阅读说明：本技术 包覆切削工具 (Coated cutting tool ) 是由 伊坂正和 于 2020-03-03 设计创作，主要内容包括：本发明的包覆切削工具具有硬质被膜,该硬质被膜包括：b层,由氮化物或碳氮化物构成；c层,c1层和c2层分别以50nm以下的膜厚交替层叠的层叠被膜,所述c1层为含有55原子％以上且75原子％以下的Al,其次Cr的含有比率多,进而至少含有Si的氮化物或碳氮化物；所述c2层为含有55原子％以上且75原子％以下的Al,其次Ti含有得多的氮化物或碳氮化物；以及d层,其为相对于金属(包括半金属)元素的总量含有55原子％以上且75原子％以下的Al,其次Cr的含有比率多,Cr的含有比率为20原子％以上,进而至少含有Si的氮化物或碳氮化物。由c层中的AlN的hcp(010)面引起的峰强度Ih与由多个规定结晶相引起的峰强度的合计Is满足Ih×100/Is≤15的关系。(The coated cutting tool of the present invention has a hard coating film including: b layer composed of nitride or carbonitride; a c layer, a c1 layer and a c2 layer, each of which is a laminated film in which layers are alternately laminated to a film thickness of 50nm or less, wherein the c1 layer contains 55 at% to 75 at% of Al, contains a large amount of Cr, and further contains at least a nitride or carbonitride of Si; the c2 layer is a nitride or carbonitride containing more than 55 at% and less than 75 at% of Al, and secondly Ti contains much more; and a d-layer which is a nitride or carbonitride containing 55 at% or more and 75 at% or less of Al with respect to the total amount of metal (including semimetal) elements, contains a large amount of Cr, has a Cr content of 20 at% or more, and further contains at least Si. The peak intensity Ih due to the hcp (010) plane of AlN in the c-layer and the total Is of the peak intensities due to the plurality of predetermined crystal phases satisfy a relationship of Ih x 100/Is < 15.)

1. A coated cutting tool characterized in that,

comprising a base material and a hard coating film formed on the base material,

the hard coating film has:

a b layer arranged on the base material and composed of nitride or carbonitride;

a c layer which is a laminated film formed by alternately laminating a c1 layer and a c2 layer each having a film thickness of 50nm or less on the b layer, wherein the c1 layer contains aluminum Al in an amount of 55 to 75 atomic% based on the total amount of metal elements, contains a large amount of chromium Cr, and further contains a nitride or carbonitride of at least silicon Si; the c2 layer is an aluminum Al layer containing 55 at% or more and 75 at% or less with respect to the total amount of metal elements, and then a nitride or carbonitride containing much titanium Ti; and

a d layer which is disposed on the c layer and contains aluminum Al in a range of 55 atomic% to 75 atomic% based on the total amount of the metal elements, a large amount of chromium Cr, a 20 atomic% or more content of chromium Cr, and a nitride or carbonitride of at least silicon Si,

wherein the metal element comprises a semimetal element,

in the c-layer, when the peak intensity due to the (010) plane of AlN of a close-packed hexagonal structure Is Ih, and the sum of the peak intensities due to the (111) plane of AlN, the (111) plane of TiN, the (111) plane of CrN, the (200) plane of AlN, the (200) plane of TiN, the (200) plane of CrN, the (220) plane of AlN, the (220) plane of TiN, and the (220) plane of CrN of a face-centered cubic lattice structure and the peak intensities due to the (010) plane of AlN, the (011) plane of AlN, and the (110) plane of AlN of a close-packed hexagonal structure Is in the intensity distribution obtained from the limited field diffraction pattern of a transmission electron microscope, a relationship of Ih x 100/Is 15 or less Is satisfied.

2. The coated cutting tool according to claim 1, wherein the c layer is the thickest film with respect to the total film thickness of the hard coating film.

3. The coated cutting tool according to claim 1 or 2, wherein the c layer is composed of columnar particles having an average width of 90nm or less.

Technical Field

The present invention relates to a coated cutting tool. The present application claims priority based on patent application No. 2019-.

Background

Conventionally, as a technique for improving the life of a cutting tool, a surface treatment technique has been employed in which a hard film made of various ceramics is coated on the surface of the cutting tool. Among the hard coatings, nitrides mainly composed of Al and Cr are excellent in heat resistance, and are widely used for coated cutting tools.

For example, patent document 1 discloses a coated cutting tool provided with a nitride of AlCrSi. Patent document 2 discloses a coated cutting tool provided with a nitride in which a metal element of groups 4a, 5a, and 6a of the periodic table is added to a nitride of AlCrSi.

Patent document 1: japanese patent laid-open publication No. 2004-306228

Patent document 2: japanese Kohyo publication No. 2010-521589

According to the studies of the present inventors, it has been confirmed that the durability of a coated cutting tool provided with a nitride of AlCrSi, which has been proposed in the past, has room for improvement.

Disclosure of Invention

One aspect of the present invention is a coated cutting tool,

comprising a base material and a hard coating film formed on the base material,

the hard coating film has: a b layer arranged on the base material and composed of nitride or carbonitride;

a c layer which is a laminated film in which a c1 layer and a c2 layer are alternately laminated with a film thickness of 50nm or less, respectively, and which is disposed on the b layer, wherein the c1 layer is a nitride or carbonitride containing 55 at% to 75 at% of aluminum (Al) with respect to the total amount of metal (including semimetal) elements, contains a large amount of chromium (Cr), and further contains at least silicon (Si); the c2 layer is aluminum (Al) containing 55 at% or more and 75 at% or less with respect to the total amount of metal (including semimetal) elements, and secondly titanium (Ti) contains much more nitrides or carbonitrides; and

a d layer which is disposed on the c layer, contains aluminum (Al) in a range of 55 atomic% to 75 atomic% based on the total amount of metal (including semimetal) elements, contains a large amount of chromium (Cr), has a chromium (Cr) content of 20 atomic% or more, and further contains at least silicon (Si) nitride or carbonitride,

in the c-layer, when the peak intensity due to the (010) plane of AlN of a close-packed hexagonal structure Is Ih, and the sum of the peak intensities due to the (111) plane of AlN, the (111) plane of TiN, the (111) plane of CrN, the (200) plane of AlN, the (200) plane of TiN, the (200) plane of CrN, the (220) plane of AlN, the (220) plane of TiN, and the (220) plane of CrN of a face-centered cubic lattice structure and the peak intensities due to the (010) plane of AlN, the (011) plane of AlN, and the (110) plane of AlN of a close-packed hexagonal structure Is in the intensity distribution obtained from the limited field diffraction pattern of a transmission electron microscope, a relationship of Ih x 100/Is 15 or less Is satisfied.

Preferably, the c-layer is the thickest film with respect to the total film thickness of the hard coating.

Preferably, the c layer is composed of columnar particles having an average width of 90nm or less.

According to the present invention, a coated cutting tool having excellent durability can be provided.

Drawings

Fig. 1 is a view showing a cross-sectional structure of a coated cutting tool according to an embodiment.

Fig. 2 shows an example of the diffraction pattern for restricting the field of view in the laminated film of example 1.

Fig. 3 is an example of an intensity distribution obtained from the limited-field diffraction pattern of fig. 2.

Detailed Description

The present inventors have studied a method for improving the tool life of a coated cutting tool provided with an AlCrSi-based nitride or carbonitride. The present inventors have found that a coated cutting tool exhibits more excellent durability by providing a laminated film in which an Al-rich AlCr-based nitride or carbonitride (hereinafter, sometimes referred to as AlCrN-based nitride) and an Al-rich AlTi-based nitride or carbonitride (hereinafter, sometimes referred to as AlTiN-based nitride) are alternately laminated on a nano-scale, further reducing AlN having an hcp structure (hexagonal close-packed structure) contained in the microstructure of the laminated film, and providing an AlCrSi-based nitride or carbonitride in the upper layer thereof, and have obtained the present invention. The following describes the details of the present embodiment.

The coated cutting tool of the present embodiment has a cross-sectional structure shown in fig. 1, for example. The coated cutting tool of the present embodiment has a base material and a hard coating formed on the base material. The hard coating film has an a-layer, a b-layer composed of nitride or carbonitride, a c-layer composed of a laminated coating film, and a d-layer composed of AlCrSi-based nitride or carbonitride, which are provided in this order from the base material side, as required. Next, each layer will be described in detail.

Substrate

In the coated cutting tool of the present embodiment, the base material is not particularly limited, and a WC — Co-based cemented carbide having excellent strength and toughness is preferably used as the base material.

Layer b

The b layer according to the present embodiment is a nitride or carbonitride disposed on the base material. The layer b is a base layer for improving adhesion between the base material and the layer c as the laminated film. The b layer disposed on the base material is a nitride or carbonitride, and thus a coated cutting tool having excellent adhesion between the base material and the hard coating film is obtained. Preferably, the b layer contains Al at 55 atomic% or more with respect to the total amount of metal (including semimetal). More preferably, Al in the b layer is 60 atomic% or more. By making the b layer Al-rich, the composition difference from the c layer composed of an Al-rich laminated film described later is reduced, and the adhesion is improved. Further, by making the b layer Al-rich, the heat resistance of the entire hard film is improved. More preferably, the b layer is a nitride excellent in heat resistance and wear resistance. However, if the content of Al in the b layer is too large, AlN having a fragile hcp structure increases. Therefore, it is preferable that Al of the b layer is 75 atomic% or less. In order to further improve the adhesion to the c layer as the laminated film, the b layer preferably contains a metal element contained in the c1 layer or the c2 layer described later. In addition, it is preferable to be about the b layer. In the intensity distribution obtained from the X-ray diffraction or the limited field diffraction pattern of the transmission electron microscope, the peak intensity due to the fcc (face centered cubic lattice) structure shows the maximum intensity. Thus, in the c layer, which is an Al-rich laminated film provided on the b layer, the durability of the coated cutting tool is improved by reducing the brittle hcp-structured AlN contained in the microstructure of the c layer. If the b-layer is a nitride or carbonitride, it may consist of a plurality of layers of different compositions.

When the thickness of the layer b is too thin, the adhesion to the substrate or the layer c tends to be lowered. On the other hand, if the thickness of the b layer is too large, chipping is likely to occur. In order to achieve more excellent durability of the coated cutting tool, the film thickness of the b layer is preferably 0.1 μm or more and 5.0 μm or less. More preferably, the film thickness of the b layer is 0.2 μm or more. More preferably, the film thickness of the b layer is 3.0 μm or less. The upper limit and the lower limit of the film thickness of the b layer may be appropriately combined.

Layer c

The c layer according to the present embodiment is an Al-rich laminated film provided between the b layer as the base layer and a d layer of an AlCrSi-based nitride or carbonitride described later.

Specifically, the c layer is a laminated coating film in which a c1 layer and a c2 layer are alternately laminated at a film thickness of 50nm or less, respectively, the c1 layer is a nitride or carbonitride containing 55 at% or more and 75 at% of aluminum (Al) with respect to the total amount of metal (including semimetal) elements, and then a large content of chromium (Cr), and containing at least silicon (Si); the c2 layer is aluminum (Al) containing 55 at% or more and 75 at% or less with respect to the total amount of metal (including semimetal) elements, and secondly titanium (Ti) contains much more nitrides or carbonitrides.

More preferably, the c layer is a laminated coating film in which a c1 layer and a c2 layer are alternately laminated at a film thickness of 50nm or less, respectively, the c1 layer is a nitride or carbonitride containing 55 at% or more and 75 at% or less of aluminum (Al), 20 at% or more of chromium (Cr), and 1 at% or more of silicon (Si), with respect to the total amount of metal elements; the c2 layer is a nitride or carbonitride containing 55 at% or more and 75 at% or less of aluminum (Al) and 20 at% or more of titanium (Ti) with respect to the total amount of the metal portion. The progress of film fracture is easily suppressed by alternately laminating Al-rich AlCrN-based hard films and Al-rich AlTiN-based hard films having different compositions on a nano-scale. Further, AlN having an hcp structure is less likely to be contained in the c-layer, and the heat resistance of the entire hard coating is improved, thereby improving the durability of the coated cutting tool.

Preferably, the content ratio of Al in the average composition of the c layer is 55 at% or more and 75 at% or less, and more preferably, the content ratio of Al is 73 at% or less. More preferably, the content ratio of Al in the average composition of the c layer is 60 atomic% or more and 70 atomic% or less. In the average composition of the layer c, the total content ratio of Cr and Ti is preferably 20 at% or more and 40 at% or less. In the average composition of the c layer, the content ratio of Si is preferably 0.5 at% or more and 5 at% or less. More preferably, the content ratio of Si in the average composition of the c layer is 1 atomic% or more and 3 atomic% or less. The average composition of the c layer may be calculated by measuring the range of 500nm × 500nm or more.

Further, the c-layer requires less AlN having an hcp structure contained in the microstructure. The present inventors found that even if the peak intensity of AlN with an hcp structure was not confirmed in X-ray diffraction in the evaluation of the c-layer, AlN with a fragile hcp structure may be contained in the microstructure. The present inventors have also confirmed that the durability of the coated cutting tool is improved by reducing the brittle hcp-structured AlN contained in the microstructure of the c-layer.

In order to quantitatively determine the amount of AlN with an hcp structure present in the microstructure of the hard coating, a limited field-of-view diffraction pattern was determined using a transmission electron microscope and an intensity distribution was determined from the limited field-of-view diffraction pattern for the machined cross section of the hard coating. Specifically, the relationship of Ih × 100/Is was evaluated in the intensity distribution of the limited field diffraction pattern of the transmission electron microscope. Ih and Is are defined as follows.

Ih: peak intensity due to (010) plane of AlN with hcp structure.

Is: the sum of the peak intensities due to the fcc-structured AlN (111) plane, TiN (111) plane, CrN (111) plane, AlN (200) plane, TiN (200) plane, CrN (200) plane, AlN (220) plane, TiN (220) plane and CrN (220) plane and the peak intensities due to the hcp-structured AlN (010) plane, AlN (011) plane and AlN (110) plane.

By evaluating the relationship between Ih and Is, in the hard coating in which the peak intensity due to the hcp-structured AlN was not confirmed by X-ray diffraction, the hcp-structured AlN contained in the microstructure could be quantitatively evaluated. A smaller value of Ih × 100/Is means that less AlN of fragile hcp structure Is present in the microstructure of the c-layer. The present inventors have confirmed that when the value of Ih × 100/Is in the c layer Is greater than 15, the durability of the coated cutting tool tends to be reduced under severe use environments. In the present embodiment, a coated cutting tool having good durability Is realized by adopting a structure in which the c-layer satisfies Ih × 100/Is ≦ 15. More preferably, the coated cutting tool of the present embodiment has a structure in which the c-layer satisfies Ih × 100/Is ≦ 10. More preferably, the coated cutting tool of the present embodiment has a structure in which the c-layer satisfies Ih × 100/Is ≦ 5. Further, in the coated cutting tool according to the present embodiment, it Is preferable that the peak intensity due to the (010) plane of AlN having an hcp structure Is not observed in the c-layer, that Is, the c-layer satisfies Ih × 100/Is of 0. Further, even if the diffraction pattern of AlN having an hcp structure Is confirmed in the limited-field diffraction pattern, if the amount thereof Is minute, a peak may not appear in the intensity distribution and the value of Ih × 100/Is may be 0. In the limited field diffraction pattern of the c-layer, AlN in which an hcp structure is not observed is preferable in order to further improve the durability of the coated cutting tool.

The microstructure of the c layer is composed of fine columnar particles. The columnar particles constituting the c layer extend in the film thickness direction (stacking direction) of the stacked coating. The layer c is composed of columnar particles of fine particles, and thus the hardness and toughness of the hard coating tend to be improved. In order to improve both hardness and toughness of the hard coating, the average width of the columnar particles in the c-layer is preferably 90nm or less. However, if the width of the columnar particles is too small, the toughness of the hard film is reduced. Therefore, the average width of the columnar particles in the c layer is preferably 30nm or more. The width of the columnar particles can be confirmed by observing the image using a transmission electron microscope. The average width of the columnar particles was calculated as an average value of the widths of 10 or more columnar particles confirmed from the cross-sectional observation image.

Layer c1

The c1 layer is a nitride or carbonitride containing 55 at% to 75 at% of aluminum (Al), a large amount of chromium (Cr), and at least silicon (Si), with respect to the total amount of metal (including semimetal) elements. More preferably, the c1 layer is a nitride or carbonitride containing 55 at% or more and 75 at% or less of aluminum (Al), 20 at% or more of chromium (Cr), and 1 at% or more of silicon (Si) with respect to the total amount of metal elements.

Nitrides or carbonitrides based on Al and Cr are film species excellent in heat resistance. In particular, when the Al content ratio is increased, the heat resistance of the hard coating tends to be improved, and the durability of the coated cutting tool tends to be improved. More preferably, the c1 layer is a nitride excellent in heat resistance and wear resistance. The c1 layer contains Al at 55 atomic% or more in order to impart high heat resistance to the hard film. More preferably, the Al content ratio of the c1 layer is 60 atomic% or more. However, if the content ratio of Al is too large, AlN having a fragile hcp structure contained in the microstructure increases, and thus the durability of the hard coating is reduced. Therefore, the Al content ratio of the c1 layer is preferably 75 atomic% or less. The Al content ratio of the c1 layer is preferably 73 atomic% or less, and more preferably 70 atomic% or less.

Regarding nitrides or carbonitrides based on Al and Cr, when the content ratio of Cr becomes too small, the wear resistance is lowered. In order to impart high wear resistance to the hard film, the c1 layer preferably contains 20 atomic% or more of Cr. In order to form the c1 layer as AlCr-based nitride or carbonitride, Al is contained most, and Cr is contained much more. However, if the content of Cr in the c1 layer is too high, the content of Al is relatively low, and thus the heat resistance is low. Therefore, the Cr content ratio of the c1 layer is preferably 40 atomic% or less, and more preferably 35 atomic% or less.

In order to further improve the heat resistance and wear resistance of the laminated film, the total content of Al and Cr is preferably 85 atomic% or more of the total amount of metal (including semimetal) elements in the c1 layer.

When the nitride or carbonitride of Al and Cr contains Si element, the coating structure becomes fine, and the wear resistance and heat resistance are further improved. Therefore, the c1 layer contains Si, and the wear resistance and heat resistance of the entire laminated film are improved. In order to sufficiently exert the effect of Si addition, the c1 layer preferably contains Si in an amount of 1 atomic% or more. However, if the Si content is too high, the durability is reduced because AlN having an hcp structure and an amorphous phase contained in the microstructure increase. Therefore, the Si content ratio of the c1 layer is preferably 5 atomic% or less, and more preferably 3 atomic% or less.

Since the c1 layers and the c2 layers are alternately stacked on the order of nanometers, the compositions of each other are mixed together at the time of coating. In addition, the mutual composition also diffuses. Therefore, the layer of c1 may contain Ti that is essential to the layer of c 2. However, in order to laminate Al-rich AlCrN-based hard films and Al-rich AlTiN-based hard films having different compositions, the content ratio of Ti in the c1 layer is smaller than that in the c2 layer.

The c1 layer may contain metal elements other than Al, Cr and Si. For example, the c1 layer may contain one or more elements selected from the group consisting of elements of groups 4a, 5a, and 6a of the periodic table and B, Y for the purpose of improving wear resistance, heat resistance, lubricity, and the like of the hard film. These elements are elements which are generally added to AlTiN-based and AlCrN-based hard films to improve the properties of the hard films, and if the content ratio is not too large, the durability of the coated cutting tool is not significantly reduced.

However, if the c1 layer contains a large amount of metal elements other than Al, Cr, and Si, the basic characteristics of the AlCrN-based hard film are impaired, and the durability of the coated cutting tool is reduced. Therefore, the total of the metal elements other than Al, Cr, and Si in the c1 layer is preferably 25 at% or less, more preferably 20 at% or less, and still more preferably 15 at% or less, with respect to the total amount of the metal (including semimetal) elements.

Layer c2

The c2 layer is a nitride or carbonitride containing 55 at% or more and 75 at% or less of aluminum (Al) and, secondly, much more of titanium (Ti) with respect to the total amount of metal (including semimetal) elements. More preferably, the c2 layer is a nitride or carbonitride containing 55 at% or more and 75 at% or less of aluminum (Al) and 20 at% or more of titanium (Ti) with respect to the total amount of metal elements. Nitrides or carbonitrides mainly composed of Al and Ti are film species excellent in wear resistance and heat resistance. In particular, when the content of Al is increased, the heat resistance of the hard coating tends to be improved, and the durability of the coated cutting tool tends to be improved. More preferably, the c2 layer is a nitride excellent in heat resistance and wear resistance. The c2 layer contains Al at 55 atomic% or more in order to impart high heat resistance to the hard film. More preferably, Al in the c2 layer is 60 atomic% or more. However, if the content ratio of Al is too large, the hard coating has reduced durability because AlN having an hcp structure increases. Therefore, the Al content ratio of the c2 layer is 75 atomic% or less. The Al content ratio of the c2 layer is preferably 73 atomic% or less, and more preferably 70 atomic% or less.

When the Ti content of the nitride or carbonitride based on Al and Ti is too small, the wear resistance is lowered. Therefore, the c2 layer preferably contains 20 atomic% or more of Ti. In order to form the c2 layer as an AlTi-based nitride or carbonitride, Al is contained at the maximum, and Ti is contained much next. However, if the content ratio of Ti is too large, the content ratio of Al is relatively low, and therefore, the heat resistance is low. Therefore, the Ti content ratio of the c2 layer is preferably 40 atomic% or less, and more preferably 35 atomic% or less.

In order to further improve the heat resistance and wear resistance of the laminated film, the total content ratio of Al and Ti in the c2 layer is preferably 80 atomic% or more with respect to the total amount of metal (including semimetal) elements.

Since the c1 layers and the c2 layers are alternately stacked on the order of nanometers, the compositions of each other are mixed together at the time of coating. In addition, the mutual composition also diffuses. Therefore, the layer c2 may contain Cr and Si, which are necessary to be contained in the layer c 1. However, in order to laminate an Al-rich AlCrN-based hard film and an Al-rich AlTiN-based hard film having different compositions, the content ratio of Cr in the c2 layer is smaller than the content ratio of Cr in the c1 layer. In addition, Si contained in the c1 layer at a small ratio may not be contained in the c2 layer.

The c2 layer may contain metal elements other than Al and Ti. For example, the c2 layer may contain one or more elements selected from the group consisting of elements of groups 4a, 5a, and 6a of the periodic table and elements of Si, B, and Y for the purpose of improving wear resistance, heat resistance, lubricity, and the like of the hard film. These elements are elements which are generally added to AlTiN-based and AlCrN-based hard films to improve the properties of the hard films, and if the content ratio is not too large, the durability of the coated cutting tool is not significantly reduced. In particular, the AlTiN-based hard coating preferably contains W (tungsten) element because it tends to have excellent durability in a more severe use environment.

However, if the c2 layer contains a large amount of metal elements other than Al and Ti, the basic characteristics of the AlTiN-based hard film are impaired, and the durability of the coated cutting tool is lowered. Therefore, in the c2 layer, the total of the metal elements other than Al and Ti is preferably 25 at% or less, more preferably 20 at% or less, and still more preferably 15 at% or less, with respect to the total amount of the metal (including semimetal) elements.

In order to further improve the adhesion between the layer b as the base layer and the layer c as the laminated film, it is preferable that the hard film having the same composition as the layer b is thicker in the portion of the layer c closer to the layer b. Specifically, if the b layer is an AlCrN-based hard film, the c1 layer is preferably thicker than the c2 layer in the portion of the c layer closer to the b layer side. In addition, if the b layer is an AlTiN-based hard film, the c2 layer is preferably thicker than the c1 layer in the portion of the c layer closer to the b layer side. By adopting such a film structure, the adhesion between the layer b as the base layer and the layer c as the laminated film tends to be improved, and the durability of the coated cutting tool may be further improved depending on the tool shape and the use environment.

In the present embodiment, the c-layer is preferably the thickest film relative to the total film thickness of the hard coating. Since the layer c is a main layer of the hard coating, the durability of the coated cutting tool is improved while the adhesion and the wear resistance are both satisfied at a high level.

The optimum film thickness of each layer varies depending on the type of tool, tool diameter, workpiece material, and the like, but the c layers are all the thickest films, and thus excellent durability can be easily achieved. When the total film thickness of the b layer, the c layer, and the d layer is 100%, the film thickness ratio of the c layer is preferably 50% or more, more preferably 60% or more, and still more preferably 70% or more. However, if the film thickness ratio of the c layer is too large, the film thicknesses of the b layer and the d layer become small, and thus the adhesion and the wear resistance are deteriorated. Therefore, the film thickness ratio of the c layer is preferably 90% or less, and more preferably 85% or less.

The film thickness ratio of the b layer is preferably 5% or more. The film thickness ratio of the d layer is preferably 10% or more.

In order to improve the adhesion of the laminated film, the thickness of each of the c1 layer and the c2 layer is preferably 20nm or less. When the film thickness of the c1 layer and the c2 layer is too small, it is difficult to form a laminated film having a different composition, and therefore the film thickness of the c1 layer and the c2 layer is preferably 2nm or more. Further, the film thickness of the c1 layer and the c2 layer is preferably 5nm or more. The upper and lower limits of the film thickness of the c1 layer and the c2 layer may be appropriately combined.

Layer d

The d layer according to the present embodiment is provided on the upper layer of the c layer as the laminated film. The d layer is a nitride or carbonitride containing aluminum (Al) at 55 at% or more and 75 at% or less with respect to the total amount of metal (including semimetal) elements, containing a large amount of chromium (Cr), containing chromium (Cr) at 20 at% or more, and further containing at least silicon (Si). By providing the d-layer of Al-rich AlCrSi-based nitride or carbonitride on the c-layer of the Al-rich laminated film, the heat resistance of the entire hard film can be further improved.

Nitrides or carbonitrides based on Al and Cr are film species excellent in heat resistance. In particular, when the Al content ratio is increased, the heat resistance of the hard coating tends to be improved, and the durability of the coated cutting tool tends to be improved. The d layer contains 55 atomic% or more of Al in order to impart high heat resistance to the hard coating. More preferably, the Al content ratio of the d layer is 60 atomic% or more. However, if the content ratio of Al is too large, AlN having a fragile hcp structure contained in the microstructure increases, and thus the durability of the hard coating is reduced. Therefore, the Al content ratio of the d layer is preferably 73 atomic% or less, and more preferably 70 atomic% or less.

Regarding nitrides or carbonitrides based on Al and Cr, when the content ratio of Cr becomes too small, the wear resistance is lowered. The d layer contains 20 atomic% or more of Cr in order to impart high wear resistance to the hard film. In order to form the d layer as AlCr based nitride or carbonitride, Al is contained most, and Cr is contained much next. However, if the content of Cr in the d layer is too large, the content of Al is relatively low, and therefore the heat resistance is low. Therefore, the content ratio of Cr in the d layer is preferably 40 atomic% or less, and more preferably 35 atomic% or less.

In the d layer, the total content of Al and Cr is preferably 85 atomic% or more based on the total amount of metal (including semimetal) elements in order to further improve heat resistance and wear resistance. The d layer is preferably a nitride having more excellent heat resistance and wear resistance.

When the nitride or carbonitride of Al and Cr contains Si element, the coating structure becomes fine, and the wear resistance and heat resistance are further improved. Therefore, the d layer contains Si, and thereby wear resistance and heat resistance are improved. In order to sufficiently exert the effect of adding Si, the d layer preferably contains Si in an amount of 1 atomic% or more. However, if the Si content is too high, the durability of the hard coating is reduced because AlN having an hcp structure and an amorphous phase contained in the microstructure increase. Therefore, the Si content ratio of the d layer is preferably 10 atomic% or less, and more preferably 5 atomic% or less.

When the thickness of the d layer is too small, the improvement of heat resistance is insufficient. In order to improve the heat resistance of the entire hard coating, the thickness of the d layer is preferably 1 μm or more. More preferably, the film thickness of the d layer is 2 μm or more. On the other hand, if the film thickness of the d layer becomes too thick, chipping is likely to occur. The thickness of the d layer is preferably 5.0 μm or less.

Other layers may be provided on the upper layer of the d layer as necessary.

The hard coating according to the present example is preferably a nitride having excellent heat resistance and wear resistance in the layers b, c, and d. The entire hard coating is nitride, which further improves the durability of the coated cutting tool. In addition, in general, even nitrides contain a small amount of oxygen and carbon. That is, in microscopic analysis, the metal nitride has a peak intensity of the bonding of the metal element and oxygen or carbon. The hard coating according to the present embodiment may partially contain carbonitride or oxynitride if it is mainly composed of nitride. If the composition and the coating structure are within the ranges described above, the durability of the coated cutting tool is not significantly reduced even if the carbonitride or oxynitride is included in a part of the nitride constituting the hard coating. In addition, when the hard film according to the present embodiment is formed of carbonitride, the content of nitrogen is preferably larger than that of carbon in order to further improve the heat resistance and wear resistance of the hard film. Even in the case of carbonitride, the content ratio of carbon is preferably 20 atomic% or less, more preferably 10 atomic% or less, with respect to the content ratio of nitrogen.

Layer a

In the present embodiment, an a layer whose nanobeam diffraction pattern is exponentially scaled to a crystal structure of WC may be provided between the base material and the b layer as a base layer, as necessary. The layer a is formed on the surface of the base material through metal ion bombardment. Since the a layer is a layer formed by diffusion of a metal element used for metal ion bombardment, when a WC — Co based cemented carbide is used as a base material, the W (tungsten) content is the largest in the total amount of the metal elements, and the metal element used for metal ion bombardment is contained next. By providing such a layer a, adhesion between the base material and the underlying layer provided thereon tends to be significantly improved.

However, when the tool diameter is reduced, in a right-angle end mill or a radius end mill in which the cutting edge is likely to become an acute angle, the cutting edge may be melted down by metal ion bombardment, and the ridge line of the cutting edge may be easily broken. Therefore, the layer a is preferably provided in a ball nose end mill having a cutting edge with a sharp edge that is less likely to be damaged by metal ion bombardment and does not form an acute angle. When the film thickness of the a layer is too thin or too thick, the effect of improving the adhesion cannot be obtained. Therefore, the film thickness of the a layer is preferably 1nm or more and 10nm or less.

Since the a layer is a layer in which a nano-beam diffraction pattern is exponentially scaled to a crystal structure of WC, it is mainly composed of carbide. If the a layer is a layer whose nanobeam diffraction pattern is exponentially scaled to the crystal structure of WC, nitrogen and oxygen may also be contained in a part. In addition, the a layer also partially contains a metal layer and a crystal phase of fcc structure. In particular, the metal ion bombardment treatment using a metal Ti or an alloy target mainly composed of Ti has a large effect of improving the adhesion. Therefore, it is preferable that W is contained most in the content ratio of the metal element of the a layer, and Ti is contained much less. However, if the content ratio of Ti contained in the a layer is too large or too small, it is difficult to obtain the effect of improving the adhesion. Preferably, the a layer contains 10 at% or more and 30 at% or less of Ti.

According to the coated cutting tool of the present embodiment described above, the c-layer, which is a laminated film of the c1 layer composed of the AlCr-based hard film and the c2 layer composed of the AlTi-based hard film and in which the content of the hcp-structured AlN is reduced, is provided below the d-layer mainly composed of the nitride of AlCrSi, whereby the heat resistance and wear resistance can be improved as compared with the conventional AlCrSi-based hard film. Therefore, according to the present embodiment, a coated cutting tool having excellent durability is provided.

Method for producing

The hard coating according to the present embodiment is preferably coated by arc ion plating with a high target ionization rate. Further, the coating may be performed by a high-output sputtering method in which the ionization rate of the target is high. In addition, in order to improve crystallinity and reduce the AlN having an hcp structure contained in the microstructure, it is preferable to use a cathode having a magnetic flux density of 10mT or more in the vertical direction near the center of the target for the Al-rich laminated coating.

In the cathode for forming the AlCr-based hard film, it is preferable that the cathode voltage is in the range of 20V to 35V. When the cathode voltage is too low, the hcp structure of the laminated film is increased in AlN, and the durability is lowered. When the cathode voltage is too high, the film structure of the laminated film becomes too coarse, and the durability is liable to be lowered.

In the cathode for forming the AlTi-based hard film, the cathode voltage is preferably in the range of 20V or more and 30V or less. When the cathode voltage is too low, the hcp structure AlN of the laminated film increases, and the durability decreases. When the cathode voltage is too high, the film structure of the laminated film becomes too coarse, and the durability is liable to be lowered. The cathode currents are preferably 120A or more and 200A or less, respectively.

In the production method of the present embodiment, it is preferable to select a film formation apparatus in which the magnetic flux density in the vertical direction in the vicinity of the target center and the cathode voltage are set to the above-described ranges, and to increase the absolute value of the negative bias voltage applied to the substrate. According to this production method, the production of AlN having an hcp structure in the microstructure is suppressed. This makes it possible to make the value of Ih × 100/Is in the c layer smaller than 15.

The negative bias voltage applied to the substrate is preferably-200V or more and less than-100V. More preferably-120V or less. When the absolute value of the bias voltage is too large, it is difficult to stabilize the film formation and to adjust the film thickness. When the absolute value of the bias voltage is too small, the hcp structure AlN of the laminated film increases, and the durability decreases. The coating temperature is preferably 400 ℃ or higher and 600 ℃ or lower. In the case of coating with nitride, nitrogen gas is introduced into the furnace to perform coating. The nitrogen pressure during coating is preferably 2.0Pa to 8.0 Pa. In the case of coating carbonitride, a part of nitrogen gas may be replaced with methane gas.

Examples

< film Forming apparatus >

For film formation, a film forming apparatus using an arc ion plating method is used. The film forming apparatus includes a plurality of cathodes (arc evaporation sources), a vacuum chamber, and a substrate rotating mechanism. As the cathode, 1 cathode (hereinafter, referred to as "C1") having a coil magnet provided on the outer periphery of the target was mounted; and 3 a cathode (hereinafter, referred to as "C2, C3, C4") having a permanent magnet on the rear surface and the outer periphery of the target, a magnetic flux density in the vertical direction on the target surface, and a magnetic flux density in the vertical direction near the target center of 14 mT.

C1 to C4 were disposed at an interval of about 90 ° around the region where the base material was disposed, and C1 and C4, and C2 and C3 were disposed so as to face each other.

The inside of the vacuum container is evacuated by a vacuum pump, and a gas is introduced from a supply port. A bias power supply is connected to each base material provided in the vacuum chamber, and a negative DC bias voltage can be applied to each base material independently.

The base material rotating mechanism is provided with a planetary gear (プラネタリー), a plate-shaped clamp arranged on the planetary gear, and a tubular clamp arranged on the plate-shaped clamp, wherein the planetary gear rotates at the speed of 3 circles per minute, and the plate-shaped clamp and the tubular clamp respectively rotate and revolve.

In example 1, the following ball nose end mill was used for the base material.

Consists of the following components: WC (remainder) -Co (8 mass%) -Cr (0.5 mass%) -V (0.3 mass%)

Hardness: 94.0HRA

Blade diameter: 1mm, number of blades: 2 pieces of the Chinese herbal medicine

A metallic titanium target was provided for C1, an AlTi-based alloy target was provided for C2, an AlCrSi-based alloy target was provided for C3, and an AlCrSi-based alloy target was provided for C4. Table 1 shows the target compositions used.

[ Table 1]

Each substrate was fixed to a tubular jig in a vacuum vessel, and the following process was performed before film formation. First, the inside of the vacuum vessel was evacuated to 5X 10^-2Pa or less. Then, the substrate was heated to 500 ℃ by a heater provided in the vacuum vessel, and vacuum evacuation was performed. The set temperature of the substrate was 500 ℃ and the pressure in the vacuum vessel was 5X 10^-2Pa or less.

< Ar bombardment >

Then, argon (Ar) gas was introduced into the vacuum vessel, and the internal pressure of the vessel was set to 0.67 Pa. Then, a current of 35A was supplied to the filament electrode, and a negative bias voltage of-200V was applied to the base material, and Ar bombardment was performed for 15 minutes.

< Ti bombardment step >

Then, vacuum evacuation was performed so that the pressure in the vacuum vessel became 8 × 10^-3Pa or less. Then, an arc current of 120A was supplied to C1, and a negative bias voltage of-800V was applied to the substrate to carry out Ti bombardment for 15 minutes.

< film Forming Process >

Then, the set temperature of the substrate was 480 ℃, nitrogen gas was introduced into the vacuum vessel, and the pressure in the furnace was 3.2 Pa.

In the coating of the b layer, the negative bias voltage applied to the substrate was set to-120V and the current applied to C2 was set to 200A for any of the samples. The b layer is set to about 0.5 μm.

In the coating of the c-layer, a negative bias voltage applied to the substrate is changed by the sample. The power applied to C3 was constant, and the power applied to C2 was gradually increased, so that the C2 layer (AlTiN system) was coated with a film thicker than the C1 layer (AlCrN system) in the portion of the C layer closer to the b layer side. The cathode voltage of C2 is 20V or more and 30V or less, and the cathode voltage of C3 is 20V or more and 35V or less during encapsulation.

In the coating of the d layer, the negative bias voltage applied to the substrate was set to-120V and the current applied to C4 was set to 150A for any of the samples. The d layer is set to about 1.5 μm.

Table 2 shows the film formation conditions for the layer c.

[ Table 2]

The coated cutting tool thus produced was subjected to a cutting test under the cutting conditions shown below.

Table 3 shows the cutting test results. The details of the cutting conditions are as follows.

< processing conditions >

The cutting method: side cutting

Workpiece material: STAVAX (52HRC)

Using a tool: double-edge ball end mill (diameter 1mm)

Depth of cut: axial, 0.04mm, radial, 0.04mm

Main shaft rotation number: 24000min^-1

Feed speed: 860mm/min

Cooling liquid: drying process (air blowing)

Cutting distance: 90m

[ Table 3]

Sample No.	Maximum wear width (mm)
		Example 1	0.018
Comparative example 1	0.026
		Comparative example 2	0.037

In example 1, a stable wear pattern with a small maximum wear width is shown, and cutting can be continued. Comparative example 1 was composed of the same coating as in example 1, but the maximum wear width was increased. In comparative example 2, the laminated film had a smaller Al content than in example 1, and the maximum wear width was increased.

In example 1, microscopic analysis of the laminated film was performed to clarify the main cause of excellent durability.

The b-layer and d-layer were analyzed for composition by wavelength dispersive electron probe microanalysis (WDS-EPMA) attached to a sample using an electron probe microanalyzer (model: JXA-8500F) manufactured by Nippon Electronics co.

In example 1, a ball end mill for physical property evaluation was machined, and the machined cross section was observed with a Transmission Electron Microscope (TEM). It was confirmed that the c layer as a laminated coating was formed of fine columnar particles having an average width of 50nm to 70 nm.

Table 4 shows an example of the results of the composition analysis of the entire laminated film. The composition of the c1 layer and the c2 layer was set to the analysis region by using an energy dispersive X-ray spectrometer (EDS)The center of each layer was analyzed. The decimal point or less is obtained by rounding.

The layer c of example 1 is Al-rich in the entire laminated film, and contains at least Si, Ti, and Cr. In example 1, the compositions of the c1 layer and the c2 layer were mixed with each other, and the c1 layer contained Ti and W in total at 10 atomic% or less. In addition, the c2 layer of example 1 contained 10 atomic% or less of Cr.

[ Table 4]

Then, the diffraction pattern of the laminated film for restricting the field of view is set to a region of the restricted field of view at an acceleration voltage of 120kVCamera length 100cm, incident electron amount 5.0pA/cm²Determined under the conditions (on a fluorescent plate). The intensity distribution is obtained by converting the brightness of the obtained limited field diffraction pattern. The analysis position is set as the middle portion in the film thickness direction.

Fig. 2 shows an example of the field-of-view-limiting diffraction pattern of the c-layer in example 1. Fig. 3 shows an example of the intensity distribution of the limited field-of-view diffraction pattern obtained by converting the brightness of the limited field-of-view diffraction pattern of the laminated film of fig. 2. In fig. 3, the horizontal axis represents the distance from the center of the (000) -plane spot (radius r), and the vertical axis represents the integrated intensity (arbitrary unit) of each radius r around the circle.

In fig. 3, arrow 1 indicates a peak due to the (111) plane of AlN, the (111) plane of TiN, and the (111) plane of CrN in the fcc structure. Arrow 2 indicates a peak due to the (200) plane of AlN, the (111) plane of TiN, and the (200) plane of CrN in the fcc structure. Arrow 3 indicates a peak due to the (220) plane of AlN, the (111) plane of TiN, and the (220) plane of CrN in the fcc structure. In FIG. 3, no peak intensity was observed due to AlN (010) having an hcp structure.

As shown in FIG. 2, in inventive example 1, no peak was observed due to AlN (010) having an hcp structure, and ih.times.100/Is was 0. On the other hand, the layer c of comparative example 1 had a peak due to the AIN (010) plane having an hcp structure as a result of the same measurement as in example 1, and Ih × 100/Is was 19.

In example 1 and comparative example 1, although the peak intensity due to the AlN with an hcp structure was not observed in the X-ray diffraction, the peak intensity due to the AlN with an hcp structure was different in the restricted field diffraction pattern. In example 1, it is assumed that the durability is significantly improved because AlN having an hcp structure is contained in a small amount in the microstructure.