JP5382594B2 - Surface coated cutting tool - Google Patents

Description

  The present invention relates to a surface-coated cutting tool.

  A surface-coated cutting tool obtained by coating a base material such as cemented carbide with various coatings is used as a cutting tool for cutting various materials. It is known that when such a cutting tool is used under high-speed cutting conditions, the cutting edge temperature is about 850 ° C. or higher at the maximum. If the cutting edge becomes hot, the heat will be transferred to the base material through the coating, but if the base material is exposed to high temperature, various adverse effects will be exerted, thus preventing heat transfer. Is desired.

  In recent years, in order to increase productivity by cutting, there has been a tendency to adopt higher-speed or higher-feed cutting conditions than before, and there are various demands for the development of cutting tools capable of cutting at a high speed of 300 to 600 m / min or more, for example. The industry is growing, especially in the auto and motorcycle manufacturers.

Therefore, in order to protect the substrate from high-temperature application under the above-described cutting conditions, various surfaces formed with a coating using ZrO ₂ (zirconium oxide) or Zr in combination with aluminum oxide, which are known as materials having excellent heat insulation properties. Coated cutting tools have been proposed (Japanese Patent Laid-Open No. 2010-110833 (Patent Document 1), Japanese Patent Laid-Open No. 2009-045729 (Patent Document 2), Japanese Patent Laid-Open No. 08-188879 (Patent Document 3)).

JP 2010-110833 A JP 2009-045729 A Japanese Patent Laid-Open No. 08-188879

Patent Document 1 discloses a surface-coated cutting tool using a film having an atomic ratio Zr / (Al + Zr) between Al and Zr in the range of 0.002 to 0.01. However, this film has a low Zr content as described above, and Zr does not exist independently as ZrO ₂ but exists as a solid solution oxide with Al. Patent Document 1 mentions that as a reason for adopting such a Zr-containing form, when Zr is contained in an atomic ratio of 0.01 or more, ZrO ₂ precipitates and the strength decreases, but Zr is excellent in heat insulation. It is considered that sufficient heat insulation cannot be obtained because the content of is limited.

  Patent Document 2 discloses a surface-coated cutting tool in which a film including an aluminum oxide layer containing zirconium oxide is formed. However, the aluminum oxide layer containing zirconium oxide is formed immediately above the single layer of α-type aluminum oxide, and has a form in which aluminum oxide crystal grains are continuously present in both layers. For this reason, although heat insulation by zirconium oxide is expected to some extent, if a crack occurs in the coating during cutting, the crack propagates along the continuous aluminum oxide crystal particles, resulting in poor intermittent cutting performance. become.

Patent Document 3 discloses a surface-coated cutting tool in which an Al ₂ O ₃ coating containing ZrO ₂ is formed. Since this ZrO ₂ has a crystal structure transformed from tetragonal to monoclinic, strength and It is said to have excellent fracture resistance. Although a certain degree of heat insulation is expected by this coating, further improvement of the heat insulation is desired depending on recent cutting conditions.

  This invention is made | formed in view of the above present conditions, The place made into the objective is to provide the surface coating cutting tool which made the heat insulation effect and cutting performance of a film compatible.

The present inventor made extensive studies to solve the above problems, and as a result, it was possible to use Al ₂ O ₃ and ZrO ₂ in combination, and to control the mixing ratio and crystal structure of ZrO ₂ in that case. The present invention has been completed by obtaining the knowledge that it is the most effective for the above and further studying based on this knowledge.

That is, the surface-coated cutting tool of the present invention includes a substrate and a coating formed on the substrate, the coating includes an aluminum oxide layer and an oxide mixed layer, and the aluminum oxide layer is oxidized. Al ₂ O ₃ is included as an oxide, and the oxide mixed layer includes Al ₂ O ₃ and ZrO ₂ as oxides, and an atomic ratio of Al to Zr is 0.01 ≦ Zr / (Al + Zr) ≦ 0.5. The ZrO ₂ is included in a state where at least cubic crystals are present as its crystal structure.

Here, the ZrO ₂ is preferably contained as crystal grains having an average grain size of 1 μm or less, and the aluminum oxide layer is preferably disposed immediately below the oxide mixed layer.

Further, the aluminum oxide layer and the oxide mixed layer preferably do not contain Al ₂ O ₃ crystal grains existing across both layers, and the coating film has a thickness of 2500 to 10,000 Js ^−1/2 m ^−. It preferably has a thermal permeability of ² K ⁻¹ .

  The surface-coated cutting tool of the present invention has an extremely excellent effect of being excellent in the heat insulating effect of the coating and effectively protecting the base material during cutting, and also in cutting performance.

Hereinafter, the present invention will be described in more detail.
<Surface coated cutting tool>
The surface-coated cutting tool of the present invention comprises a base material and a coating film formed on the base material. The surface-coated cutting tool of the present invention having such a configuration is, for example, a drill, end mill, milling or turning cutting edge replacement cutting tip, metal saw, gear cutting tool, reamer, tap, or pin shaft milling of a crankshaft. It can be used very effectively as an industrial chip.

<Base material>
As the base material of the surface-coated cutting tool of the present invention, a conventionally known material known as such a cutting tool base material can be used without any particular limitation. For example, cemented carbide (for example, WC-based cemented carbide, including WC, including Co or further including carbonitride such as Ti, Ta, Nb, etc.), cermet (TiC, TiN, TiCN, etc.) High-speed steel, ceramics (titanium carbide, silicon carbide, silicon nitride, aluminum nitride, aluminum oxide, and mixtures thereof), cubic boron nitride sintered body, diamond sintered body Etc. can be mentioned as examples of such a substrate.

  When a cemented carbide is used as such a base material, the effect of the present invention is exhibited even if such a cemented carbide contains an abnormal phase called free carbon or η phase in the structure. In addition, these base materials may have a modified surface. For example, in the case of cemented carbide, a de-β layer may be formed on the surface, and in the case of cermet, a surface hardened layer may be formed. The effect of the invention is shown.

<Coating>
The coating formed on the base material of the surface-coated cutting tool of the present invention has an effect of protecting the base material from high temperatures by having heat insulation properties, and improves cutting performance such as wear resistance and fracture resistance. Shows the effect of Such a film of the present invention includes at least an aluminum oxide layer and an oxide mixed layer.

  As long as the coating in the present invention includes the aluminum oxide layer and the oxide mixed layer as described above, the coating may further include other layers. In addition, the film in this invention may coat | cover the whole surface on a base material, and may coat | cover a base material partially.

  In addition, as a measuring method of a film thickness, it can measure by cut | disconnecting a surface coating cutting tool and observing the cross section with SEM (scanning electron microscope) or a metal microscope. The composition and crystal structure of the coating can be identified by an energy dispersive X-ray analyzer attached to the field emission scanning electron microscope, and the crystal structure can be specified by using an X-ray diffractometer. it can.

Hereinafter, each layer contained in the coating film of the present invention will be described.
<Oxide mixed layer>
The oxide mixed layer of the present invention contains Al ₂ O ₃ and ZrO ₂ as oxides in a range where the atomic ratio of Al to Zr is 0.01 ≦ Zr / (Al + Zr) ≦ 0.5, ZrO ₂ is characterized by being contained in a state where at least cubic crystals exist as its crystal structure. That is, the oxide mixed layer of the present invention is a layer containing Al ₂ O ₃ and ZrO _{2 under} the above conditions, and the coating of the present invention includes one or more such oxide mixed layers.

Generally, under severe cutting conditions in which heat generated during cutting is accumulated on the base material of the cutting tool, it is required to protect the base material from the heat. This is because if the base material is deformed or altered by the heat, the cutting performance is adversely affected. ZrO ₂ (zirconium oxide, zirconia) has a lower thermal conductivity than Al ₂ O ₃ (aluminum oxide, alumina) and is known to have excellent heat insulation. Therefore, it is conceivable to use this ZrO ₂ as a constituent element of the coating, but ZrO ₂ has a hardness lower than that of Al ₂ O ₃ and it is difficult to form a coating alone. Therefore, had been used with the conventional Al ₂ O _3, the proportion of ZrO ₂ is 0.01 or more in atomic ratio between Al and Zr ZrO ₂ is deposited strength was thought to decrease.

However, the inventor's research has provided completely new knowledge that overturns this conventional knowledge. That is, Al ₂ O ₃ and ZrO ₂ are included in a range where the atomic ratio of Al to Zr is 0.01 ≦ Zr / (Al + Zr) ≦ 0.5, and the crystal structure of ZrO ₂ is at least cubic. It has been found that the presence of ZrO ₂ provides an excellent heat insulating effect and improves the cutting performance such as wear resistance.

  Here, the atomic ratio of Al to Zr is more preferably 0.01 ≦ Zr / (Al + Zr) ≦ 0.2. When this atomic ratio is less than 0.01, a sufficient heat insulating effect is not shown, and when it exceeds 0.5, cutting performance decreases.

Moreover, it is not sufficient that the atomic ratio of Al and Zr satisfies the above range, and it is essential that ZrO ₂ has the above crystal structure. It is presumed that this is probably because the film contains a cubic crystal and is stable without changing the crystal structure even if the blade temperature rises during processing. Therefore, it is not preferable that other crystal structures such as monoclinic crystals are formed alone, and it is important that cubic crystals exist.

Such ZrO ₂ is preferably contained as crystal grains having an average grain size of 1 μm or less. This is because the effect of improving heat insulation is enhanced. Here, the average particle diameter means that the oxide mixed layer is observed with a field emission scanning electron microscope on the cut surface obtained by cutting the surface-coated cutting tool, and 5 μm of the Al ₂ O ₃ rich crystal body. The major axis (maximum particle diameter) is measured for each of the ZrO ₂ crystal grains interspersed in the crystal within a range of × 5 μm (the whole layer when the layer thickness is less than 5 μm). This measurement is performed at five arbitrary locations, and the average value is taken as the average particle size of ZrO ₂ .

  The thickness of the oxide mixed layer of the present invention is not particularly limited, but is preferably 1 μm or more and 30 μm or less, more preferably the upper limit is 25 μm or less, further preferably 20 μm or less, and the lower limit is 1.5 μm or more. More preferably, it is 2 μm or more. When the thickness is less than 1 μm, the heat insulation effect may not be sufficiently exhibited, and when it exceeds 30 μm, there is a tendency that a greater effect of improving the heat insulation is not recognized, and the blade edge strength may be reduced. Therefore, it becomes industrially disadvantageous.

Note that the crystal grain size and crystal structure of Al ₂ O ₃ contained in the oxide mixed layer are not particularly limited.

<Aluminum oxide layer>
The aluminum oxide layer of the present invention contains Al ₂ O ₃ as an oxide. That is, the aluminum oxide layer of the present invention is typically a layer made of Al ₂ O ₃ , and the coating of the present invention includes one or more such aluminum oxide layers.

  As described above, the oxide mixed layer of the present invention is a layer having excellent heat insulating properties, but when formed directly on a substrate, the adhesion strength tends to be insufficient. Therefore, the adhesion strength with the base material is improved by forming this aluminum oxide layer. Therefore, this aluminum oxide layer is preferably disposed directly below the oxide mixed layer. In addition, two or more such aluminum oxide layers may be used, and two or more of the oxide mixed layers may be used, and both of them may be alternately stacked.

Such an aluminum oxide layer can be employed without any particular limitation to a conventionally known structure that constitutes a film of such a surface-coated cutting tool. Therefore, the size of crystal grains and the crystal structure of Al ₂ O ₃ contained in the aluminum oxide layer are not particularly limited. However, it is preferable that the aluminum oxide layer and the oxide mixed layer do not include Al ₂ O ₃ crystal grains that exist across both layers. This is because if Al ₂ O ₃ crystal grains exist across these two layers, if a crack occurs in the coating, the crack may propagate along the crystal grains and destroy the entire coating. is there.

  The thickness of the aluminum oxide layer of the present invention is not particularly limited, but is preferably 1 μm or more and 15 μm or less, more preferably the upper limit is 12 μm or less, more preferably 10 μm or less, and the lower limit is 1 μm or more. Preferably it is 1.5 micrometers or more. When the thickness is less than 1 μm, the effect of improving the adhesion strength of the oxide mixed layer may not be sufficiently exhibited, and even when the thickness exceeds 15 μm, there is a tendency that a greater effect of improving the adhesion strength is not recognized, The blade edge strength may be lowered, which is industrially disadvantageous.

<Other layers>
The coating in the present invention may further contain one or more layers other than the oxide mixed layer and the aluminum oxide layer as described above. The formation position of such other layers is not particularly limited. By forming such other layers, for example, the adhesion between the coating and the substrate can be further improved, various cutting performances can be improved, lubricity can be imparted, and the adhesion to the work material can be improved. It is possible to provide an effect that it is possible to suppress wearing or to impart discriminating power to the blade edge used.

  Examples of compounds and metals constituting such other layers include group IVa elements (Ti, Zr, Hf, etc.), group Va elements (V, Nb, Ta, etc.), group VIa elements (Cr, etc.) in the periodic table of elements. , Mo, W, etc.), Al, Si, Cu, Pt, Au, Ag, Pd, Fe, Co, and Ni, or an alloy containing the metal, or an element period At least one element selected from the group consisting of group IVa elements, group Va elements, group VIa elements, Al and Si in the table, and at least one element selected from the group consisting of carbon, nitrogen, oxygen and boron; And the like. More specifically, AlN, AlCN, AlTiN, TiN, TiCN, TiC, TiCO, TiBN, TiCBN, VN, ZrC, ZrN, ZrCN, CrN, TiAlN, SiAlON, SiC, HfN, HfC, HfCN, etc. it can. Note that such other layers have a thickness of 0.01 μm or more and 20 μm or less, preferably 0.1 μm or more and 10 μm or less.

<Heat penetration rate>
The coating film having the above-described configuration of the present invention preferably has a heat permeability of 2500 to 10,000 Js ^−1/2 m ⁻² K ⁻¹ . The thermal permeability is an index of the heat insulation effect, and the closer the value is to 0, the better the heat insulation. In the present invention, by including the composition of the coating film, in particular, the oxide mixed layer, the thermal permeability of the coating film can be in the above range, thereby exhibiting a sufficient heat insulating effect.

In addition, when the said heat permeability becomes less than 2500Js < ^-1/2 > m ^<-2 > K < ^-1 >, although the heat insulation property is shown, the tendency for cutting performance to fall is shown. On the other hand, if it exceeds 10,000 Js ^−1/2 m ⁻² K ⁻¹ , sufficient heat insulating effect is not shown. Such heat permeability can be measured using a thermophysical microscope device.

<Manufacturing method>
The surface-coated cutting tool of the present invention can be produced by forming a film on a substrate by a chemical vapor deposition method (CVD method).

  Of the coating, the aluminum oxide layer and other layers excluding the oxide mixed layer can be formed by a conventionally known CVD method, and are not particularly limited.

For example, the other layers can be formed at 700 to 1300 ° C. and a pressure of 70 kPa or less using a source gas constituting each compound and a carrier gas such as hydrogen gas. The aluminum oxide layer can also be formed, for example, using a gas such as AlCl ₃ , CO ₂ , H ₂ S, HCl, and H ₂ as a source gas at 700 to 1500 ° C. and a pressure of 50 kPa or less.

On the other hand, the oxide mixed layer is preferably formed as follows.
That is, first, the reaction gas composition is 2 to 10% by volume of AlCl ₃ , 2 to 6% by volume of ZrCl ₄ , 1 to 2% by volume of CO ₂ , 0.01 to 0.02% by volume of C ₂ H. _4, 5-10 vol% of HCl, .09-0.5% by volume of H ₂ S, 7 to 20% by volume of Ar, and the remainder to H _2. This composition is characterized in that the concentration of ZrCl ₄ is higher than that of conventionally known compositions.

  The reaction atmosphere temperature is 850 to 1300 ° C., the reaction atmosphere pressure is 2 to 30 kPa, and the oxide mixed layer is formed by vapor deposition under the above conditions. This temperature and pressure can be selected over a wider range than conventional conditions.

More specifically, the flow of the reaction gas in the chemical vapor deposition apparatus is controlled by the pulse flow control by introducing ZrCl ₄ while flowing Ar in a pulsed manner after first introducing AlCl ₃ in the reaction gas. Thus, the structure of the oxide mixed layer as described above (that is, Al and Zr are included in the above atomic ratio, and ZrO ₂ has a specific crystal structure and is included as crystal grains having an average grain size of 1 μm or less. Control).

  In this way, the coating film of the present invention is formed on the substrate by a chemical vapor deposition method using a normal chemical vapor deposition apparatus.

In the case where the aluminum oxide layer is arranged immediately below the oxide mixed layer, after forming the aluminum oxide layer in the chemical vapor deposition apparatus, an Ar gas is flowed once, and the surface of the aluminum oxide layer is activated by the Ar gas. Is preferable. As a result, an oxide mixed layer is formed on the surface of the aluminum oxide layer whose surface is activated by Ar gas, and the adhesion between the two layers is improved, and Al ₂ O ₃ crystal grains exist across both layers. (That is, Al ₂ O ₃ crystal grains are continuously grown across both layers).

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.

<Preparation of substrate>
A raw material powder comprising 1% by weight of TiC powder, 3% by weight of NbC powder, 1% by weight of TaC powder, 1% by weight of TaNbC powder, 5% by weight of Co powder, and the balance of WC powder is prepared. Were mixed by ball milling in acetone for 27 hours.

  Next, the mixed powder was dried under low pressure, and then pressed into a green compact having a predetermined shape at a pressure of 100 MPa. Subsequently, this green compact was vacuum sintered at a predetermined temperature of 1300 to 1500 ° C. in a vacuum of 6 Pa.

  Thereafter, the cutting edge of the obtained sintered body is subjected to honing so that the radius (R) is 0.060 mm, whereby a base made of a WC cemented carbide having a throw-away tip shape defined in ISO CNMG120408 I got the material.

<Formation of coating>
Each of the coatings (coating No. 1 to coating No. 12) having the configuration described in Table 1 and the coatings (coating No. 13 to coating No. 18) having the configuration described in Table 2 were obtained above. A surface-coated cutting tool (blade cutting type cutting tip) was produced by forming the surface of the material by chemical vapor deposition.

  The film described in Table 1 is an example of the present invention, and the film described in Table 2 is a comparative example. In Table 2, the Zr-containing layer is a layer that serves as a comparative reference for the oxide mixed layer of the present invention.

  In addition, the film structure of Table 1 and Table 2 shows having laminated | stacked on the base material in order from the left thing, and the number in a parenthesis shows thickness (micrometer). In Tables 1 and 2, compounds other than the aluminum oxide layer and the oxide mixed layer (Zr-containing layer) correspond to the other layers described above.

  Specific conditions for forming each film by chemical vapor deposition are as follows. That is, the base material was charged into a normal chemical vapor deposition apparatus, and each layer of each coating was formed in order according to the conditions described in Tables 3 to 5.

For example, film No. Taking 1 as an example, a TiN layer having a thickness of 1 μm was first formed on a substrate with a reaction gas composition (4 vol% TiCl ₄ , 35 vol% N ₂ , and the balance H ₂ ) shown in Table 3, reaction pressure (20 kPa). ) And a reaction temperature (840 ° C.), a TiC layer having a thickness of 5 μm and an AlTiN layer having a thickness of 3 μm were formed under the same conditions as shown in Table 3. Next, an “aluminum oxide layer 1” having a thickness of 2 μm was formed under the conditions shown in Table 4 (“aluminum oxide layer 1”, “aluminum oxide layer 2”, and “aluminum oxide layer 3” in Tables 1 and 2 Is an aluminum oxide layer, but the formation conditions are different as shown in Table 4).

  Subsequently, an “oxide mixed layer 1” having a thickness of 20 μm was formed on the “aluminum oxide layer 1” formed above. In this case, after the “aluminum oxide layer 1” was formed, Ar gas was flowed at a flow rate of 30 L / min for 10 minutes, the furnace atmosphere was changed to Ar, and the surface of the formed aluminum oxide layer was activated with Ar. Thus, the coating of the present invention has coating No. 2-No. Similarly, No. 12 is characterized in that after the surface of the aluminum oxide layer is activated with Ar under these conditions, an oxide mixed layer is formed.

Thereafter, an “oxide mixed layer” was formed on the surface of the “aluminum oxide layer 1” activated with Ar at the reaction gas composition, reaction time (320 minutes), reaction pressure (5 kPa), and reaction temperature (870 ° C.) shown in Table 5. 1 "was formed. In this case, first, AlCl ₃ , H ₂ , HCl, CO ₂ , C ₂ H ₄ , and H ₂ S are introduced into the furnace as reaction gases for 350 seconds. Thereafter, ZrCl ₄ is introduced into the furnace while flowing Ar in pulses. The Ar pulse interval is every 2 seconds. The reaction gas composition shown in Table 5 indicates the composition (% by volume) after introducing ZrCl ₄ into the furnace. Note that such an oxide mixed layer is also formed in the oxide mixed layers 2 to 8 by a method of introducing ZrCl ₄ into the furnace while flowing Ar in a pulsed manner. As described above, “Oxide mixed layer 1” to “Oxide mixed layer 8” in Table 1 are all oxide mixed layers, but the formation conditions are different as shown in Table 5.

  Thereafter, a 1 μm-thick TiN layer and a 1 μm-thick TiC layer are formed on the “oxide mixed layer 1” formed as described above under the conditions shown in Table 3 to form a coating No. having a total thickness of 33 μm on the substrate. . 1 film is formed.

On the other hand, the film described in Table 2 was formed in the same manner as the film described in Table 1 except for the Zr-containing layer. The Zr-containing layer was formed according to the conditions described in Table 6. In Table 6, when “start” and “end” are indicated, when forming the Zr-containing layer, the reaction gas composition and reaction temperature are gradually changed from the start to the end as indicated. Indicates that As is clear from the reaction gas composition, “Zr-containing layer 1” to “Zr-containing layer 5” contain both Al ₂ O ₃ and ZrO ₂ , but “Zr-containing layer 6” is ZrO ₂ alone. Of layers. When the Zr-containing layer was formed on the aluminum oxide layer, the surface of the aluminum oxide layer was not activated with Ar.

<Evaluation>
<Physical properties of oxide mixed layer>
The physical properties of the oxide mixed layer and the Zr-containing layer prepared above were measured.

First, each layer contained Al ₂ O ₃ and ZrO ₂ as oxides, and the atomic ratio Zr / (Al + Zr) between Al and Zr was confirmed. Specifically, an energy dispersive X-ray analyzer (trade name: “INCA X”) attached to a field emission scanning electron microscope (trade name “SU6600”, manufactured by Hitachi High-Tech Co., Ltd., hereinafter referred to as “FE-SEM”). -ACT ", manufactured by Oxford Instruments Co., Ltd., hereinafter referred to as" EDX "), by measuring the area of the width of each layer (50 μm) x the thickness (total thickness) of each layer at 15 kV, Al ₂ O ₃ and ZrO ₂ were included, and the atomic ratio Zr / (Al + Zr) between Al and Zr was determined. As a result, each layer contained Al ₂ O ₃ and ZrO ₂ , and the atomic ratio Zr / (Al + Zr) between Al and Zr was as shown in Table 7 below.

Next, the crystal structure of ZrO ₂ contained in each layer was confirmed. Specifically, the crystal structure was specified by measuring each layer with an X-ray diffractometer (trade name: “X′Pert”, manufactured by PANalytical Co., Ltd.). Measurement conditions were such that the X-ray incident angle of θ to 2θ was 0.5 ° using a thin film method. The peak position was specified within a range of ± 0.3 degrees using a JCPDS card (JCPDS indicates Joint Committee on Powder Diffraction Standards and indicates the crystal plane spacing of a specific substance). The card numbers of tetragonal crystal, cubic crystal, and monoclinic crystal are 00-050-1089, 00-051-1149, and 00-37-1481. As a result, as shown in Table 7 below, the crystal structure of ZrO _{2 in} the oxide mixed layer was cubic, but the crystal structure of ZrO _{2 in} the Zr-containing layer was all monoclinic.

Further, the average grain size of the ZrO ₂ crystal grains contained in each layer was confirmed. Specifically, the average particle size was determined by the method defined above using the FE-SEM. The magnification of FE-SEM was 10,000 times, and the acceleration voltage was 5 kV. The results are shown in Table 7 below. As can be seen from Table 7, in the oxide mixed layer, it was confirmed that ZrO ₂ was dispersed in Al ₂ O ₃ as crystal grains having an average grain size of 1 μm or less.

  In Table 7, the oxide mixed layer 1 is the coating No. in Table 1. 1 and the oxide mixed layer 2 is the same film No. 2 and the oxide mixed layer 3 are the same film Nos. 5, the oxide mixed layer 4 is the same film No. 8 and the oxide mixed layer 5 are the same film Nos. 3 and the oxide mixed layer 6 are the same film Nos. No. 10, the oxide mixed layer 7 is the same film No. 11 and the oxide mixed layer 8 is the same film No. Twelve things were measured respectively. On the other hand, the Zr-containing layers 1 to 6 are coating Nos. Each of 13 to 18 was measured.

As is clear from Table 7, the oxide mixed layers 1 to 8 as examples of the present invention have a smaller average grain size of ZrO ₂ crystal grains than the Zr-containing layers 1 to 5 and their crystal structures. In addition, since cubic crystals were included, it was shown that these properties were provided by the film formation method unique to the present invention as described above.

<Heat penetration rate>
Coating Nos. Listed in Table 1 1-No. 12 and Table 2 listed in Table 2. 13-No. The thermal permeability of each of the 18 coatings was measured using a thermophysical microscope device (trade name: “Thermal Microscope TM3”, manufactured by BETHEL Co., Ltd.). Note that the measurement was performed at room temperature and the heating laser frequency was 2000 kHz. The results are shown in Table 8 below.

<Cutting performance>
Coating Nos. Listed in Table 1 1-No. 12 and Table 2 listed in Table 2. 13-No. The cutting performance was confirmed for each surface-coated cutting tool on which each of the 18 coatings was formed. Test conditions for confirming the cutting performance were as follows, and continuous cutting was performed with a round bar work material. Then, the time until the cutting edge was plastically deformed or chipped from the cutting heat, or the time until the flank maximum wear width Vbmax was 0.5 mm or more was measured, and the time was determined as the tool life. The cutting edge was observed with an optical microscope having a magnification of 100 times. The results are shown in Table 8 below. The longer the tool life, the better the cutting performance.

(Test conditions)
Work material: S55C (Round bar)
Machining method: Turning Cutting speed: 400 m / min
Feed: 0.5mm / rev
Cutting depth: 1.5mm
Cutting fluid: None (dry processing)

  As is apparent from Table 8, the film No. which is an example of the present invention. 1-No. The surface-coated cutting tool formed with No. 12 is a coating No. 1 as a comparative example. 13-No. It is clear that the tool life is twice or more longer than that of the surface-coated cutting tool formed with 18 and shows excellent cutting performance. As is clear from Table 1, the film No. 1-No. No. 12 is provided with the oxide mixed layer of the present invention, and since the thermal permeability of the coating is lower than Table 8, these coatings showed excellent heat insulating properties, so that the cutting performance was It is clear that it has improved.

  In addition, film No. which is an example of the present invention. 1-No. It is clear that 12 shows such an excellent heat insulating effect because each oxide mixed layer has properties defined in the present invention as shown in Table 7.

In addition, film No. which is an example of the present invention. 1-No. In No. 12, since the aluminum oxide layer was disposed directly under the oxide mixed layer, the adhesion of the film was high, and no chipping or the like of the film was observed, and normal wear was observed. As a Zr-containing layer, a comparative film No. 1 composed of ZrO ₂ alone was used. Although the surface-coated cutting tool formed with 18 had a low thermal permeability and excellent heat insulation, the crater was dug at a very early stage due to a decrease in coating hardness, and the tool life was extremely short.

  As described above, it was confirmed that the surface-coated cutting tool of the present invention was excellent in the heat insulating effect of the coating and effectively protected the substrate during the cutting process, and also exhibited an extremely excellent effect of being excellent in cutting performance.

  Although the embodiments and examples of the present invention have been described as described above, it is also planned from the beginning to appropriately combine the configurations of the above-described embodiments and examples.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

Claims (5)

A substrate and a coating formed on the substrate;
The coating includes an aluminum oxide layer and an oxide mixed layer,
The aluminum oxide layer includes Al ₂ O ₃ as an oxide,
The oxide mixed layer includes Al ₂ O ₃ and ZrO ₂ as oxides in a range where the atomic ratio of Al to Zr is 0.01 ≦ Zr / (Al + Zr) ≦ 0.5,
The ZrO ₂ is a surface-coated cutting tool that is included in a state in which at least cubic crystals exist as its crystal structure. The surface-coated cutting tool according to claim 1, wherein the ZrO ₂ is contained as crystal grains having an average particle diameter of 1 μm or less.   The surface-coated cutting tool according to claim 1, wherein the aluminum oxide layer is disposed immediately below the oxide mixed layer. The surface-coated cutting tool according to any one of claims 1 to 3, wherein the aluminum oxide layer and the oxide mixed layer do not contain Al ₂ O ₃ crystal grains existing across both layers. The surface-coated cutting tool according to any one of claims 1 to 4, wherein the coating has a thermal permeability of 2500 to 10,000 Js ^-1/2 m ^-2 K ^-1 .