JP7037121B2 - Surface-coated TiN-based cermet cutting tool with excellent chipping resistance due to the hard coating layer - Google Patents

Description

The present invention relates to a surface-coated TiN-based cermet cutting tool having excellent chipping resistance.

Conventionally, on the surface of a substrate made of titanium carbonitride (hereinafter referred to as TiCN) -based cermet or the like, a carbide (hereinafter referred to as TiC) layer of Ti formed by chemical vapor deposition and a nitride (hereinafter also referred to as TiN) are used. A Ti compound layer consisting of two or more of a layer (shown), a carbide (hereinafter referred to as TiCN) layer, a carbide oxide (hereinafter referred to as TiCO) layer, and a carbonitride oxide (hereinafter referred to as TiCNO) layer. A surface-coated cermet cutting tool having a hard coating layer having an aluminum oxide (hereinafter referred to as Al ₂ O ₃ ) layer formed by chemical vapor deposition as an upper layer is well known.
However, the above-mentioned conventional surface-coated cermet cutting tool is prone to abnormal wear such as chipping and chipping under cutting conditions where a high load acts on the cutting edge, and the tool life is shortened. Various proposals have been made to this end.

For example, Patent Document 1 describes one or more hard dispersed phase forming components of cermet (Ti, Zr, Hr, Ta, Nb, W, Mo, Cr carbides, nitrides, and carbonitrides: 70 to A surface formed by chemical vapor deposition of a TiN layer or a TiCN layer on a substrate consisting of 95% by weight and a cermet consisting of one or more bonded phase forming components of Co, Ni, Al: 5 to 30% by weight). In the production of the coated cermet cutting tool, a mixed gas containing NH ₃ is used when forming the TiN layer, and a mixed gas containing CH ₃ CN is used when forming the TiCN layer. It has been proposed to improve the wear resistance of a surface-coated cermet cutting tool by preventing the bonded phase-forming component in the cermet substrate from diffusing and mixing into the TiN layer or the TiCN layer.

Further, in Patent Document 2, a carbide of Ti is described on the surface of a TiCN-based cermet substrate containing 12 to 20% by weight of a bonded phase forming component mainly composed of Co and Ni by using a chemical vapor deposition method or a physical vapor deposition method. In a surface-coated cermet cutting tool formed by forming a multi-layered hard coating layer composed of two or more of nitrides, carbonitrides, and aluminum oxide, the surface portion of the substrate is set to 0.5. The hard coating layer having an average layer thickness of about 1.5 μm and being composed of a soft elution alloy layer composed of bonded phase constituents and in contact with the elution alloy layer on the surface of the substrate is 0.5 to 5 μm. It has been proposed to construct a bonded phase component diffusion-preventing layer made of titanium nitride with an average layer thickness, and this surface-coated cermet cutting tool has excellent toughness due to the elution alloy layer formed on the surface of the substrate. It is said that it is possible to suppress the occurrence of chipping and chipping on the cutting edge.

Further, in Patent Document 3, in a surface-coated cermet cutting tool in which a Ti compound layer is vapor-deposited and formed as a first layer on the surface of a TiCN-based cermet substrate containing W and Mo, the TiCN phase and the hard coating layer of the substrate are described. A Mo-enriched layer having an average thickness of 0.5 to 10 nm or a W-enriched layer is further formed at the interface between the two, and the Mo content and W content of the concentrated layer are preferably 5 to 50 atomic%. Proposes a surface-coated cermet cutting tool in which a concentrated layer is formed at an interface of 60% or more of the interface length between the TiCN phase of the substrate and the hard coating layer.
Since this surface-coated cermet cutting tool enhances the chemical bond between the TiCN-based cermet substrate and the hard coating layer, the adhesion strength between the hard coating layer and the substrate is excellent, and high-speed intermittent cutting in which a high load acts on the cutting edge. Even when used for processing, it is said to exhibit excellent chipping resistance and wear resistance.

Non-Patent Document 1 discusses the influence of the structure near the interface between the substrate and the coating when the coating is formed on the cermet substrate by the CVD method, and is a TiC-Mo ₂ C-Ni cermet substrate. When TiC is coated on the surface by the CVD method, micropores are formed on the substrate side near the interface between the substrate and the coating in the initial stage of CVD, and Ni is incorporated into the coating to form the substrate and the coating. A NiTi compound phase is formed on the coating side near the interface of the film, and as the coating grows, the NiTi compound phase moves to the vicinity of the coating surface. It is stated that micropores are formed.
The decrease in the strength of the coated cermet decreased with the increase in the thickness of the coating. In this decrease in strength, the sum of the film thickness and the thickness of the micropore formation region generated near the interface acts as a stress concentration source for fracture. It is stated that it is thought to be due to the fact that it is done.

Japanese Unexamined Patent Publication No. 3-226576 Japanese Unexamined Patent Publication No. 4-289003 Japanese Unexamined Patent Publication No. 2015-178172

"Powder and Powder Metallurgy" Vol. 33, No. 5 (July 1986) p.274-279

In recent years, the performance of cutting equipment has been remarkably improved, while there is a strong demand for labor saving, energy saving, and cost reduction for cutting processing, and along with this, cutting processing tends to be faster and more efficient. Surface-coated cermet cutting tools are further required to have abnormal damage resistance such as chipping resistance, chipping resistance, and peeling resistance, as well as excellent wear resistance over a long period of use. There is.

For example, in the surface-coated cermet cutting tool proposed in Patent Document 1, when a TiN layer or a TiCN layer is chemically vapor-deposited on a cermet substrate, a bonded phase is formed in the cermet substrate in the TiN layer or the TiCN layer. By forming a film so that the components do not diffuse or mix, the wear resistance of the surface-coated cermet cutting tool is improved. Further, in Patent Document 2, the surface portion of the cermet substrate is covered with cermet. To form an elution alloy layer consisting of Co and Ni, which are the main components of the bonded phase, to increase toughness, while preventing the bonded phase components mainly composed of Co and Ni from diffusing and moving to the hard coating layer. By forming a hard coating layer on the surface, the occurrence of chipping and chipping of the surface-coated cermet cutting tool is suppressed, and the TiCN-based cermet containing W and Mo proposed in Patent Document 3 is used as a substrate. In the surface-coated cermet cutting tool, the adhesion strength between the TiCN-based cermet substrate and the hard coating layer is increased by forming a Mo-concentrated layer or a W-concentrated layer at the interface between the TiCN phase of the substrate and the hard coating layer. , Chipping resistance and wear resistance are improved.
However, the surface-coated cermet cutting tools proposed in Patent Documents 1 to 3 in which a hard coating layer made of a Ti compound is vapor-deposited on the surface of a cermet substrate exhibit some cutting performance in cutting under normal conditions. Even so, the toughness of the cermet substrate itself is not sufficient when it is subjected to cutting conditions such as wet high-speed milling of alloy steel where an intermittent and shocking high load acts on the cutting edge. Since the adhesion between the cermet substrate and the hard coating layer is not sufficient, chipping is likely to occur, and as a result, the tool life is short.
Therefore, in a surface-coated cermet cutting tool in which a hard coating layer made of a Ti compound is vapor-deposited on the surface of a cermet substrate, improvement in chipping resistance under cutting conditions in which a high load acts on the cutting edge has been strongly desired.

In order to solve the above problems, the present inventors exhibit excellent chipping resistance and exhibit excellent chipping resistance even when subjected to cutting work such as wet high-speed milling of alloy steel in which a high load acts on the cutting edge. As a result of diligent research to provide a surface-coated cermet cutting tool that exhibits excellent wear resistance over a long period of time, the following findings were obtained.

The non-patent document 1 describes changes in the structure of the substrate and the coating over time when the surface of the TiC-Mo ₂ C-Ni cermet substrate is coated with TiC by the CVD method, and the surface of the cermet substrate is hard coated. Although it does not disclose the general characteristics of a surface-coated cermet cutting tool in which a layer is vapor-deposited, micropores formed near the interface between the substrate and the coating are cited as one of the factors for reducing the strength of the substrate.
Furthermore, it is clear that the micropores formed near the interface between the substrate and the coating deteriorate the adhesion between the substrate and the coating in addition to the decrease in the strength of the substrate. It can be said that it suggests that it contributes.

Therefore, the present inventors use a TiN-based cermet as a substrate, and have a hard coating layer (specifically, a nitride of titanium (hereinafter referred to as "TiN") and a carbide of titanium (hereinafter, "TiC") on the surface thereof. (Represented by), titanium carbide (hereinafter referred to as "TiCN") and aluminum oxide (hereinafter referred to as "Al ₂ O ₃ "), one layer or two or more layers) are coated and formed by a chemical vapor deposition method. In the surface-coated TiN-based cermet cutting tool, the formation of micropores is avoided by adjusting the component composition of the TiN-based cermet and the sintering conditions, and the vicinity of the interface between the TiN-based cermet substrate and the hard coating layer. It has been found that by forming a unique structure, the toughness of the TiN-based cermet substrate itself can be improved, and at the same time, the adhesion between the TiN-based cermet substrate and the hard coating layer can be improved.
A surface-coated TiN-based cermet cutting tool in which a hard coating layer having excellent adhesion to the TiN-based cermet substrate is coated and formed on the surface of the TiN-based cermet substrate with improved toughness by a chemical vapor deposition method is used. Even when it is used for cutting such as wet high-speed milling of alloy steel, which has an intermittent and shocking high load on the cutting edge, the occurrence of chipping is suppressed and excellent wear resistance is exhibited. Therefore, it was found that it exhibits excellent cutting performance over a long period of use.

The present invention has been made based on the above findings.
"(1) In a surface-coated TiN-based cermet cutting tool whose substrate is a TiN-based cermet and whose surface is coated with a hard coating layer.
(A) The TiN-based cermet contains a TiN phase having an average area ratio of 70 to 94 area% and a Mo _2C phase having an average area ratio of 1 to 25 area% when the cross section is observed, and the balance is bonded. It has a sintered structure consisting of phases and has a
(B) In the TiN-based cermet, a graphite-containing layer containing a graphite phase having an area ratio of 0.5 to 20 area% is present from the surface of the substrate toward the inside thereof with an average layer thickness of 2 to 20 μm.
(C) The surface-coated TiN-based cermet cutting tool, wherein the hard coating layer is composed of one layer or two or more layers selected from the TiN layer, the TiC layer, the TiCN layer _, and the _Al2O3 layer. ..
(2) One layer or two or more Ti compound layers selected from the TiN layer, the TiC layer and the TiCN layer are formed on the surface of the TiN-based cermet with an average layer thickness of 5 μm or more, and the TiN is formed. The Ti compound layer immediately above the surface of the base cermet contains 2 to 10 atomic% of Mo, and the Mo-containing Ti compound layer having an average particle size of 1 to 50 nm is formed with an average layer thickness of 1 to 5 μm. The surface-coated TiN-based cermet cutting tool according to (1) above.
(3) The above-mentioned (1) or (2), wherein the average microhardness of the graphite-containing layer is 50 to 80% of the average microhardness inside the TiN-based cermet. Surface-coated TiN-based cermet cutting tool. "
It has the characteristics of.

In the surface-coated TiN-based cermet cutting tool of the present invention, the formation of micropores in the sintered structure is suppressed by specifying the component composition of the TiN-based cermet substrate, and the substrate has a predetermined hardness and excellent toughness. In particular, the presence of the low-hardness graphite-containing layer only in a predetermined layer thickness (depth region) on the surface of the TiN-based cermet substrate improves the toughness of the substrate surface. Demonstrates excellent chipping resistance and wear resistance in cutting processes such as wet high-speed milling where an intermittent and shocking high load acts on the cutting edge.

Further, the surface-coated TiN-based cermet cutting tool of the present invention has a Mo-containing Ti compound layer having a predetermined Mo content and a predetermined average particle size in a predetermined thickness region of the hard coating layer immediately above the substrate surface. Therefore, the adhesion between the substrate and the hard coating layer is improved, which greatly contributes to the improvement of the chipping resistance of the surface-coated TiN-based cermet cutting tool.

An example of a vertical cross-sectional SEM image (magnification: 2000 times) of the surface-coated TiN-based cermet cutting tool of the present invention is shown.

Next, the surface-coated TiN-based cermet cutting tool of the present invention (hereinafter, also referred to as “coated TiN-based cermet tool”) will be described more specifically.

FIG. 1 shows an example of the cross-sectional structure of the coated TiN _- based cermet tool of the present invention. A hard coating layer (TiCN layer and _Al2O3 layer in FIG. ₁ ) is formed by a chemical vapor deposition method, and a graphite-containing layer is further formed in a specific region from the surface of the TiN-based cermet toward the inside. Further, a Mo-containing Ti compound layer is formed in a specific region of the hard coating layer (TiCN layer) directly above the TiN-based cermet.

First, the TiN phase, the Mo _2C phase, the bonded phase, and the graphite-containing layer constituting the TiN-based cermet will be described, and then the Mo-containing Ti compound layer formed on the hard coating layer directly above the TiN-based cermet will be described.

TiN phase:
When the vertical cross section of the coated TiN-based cermet tool of the present invention is observed, if the average area ratio of the TiN phase to the TiN-based cermet substrate is less than 70 area%, the hardness of the substrate is not sufficient, while the hardness of the substrate is not sufficient. When the average area ratio of the TiN phase exceeds 94 area%, micropores (fine voids) are likely to be formed in the sintered structure, which reduces toughness. Therefore, the average TiN phase in the TiN-based cermet substrate is average. The area ratio is 70 to 94 area%.
The preferred average area ratio of the TiN phase is 75 to 90 area%, and the more preferable average area ratio is 85 to 90 area%.
In the present invention, the vertical cross section of the TiN-based cermet substrate is observed with a scanning electron microscope (SEM) equipped with an energy dispersive X-ray analyzer (EDS), and the region in the obtained secondary electron image (for example, for example). The amount of elements contained in the region (40 × 50 μm ² region) is measured to identify the TiN phase, Mo ₂ C phase and bonded phase components (for example, Fe phase, Ni phase or Fe—Ni alloy phase), and each phase is the region. The area ratio was calculated, and the area ratio was calculated in a plurality of regions having at least 5 regions, and the average value of these was taken as the area% of each phase.
In the TiN-based cermet substrate of the present invention, the unavoidable impurity component inevitably mixed from the manufacturing process or the like is within a range that does not impair the object of the present invention (that is, a range that does not reduce the hardness and toughness of the TiN-based cermet substrate). (Inside), a small amount of content (mixture) is allowed.

Mo ₂ C phase:
If the average area ratio of the Mo ₂ C phase in the TiN-based cermet substrate is less than 1 area%, the wettability between the TiN phase and the bonded phase is insufficient, and micropores are formed in the sintered structure, resulting in a decrease in toughness. ..
On the other hand, when the average area ratio of the Mo ₂ C phase exceeds 25 area%, double carbides such as Fe ₃ Mo ₃ C phase and double nitrides such as Fe ₃ Mo ₃ N phase are likely to be generated, which causes a decrease in toughness. Therefore, the average area ratio of the Mo _2C phase in the TiN-based cermet substrate is 1 to 25 area%.
The preferred average area ratio of the Mo _2C phase is 1 to 15 area%, and the more preferable average area ratio is 1 to 10 area%.

Bonded phase:
In the coated TiN-based cermet tool of the present invention, there are no particular restrictions on the bonded phase components constituting the TiN-based cermet and their average area ratios, but from the viewpoint of increasing the toughness of the TiN-based cermet, Fe and Ni are bonded phases. The average area ratio of the bonded phase (total average area ratio of Fe phase, Ni phase, and Fe—Ni alloy phase) contained as a component and occupied in the TiN-based cermet substrate is preferably 5 to 15 area%.
Here, when the average area ratio of the bonded phase is less than 5 area%, the toughness of the TiN-based cermet substrate decreases due to the small amount of the bonded phase, while the average area ratio of the bonded phase exceeds 15 area%. This is because the amount of the TiN phase, which is a hard phase component, is relatively reduced, so that the hardness required for the substrate cannot be secured.

Further, in the bonded phase, the content ratio of Ni to the total content of Fe and Ni constituting the bonded phase (= Ni / (Fe + Ni) × 100) is set to 15 to 35% by mass, whereby the TiN-based cermet substrate is formed. The toughness and hardness of the product can be further increased.
This is because when the content ratio of Ni to the total content of Fe and Ni (= Ni / (Fe + Ni) × 100) is less than 15% by mass, Ni is solid-dissolved in Fe, but the bonded phase is solid-dissolved. When the hardness of the bonded phase is insufficient because the effect of strengthening is not exhibited, and the content ratio of Ni to the total content of Fe and Ni (= Ni / (Fe + Ni) × 100) exceeds 35% by mass. This is because the intermetallic compound FeNi ₃ is likely to be generated, and thus the toughness of the bonded phase is lowered.

Graphite-containing layer:
For the coated TiN-based cermet tool of the present invention, a scanning electron microscope (SEM) equipped with an energy dispersive X-ray analyzer (EDS) is used to include the surface of the TiN-based cermet substrate and toward the inside of the substrate. When the vertical cross section of the TiN-based cermet substrate is observed over a depth of 500 μm, the presence of a region containing a graphite phase is confirmed from the surface of the substrate toward the inside of the substrate.
When the region in which the area ratio of the graphite phase occupies 0.5 to 20 area% of the observation region is defined as the graphite-containing layer, the TiN-based cermet substrate of the present invention faces from the surface of the substrate to the inside of the substrate. Therefore, a graphite-containing layer is formed with an average layer thickness of 2 to 20 μm.
The presence of the graphite-containing layer improves the chipping resistance of the coated TiN-based cermet tool by improving the toughness of the surface of the substrate, but when the average layer thickness of the graphite-containing layer is less than 2 μm or the average area of the graphite phase. When the ratio is less than 0.5 area%, the effect of surface toughness of the TiN-based cermet substrate is not sufficient.
On the other hand, when the average layer thickness of the graphite-containing layer in the graphite-containing layer exceeds 20 μm or the average area ratio of the graphite phase exceeds 20 area%, the hardness of the graphite-containing layer is excessively lowered. Deformation of the TiN-based cermet substrate or peeling of the hard coating layer is likely to occur.
Therefore, in the present invention, the surface of the TiN-based cermet substrate contains a graphite phase having an average layer thickness of 2 to 20 μm and an average area ratio of 0.5 to 20 area% from the surface of the substrate toward the inside of the substrate. Form a graphite-containing layer.

Hardness of graphite-containing layer:
The vertical cross section of the TiN-based cermet substrate containing the graphite-containing layer contains 0.5 to 20 area% of graphite when the microhardness is measured at intervals of 10 μm over a depth of 500 μm in the internal direction from the surface of the cermet substrate. The average microhardness in the graphite-containing layer may be within the range of 50 to 80% of the average microhardness inside the cermet substrate (hereinafter, simply referred to as “inside the cermet substrate”) exceeding 500 μm from the surface of the cermet substrate. preferable.
Here, when the average microhardness in the graphite-containing layer is less than 50% of the average microhardness inside the cermet substrate, the graphite-containing layer is likely to undergo plastic deformation and is coated on the surface of the graphite-containing layer. The hard coating layer is easily peeled off.
On the other hand, when the average microhardness in the graphite-containing layer exceeds 80% of the average microhardness inside the cermet substrate, the toughness improving effect of the TiN-based cermet substrate is reduced, and the coated TiN-based cermet It cannot be expected that the chipping resistance of the tool will be improved.
Therefore, the hardness of the graphite-containing layer formed from the surface of the cermet substrate toward the inside thereof is 50, which is the average microhardness inside the cermet substrate (for example, an internal region having a depth of more than 500 μm from the surface of the cermet substrate). It is preferably -80%.

Mo-containing Ti compound layer:
In the coated TiN-based cermet tool of the present invention, when the hard coating layer formed by coating directly on the surface of the cermet substrate is a Ti compound layer, the vertical cross section of the hard coating layer including the interface between the surface of the cermet substrate and the Ti compound layer is displayed. Observe with a scanning electron microscope (SEM) equipped with an energy dispersive X-ray analyzer (EDS), and measure the amount of contained elements in a region (for example, a region of 40 × 50 μm ² ) in the obtained secondary electron image. If this is the case, the formation of a Mo-containing region containing a trace amount of Mo is confirmed in the Ti compound layer immediately above the surface of the substrate.
The Mo component contained in the Mo-containing region is formed by diffusing Mo from the surface of the TiN-based cermet to the Ti compound layer during chemical vapor deposition, but Mo is diffused into the Ti compound layer. By doing so, the adhesion between the TiN-based cermet substrate and the Ti compound layer is improved.
When the region containing 2 to 10 atomic% of Mo in the Mo-containing region is defined as the Mo-containing Ti compound layer, the average layer thickness of the Mo-containing Ti compound layer is preferably 1 to 5 μm, and further. The average particle size of the Mo-containing Ti compound particles in the Mo-containing Ti compound layer (the average value of the particle size measured in the direction parallel to the surface of the TiN-based cermet substrate) is preferably 1 to 50 nm.

Here, when the Mo content in the Mo-containing Ti compound layer is less than 2 atomic% or the average layer thickness of the Mo-containing Ti compound layer is less than 1 μm, the adhesion between the TiN-based cermet substrate and the hard coating layer is improved. On the other hand, when the Mo content in the Mo-containing Ti compound layer exceeds 10 atomic%, or when the average layer thickness of the Mo-containing Ti compound layer exceeds 5 μm, the TiN-based cermet substrate is used. The Mo content in the Mo-containing Ti compound layer is 2 to 10 atomic%, and the average layer of the Mo-containing Ti compound layer is high, because the outflow of Mo is excessive and voids are likely to be generated in the TiN-based cermet substrate. The thickness is preferably 1 to 5 μm.
Further, the Mo-containing Ti compound particles are preferably fine particles having an average particle size of 1 to 50 nm because the adhesion strength of the coating layer decreases when they become coarse particles.

Here, the measurement of the Mo content in the Mo-containing Ti compound layer, the measurement of the average layer thickness of the Mo-containing Ti compound layer, and the measurement of the particle size of the Mo-containing Ti compound particles in the Mo-containing Ti compound layer are, for example, as follows. Can be done.
Using a scanning electron microscope (SEM) and an energy dispersive X-ray analyzer (EDS), the vertical cross section of a coated TiN-based cermet tool including the interface between the surface of the TiN-based cermet substrate and the hard coating layer is 5000 times larger. In the visual field, the composition of Mo and Ti is analyzed in the thickness direction of the hard coating layer (that is, the direction perpendicular to the surface of the TiN-based cermet substrate).
From the result, a region in the layer thickness direction in which the Mo content (that is, Mo × 100 / (Mo + Ti)) is 2 to 10 atomic% is specified, and this is determined as the layer thickness of the Mo-containing Ti compound layer.
Further, this measurement is performed in five fields of view, and the average value is taken as the average thickness of the Mo-containing Ti compound layer.
Further, in the region of the Mo-containing Ti compound layer specified above, the particle size of the Mo-containing Ti compound particles is measured in a direction parallel to the surface of the substrate using a scanning electron microscope (SEM), and this measurement is performed in five fields. The average value thereof is obtained as the average particle size of the Mo-containing Ti compound particles.

Fabrication of coated TiN-based cermet tools:
In producing the coated TiN-based cermet tool of the present invention, for example, as the raw material powder thereof, TiN: 55 to 92% by mass, Mo ₂ C: 1 to 40% by mass, Fe: 5 to 18% by mass, Ni: 1 to 1 to It is preferable to use a raw material powder having a component and composition which is 5% by mass and satisfies the relationship that the mass% of Ni (= Ni × 100 / (Fe + Ni)) is 15 to 35% by mass with respect to the total amount of Ni and Fe. Is.
Then, the raw material powder satisfying the above conditions is mixed by a ball mill, and the mixed powder is press-molded to prepare a powder compact.
Then, the powder compact was baked in a temperature range of 1350 to 1450 ° C. for 30 to 120 minutes while flowing a mixed gas having a hydrogen concentration of 1 to 3% and a nitrogen concentration of 97 to 99% (nitrogen-diluted hydrogen atmosphere). The TiN-based sintered body of the present invention having excellent toughness and hardness can be produced by connecting, then switching to an Ar gas atmosphere, and naturally cooling to room temperature.
The reason why the powder compact is sintered in a nitrogen-diluted hydrogen atmosphere is to improve the wettability between the TiN powder and the bonded phase (mainly the Fe component) and at the same time to improve the sinterability.
Next, the TiN-based cermet substrate is charged into a chemical vapor deposition apparatus to form a hard coating layer by vapor deposition.
As the hard coating layer, one layer or two or more layers selected from the TiN layer, the TiC layer _, the TiCN layer and the _Al2O3 layer are coated, and the TiN layer is directly above the surface of the TiN-based cermet substrate. It is preferable that one or two or more Ti compound layers selected from the TiC layer and the TiCN layer are first vapor-deposited.
The total thickness of the hard coating layer is preferably 3 to 20 μm.
There are no particular restrictions on the vapor deposition conditions of the hard coating layer, but for example, for the TiCN layer,
Reaction gas (volume%):
TiCl _{42%, CH 3 CN} 0.7%, N ₂ 10%, H ₂ remaining,
Reaction pressure: 7 kPa,
Reaction temperature: 900 ° C
It can be formed under the vapor deposition condition.
For the aluminum oxide layer,
Reaction gas (volume%):
AlCl ₃ 2.2%, CO ₂ 5.5%, HCl 2.2%,
H ₂ S 0.2%, H ₂ remaining,
Reaction pressure: 7 kPa,
Reaction temperature: 1000 ° C
It can be formed under the vapor deposition condition.
A coated TiN-based cermet tool can be manufactured by forming a hard coating layer by vapor deposition and then machining it into a predetermined shape.
Then, by manufacturing the coated TiN-based cermet tool in the above step, it has a sintered structure composed of TiN phase and Mo _2C phase having a specific area ratio and reduced micropores, and the TiN-based cermet substrate has a sintered structure. A coated TiN-based cermet tool having a graphite-containing layer having a predetermined layer thickness from the surface to the inside and having excellent toughness and excellent chipping resistance can be produced.
Further, when the first layer formed by vapor deposition immediately above the surface of the cermet substrate is one layer or two or more Ti compound layers selected from the TiN layer, the TiC layer and the TiCN layer, at least the first layer is used. A Mo-containing Ti compound layer having a predetermined amount of Mo content, a predetermined average particle size, and a predetermined average particle size is formed in the layer, thereby improving the adhesion between the TiN-based cermet substrate and the hard coating layer. , A coated TiN-based cermet tool with even better chipping resistance can be obtained.

Next, the coated TiN-based cermet tool of the present invention will be specifically described with reference to Examples.
As an example of the present invention, an example in which a Ti compound layer is coated and formed as a first layer on the surface of a TiN-based cermet substrate by chemical vapor deposition is shown.

As powders for producing a TiN-based cermet substrate, TiN powder having an average particle size of 10 μm, Mo ₂ C powder having an average particle size of 2 μm, Fe powder having an average particle size of 2 μm, and Ni powder having an average particle size of 1 μm are prepared. Raw material powders 1 to 8 were prepared by blending so as to have the blending ratio shown in 1 and blending the Fe powder and Ni powder so as to have the blending ratio shown in Table 1.
The average particle size referred to here means the median diameter (d50).

Next, the raw material powders 1 to 8 are filled in a ball mill and mixed to prepare mixed powders 1 to 8, and the mixed powders 1 to 8 are dried and then press-molded at a pressure of 100 to 500 MPa. Powder compacts 1 to 8 were produced.

Next, the powder compacts 1 to 8 are sintered under the conditions shown in Table 2 and then cooled to room temperature to cool the TiN-based cermet substrate of the present invention shown in Table 3 (hereinafter referred to as "the substrate of the present invention"). ) 1 to 8 were prepared.

For comparison, various powders having an average particle size equivalent to that of the tool of the present invention are blended so as to have the blending composition shown in Table 4 to prepare raw material powders 11 to 18, and then raw material powders 11 to 18 are added. The mixed powders 11 to 18 were prepared by filling and mixing in a ball mill, and the mixed powders 11 to 18 were dried and then press-molded at a pressure of 100 to 500 MPa to prepare powder compacts 11 to 18.
Next, the powder compacts 11 to 18 were sintered under the conditions shown in Tables 2 and 5, and then cooled to room temperature to obtain a cermet substrate of Comparative Example shown in Table 6 (hereinafter, “Comparative Example Substrate””. ) 11-18 were produced.

Next, the substrates 1 to 8 of the present invention and the substrates 11 to 18 of Comparative Examples were charged into a chemical vapor deposition apparatus, and the hard coating layers of the film types shown in Tables 7 and 8 were used as a multi-layered laminated structure in Table 7. The average layer thickness shown in Table 8 was used for vapor deposition.
Here, the hard coating layer is formed by vapor deposition as a laminated structure of up to four layers, but the number of layers is not limited, and a laminated structure of a larger number of layers may be used.
The vapor deposition conditions for the hard coating layer are not particularly limited, but the chemical vapor deposition conditions for TiN, TiC, TiCN _, and Al ₂ O3 in the substrates 1 to 8 of the present invention and the substrates 11 to 18 of the comparative examples are as follows. be.
[Chemical vapor deposition conditions for TiN]
Reaction gas (volume%):
TiCl _{42%, N 2 30%, H 2 remaining ,}
Reaction pressure: 7 kPa,
Reaction temperature: 1000 ° C
[Chemical vapor deposition conditions for TiC]
Reaction gas (volume%):
TiCl _{42%, CH 47%, H 2 remaining ,}
Reaction pressure: 7 kPa,
Reaction temperature: 1000 ° C
[Chemical vapor deposition conditions for TiCN]
Reaction gas (volume%):
TiCl _{42%, CH 3 CN} 0.7%, N ₂ 10%, H ₂ remaining,
Reaction pressure: 7 kPa,
Reaction temperature: 900 ° C
[Chemical vapor deposition conditions for Al ₂ O ₃ ]
Reaction gas (volume%):
AlCl ₃ 2.2%, CO ₂ 5.5%, HCl 2.2%,
H ₂ S 0.2%, H ₂ remaining,
Reaction pressure: 7 kPa,
Reaction temperature: 1000 ° C

The coated TiN-based cermet tool of the present invention (hereinafter referred to as "tool of the present invention") 1 to 8 and the coated TiN-based cermet tool of the present invention shown in Table 7 having an insert shape of ISO standard SEEN1203AFSN by subjecting the hard coating layer to vapor deposition and then grinding. Covered cermet tools (hereinafter referred to as "comparative example tools") 11 to 18 of the comparative examples shown in Table 8 were produced.

Then, the vertical cross sections of the tools 1 to 8 of the present invention and the tools 11 to 18 of the comparative examples were observed with a scanning electron microscope (SEM) equipped with an energy dispersive X-ray analyzer (EDS), and the two obtained. The amount of contained elements in the measurement region (for example, a measurement region of 100 μm × 100 μm) in the secondary electron image is measured to identify the TiN phase, Mo _2C phase and Fe—Ni phase, and the area occupied by each phase in the measurement region. The ratio was calculated, the area ratio was calculated in the measurement area of 5 visual fields, and the value obtained by averaging these calculated values was obtained as the area% of each phase in the sintered structure.
Further, with respect to the Fe—Ni phase, the Ni content and the Fe content in the phase were measured at 10 points on the Fe—Ni phase using an Auger electron spectroscope, and the obtained calculated values were averaged. From the value, the content ratio of Ni to the total content of Fe and Ni (= Ni × 100 / (Fe + Ni)) was determined as% by mass.
Tables 3 and 6 show these values.

Next, for the tools 1 to 8 of the present invention and the comparative examples tools 11 to 18, a scanning electron microscope (SEM) equipped with an energy dispersive X-ray analyzer (EDS) was used to include the surface of the TiN-based cermet substrate. In addition, the area of the graphite phase was measured over a depth of 500 μm toward the inside of the substrate, and the region where the average area ratio of the graphite phase was 0.5 to 20 area% was specified as the graphite-containing layer, and the graphite-containing layer was identified. The layer thickness was determined, and the layer thickness of the graphite-containing layer measured in five fields was averaged, and this was determined as the average layer thickness of the graphite-containing layer.
Tables 3 and 6 show these values.

Next, with respect to the tools 1 to 8 of the present invention and the tools 11 to 18 of the comparative examples, the micro-hardness was measured at intervals of 10 μm over a depth of 500 μm toward the inside of the substrate, including the surface of the TiN-based cermet substrate, and different. The average value measured at 5 points was taken as the average microhardness in the graphite-containing layer.
In addition, the micro-hardness inside the cermet substrate was also measured, and the average value measured at five different points was taken as the average micro-hardness inside the cermet substrate, and the average micro-hardness in the graphite-containing layer relative to the average micro-hardness inside the cermet substrate. The ratio (%) of was calculated.
Tables 3 and 6 show these values.

Next, for Tools 1 to 8 of the present invention and Comparative Examples Tools 11 to 18, the Mo content in the Mo-containing Ti compound layer was measured, the average thickness of the Mo-containing Ti compound layer was measured, and the Mo content in the Mo-containing Ti compound layer was measured. The particle size of the Ti compound particles was measured.
First, using a scanning electron microscope (SEM) and an energy dispersive X-ray analyzer (EDS), the vertical cross section of the coated TiN-based cermet tool including the interface between the surface of the TiN-based cermet substrate and the hard coating layer is 5000. The composition of Mo and Ti was analyzed in the thickness direction of the hard coating layer (that is, the direction perpendicular to the surface of the TiN-based cermet substrate) with a double field of view.
From the result, a region in the layer thickness direction in which the Mo content (that is, Mo × 100 / (Mo + Ti)) is 2 to 10 atomic% was specified, and this was determined as the layer thickness of the Mo-containing Ti compound layer. This measurement was performed in 5 fields of view, and the average value was taken as the average layer thickness of the Mo-containing Ti compound layer.
Then, in the region of the Mo-containing Ti compound layer specified above, the particle size of the Mo-containing Ti compound particles was measured in a direction parallel to the surface of the substrate using a scanning electron microscope (SEM), and this measurement was performed in 5 fields. The average value thereof is obtained as the average particle size of the Mo-containing Ti compound particles.
Tables 7 and 8 show these values.

Next, with the tools 1 to 8 of the present invention and the tools 11 to 18 of the comparative examples all screwed to the tip of the tool steel cutter with a fixing jig, the wet milling of the alloy steel shown below is performed. A test was carried out, the flank wear width of the cutting edge was measured, and the wear state of the cutting edge was observed.
Cutting conditions:
Work material: JIS / SCM440 block,
Cutting speed: 750 m / min,
Notch: 1.0 mm,
Feed: 0.11 mm / rev,
Cutting time: 13 minutes,
Table 9 shows the results of the cutting test.

As shown in Tables 3 and 6-9, in the tools 1 to 8 of the present invention, the TiN-based cermet substrate is formed with a predetermined component and composition, and the predetermined depth (layer thickness) from the surface of the substrate to the inside thereof is formed. Due to the formation of a graphite-containing layer or the formation of a Mo-containing Ti compound layer directly above the substrate, the cutting edge is subject to intermittent and shocking mechanical loads and a thermal cycle of rapid heating and quenching. Even in the cutting process where a heat load (thermal shock) acts, only slight chipping that does not cause an abnormality in the cutting edge or does not affect the cutting life occurs, which affects the cutting life seen in the comparative example tool. It showed excellent wear resistance over long-term use without causing chipping.
On the other hand, the tools 11 to 18 of Comparative Examples have wear resistance because the TiN-based cermet substrate deviates from the component composition specified in the present invention or the graphite-containing layer is not formed on the substrate. Not only is it not sufficient, but the tool life has been shortened due to chipping of the cutting edge, which is the main cause of the generation and propagation of thermal cracks.

Since the surface-coated TiN-based cermet cutting tool of the present invention has excellent chipping resistance and wear resistance, it can be applied not only to high-speed wet intermittent cutting but also as a cutting tool under other cutting conditions. It exhibits excellent cutting performance over a long period of use, and can fully satisfy the labor saving and energy saving of cutting processing and the cost reduction.

Claims (3)

In a surface-coated TiN-based cermet cutting tool whose surface is a TiN-based cermet as a substrate and whose surface is coated with a hard coating layer.
(A) The TiN-based cermet contains a TiN phase having an average area ratio of 70 to 94 area% and a Mo _2C phase having an average area ratio of 1 to 25 area% when the cross section is observed, and the balance is bonded. It has a sintered structure consisting of phases and has a
(B) In the TiN-based cermet, a graphite-containing layer containing a graphite phase having an average area ratio of 0.5 to 20 area% exists from the surface of the substrate toward the inside thereof with an average layer thickness of 2 to 20 μm. ,
(C) The surface-coated TiN-based cermet cutting tool, wherein the hard coating layer is composed of one layer or two or more layers selected from the TiN layer, the TiC layer, the TiCN layer _, and the _Al2O3 layer. .. Immediately above the surface of the TiN-based cermet, one or more Ti compound layers selected from the TiN layer, the TiC layer and the TiCN layer are formed with an average layer thickness of 5 μm or more, and the TiN-based cermet has an average layer thickness of 5 μm or more. The Ti compound layer immediately above the surface contains 2 to 10 atomic% of Mo, and the Mo-containing Ti compound layer having an average particle size of 1 to 50 nm is formed with an average layer thickness of 1 to 5 μm. The surface-coated TiN-based cermet cutting tool according to claim 1. The surface-coated TiN-based cermet according to claim 1 or 2, wherein the average micro-hardness of the graphite-containing layer is 50 to 80% of the average micro-hardness inside the TiN-based cermet. Cutting tool.

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