. The particle size was calculated, and an intermittent dry cutting test, a medium-low speed continuous cutting test, and a high-speed continuous cutting test were conducted under the same conditions as in Example 1, and the results are shown in Table 2.

Example 10 Nitrogen gas and acetylene gas were continuously changed to have a plurality of minimum values Qmin and maximum values Qmax, respectively, as shown in FIG. A single hard layer of titanium carbonitride with a thickness of 13 μm was formed on the surface of the WC-based cemented carbide chip prepared in Example 1 by adjusting the supply time, and the hard layer-coated cemented carbide chip 10 of the present invention was formed. Ten pieces were produced each.

Regarding these hard layer coated cemented carbide chips 10 of the present invention, a single hard layer of titanium carbonitride was subjected to X-ray diffraction, and the average crystal grain size was determined by Scherrer's equation using the half width of the (200) plane. Further, an intermittent dry cutting test, a medium-low speed continuous cutting test, and a high-speed continuous cutting test were conducted under the same conditions as in Example 1, and the results are shown in Table 2.

Conventional Examples 2 to 6 On the other hand, for comparison, after bombardment cleaning in the same manner as in Example 1, a mixed gas of nitrogen gas and acetylene gas was heated at a fixed ratio of nitrogen gas: acetylene gas = 1:1 for a predetermined period of time. By physical vapor deposition while flowing, ten conventional hard layer-coated cemented carbide chips 2 to 6 each consisting of a titanium carbonitride layer with a thickness shown in Table 3 are deposited on the surface of the above-mentioned WC-based cemented carbide chips. Manufactured. These conventional hard layer coated cemented carbide chips 2 to 6 were subjected to X-ray diffraction in the same manner as in Conventional Example 1, and the average crystal grain size was calculated using the Scherrer formula using the half width of the (200) plane. An intermittent dry cutting test, a medium-low speed continuous cutting test, and a high-speed continuous cutting test were conducted under the same conditions as in Example 1, and the results are shown in Table 3.

[0042]

[Table 2]

[0043]

[Table 3]

From the results shown in Tables 2 and 3, the hard layer-coated cemented carbide chips 3 to 9 of the present invention have fine crystal grain sizes in the hard coating layer, and no chipping occurs in any of them during intermittent dry cutting. In contrast, the conventional hard layer-coated cemented carbide tips 2 to 6 have a coarse grain size in the hard coating layer, and exhibit excellent cutting performance over a long period of time in continuous cutting at medium to low speeds and high speeds. , Frequent chipping occurs during intermittent dry cutting, and it takes a short time for the flank wear width to reach 0.3 mm during medium- and low-speed continuous cutting, and cutting edge chipping occurs in a short period of time during high-speed continuous cutting.
It can be seen that the cutting performance was inferior due to the short life of the tip, and almost the same results as in Example 1 were obtained.

Furthermore, in the hard layer coated cemented carbide chips 7 and 10 of the present invention, the thickness of the single hard layer of titanium carbonitride is 13 μm, but the minimum value Qmin and the maximum value of nitrogen gas and acetylene gas are In order to have a plurality of Qmax, that is, as shown in FIG.
Thickness: 13 μm manufactured by adjusting the gas supply amount while continuously changing nitrogen gas and acetylene gas so that one or more minimum value Qmin and maximum value Qmax exist.
The single hard titanium carbonitride layer 10 of 10 has only one minimum value Qmin and one maximum value Qmax of nitrogen gas and acetylene gas, that is, as shown in FIG. 2, nitrogen gas and acetylene gas are continuously supplied. Thickness made by adjusting gas supply time while changing: 13μ
It can be seen that the crystal grain size of the covering hard layer is finer than that of the titanium carbonitride single hard layer 7 of m, and exhibits excellent performance.

[0046]

[Effects of the Invention] As mentioned above, the hard layer-coated cemented carbide cutting tool of the present invention has excellent fracture resistance, so it can exhibit excellent cutting performance over a long period of time, and has excellent industrial effects. It brings about

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a physical vapor deposition apparatus used in the present invention.

FIG. 2 is a graph schematically showing the amounts of nitrogen gas and hydrocarbon gas introduced in the present invention.

FIG. 3 is a graph schematically showing the amounts of nitrogen gas and hydrocarbon gas introduced in the present invention.

FIG. 4 is a graph schematically showing the amounts of nitrogen gas and hydrocarbon gas introduced according to the present invention.

FIG. 5 is a graph schematically showing the amounts of nitrogen gas and hydrocarbon gas introduced according to the present invention.

FIG. 6 is a graph schematically showing the amounts of nitrogen gas and hydrocarbon gas introduced in the present invention.

FIG. 7 is a graph showing the amounts of nitrogen gas and hydrocarbon gas introduced in Example 1 of the present invention.

8 is a graph showing the concentration distribution of C and N in a single hard titanium carbonitride layer obtained in Example 1. FIG.

FIG. 9 is a graph showing the amounts of nitrogen gas and hydrocarbon gas introduced in Example 2 of the present invention.

10 is a graph showing the concentration distribution of C and N in a single hard titanium carbonitride layer obtained in Example 2. FIG.

FIG. 11 is a graph showing the amounts of nitrogen gas and hydrocarbon gas introduced in Example 10 of the present invention.

[0047]

[Explanation of symbols]

1 Reactor 2 Reactant gas inlet 3 Base 4 Crucible 5　Discharge electrode 6 Metal titanium 7　Electron beam 8 Heater 9 Mass flow controller 10 Vacuum gauge 11 Pressure controller Qmax Maximum value Qmin Minimum value

Claims (4)

[Claims] Claim 1: Ti(CxN
y) In a cutting tool coated with a single hard layer of titanium carbonitride having a composition shown by x+y=1, x of the single hard layer of titanium carbonitride Ti (CxNy)
has at least one maximum value between the innermost and outermost surfaces of the single hard titanium carbonitride layer, while y has at least one maximum value between the innermost and outermost surfaces of the single hard titanium carbonitride layer. A hard layer-coated cemented carbide cutting tool characterized in that the concentrations of C and N vary so as to take one minimum value. 2. A hard layer coating method in which a hard metal substrate is equipped in a physical vapor deposition reactor, and a single hard layer of titanium carbonitride is physically deposited while introducing a mixed gas of hydrocarbon gas and nitrogen gas as a reaction gas. In a method for manufacturing a cutting tool made of hard metal, the ratio of hydrocarbon gas in the mixed gas is changed to take at least one maximum value from the start to the end of physical vapor deposition, and at the same time, the ratio of nitrogen gas in the mixed gas is changed to take at least one maximum value from the start to the end of physical vapor deposition. the ratio,
A method for manufacturing a hard layer-coated cemented carbide cutting tool, characterized in that the hard layer is changed to take at least one minimum value from the start to the end of physical vapor deposition. 3. Ti(CxN) on the surface of the cemented carbide substrate.
y) In a cutting tool coated with a single hard layer of titanium carbonitride having a composition shown by x+y=1, x of the single hard layer of titanium carbonitride Ti (CxNy)
takes at least one minimum value between the innermost and outermost surfaces of the single hard titanium carbonitride layer, while y takes at least one minimum value between the innermost and outermost surfaces of the single hard titanium carbonitride layer. A cutting tool made of a hard layer coated cemented carbide, characterized in that the concentrations of C and N vary so as to take one maximum value. 4. A hard layer coating method in which a hard metal substrate is equipped in a physical vapor deposition reactor, and a single hard layer of titanium carbonitride is physically deposited while introducing a mixed gas of hydrocarbon gas and nitrogen gas as a reaction gas. In a method for manufacturing a hard metal cutting tool, the ratio of hydrocarbon gas in the mixed gas is changed to take at least one minimum value from the start to the end of physical vapor deposition, and at the same time, the ratio of nitrogen gas in the mixed gas is changed to take at least one minimum value from the start to the end of physical vapor deposition. the ratio,
A method for producing a hard layer-coated cemented carbide cutting tool, characterized in that the hard layer is changed to take at least one maximum value from the start to the end of physical vapor deposition.