JP2010253594A - Surface coated tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface coated tool suppressing chipping of a cutting edge without peeling a hard layer in cutting with large shock on the cutting edge. <P>SOLUTION: In a cutting tool 1, cemented carbide contains at a rate of 85 to 95 mass% of WC, 0 to 5 mass% of one or more of carbide, nitride and carbonitride of 4, 5 and 6 group metal in a periodic table except WC and 5 to 10 mass% of Co, an average particle size of WC particles 3 is 0.1 to 2.0 μm at the inside, more coarse WC particles 5 having major axes of 5 to 20 μm exist on the surface than the inside and a content ratio of Co is 85 to 95% on the surface in relation to the inside, and a coating layer 10 includes a TiCN layer 12 and a αAl<SB>2</SB>O<SB>3</SB>layer 14. In a section structure, projections 16 having an average height of 0.2 μm to 1.0 μm and an average width of 0.1 μm to 1.5 μm are formed to be arranged side by side from the TiCN layer 12 between the TiCN layer 12 and the αAl<SB>2</SB>O<SB>3</SB>layer 14. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a surface-coated tool in which a coating layer is formed on the surface of a cemented carbide substrate.

Conventionally, as a cutting tool widely used for metal cutting, a surface-coated cutting tool in which a plurality of coating layers are formed on the surface of a substrate such as cemented carbide, cermet, or ceramic is frequently used. As the coating layer, a coating layer having a multilayer structure such as a titanium carbide (TiC) layer, a titanium nitride (TiN) layer, a titanium carbonitride (TiCN) layer, and an aluminum oxide (Al ₂ O ₃ ) layer is known. A coating layer formed in the order of a titanium carbonitride layer, an intermediate layer (bonding layer), and an aluminum oxide layer is often used. In particular, when the aluminum oxide layer is composed of an α-aluminum oxide layer made of α-type crystals, peeling is likely to occur between the titanium carbonitride layer and the α-aluminum oxide layer, thereby increasing the adhesion of the aluminum oxide layer. There was a need.

  In Patent Document 1, the bonding layer is composed of any one of needle-like, rod-like, and plate-like crystals, and the [110] plane of the bonding layer and the [100] plane of the aluminum oxide layer thereon are arranged in the growth direction of the coating layer. It is described that by arranging them in parallel, the mechanical strength of the bonding layer is improved, the bonding layer is hardly broken, and peeling of the aluminum oxide layer can be prevented. Moreover, in patent document 2, about the intermediate | middle layer which consists of titanium carbonate or titanium carbonitride oxide formed on the titanium carbonitride layer, by making the interface with an aluminum oxide layer into a sharp needle-like crystal structure, the aluminum oxide layer It is described that the adhesive strength of can be improved. Further, in Patent Document 3, from a Ti oxide, an oxynitride, a carbonate, and a carbonitride oxide on a bonding layer made of an oxide of Ti and Al, an oxynitride, a carbonate, and a carbonitride oxide. In the configuration in which an aluminum oxide layer is further formed on the surface of the bonding layer, the bonding strength of the aluminum oxide layer is improved by providing a number of protrusions protruding toward the aluminum oxide layer on the surface of the bonding layer. At the same time, it is described that the amount of oxygen in the bonding layer is increased and the aluminum oxide layer is stably formed into an α-type crystal structure.

  On the other hand, cutting tools in which a coating layer of titanium carbide, titanium nitride, titanium carbonitride, or the like is formed on the surface of a substrate made of a cemented carbide mainly composed of tungsten carbide (WC) particles have been widely used. It has been. In such a cemented carbide, attempts are being made to adjust the hardness and toughness of the cemented carbide by adjusting the particle size of the WC particles.

  For example, in Patent Document 4, when a diamond film is formed on the surface of a cemented carbide substrate, a ratio of 7.5 to 45 area% of coarse particles having the longest intragranular diameter of 15 to 80 μm is formed on the surface region of the cemented carbide. It is described that the adhesion strength of the diamond coating can be increased. Patent Document 5 discloses a method of precipitating coarse WC particles on the surface of a cemented carbide by further heat treatment after firing the cemented carbide.

JP 2004-148503 A JP 09-174304 A JP 2004-074324 A Japanese Patent Laid-Open No. 10-43911 JP-T-2004-514790

  However, the coated tools described in any of Patent Documents 1 to 3 described above have insufficient adhesion between the aluminum oxide layer and the bonding layer, and suddenly such as cutting of alloy steel, carbon steel, castings, etc. It has been difficult to exhibit sufficient cutting performance in such a cutting process where a large impact is applied, and further improvement in fracture resistance has been demanded in the cutting process of such a work material.

  Moreover, even if the cemented carbide described in the said patent documents 4 and 5 was used, the abrasion resistance and fracture resistance of the cutting tool were inadequate.

  Accordingly, the present invention has been made to solve the above-described problems, and an object of the present invention is to provide a cutting tool exhibiting an excellent tool life having high wear resistance and fracture resistance.

The surface-coated tool of the present invention has a coating layer formed on the surface of a substrate made of cemented carbide,
The cemented carbide is
85 to 95% by mass of WC, 0 to 5% by mass of one or more of carbides, nitrides, and carbonitrides of periodic tables 4, 5, and 6 metals other than WC, 5 to 10% by mass of Co, In a proportion of
Whether it consists of WC particles and a binder phase mainly composed of Co,
Or composed of WC particles, B1 type solid solution particles composed of one or more of carbides, nitrides and carbonitrides of periodic tables 4, 5, and 6 metals other than WC particles, and a binder phase mainly composed of Co. ,
The average particle diameter of the WC particles inside is 0.1 to 2.0 μm, and there are more coarse WC particles having a major axis of 5 to 20 μm on the surface of the cemented carbide than the inside, and the surface The Co content ratio in is 85 to 95% with respect to the Co content in the interior,
The coating layer is
Including at least a titanium carbonitride layer and an α-type crystal α-aluminum oxide layer in order from the substrate side;
In the cross-sectional structure, between the titanium carbonitride layer and the α aluminum oxide layer, the average height from the titanium carbonitride layer is 0.2 μm to 1.0 μm, and the width at the intermediate height is average. Protrusions of 0.1 μm to 1.5 μm are formed side by side.

  Here, the coarse WC particles are 15 to 21 area% on the surface of the cemented carbide, 6 to 15 area% at a depth position of 500 μm from the surface, and 2 to 6 area at a depth position of 1000 μm from the surface. %, Preferably at a depth of 1500 μm or more from the surface in a ratio of 0.5 to 2 area%.

  Moreover, it is desirable that the particle size distribution of the WC particles other than the coarse WC particles in the cemented carbide has two peaks: a fine particle having a particle size of 1 μm or less and a medium particle having a particle size of 2 to 4 μm.

  Furthermore, it is desirable that small projections having an average height of 20 nm to 100 nm and an average width of 10 nm to 50 nm are formed side by side on the side surface of the projection of the coating layer.

  In addition, it is desirable that an average of 4 to 15 small protrusions is formed on both side surfaces of one protrusion.

  Furthermore, it is desirable that the small protrusions contain more oxygen and aluminum than the protrusions.

  Further, between the small protrusion or the protrusion adjacent to the α aluminum oxide layer and the α aluminum oxide layer, at least Ti, Al, C and O elements are contained, and the content of the O element is It is desirable that the bonding layer composed of 15 to 25 atomic% is formed with a thickness of 5 nm to 30 nm.

  According to the surface-coated tool of the present invention, the toughness of the substrate itself is improved by the combination of the substrate having the above structure and the hard phase having the above structure, and the adhesion with the coating layer is improved in the vicinity of the surface of the substrate. .

  Here, the coarse WC particles are 15 to 21 area% on the surface of the cemented carbide, 6 to 15 area% at a depth position of 500 μm from the surface, and 2 to 6 area at a depth position of 1000 μm from the surface. %, The toughness in the vicinity of the cutting edge is improved and the fracture resistance is further improved by being present at a ratio of 0.5 to 2 area% at a depth position of 1500 μm or more from the surface.

  When the particle size distribution of the WC particles other than the coarse WC particles in the cemented carbide has two peaks, a fine particle having a particle size of 1 μm or less and a medium particle having a particle size of 2 to 4 μm, Toughness is further improved.

  Further, small protrusions having an average height of 20 nm to 100 nm and an average width of 10 nm to 50 nm are formed side by side on the side surfaces of the protrusions of the covering layer. When an average of 4 to 10 small protrusions are present on both side surfaces of one of the protrusions, adhesion between the titanium carbonitride layer, the protrusions, the small protrusions, and the α-aluminum oxide layer can be further improved.

  Further, the small protrusions contain more oxygen and aluminum than the protrusions, so that the adhesion of the α-aluminum oxide layer can be improved.

  Further, at least Ti, Al, C and O elements are included between the small protrusions adjacent to the aluminum oxide layer or between the protrusions and the aluminum oxide layer, and the content of the O element is 15 to 25 The bonding layer composed of atomic% is formed with a thickness of 5 nm to 30 nm to suppress film peeling of the α aluminum oxide layer, and the crystal constituting the α aluminum oxide layer becomes an α-type crystal. It is desirable because it can be easily controlled.

It is a cross-sectional schematic diagram about an example of the cutting tool which is a suitable example of the surface coating tool of this invention. It is a scanning electron microscope (SEM) photograph about the base | substrate of the cutting tool of FIG. 1, and is shown for every depth position from the surface. It is an expansion schematic diagram about the principal part of the coating layer of the cutting tool of FIG.

As shown in the schematic cross-sectional view of FIG. 1, a cutting tool 1 which is a preferred example of the surface-coated tool of the present invention has at least a TiCN layer 12 and an α-type crystal α-aluminum oxide layer (hereinafter referred to as αAl). referred to as ₂ O ₃ layer.) 14 coating layer 10 formed in this order from the substrate 2 side is formed.

  The substrate 2 has 85 to 95% by mass of WC, 0 to 5% by mass of one or more of carbides, nitrides, and carbonitrides of periodic tables 4, 5, and 6 metals other than WC, and 5 to 10% of Co. It consists of a composition that is contained in a proportion of mass%.

  Further, as shown in FIG. 2, the substrate 2 is composed of WC particles 3 and a binder phase 4 containing Co as a main component, or WC particles 3 and periodic tables 4 and 5 other than the WC particles 3. The WC particles are composed of B1 type solid solution particles (not shown) made of one or more of group 6 metal carbides, nitrides and carbonitrides, and a binder phase 4 containing Co as a main component. 3 having a mean particle size of 0.1 to 2.0 μm and a structure in which coarse WC particles 5 having a major axis (particle size) of 5 to 20 μm are present on the surface of the substrate 2 more than the inside. Become.

  By using the cemented carbide of the above configuration as the base 2, the toughness in the vicinity of the cutting edge of the cutting tool 1 is improved, chipping resistance is improved, and the hardness necessary to ensure wear resistance is achieved by the internal structure. can do. Further, the presence of the coarse WC particles 5 near the surface causes an anchor effect at the interface with the coating layer 10 and improves the adhesion with the coating layer 10. Such tool damage can be suppressed.

  Here, when the major axis of the coarse WC particles 5 is less than 5 μm, sufficient toughness cannot be imparted to the cutting edge, and the chip is likely to be lost suddenly. On the other hand, if the major axis of the coarse WC particles 5 exceeds 20 μm, the hardness of the substrate 2 is insufficient and the wear resistance is lowered. In addition, as a method of measuring the major axis (particle diameter) of the WC particles 3 (and coarse WC particles 5) of the substrate 2, a scanning electron microscope (SEM) is used with respect to the mirror-finished surface of the cross section of the cutting tool 1. It can be calculated by observing at a magnification of 3000 to 5000 times and performing image analysis using an SEM photograph taken for an arbitrary region.

  The coarse WC particles 5 are 15 to 21% by area on the surface of the substrate 2, 6 to 15% by area at a depth of 500 μm from the surface, 2 to 6% by area at a depth of 1000 μm from the surface, and 1500 μm from the surface. It exists in the point which the toughness of the blade edge vicinity improves and the fracture resistance of the cutting tool 1 improves by existing in the ratio of 0.5-2 area% in the above depth position.

  Further, the particle size distribution of the WC particles 3 other than the coarse WC particles 5 inside the substrate 2 is a mixed structure having two peaks of a fine particle having a particle size of 1 μm or less and a medium particle having a particle size of 2 to 4 μm. 2 is desirable in that the toughness of 2 is improved.

On the other hand, the covering layer 10 is formed with a TiCN layer 12 and an αAl ₂ O ₃ layer 14 as shown in the schematic cross-sectional views shown in FIGS. The protrusions 16 having an average width of 2 μm to 1.0 μm and an average width of 0.1 μm to 1.5 μm are formed side by side, and the width of the protrusion 16 is 20 nm to 100 nm at the intermediate height. However, the small protrusions 17 having an average of 10 nm to 50 nm are formed side by side. Thus, along with the alpha Al ₂ O ₃ layer 14 of α-type crystal structure can be stably formed and can have a high adhesive force alpha Al ₂ O ₃ layer 14, peeling of the alpha Al ₂ O ₃ layer 14 It is possible to suppress abnormal wear of the cutting edge and chipping of the cutting edge.

That is, if the height H of the protrusion 16 at the interface on the TiCN layer 12 side is smaller than 0.2 μm on average, the contact area with the αAl ₂ O ₃ layer 14 is too small, and the adhesion of the αAl ₂ O ₃ layer 14 is reduced. can not be improved, the crystal growth and 1.0μm greater on average height H alpha Al ₂ O ₃ layer 14 becomes cluttered, adhesion and toughness of alpha Al ₂ O ₃ layer 14 is reduced. Further, if the width W at the intermediate height (1/2) H of the protrusion 16 is smaller than 0.1 μm on average, the strength of the protrusion 16 is lowered and broken, which may cause the αAl ₂ O ₃ layer 14 to peel off. If the width W is larger than 1.5 μm on average, the contact area between the protrusion 16 and the αAl ₂ O ₃ layer 14 becomes small, and the adhesion force of the αAl ₂ O ₃ layer 14 cannot be secured, so that the αAl ₂ O ₃ The layer 14 may be peeled off.

Further, the small protrusions 17 are present at an average height h of 20 nm or more, and the width w at the intermediate height (1/2) h of the small protrusions 17 is an average of 10 nm or more, whereby an αAl ₂ O ₃ layer 14 can sufficiently exhibit an anchoring effect for improving the adhesion of the αAl ₂ O ₃ layer 14 at the contact portion with 14, the average height h of the small protrusions 17 is 100 nm or less, and the width w of the small protrusions 17 When the average is 50 nm or less, the small protrusions 17 are scattered on the side surfaces of the protrusions 16, and the adhesion of the αAl ₂ O ₃ layer 14 can be further improved.

  Here, the measurement method of the height and width of the protrusion 16 and the small protrusion 17 is as follows. The measurement is performed by observing a cross section by HR-TEM observation. An example of TEM observation conditions is shown below.

Apparatus: Transmission electron microscope (H-9000UHR III manufactured by Hitachi, Ltd.)
Measurement conditions: acceleration voltage 300 kV
Sample preparation: mechanical polishing + ion milling PIPS691 type manufactured by GATAN Co. Further, in order to measure the height H of the protrusion 16, it is a schematic diagram of a cross-sectional photograph taken by HR-TEM as shown in FIG. Of the valleys on both sides of each projection 16 in the upper part of the projection, the length in the direction perpendicular to the plane of the substantially horizontal plane from the position of the lower valley to the highest position of the top of the projection 16 is set. taking measurement. In order to measure the width W of the protrusion 16, the width W of the protrusion 16 in a direction substantially horizontal to the base 2 at the position of the height (½) H that is half the height H is measured.

  Further, in order to measure the height h of the small protrusion 17, as shown in FIG. 3, from the top of each small protrusion to the interface between the protrusion 16 and the small protrusion 17 (side surface of the protrusion 16), the interface is substantially Measure the length h of the vertical straight line. Further, in order to measure the width w of the small protrusion 17, the protrusion of the small protrusion 17 is located at the middle point (position) (1/2) h of the straight line perpendicular to the interface when the height h is measured. The width w in a direction substantially horizontal to the 16 interfaces is measured.

Here, the adhesion force of the αAl ₂ O ₃ layer 14 can be improved by having 10 to 30 protrusions 16 per length of 10 μm in the width direction of the coating layer 10. That is, by increasing the number of protrusions 16 to 10 or more, the adhesion of the αAl ₂ O ₃ layer 14 is improved, and by setting the number of protrusions to 30 or less, the width W of the protrusions 16 can be easily within the scope of the present invention. desirable. At this time, the number of protrusions 16 is measured for each of the photographs obtained by observing the cross-sectional view of the HR-TEM in arbitrary three fields of view, and is set as an average value.

In addition, the average of 4 to 10 small protrusions 17 on both sides of one protrusion 16 can improve the adhesion of the αAl ₂ O ₃ layer 14. That is, the adhesion of the αAl ₂ O ₃ layer 14 can be improved by setting the number of the small protrusions 17 to 4 or more. Further, by setting the number of the small protrusions 17 to 10 or less, the small protrusions 17 can exist in a scattered state without being layered, and thus the anchor effect of the small protrusions 17 is enhanced. At this time, the number of the small protrusions 17 is an average value obtained by observing five or more protrusions 16 and measuring the number of small protrusions 17 present on each protrusion 16. In addition, with respect to H, W, h, and w, an arbitrary value of 10 or more is measured and an average value thereof is taken.

Furthermore, since the small protrusion 17 contains more oxygen and aluminum than the protrusion 16, the composition of the contained elements is inclined in the order of the αAl ₂ O ₃ layer 14, the small protrusion 17, and the protrusion 16. The difference in thermal expansion coefficient between the ₂ O ₃ layer 14 and the small protrusion 17 is reduced, and the adhesion of the αAl ₂ O ₃ layer 14 can be improved. In particular, since the difference in thermal expansion coefficient between the protrusion 16 and the TiCN layer 12 is reduced when the oxygen content in the protrusion 16 is small, the adhesion between the protrusion 16 and the TiCN layer 12 can be improved. .

Here, between the alpha Al ₂ O ₃ layer 14 small projection 17 or projections 16 adjacent to the alpha Al and ₂ O ₃ layer 14, containing at least Ti, Al, C and O elements, and the content of the element O Is formed with a thickness of 5 nm to 30 nm to form the αAl ₂ O ₃ layer 14 without reducing the adhesion of the αAl ₂ O ₃ layer 14. This is desirable because the crystal structure can be uniformly formed into an α-type crystal structure.

At this time, by setting the amount of oxygen contained in the bonding layer 13 to 45 atomic% or less, a decrease in strength of the bonding layer 13 can be suppressed, and film peeling and chipping can be suppressed. Further, by making the amount of oxygen contained in the bonding layer 13 and 25 atomic percent or more, can be obtained an oxygen source required for the alpha Al ₂ O ₃ layer 14 in a high cutting performance α-type crystal structure sufficiently The αAl ₂ O ₃ layer 14 is desirable because it can be easily manufactured.

Note that the TiCN layer contains 20.0 to 40.0 atomic percent of titanium atoms contained in the bonding layer 13 and 5.0 to 15.0 atomic percent of aluminum atoms contained in the bonding layer 13. 12, the protrusion 16, the small protrusion 17, the bonding layer 13, and the α-type Al ₂ O ₃ layer 14 each have a gradient composition, and the difference in the thermal expansion coefficient between the respective layers can be obtained by firmly bonding the respective portions. Since it can be made small, it is desirable in terms of excellent impact resistance by preventing the occurrence of cracks due to impact.

In addition, the thickness of the bonding layer 13 is desirably 30 nm or less. If this thickness is used, the TiCN layer 12 and the αAl ₂ O ₃ layer 14 are firmly formed even if the bonding layer 13 is relatively brittle because it contains oxygen. together to allow binding, it is possible to suppress the chipping peeling peeling or alpha Al ₂ O ₃ layer 14 of alpha Al ₂ O ₃ layer 14 as a starting point. Further, when the bonding layer 13 is 5 nm or more, the crystal structure of the αAl ₂ O ₃ layer 14 can be stably formed into an α-type crystal structure, and excellent cutting performance can be exhibited. Further, it is assumed that the adhesion force is also excellent between alpha Al ₂ O ₃ layer 14 and the TiCN layer 12.

  In the present invention, the thickness of the bonding layer 13 formed by utilizing the diffusion phenomenon can be measured by a transmission electron microscope (TEM) photograph in a cross section including the coating layer 10. In addition, the atomic species constituting the bonding layer 13 formed by utilizing the diffusion phenomenon and the composition ratio thereof are determined by energy dispersive X-ray spectroscopy (TEM) observation in a transmission electron microscope (TEM) observation as shown in FIGS. It is possible to measure by the presence determination of elements and quantitative analysis by a measurement method using EDS) or electron energy loss spectroscopy (EELS).

Further, by forming at least one layer (another Ti-based coating layer) selected from the group consisting of a TiN layer, a TiC layer, a TiCNO layer, a TiCO layer, and a TiNO layer as a surface layer 15 on the αAl ₂ O ₃ layer 14. It is possible to adjust the slidability and appearance of the surface of the coating layer. That is, by forming the surface layer 15 made of the TiN layer on the surface of the coating film, the tool exhibits a gold color. In addition, it is desirable because the progress of wear can be easily confirmed. Furthermore, the surface layer 15 is not limited to a TiN layer, and a DLC (diamond-like carbon) layer or a CrN layer may be formed in order to improve slidability. It is desirable thickness of the TiN layer constituting the surface layer 15 is 2.0μm or less, such peel strength of the surface layer 15 is easily visually confirmed whether the low is used than the peel strength of the alpha Al ₂ O ₃ film 14 Desirable in terms.

  In addition, by forming a Ti-based coating layer as the base layer 11 between the TiCN layer 12 and the substrate 2, there is an effect of suppressing diffusion of the substrate component.

Furthermore, the cutting tool 1 having the above-described configuration can be applied to various uses of tools such as wear-resistant tools such as sliding parts and dies, cutting tools, excavation tools, and cutting tools. The cutting tool 1 can exhibit the above-described excellent effect when the cutting edge formed at the intersection of the rake face and the flank face is applied to the workpiece and is used for other purposes. Even if it is, it has excellent mechanical reliability.
(Production method)
Next, an example of a method for producing the cutting tool of the present invention will be described.

  First, metal powder, carbon powder, etc. are appropriately added to and mixed with inorganic powders such as metal carbide, nitride, carbonitride, oxide, etc. that can form a hard alloy to be the base 2 by firing, press molding, casting After forming into a predetermined tool shape by a known forming method such as forming, extrusion forming, cold isostatic pressing, etc., the substrate 2 made of the hard alloy described above is fired in a vacuum or non-oxidizing atmosphere. Make it. At this time, WC powder having an average particle diameter of 1.0 to 9.0 μm, Co powder having an average particle diameter of 1.5 μm, and TaC powder having an average particle diameter of 1.5 μm are blended in a predetermined ratio as a starting material, and wet pulverization is performed. To do. After pulverization, a molding aid or the like was added as necessary and dried with a spray dryer to prepare granules.

After degreasing the molded body formed by uniaxial pressing of the produced granules at an appropriate temperature,
(A) Vacuum heating from room temperature to a first temperature of 1100 ° C. to 1200 ° C. at a heating rate of 5 to 10 ° C./min,
(B) When the temperature reaches the first temperature, the heating rate is switched to 15 to 30 ° C./min and rapidly heated to a second temperature of 1450 to 1550 ° C.,
(C) hold at the second temperature for 5-10 minutes,
(D) Cool to a third temperature of 1300 to 1400 ° C., hold at the third temperature for 2 to 3 hours under a reducing atmosphere such as hydrogen at this third temperature, and then cool to room temperature .

  By performing firing in the firing steps (a) to (d) above, a cemented carbide having the above-described structure can be obtained.

  Next, the surface of the base body 2 is subjected to a polishing process or a honing process for the cutting edge as required. Then, a surface coating layer is formed on the surface by chemical vapor deposition (CVD). An example of specific film forming conditions for the coating layer will be described below.

First, a mixed gas composed of 0.5 to 10% by volume of titanium tetrachloride (TiCl ₄ ) gas, 10 to 60% by volume of nitrogen (N ₂ ) gas, and the balance of hydrogen (H ₂ ) gas is prepared as a reaction gas composition. Then, it is introduced into the reaction chamber, and a TiN layer as a base layer is formed in the chamber under conditions of 800 to 940 ° C. and 8 to 50 kPa.

Next, as a reaction gas composition, titanium tetrachloride (TiCl ₄ ) gas is 0.5 to 10% by volume, nitrogen (N ₂ ) gas is 10 to 60% by volume, and acetonitrile (CH ₃ CN) gas is 0% by volume. A mixed gas consisting of 0.1 to 3.0% by volume and the remainder consisting of hydrogen (H ₂ ) gas was prepared and introduced into the reaction chamber, and the TiCN layer 12 was formed at a film formation temperature of 780 to 880 ° C. and 5 to 25 kPa. The lower part is deposited.

  Here, of the above film forming conditions, the ratio of acetonitrile gas in the reaction gas is adjusted to 0.1 to 0.4% by volume, and the film forming temperature is set to 780 ° C. to 880 ° C. In this case, the TiCN layer (MT-TiCN layer) 3 in which the lower portion forms fine streak crystals is desirable.

The film formation conditions for the lower portion of the TiCN layer 12 may be formed under a single condition, but the structure state may be changed by changing the film formation conditions for the TiCN layer 12 halfway. For example, during the film formation of the TiCN layer 12, the film formation conditions are as follows: titanium tetrachloride (TiCl ₄ ) gas is 1 to 5% by volume, methane (CH ₄ ) gas is 4 to 10% by volume, and nitrogen (N ₂ ). By adjusting a mixed gas consisting of 10 to 30% by volume of gas and the remainder consisting of hydrogen (H ₂ ) gas into the reaction chamber and changing the inside of the chamber to 950 to 1100 ° C. and 5 to 40 kPa, The upper crystal of the TiCN layer 12 can be a columnar crystal that is wider than the lower crystal. At this time, the desired TiCN layer 12 can also be formed by using acetonitrile (CH ₃ CN) gas instead of methane (CH ₄ ) gas.

Next, an HT-TiCN layer constituting the upper part of the TiCN layer 12 is formed. By forming the MT-TiCN layer and the HT-TiCN layer, protrusions 16 are formed on the surface of the TiCN layer 12. The specific film formation conditions of the HT-TiCN layer are as follows: titanium tetrachloride (TiCl ₄ ) gas is 2.5 to ₄ % by volume, methane (CH ₄ ) gas is 0.1 to 10% by volume, and nitrogen (N ₂ ). A gas mixture of 0 to 15% by volume and the remainder consisting of hydrogen (H ₂ ) gas was prepared and introduced into the reaction chamber, the chamber was 950 to 1100 ° C. and 5 to 40 kPa, and the film formation time was 20 to 20%. 60 minutes is desirable. By this step, the HT-TiCN layer 12 including the protrusion 16 of the present invention can be produced.

Furthermore, after producing the protrusion 16, the small protrusion 17 is produced. Specific film forming conditions for generating the small protrusions 17 are 1 to 5% by volume of titanium tetrachloride (TiCl ₄ ) gas, ₄ to 10% by volume of methane (CH ₄ ) gas, and nitrogen (N ₂ ) gas. Is adjusted to 10 to 30% by volume, carbon monoxide (CO) gas is 4 to 8% by volume, and the balance is hydrogen (H ₂ ) gas. At this time, in the present invention, as well as mixing the prescribed amounts of carbon monoxide (CO) gas, titanium tetrachloride (TiCl ₄₎ in the process of forming the HT-TiCN layer comprising the projections 16 gas, methane (CH ₄ ) The mixing ratio must be within ± 10% by volume with respect to the mixing ratio of gas and nitrogen (N ₂ ) gas. These mixed gases are adjusted and introduced into the reaction chamber, and the film is formed under the conditions of 950 to 1100 ° C., 5 to 40 kPa, and a film formation time of 20 to 60 minutes. The protrusion 17 can be easily generated.

Next, a mixed gas composed of carbon dioxide (CO ₂ ) gas at 0.5 to 4.0 volume% by volume and nitrogen (N ₂ ) gas as a balance is prepared as a treatment gas composition and introduced into the reaction chamber. Then, at the film forming temperature of 950 to 1100 ° C. and 5 to 40 kPa, the surface of the protrusions and small protrusions exposed on the surface of the coating layer formed under the above conditions is treated (oxidation treatment) to oxidize the surface of the coating layer Form a layer. In this step, the nitrogen (N ₂ ) gas may be changed to argon (Ar) gas.

Next, as a processing gas composition, a mixed gas composed of 0.5 to 5.0% by volume of aluminum trichloride (AlCl ₃ ) gas by volume% and the remaining hydrogen (H ₂ ) gas is prepared in the reaction chamber. Then, the oxide layer is aluminized at a film forming temperature of 950 to 1100 ° C. and 5 to 40 kPa. The bonding layer 13 can be produced by the above oxidation treatment and aluminization treatment.

Subsequently, an Al ₂ O ₃ layer 14 is formed. As a method of forming the Al ₂ O ₃ layer 14, aluminum trichloride (AlCl ₃ ) gas is 0.5 to 5.0 vol%, hydrogen chloride (HCl) gas is 0.5 to 3.5 vol%, dioxide dioxide A mixed gas composed of 0.5 to 5.0% by volume of carbon (CO ₂ ) gas, 0.0 to 0.5% by volume of hydrogen sulfide (H ₂ S) gas, and the remaining hydrogen (H ₂ ) gas is used. 950-1100 ° C., 5-10 kPa is desirable.

Further, a surface layer (TiN layer) 15 is formed as desired. Specific film forming conditions are as follows: titanium tetrachloride (TiCl ₄ ) gas is 0.1 to 10% by volume, nitrogen (N ₂ ) gas is 0 to 60% by volume, and the remainder is hydrogen (H ₂ ) gas. The mixed gas consisting of the above may be adjusted and introduced into the reaction chamber, and the inside of the chamber may be set to 960 to 1100 ° C. and 10 to 85 kPa.

  Then, if desired, at least the cutting edge portion on the surface of the formed coating layer 10 is polished. By this polishing process, the cutting edge portion is processed smoothly, the welding of the work material is suppressed, and the tool is further excellent in fracture resistance.

  6% by mass of metallic cobalt (Co) powder having an average particle size of 1.2 μm and 0.1% by mass of TaC powder having an average particle size of 1.0 μm with respect to tungsten carbide (WC) powder having an average particle size of 1.0 μm. After being formed into a cutting tool shape (CNMA 120204) by press molding, the binder removal treatment was performed, and firing was performed under the firing conditions shown in Table 1 to form a cemented carbide (base Nos. 1 to 7). Was made. Furthermore, the cutting edge process (R honing) was given to the rake face side by brushing to the manufactured cemented carbide.

  A tool is cut with respect to the base body in a direction perpendicular to the rake face, and the cut face is mirror-finished, and the mirror face is observed with a scanning electron microscope (SEM). The image is taken at a magnification of 3000 to 5000 times, and the image is measured using an image analyzer to measure the particle size of the hard phase of the substrate in a range from the surface to 1 mm and 5 mm or more inside the surface to coarse particles. The average value of WC particles in the observation region (average particle size including coarse particles and average particle size excluding coarse particles) was defined as the particle size. The results are shown in Table 2.

  Next, various coating layers were formed on the cemented carbide alloy by the CVD method under the film formation conditions shown in Table 3, and the coating layers having the structures shown in Tables 5 and 6 were formed under the conditions in Table 4. And after film-forming, it brushed for 30 second with respect to the surface of a coating layer from the rake side, and sample No. 1 to 19 cutting tools were produced.

  The obtained tool was subjected to polishing by mechanical polishing and ion milling so that the coating layer described in Tables 5 and 6 could be observed using a field emission transmission electron microscope (HR-TEM) to expose the cross section. It was. The microstructural state of each layer viewed from a direction substantially perpendicular to the cross section of each layer was observed, and the layer thickness was observed. Then, confirmation of the atomic species present in each layer, composition, and the like were also observed by energy dispersive X-ray spectroscopy (EDS), electron energy loss spectroscopy (EELS), and the like. Further, transmission electron micrographs were taken at five arbitrary fractured surfaces including the cross section of the coating layer, and the state near the interface between the aluminum oxide layer and the titanium carbonitride layer was observed in each photo. At that time, the height and width of the protrusions, the number per unit length of 10 μm, the height and width of the minute protrusions, and the number of minute protrusions per protrusion were measured. The results are shown in Table 5.

And the intermittent cutting test was done on condition of the following using this cutting tool, and fracture resistance was evaluated.
Work Material: Ductile Iron 8 Slotted Sleeve Material (FCD700)
Tool shape: CNMA120204
Cutting speed: 300 m / min Feeding speed: 0.3 mm / rev
Cutting depth: 2.0mm
Others: Use of water-soluble cutting fluid Evaluation item: The cutting time when the amount of wear was 0.3 mm was measured. Moreover, the state of the cutting blade was observed immediately after cutting and after 3 minutes of cutting time. The results are shown in Table 7.

From Tables 1-7, sample no. In 8, 10 to 12, and 15 to 18, Al ₂ O ₃ peeling occurred when the number of impacts was 2,000 to 4,000, and the damage reached the substrate, resulting in poor fracture resistance.

On the other hand, in samples 1 to 7, 9, 13, and 14 that are formed of the substrate according to the present invention and have protrusions at the interface between the αAl ₂ O ₃ layer and the TiCN layer, αAl ₂ O _{3 is} evaluated in cutting evaluation. The peeling of the layer was suppressed, and the cutting performance was excellent in fracture resistance.

DESCRIPTION OF SYMBOLS 1 Cutting tool 2 Base | substrate 3 WC particle | grain 4 Bonding phase 5 Coarse WC particle | grain 10 Covering layer 11 Underlayer 12 TiCN layer 13 Bonding layer 14 αAl ₂ O ₃ layer 15 Surface layer 16 Protrusion 17 Small protrusion

Claims (7)

A surface coating tool in which a coating layer is formed on the surface of a substrate made of cemented carbide,
The cemented carbide is
85 to 95% by mass of WC, 0 to 5% by mass of one or more of carbides, nitrides, and carbonitrides of periodic tables 4, 5, and 6 metals other than WC, 5 to 10% by mass of Co, In a proportion of
Whether it consists of WC particles and a binder phase mainly composed of Co,
Or composed of WC particles, B1 type solid solution particles composed of one or more of carbides, nitrides and carbonitrides of periodic tables 4, 5, and 6 metals other than WC particles, and a binder phase mainly composed of Co. ,
The average particle diameter of the WC particles inside is 0.1 to 2.0 μm, and there are more coarse WC particles having a major axis of 5 to 20 μm on the surface of the cemented carbide than the inside, and the surface The Co content ratio in is 85 to 95% with respect to the Co content in the interior,
The coating layer is
Including at least a titanium carbonitride layer and an α-type crystal α-aluminum oxide layer in order from the substrate side;
In the cross-sectional structure, between the titanium carbonitride layer and the α aluminum oxide layer, the average height from the titanium carbonitride layer is 0.2 μm to 1.0 μm, and the width at the intermediate height is average. A surface-coated tool, wherein protrusions of 0.1 μm to 1.5 μm are formed side by side.   The coarse WC particles are 15 to 21% by area on the surface of the cemented carbide, 6 to 15% by area at a depth of 500 μm from the surface, 2 to 6% by area at a depth of 1000 μm from the surface, The surface-coated tool according to claim 1, wherein the surface-coated tool is present at a ratio of 0.5 to 2 area% at a depth of 1500 μm or more from the surface.   2. The particle size distribution of WC particles other than the coarse WC particles inside the cemented carbide has two peaks: a fine particle having a particle size of 1 μm or less and a medium particle having a particle size of 2 to 4 μm. Or the surface coating tool of 2.   The small protrusions having an average height of 20 nm to 100 nm and an average width of 10 nm to 50 nm are formed side by side on the side surface of the protrusion of the coating layer. The surface-coated tool according to 1.   5. The surface-coated tool according to claim 4, wherein an average of 4 to 15 small protrusions are formed on both side surfaces of one protrusion in total.   The surface-coated tool according to claim 4 or 5, wherein the small protrusion contains more oxygen and aluminum than the protrusion.   Between the small protrusions or the protrusions adjacent to the α aluminum oxide layer and the α aluminum oxide layer, at least Ti, Al, C and O elements are contained, and the content of the O element is 25 to 25 The surface-coated tool according to any one of claims 4 to 6, wherein the bonding layer composed of 45 atomic% is formed with a thickness of 5 nm to 30 nm.