JP5950230B2 - Ceramic coating - Google Patents

Description

  The present invention relates to a ceramic coating.

  Ceramic coatings are used in various industrial fields because of their excellent heat resistance and hardness. For example, in a surface-coated cutting tool in which the surface of a base material is coated with this, further excellent heat resistance and hardness are required due to high efficiency of cutting.

  Since zirconium oxide or a combination of zirconium and aluminum oxide has excellent heat resistance, various materials for such a ceramic coating have been proposed.

  For example, Japanese Patent Application Laid-Open No. 2002-239808 (Patent Document 1) discloses a surface-coated cutting tool using a zirconium oxide film as a heat-resistant ceramic film. JP 2009-045729 A (Patent Document 2) discloses a film that aims to achieve both the heat resistance of zirconium oxide and the high hardness characteristics of aluminum oxide by containing zirconium oxide in the aluminum oxide layer. Disclosure. Japanese Patent Application Laid-Open No. 2004-042150 (Patent Document 3) is a composite oxide film of zirconium and aluminum, in which a zirconium oxide high content layer and an aluminum oxide high content layer are laminated by a thermal CVD method. Is disclosed.

JP 2002-239808 A JP 2009-045729 A JP 2004-042150 A

  Since the coating described in Patent Document 1 is composed of zirconium oxide alone, heat resistance is expected, but further improvement in hardness is required.

  For example, as shown in FIG. 4, the coating described in Patent Document 2 does not have a structure in which zirconium oxide is uniformly distributed in aluminum oxide. The structure is such that zirconium oxide is segregated. For this reason, although a certain degree of improvement in heat resistance is expected, it is presumed that cracks are likely to occur at the crystal boundary between aluminum oxide and zirconium oxide, and sufficient hardness cannot be obtained.

  Moreover, since the film of patent document 3 forms the laminated structure by switching source gas by thermal CVD method, it is thought that film-forming conditions become unstable and it is difficult to obtain a uniform film. For this reason, it is estimated that not only the production efficiency is inferior, but also a film having sufficient hardness cannot be obtained.

  In this way, ceramic coatings containing zirconium oxide are expected to improve heat resistance due to the excellent heat resistance of zirconium oxide itself, but those with sufficient hardness have not been obtained, and heat resistance has been improved. Therefore, it is required to achieve both improvement of hardness and hardness.

  This invention is made | formed in view of such a condition, The place made into the objective is to provide the ceramic film which made the improvement of heat resistance and the improvement of hardness compatible.

The present inventor has made extensive studies to solve the above problems, and in order to achieve both improvement in heat resistance and improvement in hardness, Al ₂ O ₃ (aluminum oxide) and ZrO ₂ (zirconium oxide) The present invention has been completed by further finding out that it is most effective to control the lamination state of the two and controlling the lamination state of the two.

That is, the ceramic film of the present invention includes a multilayer structure in which the first layer and the second layer are alternately laminated, and is formed by a laser CVD method. The first layer is formed of Al ₂ O _3. As a main component, and the second layer includes Al ₂ O ₃ and ZrO ₂ as main components, and at least a part of the multilayer structure has a stacking direction with respect to a thickness direction of the entire ceramic coating. It is characterized by being inclined.

Here, the multilayer structure preferably has a dendritic structure, and both the first layer and the second layer preferably have a thickness of 300 nm or less. The multilayer structure preferably contains tetragonal ZrO ₂ .

  The ceramic coating of the present invention has an excellent effect of having both the improvement in heat resistance and the improvement in hardness by having the above-described configuration.

It is the schematic of a laser CVD film-forming apparatus. 4 is a transmission electron micrograph of the ceramic coating film of Example 3. 4 is an enlarged transmission electron micrograph of the ceramic film of Example 3. It is the transmission electron micrograph which expanded the ceramic film of Example 3 further. 4 is a transmission electron micrograph of the ceramic coating film of Example 4. It is the transmission electron micrograph which expanded the ceramic film of Example 4. FIG.

Hereinafter, the present invention will be described in more detail.
<Ceramic coating>
The ceramic coating of the present invention includes a multilayer structure in which first layers and second layers are alternately laminated. As long as such a multilayer structure is included, other additional configurations (for example, layers other than the first layer and the second layer and structures other than the multilayer structure) may be included.

  Such a ceramic coating can have a thickness of 0.5 to 20 μm, preferably 5 to 15 μm. If the thickness is less than 0.5 μm, sufficient heat resistance and hardness may not be obtained, and if it exceeds 20 μm, the coating itself may be destroyed.

  Such a ceramic coating of the present invention can be used in a wide range of industrial fields where heat resistance and hardness are usually required by coating various substrates. For example, examples of such applications include cutting tools, machine parts, valves, and the like.

  The substrate to be coated is not particularly limited, and examples thereof include various ceramics such as aluminum nitride, various sintered bodies such as cubic boron nitride and diamond, cemented carbide, and glass. Can do. In particular, when aluminum nitride (AlN) is used as the base material, excellent heat resistance and hardness can be improved.

<First layer>
The first layer of the present invention is characterized by containing Al ₂ O ₃ as a main component. Here, “comprising Al ₂ O ₃ as a main component” means that the presence of Al ₂ O ₃ in the first layer can be confirmed by X-ray diffraction and Al is contained in all metal atoms contained in the first layer. Is contained 99 atomic% or more. A more preferable content of Al with respect to all metal atoms contained in the first layer is 99.5 atomic% or more.

  In the present invention, the “metal atom” is hydrogen, helium, neon, argon, krypton, xenon, radon, fluorine, chlorine, bromine, iodine, astatine, oxygen, sulfur, selenium, tellurium, nitrogen, phosphorus, arsenic, An atom of an element other than antimony and carbon.

Thus, the first layer of the present invention means that most of it is composed of Al ₂ O ₃ , and it may be composed of only Al ₂ O ₃ except for inevitable impurities. However, such a first layer can also contain ZrO ₂ in addition to Al ₂ O ₃ , and it does not depart from the scope of the present invention to contain ZrO ₂ in this way.

  Such a first layer preferably has a thickness of 300 nm or less, and more preferably 150 nm or less. When the thickness exceeds 300 nm, even if the second layer and the multilayer structure are formed, the characteristics of the first layer alone tend to be exhibited, and it may be difficult to achieve both heat resistance and hardness. On the other hand, the lower limit of the thickness is preferably 1 nm or more. This is because if the thickness is less than 1 nm, the first layer itself may not be present stably.

<Second layer>
The second layer of the present invention is characterized by containing Al ₂ O ₃ and ZrO ₂ as main components. Here, “containing Al ₂ O ₃ and ZrO ₂ as main components” means that the presence of Al ₂ O ₃ and ZrO ₂ in the second layer can be confirmed by X-ray diffraction, It means that Al is contained at 40 atom% or more and 90 atom% or less with respect to all metal atoms, Zr is contained at 10 atom% or more and 60 atom% or less, and the sum of both is 99 atom% or more. The more preferable content of Al with respect to all the metal atoms contained in the second layer is 50 atomic percent or more and 80 atomic percent or less, and the more preferable content of Zr is 20 atomic percent or more and 50 atomic percent or less. The total content is 99.5 atomic% or more. Such a second layer may be composed of only Al ₂ O ₃ and ZrO ₂ except for inevitable impurities.

  Such a second layer preferably has a thickness of 300 nm or less, and more preferably 150 nm or less. When the thickness exceeds 300 nm, even if the first layer and the multilayer structure are formed, the characteristic of the second layer alone tends to be exhibited, and it may be difficult to achieve both heat resistance and hardness. On the other hand, the lower limit of the thickness is preferably 1 nm or more. This is because if the thickness is less than 1 nm, the second layer itself may not be present stably.

<Multilayer structure>
The multilayer structure of the present invention has a configuration in which the first layer and the second layer are alternately stacked, and at least a part of the stacking direction is inclined with respect to the thickness direction of the entire ceramic film. It is characterized by. Such a multilayer structure preferably has a dendritic structure.

  Here, “the first layer and the second layer are alternately laminated” means a structure in which the first layer and the second layer are alternately laminated one by one. In addition, “the laminating direction is inclined with respect to the thickness direction of the entire ceramic coating” means that the first layer and the second layer constituting the multilayer structure are assumed to be planes, and are perpendicular to each plane. When a straight line (that is, the direction of this straight line becomes the stacking direction) and a straight line parallel to the thickness direction of the entire ceramic film are on the same plane, it means a state where they intersect at a certain angle. In other words, when the ceramic coating is formed on a certain substrate, the entire ceramic coating is formed parallel to the substrate surface, but the multilayer structure included in the ceramic coating is parallel to the substrate surface. It means not formed.

  In addition, the “dendritic structure” means a state in which a plurality of lamination units having different lamination directions are mixed, as shown in FIGS. In other words, if such a lamination unit is regarded as a lamellar structure, the multilayer structure of the present invention can have a plurality of different lamellar structures, and the laminating direction of each lamellar structure is relative to the thickness direction of the ceramic coating. Will have different angles.

  The ceramic coating according to the present invention has both the heat resistance and the hardness improved by including a multilayer structure having such a structure, which is probably the first layer in such a multilayer structure. Since the second layer and the second layer are alternately laminated in the specific thickness and in the specific stacking direction, the synergistic characteristics produced by both layers are expressed more than the characteristics of each layer alone. It is estimated that. That is, in the bulk ceramic coating, the first layer and the second layer are homogeneously present as a secondary phase, thereby improving the fracture resistance and suppressing the propagation of cracks. It is presumed that the characteristics of both of these were highly expressed in combination with the heat resistance inherent in zirconium oxide.

  In this respect, it is preferable that both the first layer and the second layer have a thickness of 300 nm or less. In addition, each thickness of a 1st layer and a 2nd layer may mutually differ, and may be the same.

Such a multilayer structure preferably contains tetragonal ZrO ₂ . This is because the inclusion of such tetragonal type ZrO ₂ makes a significant improvement in hardness. Tetragonal ZrO ₂ is usually unstable at room temperature and cannot exist stably, but is considered to have been stabilized by the multilayer structure having the above-described configuration. In particular, the stabilization of this tetragonal type ZrO ₂ is presumed to involve Al ₂ O ₃ due to the multilayer structure of the present invention, although the detailed mechanism is unknown.

As long as such tetragonal type ZrO ₂ is contained in the multilayer structure of the present invention, it may be contained in the first layer or in the second layer. Not.

  In addition, as long as the thickness of the whole ceramic film and the thickness of the first layer and the second layer are within the above ranges, the number of stacked layers of the first layer and the second layer constituting the multilayer structure is particularly limited. However, it is usually 1 layer to 10000 layers, more preferably 50 layers to 1500 layers. Further, the boundary between the first layer and the second layer constituting the multilayer structure can be confirmed by the contrast of the enlarged bright field image by, for example, TEM (transmission electron microscope) observation as shown in FIG. .

  In the multilayer structure, the start and end of lamination may be the first layer or the second layer, and is not particularly limited.

<Manufacturing method>
The ceramic film of the present invention is formed by a laser CVD (chemical vapor deposition) method. The laser CVD method is a kind of chemical vapor deposition method, and can be executed using, for example, a laser CVD film forming apparatus 1 as schematically shown in FIG. Such a laser CVD method is characterized in that a laser is used to excite the source gas introduced into the chamber 14 of the laser CVD film forming apparatus 1.

Specifically, for example, in the laser CVD film forming apparatus 1, argon (Ar) gas as a carrier gas is introduced through the gas flow rate control apparatus 2, and the Al ₂ O ₃ forming raw material is vaporized by the heater chamber 5 and vaporized. Al is sent to the nozzle 7 together with Ar gas. Similarly, Ar gas as a carrier gas is introduced through the gas flow rate control device 3, the ZrO ₂ forming raw material is vaporized by the heater chamber 6, and the vaporized Zr is sent to the nozzle 7 together with the Ar gas. On the other hand, oxygen gas is also sent to the nozzle 7 through the gas flow rate control device 4.

  Then, Al, Zr, and oxygen gas introduced into the chamber 14 from the nozzle 7 are excited by the laser 9 irradiated through the quartz window 10 and are deposited on the surface of the base material 13 placed on the heating stage 11. The ceramic film of the present invention is formed.

  A thermocouple 12 is attached to the heating stage 11, and the temperature in the chamber 14 (that is, the film forming temperature) is monitored. Further, the gas in the chamber 14 is exhausted by the vacuum pump 8.

Here, aluminum acetylacetonate (Al (acac) ₃ ) can be used as the raw material for forming Al ₂ O ₃ to be vaporized, and zirconium dipivaloyl as a raw material for forming ZrO ₂ to be vaporized. Methanate (zirconium dipivaloylmethanato, Zr (dpm) ₄ ) or zirconium acetylacetonate (Zr (acac) ₄ ) can be used.

  As the substrate, polycrystalline aluminum nitride (AlN, shape: 12 mm × 12 mm × 1 mm) can be used.

The temperature at which the raw material for forming Al ₂ O ₃ is vaporized (Al vaporization temperature) can be 400 to 500K, and the temperature at which the raw material for forming ZrO ₂ is vaporized (Zr vaporization temperature) is 400 to 500K. it can. The flow rate of the carrier gas (Ar gas) can be 50 to 125 sccm, and the flow rate of the oxygen gas can be 100 to 200 sccm.

  The pressure in the chamber (film formation pressure) can be 100 to 200 Pa, and the temperature in the chamber (film formation temperature) can be 700 to 1400K.

  Furthermore, a semiconductor laser (wavelength: 808 nm, continuous oscillation mode) can be used as the laser, and the laser output can be 60 to 200 W.

  In addition, when Al vaporization temperature and Zr vaporization temperature are made high, the amount of raw material vaporization will increase and the corresponding composition will increase in a ceramic film according to it. That is, it is considered that the vaporization amount and the film composition coincide with each other. On the other hand, when the laser output is increased, the film formation temperature rises and the film formation rate increases accordingly.

  In this way, the ceramic coating (that is, the multilayer structure) of the present invention is preferably produced by the laser CVD method.

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

<Examples 1-4>
The ceramic coating of the present invention is formed on a substrate (polycrystalline aluminum nitride (AlN), shape: 12 mm × 12 mm × 1 mm plate shape) by laser CVD using the laser CVD film forming apparatus having the configuration of FIG. did. Details of the laser CVD method are as described above, and specific conditions are shown in Table 1 below.

<Comparative Examples 1-2>
As a ceramic film of a comparative example, an aluminum oxide film (Comparative Example 1) and a composite oxide film of aluminum oxide and zirconium oxide (Comparative Example 2) are formed on the same substrate as the examples by a conventionally known thermal CVD method. did. Specific conditions of the thermal CVD method are shown in Table 2 below.

<Specification of coating structure>
The following identification was performed about each ceramic film of the Example and comparative example which were obtained as mentioned above.

  That is, for each ceramic coating, a transmission electron microscope (trade name: “Topcon EM-002B”, manufactured by Topcon Corporation), a scanning electron microscope (trade name: “SU-6600”, manufactured by Hitachi Ltd.), and an energy dispersive type Using an X-ray analyzer (trade name: “INCA Energy”, manufactured by OXFORD INSTRUMENTS), the presence or absence of a multilayer structure, the thickness of the first layer and the second layer, the composition and crystal structure, and the total number of layers, the total thickness, The overall composition was confirmed. The results are shown in Table 3.

  In Table 3, when the columns of the first layer and the second layer are blank, it indicates that the multilayer structure was not confirmed. That is, Examples 1 to 4 could confirm the multilayer structure, but Comparative Examples 1 to 2 could not confirm the multilayer structure. In addition, the thickness of the 1st layer and the 2nd layer was measured about the part which shows a clear multilayer structure, and was taken as the average value.

  Further, the composition of the first layer represents atomic% (at%) of Al with respect to all metal atoms of the first layer, and the composition of the second layer represents atomic% (at%) of Al with respect to all metal atoms of the second layer. ) And atomic% (at%) of Zr (the numerical values in the column “Al / Zr (at%)” mean this).

Regarding the crystal structures of the first layer and the second layer, in addition to the measurement by the X-ray diffraction pattern of the transmission electron microscope, the X-ray diffractometer (trade name: “Rigaku RAD-2C” is used for Examples 1 and 2. And the confirmation by the θ-2θ method using Rigaku Corporation). In Table 3, “α-Al ₂ O ₃ ” indicates that α-type Al ₂ O ₃ is observed, “γ-Al ₂ O ₃ ” indicates that γ-type Al ₂ O ₃ is observed, and “t-ZrO”. “ ₂ ” indicates that tetragonal ZrO ₂ was observed, and “m-ZrO ₂ ” indicates that monoclinic ZrO ₂ was observed. The ratio of m-ZrO ₂ to t-ZrO ₂ in Example 3 (intensity ratio of X-ray diffraction) was m-ZrO ₂ : t-ZrO ₂ = 1: 1.

  In addition, the “total number of layers” is the number of layers for a portion having a thickness of about 2 to 3 μm and showing a clear layered structure, and calculating the number of layers per 1 μm. The numerical value converted into thickness was described.

  Further, “total thickness” indicates the thickness of the entire ceramic film, and “total composition” indicates atomic% (at%) of Al and atomic% (at%) of Zr with respect to all metal atoms in the entire ceramic film. .

  Note that transmission electron micrographs of multilayer structures of the ceramic coatings of Example 3 and Example 4 are shown in FIGS.

  FIG. 2 shows the ceramic film 21 of Example 3 formed on the base material 22. The ceramic film 21 has a thickness of about 7.5 μm and includes a multilayer structure in which the stacking direction is inclined with respect to the thickness direction of the entire ceramic film by the lower left gauge (1 μm) in FIG. I understand. It is also recognized that the multilayer structure has a dendritic structure.

  FIG. 3 is an enlarged view of the ceramic film portion of FIG. 2, and it is recognized that the multilayer structure is obtained by alternately laminating the first layer (white to light color) and the second layer (gray to black). . FIG. 4 is a further enlargement of FIG. 3. From the lower left gauge (50 nm), it is recognized that the first layer has a thickness of 40 to 60 nm and the second layer has a thickness of 20 to 30 nm. . Thus, the first layer and the second layer of the present invention may have different thicknesses.

  On the other hand, FIG. 5 shows the ceramic film 31 of Example 4 formed on the substrate 32. FIG. 6 is an enlarged view of the ceramic coating portion of FIG. 5, and it can be confirmed that the multilayer structure has a dendritic structure similar to that of FIG.

  In addition, it confirmed that the ceramic film of Example 1 and Example 2 also has the structure similar to FIGS.

That is, the ceramic coating of each example is a ceramic coating including a multilayer structure in which first layers and second layers are alternately stacked, and is formed by a laser CVD method. The first layer is made of Al ₂ O. ₃ as a main component, the second layer includes Al ₂ O ₃ and ZrO ₂ as main components, and the multilayer structure has at least a part thereof in which the stacking direction is inclined with respect to the thickness direction of the entire ceramic film. And confirmed to have a dendritic tissue.

On the other hand, the composite oxide film of Comparative Example 2 has a configuration as shown in FIG. 4 of Patent Document 2, and Al ₂ O ₃ and ZrO ₂ are segregated, confirming the multilayer structure as in the present invention. could not.

<Physical property evaluation>
The following physical properties of the ceramic coatings of the examples and comparative examples were evaluated.

<Heat penetration rate>
Using a thermophysical microscope (trade name: “TM3”, manufactured by BETHEL), the thermal permeability of each ceramic film was measured by the thermoreflectance method. The results are shown in Table 4 below. A lower heat penetration rate indicates better heat resistance.

<Hardness>
The hardness of each ceramic coating was measured using a micro Vickers hardness meter (trade name: “Automatic Micro Hardness Test System AAV-502”, manufactured by Akashi Co., Ltd.). The results are shown in Table 4 below. The higher the value, the higher the hardness.

<Presence of cracks>
Using a scanning electron microscope (trade names: “S-3100H” and “S-3400”, manufactured by Hitachi Ltd.), it is confirmed by observing the cross section of the coating whether or not cracks have occurred in each ceramic coating. did. The results are shown in Table 4 below. “None” indicates that no crack has occurred, and “Yes” indicates that a crack has occurred.

As is clear from Table 4, the ceramic coating of each example shows a hardness higher than that of ZrO ₂ alone (reference value: 1200 mHV), and more than the heat resistance of Al ₂ O ₃ alone (Comparative Example 1). Excellent heat resistance. Moreover, generation | occurrence | production of the crack was not confirmed in the film.

  Therefore, it is clear that the ceramic coating of the present invention exhibits an excellent effect of achieving both improvement in heat resistance and improvement in hardness.

Incidentally, the ceramic film of Comparative Example 2 is a composite oxide film of Al ₂ O ₃ and ZrO _2, Al ₂ O ₃ and ZrO ₂ and are segregated, because cracks are generated in the grain boundary Moreover, the hardness was inferior. That is, although the hardness in the part where the crack did not occur was relatively high (see the numerical values described in Table 4), a large number of cracks occurred, and the hardness at the crack part could not be measured, The hardness of the entire coating was inferior to that of the examples.

  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.

  DESCRIPTION OF SYMBOLS 1 Laser CVD film-forming apparatus, 2,3,4 Gas flow control apparatus, 5,6 Heater chamber, 7 Nozzle, 8 Vacuum pump, 9 Laser, 10 Quartz window, 11 Heating stage, 12 Thermocouple, 13 Base material, 14 Chamber, 21, 31 Ceramic coating, 22, 32 Substrate.

Claims (3)

A ceramic film including a multilayer structure in which first layers and second layers are alternately laminated ,
The first layer includes Al ₂ O ₃ as a main component,
The second layer includes Al ₂ O ₃ and ZrO ₂ as main components,
Wherein the multilayer structure comprises at least a portion Te odor product layer direction inclined with respect to the thickness direction of the entire ceramic film, and dendritic structure, the ceramic film. The ceramic film according to claim 1, wherein both the first layer and the second layer have a thickness of 300 nm or less. The ceramic film according to claim 1, wherein the multilayer structure includes tetragonal type ZrO ₂ .