JP7325720B2 - surface coated cutting tools - Google Patents

Description

In particular, the present invention provides a surface coating that exhibits excellent cutting performance over long-term use, even in high-speed interrupted cutting of cast iron, etc., because the hard coating layer has excellent chipping resistance and thermal crack resistance. It relates to a tool (hereinafter sometimes referred to as a coated tool).

Conventionally, there is a coated tool in which a Ti—Al-based composite carbonitride layer is formed by vapor deposition as a hard coating layer on the surface of a tool substrate such as a tungsten carbide (hereinafter referred to as WC)-based cemented carbide. These are known to exhibit excellent wear resistance.
However, although the conventional coated tool coated with the Ti—Al-based composite carbonitride layer has relatively excellent wear resistance, it may cause abnormalities such as chipping when used under severe cutting conditions such as high-speed interrupted cutting. Various proposals have been made to improve the hard coating layer because it is prone to wear.

For example, Patent Document 1 describes (Tix ₁ , Aly ₁ )N (where x ₁ and y ₁ are x ₁ =0.005 to 0.1 and y ₁ =0.995 to 0.995 to 0.1 in terms of atomic ratios, respectively). 9) and (Tix ₂ , Aly ₂ )N (where x ₂ and y ₂ are each atomic ratio x ₂ =0.5 to 0.5). 9 and y ₂ = 0.5 to 0.1), and the high Al-content TiAlN is the network-like high Ti content TiAlN A coated tool is described having a titanium aluminum nitride hard coating characterized by being surrounded by a.

Further, for example, Patent Document 2 discloses a surface-coated cutting tool including a substrate (tool substrate) and a coating formed on the surface thereof, wherein the coating includes one or two or more layers, At least one of the layers is an Al-rich layer containing hard particles, the hard particles having a sodium chloride-type crystal structure, and a plurality of massive first unit phases and between the first unit phases The first unit phase is composed of a nitride or carbonitride of Al _x Ti _1-x , and the atomic ratio x of Al in the first unit phase is 0.7 or more. is 0.96 or less, the second unit phase is composed of a nitride or carbonitride of Al _y Ti _1-y , and the atomic ratio y of Al in the second unit phase is more than 0.5 and 0.5. 7, and the Al-rich layer exhibits a maximum peak in the (200) plane when analyzed from the normal direction of the surface of the coating using X-ray diffraction.

Furthermore, for example, in Patent Document 3, the coating includes a first hard coating layer containing crystal grains having a sodium chloride type crystal structure, and the crystal grains are nitrides or carbonitrides of Al _x Ti _1-x and a second layer made of a nitride or carbonitride of Al _y Ti _1-y are alternately laminated one or more layers, and the atoms of Al in the first layer The ratio x varies in the range of 0.76 or more and less than 1, the atomic ratio y of Al in the second layer varies in the range of 0.45 or more and less than 0.76, and the atomic ratio x and the The atomic ratio y is such that the maximum value of the difference is 0.05≦xy≦0.5, the total thickness of the adjacent first layer and the second layer is 3 to 30 nm, and the The crystal grains are the crystal planes of the crystal grains (200 ) The intersection angle between the normal to the surface and the normal to the surface of the base material is measured, and the crystal grains having the intersection angle of 0 to 45 degrees are divided in units of 0 degrees to 5 degrees and divided into 9 groups. When constructing and calculating the frequency that is the sum of the areas of the crystal grains contained in each group, the sum of the frequencies of the four groups containing the crystal grains having the intersection angle of 0 to 20 degrees is 50% or more and 100% or less of the total frequency of all groups, and the surface-coated cutting tool is such that the total frequency of the two groups containing the crystal grains having the intersection angle of 10 to 20 degrees is the above A coated tool is described that is 30% or more and 100% or less of the sum of said powers of all groups.

WO2017/090540 WO2018/158974 Japanese Patent No. 6037255

In recent years, there is a strong demand for labor saving and energy saving in cutting. Abnormal damage resistance such as thermal crack resistance is required, and excellent wear resistance over long-term use is required. However, it was not sufficient to meet these demands.

Therefore, the present invention has been made in view of such circumstances, and even when subjected to high-speed interrupted cutting of cast iron, etc., it has excellent chipping resistance over long-term use and is resistant to thermal cracking. An object of the present invention is to provide a coated tool with improved

The present inventors have found that the chipping resistance of a coated tool containing a composite nitride layer or composite carbonitride layer of Ti and Al (hereinafter collectively referred to as "TiAlCN layer") as a hard coating layer, In order to improve the resistance to thermal cracking, we conducted extensive studies.

As a result, crystal grains having a NaCl-type face-centered cubic structure in the TiAlCN layer, in which a region with a low Al content in the grain exists at a specific location at a certain ratio, has a specific distribution The new knowledge was obtained that the toughness of the TiAlCN layer is improved, the chipping resistance and thermal crack resistance are improved, and the coated tool has a long life even when performing high-speed intermittent cutting of cast iron, etc.

The present invention is based on the above findings, and is as follows.
"(1) A surface-coated cutting tool having a tool substrate and a hard coating layer on the surface of the tool substrate,
(a) the hard coating layer includes a composite nitride layer or a composite carbonitride layer of Ti and Al,
(b) The composite nitride layer or composite carbonitride layer of Ti and Al has a composition of
When represented by the composition formula: (Ti _1-x Al _x ) (C _y N _1-y ),
The average value x _avg of the content ratio x of Al in the total amount of Al and Ti and the average value y _avg of the content ratio y of C in the total amount of C and N are 0.65≦x _avg ≦0, respectively. .95, 0.000≦y _avg ≦0.050 (where x, y, x _avg and y _avg are atomic ratios) and the area occupied by crystal grains having a NaCl-type face-centered cubic structure The ratio is 70 area% or more,
(c) a two-region crystal grain having a high Al region with a high Al content x and a low Al region with a low x in the crystal grain,
(d) The two-region crystal grain is surrounded by the low Al-containing region surrounded only by the high Al region, and surrounded by the high Al region and a grain boundary defining one crystal grain. The low Al region contained in the grain contains a unique two-region crystal that is 70 area% or more of all the low Al regions in the grain,
(e) When the peculiar two-region crystal grains have the average value x _h of x in the high Al region and the average value x _l of x in the low Al region (however, these x _h , x _l atomic ratio), satisfying 0.05≦x _h −x _l ≦0.60,
(f) 10 to 40 area % of the peculiar two-domain crystal grains are included on the surface side of the layer obtained by bisected the composite nitride layer or composite carbonitride layer of Ti and Al in the layer thickness direction. ,
A surface-coated cutting tool characterized by:
(2) The surface-coated cutting tool according to (1), wherein the difference between the maximum and minimum widths of the high Al regions in the peculiar two-region crystal grains is 50 to 300 nm.
(3) The surface-coated cutting tool according to (1) or (2), characterized in that, in the peculiar two-region crystal grains, the average width of the high Al region is 30 nm or more.
(4) In the composite nitride layer or composite carbonitride layer of Ti and Al, the crystal grains having the NaCl-type face-centered cubic structure have an average grain width W of 0.1 to 3.0 μm and an average aspect The surface-coated cutting tool according to any one of (1) to (3), wherein the ratio A is 2.0 to 10.0. ”

The surface-coated cutting tool of the present invention has improved hardness and toughness of the hard coating layer, improved chipping resistance and thermal crack resistance, and exhibits excellent tool life even in high-speed interrupted cutting of cast iron and the like.

: A schematic diagram showing an example of a peculiar two-domain crystal grain having a high Al region and a low Al region in the grain.

The present invention is described in detail below. In addition, when a numerical range is expressed as "A to B" in the present specification and claims, the range includes the upper limit (B) and the lower limit (A). Also, the units of the upper limit (B) and the lower limit (A) are the same.

Average layer thickness of TiAlCN layer:
The TiAlCN layer of the present invention constitutes the hard coating layer. The average layer thickness of this TiAlCN layer is preferably 1.0 to 25.0 μm. If the average layer thickness is less than 1.0 μm, the layer thickness is too thin to ensure sufficient wear resistance over a long period of use. The grains tend to coarsen, and chipping tends to occur. More preferably, the average layer thickness is 3.0 to 15.0 μm.

Here, the average layer thickness of the TiAlCN layer can be obtained by, for example, cutting the TiAlCN layer along a vertical cross section (a plane perpendicular to the surface of the tool substrate) at an arbitrary position to prepare a sample for observation, and measuring the cross section with a scanning electron microscope. It can be obtained by observing a plurality of locations (for example, 5 locations) with a microscope (SEM: Scanning Electron Microscope) and averaging them.

Average composition of TiAlCN layer:
The composition of the TiAlCN layer in the present invention is represented by the composition formula: (Ti _1-x Al _x )(C _y N _1-y ),
the average of the content ratio x of Al in the total amount of Ti and Al (hereinafter referred to as “average of the Al content ratio”) x _avg ;
The average content ratio y of C in the total amount of C and N (hereinafter referred to as “average of C content ratio”) y _avg is
They preferably satisfy 0.65≦x _avg ≦0.95 and 0.00≦y _avg ≦0.050 (where x _avg and y _avg are both atomic ratios).
The ratio of (Ti _1-x Al _x ) and (C _y N _1-y ) is not particularly limited, but when (Ti _1-x Al _x ) is 1, (C _y N _1-y ) is preferably 0.8 to 1.2.

The reason is as follows.
When the average x _avg of the Al content is less than 0.65, the TiAlCN layer has a reduced hardness, so when subjected to high-speed intermittent cutting of cast iron or the like, the wear resistance is not sufficient. If it exceeds 0.95, hexagonal TiAlCN crystal grains are precipitated and the wear resistance is lowered. Therefore, 0.65≦x _avg ≦0.95, but more preferably 0.70≦x _avg ≦0.90.
The reason why the average y _avg of the C content is preferably 0.000≦y _avg ≦0.050 is that the hardness can be improved while maintaining the chipping resistance within the above range.

The average x _avg of the Al content of the TiAlCN layer was obtained by using Auger Electron Spectroscopy (AES) and irradiating an electron beam from the longitudinal section (a section perpendicular to the tool substrate) of a sample whose cross section was polished. Then, the analysis results of Auger electrons obtained by performing at least five line analyzes over the entire length in the film thickness direction are averaged.

Also, the average _yavg of the C content ratio is determined by secondary ion mass spectrometry (SIMS). That is, in a sample having a polished sample surface, an ion beam is irradiated in a range of 70 μm×70 μm from the surface side of the TiAlCN layer, and surface analysis by the ion beam and etching by the sputtered ion beam are alternately repeated, thereby increasing the depth direction. Composition measurements are taken. First, the average of data obtained by measuring a depth of at least 0.5 μm at a pitch of 0.1 μm or less from a portion of the TiAlCN layer intruded by 0.5 μm or more in the depth direction of the layer is obtained. Furthermore, the average y _avg of the C content ratio is obtained by averaging the results obtained by repeating this calculation at least at five locations on the sample surface.

Area ratio of crystal grains constituting the TiAlCN layer having a NaCl-type face-centered cubic structure:
The area ratio of the crystal grains forming the TiAlCN layer having a NaCl-type face-centered cubic structure is preferably 70 area % or more in the longitudinal section. The reason for this is that the object of the present invention can be achieved more reliably if the area is 70 area % or more. All of the crystal grains may have a NaCl-type face-centered cubic structure (may be 100 area %). Here, the calculation target of the area ratio of the crystal grains having the NaCl-type face-centered cubic structure is the crystal grains constituting the TiAlCN layer, and is not limited to the crystal grains having a high Al region and a low Al region in the TiAlCN layer. .

Bi-regional grains and singular bi-regional grains having a high Al region and a low Al region included in the TiAlCN layer:
The TiAlCN layer includes two-region grains having a high Al region with a high Al content and a low Al region with a low Al content within the grain. Here, the Al content ratio of the high Al content region is x _avg +0.025 or more, and the Al content ratio of the low Al region is x _avg −0.025 or less. Between the high Al region and the low Al region, there is a region of less than x _avg ±0.025 (hereinafter referred to as a transition region) where the Al content ratio of these regions transitions. , ignore the existence of this transition region.
In the two-region crystal grain, the low Al-containing region surrounded only by the high Al region and the grain boundary defining the high Al region and the one crystal grain surround the low Al content region. The toughness and wear resistance of the TiAlCN layer are improved when there is a singular two-region crystal where the low Al region is 70 area % or more with respect to all the low Al regions in the grain.

Difference in Al content x between the high Al region and the low Al region:
When x h and x l _{are the area-weighted average values of the Al content ratio x in the high Al region and the low Al region in the specific two-region crystal grain, respectively (where x h and x l are atomic} ratios ₎ , Satisfying 0.05≦x _h −x _l ≦0.60 improves the toughness and wear resistance of the TiAlCN layer.

Area ratio of two-region crystal grains in longitudinal section of TiAlCN layer:
It is preferable that the two-region crystal grains are included at 20 to 100 area % in the longitudinal section. Within this range, variations in toughness and wear resistance of the TiAlCN layer can be suppressed to a certain level or less.

Area ratio of unique two-region crystal grains in the TiAlCN layer surface side region of the surface-coated cutting tool:
In the surface-side region of the TiAlCN layer (hard coating layer) of the surface-coated cutting tool obtained by halving the hard coating layer in the layer thickness direction (direction perpendicular to the tool substrate surface), the specific two-region crystal grains are 10 to 40 area%. preferably included. When the area ratio is within this range, the amount of the crystal grains is appropriate, and the toughness and wear resistance of the TiAlCN layer are improved.
On the other hand, in the tool base side region, the reason why the area ratio of the peculiar two-region crystal grains is not specified is that the region includes the region where the TiAlCN layer starts to grow, so the crystal grain size is larger than that of the tool surface side region. This is because the area ratio of the crystal grains in the tool substrate side region does not greatly affect the toughness and wear resistance of the TiAlCN layer.

Determination of grain boundaries:
The grain boundaries of the crystal grains forming the TiAlCN layer are determined as follows, and the high Al region and the low Al region are discriminated as follows. That is, using a high-resolution electron backscatter diffraction device (EBSD: Electron Backscatter Diffraction), a crystal with a width of 10 μm in a direction parallel to the surface of the tool substrate and a layer thickness (average layer thickness) in the vertical direction. Determine grain boundaries. The inside of this observation field plane is analyzed at intervals of 0.02 μm to obtain measurement points having a NaCl-type face-centered cubic structure within the observation field plane. If there is an orientation difference of 5 degrees or more between adjacent measurement points (hereinafter also referred to as pixels, which are regions of what is described as points) among the measurement points having this NaCl-type face-centered cubic structure, Alternatively, if there is no adjacent measurement point having a NaCl-type face-centered cubic structure, a measurement point that detected an orientation difference of 5 degrees or more, or a measurement point that does not have a NaCl-type face-centered cubic structure and a NaCl-type face-centered cubic structure A boundary between measurement points having a structure (a boundary between measurement regions) is defined as a grain boundary. One crystal grain is defined as a region surrounded by grain boundaries and including a measurement point having a NaCl-type face-centered cubic structure. However, a single pixel that has an orientation difference of 5 degrees or more from all adjacent pixels, or that has no measurement point with an adjacent NaCl-type face-centered cubic structure, is not regarded as a crystal grain, and is two pixels or more. are connected as crystal grains. In this manner, grain boundary determination is performed to specify crystal grains.

Here, a grain boundary zone is defined as a region having a width of 50 nm perpendicular to the tangent line at each position of the grain boundary and extending toward the inside of the grain. When the high Al region or the low Al region is in contact with or overlaps with the grain boundary zone, it is determined that each region is in contact with the grain boundary. The reason for this is that the EBSD analysis for determining grain boundaries and the TEM-EDS analysis for measuring Al content, which will be described later, use different analysis methods, so the overlap of measurement data around grain boundaries becomes difficult to match. is.

Next, a longitudinal section of the TiAlCN layer (layer thickness direction section) in which the crystal grains are specified is observed using a SEM and a TEM (Transmission Electron Microscope). FIG. 1 shows an example of a schematic diagram of a SEM image (backscattered electron image) in a vertical section (layer thickness direction section) of the TiAlCN layer of the present invention (in FIG. 1, only one crystal grain has a high Al content region and a low Al In addition, the transition region is included in the low Al region represented by the black region.) .

Some of the crystal grains forming the TiAlCN layer of the present invention include two-region crystal grains in which there is a difference in content ratio (concentration difference) of the constituent element Al, as shown in FIG. Energy dispersive X-ray spectrometry (TEM-EDS analysis) using a TEM was performed on each crystal grain in the observation range, and the average of the Al content of the TiAlCN layer measured separately x _avg Based on this, x _avg +0.025 or more high Al content region (white region in FIG. 1) and x _avg −0.025 or less low Al content region (black region in FIG. 1) divides the inside of the grain into two regions. In this way, a two-region crystal grain having a high Al content region and a low Al content region, and a high Al content region in which each region in the crystal grain is less than ± 2.5% of the average Al concentration Discriminate from crystal grains that do not have a low Al content region.

Furthermore, with respect to the two-region crystal grain, the low Al-containing region surrounded only by the high Al region, and the crystal grain boundary surrounding the high Al region and the one crystal grain A peculiar two-region crystal is sought in which the low Al region surrounded by the grain boundary zone for the grain is 70 area % or more of all the low Al regions in the grain.

Difference and average value of maximum and minimum widths of high Al regions in singular two-domain grains:
In the peculiar two-domain crystal grain, the difference between the maximum width and the minimum width of the high Al region is preferably 50 to 300 nm. Within this range, the toughness and wear resistance of the TiAlCN layer are further improved. Here, the width of the high Al region means the length of the high Al region in the direction (film thickness direction) perpendicular to the surface of the tool substrate.

A method for measuring this length will be described. For all the crystal grains within the observation range constituting the TiAlCN layer of the present invention in which the concentration difference of the constituent element Al exists as schematically shown in FIG. On the other hand, line analysis (measurement intervals of 0.5 nm or less) is performed on the surface of the tool substrate in the film thickness direction at five different positions.
Next, the relationship between the position in the observation direction and the repetition of increase/decrease in the Al content x is graphed, and the length in the film thickness direction of the region above the average Al content x _avg +0.025 of the TiAlCN layer is obtained. The difference between the maximum value (maximum width) and the minimum value (minimum width) of this length is calculated. In addition, the average width of said length is also calculated.
It goes without saying that a well-known measurement noise removal method (for example, a moving average method) is performed in graphing.

Average grain width W and average aspect ratio A of TiAlCN layer:
In the present invention, the TiAlCN layer has a columnar crystal structure, the average grain width W in the longitudinal section of the crystal grains in the structure is 0.1 to 3.0 μm, and the average aspect ratio A is 2.0 to 10.0. is more preferable. The reason for this is that fine grain crystals with an average grain width W of less than 0.1 μm may be prone to abnormal damage due to a decrease in plastic deformation resistance and oxidation resistance due to an increase in grain boundaries. This is because if the grain width W is greater than 3.0 μm, the presence of coarsely grown grains may tend to lower the toughness. In addition, if the average aspect ratio A is less than 2.0, the interface between the granular crystals becomes likely to become a fracture starting point against the shear stress generated on the surface of the hard coating layer during cutting, which may cause chipping. In addition, when the average aspect ratio A exceeds 10.0, fine chipping occurs on the cutting edge during cutting, and when adjacent columnar crystal structures are chipped, resistance to shear stress generated on the surface of the hard coating layer When the columnar crystal structure is fractured, the damage progresses at once, and large chipping may occur. Therefore, it is more preferable that the average grain width W of the crystal grains is 0.1 to 3.0 μm and the average aspect ratio A is 2.0 to 10.0.

Next, a method for calculating the average grain width W and average aspect ratio A of the crystal grains, and the area ratio of the crystal grains having a NaCl-type face-centered cubic structure with a columnar crystal structure will be described. First, as described above, grain boundaries are determined to identify crystal grains. Next, image processing is performed, and for a certain crystal grain i, the maximum length H _i in the direction perpendicular to the tool substrate (film thickness direction), the grain width W _i that is the maximum length in the horizontal direction to the tool substrate, and the area Obtain S _i . The aspect ratio A _i of the crystal grain i is calculated as A _i =H _i /W _i . In this way, the grain widths W ₁ to W _n (n ≥ 20) of at least 20 or more (i = 1 to 20 or more) crystal grains in the observation field are averaged by area weighted by Equation 1, and the average of the crystal grains Let W be the grain width. Similarly, the aspect ratios A ₁ to A _n (n≧20) of the crystal grains are obtained, and the average aspect ratio A of the crystal grains is obtained by area-weighted averaging according to Equation 2.

Other layers:
As a hard coating layer, the hard coating layer containing the TiAlCN layer of the present invention has sufficient chipping resistance and thermal crack resistance even in high-speed interrupted cutting of cast iron or the like. Ti having a total average layer thickness of 0.1 to 20.0 μm consisting of one or more layers selected from a Ti carbide layer, a nitride layer, a carbonitride layer, a carbonate layer and a carbonitride layer If a lower layer comprising a compound (not limited to stoichiometric compounds) layer is provided adjacent to the tool substrate and/or a layer comprising at least an aluminum oxide (not limited to stoichiometric compounds) layer. is provided on the TiAlCN layer as an upper layer with a total average layer thickness of 1.0 to 25.0 μm, combined with the effects of these layers, further excellent chipping resistance, And, heat crack resistance can be exhibited.

Here, if the total average layer thickness of the lower layer is less than 0.1 μm, the effect of the lower layer is not sufficiently exhibited, while if it exceeds 20.0 μm, the crystal grains of the lower layer tend to coarsen, causing chipping. easier to do. When the total average layer thickness of the upper layer including the aluminum oxide layer is less than 1.0 μm, the effect of the upper layer is not sufficiently exhibited. , chipping is more likely to occur.

Tool substrate:
As the tool substrate, any conventionally known substrate for this type of tool substrate can be used as long as it does not interfere with the achievement of the object of the present invention. For example, cemented carbide (WC-based cemented carbide, containing Co in addition to WC, and further containing carbonitrides such as Ti, Ta, Nb, etc.), cermet (TiC, TiN, TiCN, etc. as a main component), ceramics (titanium carbide, silicon carbide, silicon nitride, aluminum nitride, aluminum oxide, etc.), or cBN sintered body.

Production method:
The TiAlCN layer of the present invention is, for example, at least one layer of a carbide layer, a nitride layer, a carbonitride layer, a carbonate layer and a carbonitride oxide layer of Ti, which is the tool substrate or the lower layer on the tool substrate. above, for example, gas group A consisting of _NH3 , _N2 , _C2H4 , _CH4 and _H2 , and gas group B consisting of _AlCl3 , _{TiCl4 , N2} , _CH4 and _H2, and can be obtained by supplying two types of reaction gases consisting of two systems and combining the two types of reaction gases in a CVD furnace.

Examples of the two kinds of reaction gas compositions are as follows. The gas composition is such that the composition sum of gas group A and gas group B is 100% by volume.
Gas group A: NH ₃ : 1.0 to 3.0%, N ₂ : 0.0 to 5.0%,
_{CH4 : 0.0-6.0%, C2H4 :} 0.0-12.0%, _H2 : 20-40%
Gas group B: AlCl ₃ : 0.50 to 1.00%, TiCl ₄ : 0.10 to 0.30%,
N ₂ : 2.0 to 10.0%, CH ₄ : 0.1 to 1.0%,
H ₂ : Residual reaction atmosphere pressure: 4.5 to 5.0 kPa
Reaction atmosphere temperature: 650-850°C
Gas supply cycle: 1.0 to 5.0 seconds Gas supply time per cycle: 0.15 to 0.25 seconds Supply phase difference between gas group A and gas group B: 0.10 to 0.20 seconds

Next, examples will be described.
Here, as a specific example of the coated tool of the present invention, an insert cutting tool using a WC-based cemented carbide as a tool substrate will be described. The same applies to drills and end mills.

As raw material powders, WC powder, TiC powder, TaC powder, NbC powder, Cr ₃ C ₂ powder, ZrC powder, TiN powder and Co powder, all having an average particle size of 1 to 3 μm, were prepared. It was blended according to the formulation shown in Table 1, further wax was added, ball mill mixed in acetone for 24 hours, and dried under reduced pressure. Vacuum sintered in a vacuum of 5 Pa at a predetermined temperature within the range of 1370 to 1470° C. for 1 hour, and after sintering, a tool substrate made of WC-based cemented carbide having an insert shape of ISO standard SEEN1203AFSN. Tool substrates A to C and tool substrates D to F made of WC-based cemented carbide with insert geometry of ISO standard CNMG120412 were produced respectively.

Next, a TiAlCN layer was formed on the surfaces of these tool substrates A to F using a CVD apparatus under the film forming conditions shown in Table 2, and the coated tools 1 to 16 of the present invention shown in Table 5 were obtained. Here, the coated tool of the present invention provided with the lower layer and/or the upper layer was provided with the layers shown in Table 4 under the film forming conditions shown in Table 3. Note that x _avg , y _avg , x _h , x _l , etc. in Table 5 are measured by the method described above.

For comparison, a TiAlCN layer was formed on the surfaces of these tool substrates A to F using a CVD apparatus under the film forming conditions shown in Table 2, and comparative coated tools 1 to 16 shown in Table 6 were obtained. Ta. Here, the coated tool of the present invention provided with the lower layer and/or the upper layer was provided with the layers shown in Table 4 under the film forming conditions shown in Table 3.

Subsequently, for the coated tools 1 to 8 of the present invention and the comparative coated tools 1 to 8, the various tool substrates A to C (ISO standard SEEN 1203 AFSN shape) were all fixed to the tip of the alloy steel cutter with a cutter diameter of 125 mm. In a state of being clamped with a tool, a wet high-speed face milling, center cut cutting test 1 shown below was performed to measure the flank wear width of the cutting edge. Table 6 shows the results of cutting test 1. As for the comparative coated tools 1 to 8, the life was reached before the end of the cutting time due to the occurrence of chipping, so the time until the life is reached is shown.

Cutting test 1: Wet high-speed face milling, center cut cutting test Cutter diameter: 125 mm
Work material: JIS FCD700 block material with a width of 100 mm and a length of 400 mm Rotational speed: 764 min ^-1
Cutting speed: 300m/min
Notch: 2.0mm
Feed: 0.2 mm/blade Cutting time: 8 minutes (normal cutting speed is 200 m/min)

For the coated tools 9 to 16 of the present invention and the comparative coated tools 9 to 16, each of the various coated tool substrates D to F (ISO standard CNMG120412 shape) was fixed to the tip of the alloy steel cutting tool with a jig. In the screwed state, the wet high-speed intermittent cutting test 2 of cast iron shown below was performed to measure the flank wear width of the cutting edge. Table 7 shows the results of cutting test 2. As for the comparative coated tools 9 to 16, the life was reached before the end of the cutting time due to the occurrence of chipping, so the time until the life is reached is shown.

Cutting test 2: Wet high-speed intermittent cutting test Work material: JIS FCD800 round bar with 8 equally spaced longitudinal grooves Cutting speed: 300 m/min
Notch: 2.0mm
Single blade feed amount: 0.2 mm/rev.
Cutting time: 5 minutes (normal cutting speed is 200m/min)

From the results shown in Tables 6 and 7, the coated tools 1 to 16 of the present invention all have excellent chipping resistance and thermal crack resistance in the hard coating layer, so they are suitable for high-speed interrupted cutting of cast iron and the like. Even when used, chipping does not occur and excellent wear resistance is exhibited over a long period of time. On the other hand, the comparative coated tools 1 to 16, which do not satisfy even one of the items specified for the coated tool of the present invention, cause chipping when used for high-speed interrupted cutting of cast iron, etc., and can be cut in a short time. It has reached the end of its service life.

As described above, the coated tool of the present invention can be used as a coated tool for high-speed interrupted cutting of materials other than cast iron, and exhibits excellent chipping resistance and thermal crack resistance over a long period of time. It is possible to fully satisfy the improvement of the performance of the cutting device, the saving of labor and energy in the cutting process, and the reduction of the cost.

Claims (4)

A surface-coated cutting tool having a tool substrate and a hard coating layer on the surface of the tool substrate,
(a) the hard coating layer includes a composite nitride layer or a composite carbonitride layer of Ti and Al,
(b) The composite nitride layer or composite carbonitride layer of Ti and Al has a composition of
When represented by the composition formula: (Ti _1-x Al _x ) (C _y N _1-y ),
The average value x _avg of the content ratio x of Al in the total amount of Al and Ti and the average value y _avg of the content ratio y of C in the total amount of C and N are 0.65≦x _avg ≦0, respectively. .95, 0.000≦y _avg ≦0.050 (where x, y, x _avg and y _avg are atomic ratios) and the area occupied by crystal grains having a NaCl-type face-centered cubic structure The ratio is 70 area% or more,
(c) a two-region crystal grain having a high Al region with a high Al content x and a low Al region with a low x in the crystal grain,
(d) The two-region crystal grain is surrounded by the low Al-containing region surrounded only by the high Al region, and surrounded by the high Al region and a grain boundary defining one crystal grain. The low Al region contained in the grain contains a unique two-region crystal that is 70 area% or more of all the low Al regions in the grain,
(e) When the peculiar two-region crystal grains have the average value x _h of x in the high Al region and the average value x _l of x in the low Al region (however, these x _h , x _l atomic ratio), satisfying 0.05≦x _h −x _l ≦0.60,
(f) 10 to 40 area % of the peculiar two-domain crystal grains are included on the surface side of the layer obtained by bisected the composite nitride layer or composite carbonitride layer of Ti and Al in the layer thickness direction. ,
A surface-coated cutting tool characterized by: 2. The surface-coated cutting tool according to claim 1, wherein in the unique two-region crystal grain, the difference between the maximum width and the minimum width of the high Al region is 50 to 300 nm. 3. The surface-coated cutting tool according to claim 1, wherein the average width of the Al-rich regions in the unique two-region crystal grains is 30 nm or more. In the composite nitride layer or composite carbonitride layer of Ti and Al, the crystal grains having the NaCl-type face-centered cubic structure have an average grain width W of 0.1 to 3.0 μm and an average aspect ratio A of The surface-coated cutting tool according to any one of claims 1 to 3, characterized in that it is 2.0 to 10.0.

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