JP2022147327A - Surface coating cutting tool - Google Patents

Abstract

To provide a surface coating cutting tool which presents excellent abrasion resistance and defect resistance for an extended period even when subjecting a material having a high deposition property to high speed intermittent cutting or high speed continuous cutting.SOLUTION: A surface coating cutting tool has a tool base body and a coating layer on a surface of the tool base body. The coating layer has an average layer thickness of 0.5-10.0 μm. When an average composition is represented by a composition formula: (Ti1-x-yAlxMoy)N, x is 0.50-0.65, and y is more than 0.00 and equal to or less than 0.20. The coating layer includes crystal grains having an NaCl-type face-centered cubic structure with an average grain diameter of 20-100 nm. An area ratio occupied by large contamination droplets is 0.100% or less, and an area ratio occupied by small contamination droplet is 0.001-0.100%.SELECTED DRAWING: None

Description

The present invention relates to a surface-coated cutting tool (hereinafter sometimes referred to as a coated tool).

Conventionally, there has been known a coated tool in which a WC-based cemented carbide or the like is used as a tool substrate and a coating layer is formed on the surface of the tool substrate by vapor deposition. Although this coated tool has wear resistance, various proposals have been made in order to further improve this wear resistance, and proposals have also been made regarding the composition of the coating layer.

For example, in Patent Document 1, the coating layer is a solid solution of Mo and N represented by MoN _y (0.01 ≤ y ≤ 0.2), Mo ₂ N, MoN, or a mixture thereof. and a layer B made of Ti _1-x Al _x N (0.3≦x≦0.7) are alternately laminated in two or more layers, and the layer thickness λa of the A layer and the layer thickness λb of the B layer are each 2 to 000 nm,
The layer thickness ratio λa/λb increases from the tool substrate side to the outermost surface side of the coating layer, and the layer thickness ratio λa/λb closest to the tool substrate is 0.1 to 0.7, and the outermost surface side A coated tool having a layer thickness ratio λa/λb of 1.5 to 10, which is the closest to , is said to be excellent in wear resistance.

JP 2010-137305 A

The present invention has been made in view of the above circumstances and proposals. An object of the present invention is to obtain a surface-coated cutting tool that exhibits wear resistance and chipping resistance for a long period of time.

Here, high-speed continuous cutting of a highly adhesive material refers to, for example, austenitic stainless steel in which the cutting edge of the cutting tool continuously cuts at a cutting speed higher than 60 m/min.

A surface-coated cutting tool according to an embodiment of the present invention is
A tool base and a coating layer on the surface of the tool base,
The coating layer is
The average layer thickness is 0.5 to 10.0 μm,
When the average composition is represented by the composition formula: (Ti _1-x-y Al _x Mo _y )N, x is 0.50 to 0.65, y is more than 0.00 and 0.20 or less,
Containing crystal grains having an NaCl-type face-centered cubic structure with an average grain size of 20 to 100 nm,
And,
The area ratio occupied by large mixed droplets is 0.100% or less, and the area ratio occupied by small mixed droplets is 0.001 to 0.100%.

Furthermore, the surface-coated cutting tool according to the embodiment may satisfy the following item (1).

(1) The nanoindentation hardness of the coating layer is 30 GPa or more.

According to the above, for example, even when a material with high adhesion to coated tools, such as austenitic stainless steel, is subjected to high-speed interrupted cutting or high-speed continuous cutting, excellent wear resistance and fracture resistance exert over a long period of time.

As a result of examining the coated tool described in Patent Literature 1, the present inventor recognized the following (1).

(1) The coating layer exhibits solid lubricity due to Mo oxides, and although it exhibits excellent wear resistance in terms of cutting performance of alloy steel or high-hardness steel, for example, in cutting austenitic stainless steel, it has heat resistance. Inferior in durability, and further extension of tool life is required.

Based on this recognition, the present inventors diligently studied the composition of the coating layer and the entrained liquid droplets. As a result, by adding Mo in addition to Ti and Al as components of the coating layer and controlling the size of the mixed droplets, a material with high adhesion to the coated tool, such as austenitic stainless steel, can be produced at high speed. The present inventors have found that it is possible to obtain a coated tool that exhibits excellent wear resistance and chipping resistance over a long period of time even when subjected to continuous cutting.

A surface-coated cutting tool according to one embodiment of the present invention will be described below. In the present specification and claims, when a numerical range is expressed as "A to B" (both A and B are numerical values), the range includes the numerical values of the upper limit (B) and the lower limit (A). , and the units of the upper limit (B) and the lower limit (A) are the same. Also, the numerical values include tolerances.

1. Coating Layer (1) Average Layer Thickness The average layer thickness of the coating layer is preferably 0.5 to 10.0 μm. The reason for this is that if the average layer thickness is less than 0.5 μm, it is difficult to exhibit wear resistance and chipping resistance over a long period of time. This is because the layer tends to peel off from the tool substrate, and chipping tends to occur.
More preferably, the average layer thickness is 0.5 to 3.0 μm.

In addition, the average layer thickness of the coating layer can be obtained by, for example, using a focused ion beam system (FIB), a cross section polisher (CP), or the like, for the hard coating layer at any position. Surface (For inserts, the cross section perpendicular to this surface when the surface of the tool base is treated as a flat surface, ignoring minute irregularities on the surface of the tool base. For shaft tools, the cross section perpendicular to the shaft.) A sample for observation is prepared by cutting with , and the longitudinal section is observed using a scanning electron microscope (SEM). be.

(2) Average composition The average composition of the coating layer is represented by the composition formula: (Ti _1-xy Al _x Mn _y )N, where x is 0.50 to 0.65 and y is more than 0.00. It is preferably 0.20 or less.
The reason is as follows.
When x is less than 0.50, the hardness and oxidation resistance of the coating layer are not sufficient. It's for.

If y does not exceed 0.00, the lubricity provided by Mo cannot be used to improve wear resistance. This is because the hardness decreases.
When Mo is uniformly dispersed in the coating layer, sudden chipping and dropout of coating crystal grains do not occur, and stable cutting performance can be exhibited.

More preferably, x is 0.56 to 0.61 and y is 0.05 to 0.10.

For the average composition, an electron beam microanalyzer (EPMA: Electron Probe Micro Analyzer) is used to irradiate the surface of the hard coating layer with an electron beam, or five longitudinal sections at arbitrary positions of the coating layer, and The content of each element is quantified by analyzing the characteristic X-rays corresponding to the elements forming the obtained coating layer, and the result is calculated by arithmetic mean.

According to an example of the manufacturing method described later, the ratio of (Ti _1-xy Al _x Mo _y ) to N is 1:1, but inevitably (unintentionally 2) There may be cases where the ratio is not 1:1.

(3) NaCl-type face-centered cubic crystal grains The coating layer preferably has NaCl-type face-centered cubic crystal grains in order to provide hardness, and the ratio of the NaCl-type face-centered cubic crystal grains is In the longitudinal section, the area ratio is preferably 70% or more. The upper limit of this area ratio may be 100%, that is, all crystal grains may have a NaCl-type face-centered cubic structure.

The average grain size of the NaCl-type face-centered cubic structure crystal grains is preferably 20 to 100 nm. The reason for this is that if it is less than 20 nm, diffusion of oxygen and components of the work material tends to occur due to an increase in the grain boundary interface, and the adhesion resistance decreases. This is because the unit of breakage when adhesion breakage occurs becomes larger and the chipping resistance is lowered.

Here, the average particle size is determined as follows. That is, analysis using automated crystal orientation mapping (ACOM)-TEM is performed by a transmission electron microscope (TEM) to define grain boundaries. After that, the range closed by the grain boundary is defined as the crystal grain, and the maximum length of the crystal grain is determined as the grain size. The grain size is obtained for each of 20 arbitrary crystal grains, and the arithmetic mean thereof is taken as the average grain size.

(4) Mixed droplets In the coating layer, the area ratio occupied by large mixed droplets is 0.100% or less (may be 0.000%), and the area ratio occupied by small mixed droplets is 0.001 to 0.100% is preferred.
The reason for this is that if the area ratio occupied by large mixed droplets is 0.100% or less, it can be treated as if there are no large mixed droplets, the coating layer has few starting points for defects, and the abrasion resistance is excellent. On the other hand, when the area ratio occupied by small entrained droplets is 0.001 to 0.100%, the presence of an appropriate amount of small entrained droplets produces a metal oxide, thereby solidifying This is to provide lubricity.

Also, by controlling the mixed droplets in this way, even if the coating layer contains Mo, it is possible to have crystal grains of NaCl-type face-centered cubic structure.

Here, the mixed liquid droplet means the following. That is, when the Al, Ti, Mo, and N components are measured by SEM-EDS mapping analysis and TEM-EDS mapping analysis for the longitudinal section of the coating layer, the metal components of Al, Ti, and Mo are detected, A region where N is not detected is treated as a mixed droplet.

The size of an entrained droplet is defined by its maximum length, that is, the maximum length between any two points on the outline of the entrained droplet. In the claims and the specification, a large entrained droplet has a maximum length of 50 nm or more, and a small entrained droplet has a maximum length of 10 nm or more and less than 50 nm.

The area ratio of entrained droplets is determined as follows.
The area ratio of the large mixed droplets is an observation field of 2 μm (direction parallel to the surface of the tool substrate)×2 μm (direction perpendicular to the surface of the tool substrate, however, if the layer thickness is less than 1 μm, the layer thickness). At 3 or more points, the longitudinal section is observed at a magnification of 50,000 times by SEM-EDS mapping analysis, and the area ratio occupied by the mixed droplets is obtained.
The area ratio of small mixed droplets is an observation field of 1 μm (direction parallel to the surface of the tool substrate)×1 μm (direction perpendicular to the surface of the tool substrate, however, if the layer thickness is less than 1 μm, the layer thickness). , 10 or more points are observed by TEM-EDS mapping analysis at a magnification of 100,000 times, and the area ratio occupied by the mixed droplets is determined.

Here, the surface of the tool substrate is a known image of an elemental map obtained by performing elemental mapping using energy dispersive X-ray spectroscopy (EDS) in a longitudinal section. The interface between the coating layer and the tool substrate is determined by performing the treatment, and the average line of the roughness curve of the interface between the coating layer and the tool substrate thus obtained is arithmetically determined, and this is used as the surface of the tool substrate. The direction perpendicular to the average line is defined as the direction perpendicular to the tool substrate (layer thickness direction).

Also, even if the tool base has a curved surface such as a drill or an end mill, if the tool diameter is sufficiently large relative to the thickness of the coating layer, the distance between the coating layer and the tool base in the measurement area will increase. Since the interface is substantially planar, the surface of the tool substrate can be determined in a similar manner.

That is, for example, in the case of drills and end mills, elemental mapping is performed using EDS in a longitudinal section of the coating layer perpendicular to the axial direction, and the obtained elemental map is subjected to known image processing. The interface between the layer and the tool substrate is defined, and the mean line is arithmetically obtained for the roughness curve of the interface between the coating layer and the tool substrate thus obtained, and this is used as the surface of the tool substrate. Then, the direction perpendicular to this average line is defined as the direction perpendicular to the tool substrate (layer thickness direction).

(5) Nanoindentation hardness It is more preferable that the nanoindentation hardness is 30 GPa or more. When the nanoindentation hardness is 30 GPa or more, wear resistance is further improved, and excellent cutting performance can be exhibited even for work-hardened stainless steel.

The hardness of nanoindentation is measured using an ultra-micro indentation hardness tester. The indentation hardness is measured by indenting a predetermined indenter (for example, a triangular pyramid-shaped diamond indenter called a Berkovich-shaped indenter) with a predetermined load of 1.96 × 10 ^-3 N (200 mgf) perpendicular to the thickness direction of the hard coating layer. , is calculated based on the indentation depth of the indenter.

2. Tool Substrate (1) Material Any material can be used as long as it is a conventionally known material for a tool substrate, as long as it does not interfere with the achievement of the above-mentioned object. For example, cemented carbide (WC-based cemented carbide, WC, containing Co, or further containing carbonitrides such as Ti, Ta, Nb, etc.), cermet ( TiC, TiN, TiCN, etc. as main components), ceramics (titanium carbide, silicon carbide, silicon nitride, aluminum nitride, aluminum oxide, etc.), cBN sintered body, or diamond sintered body is preferred.

(2) Shape The shape of the tool base is not particularly limited as long as it is a shape used as a cutting tool, examples of which include the shape of an insert and the shape of a drill.

3. Manufacturing Method A sputtering method or a high-power pulse sputtering (HiPIMS) method, which facilitates suppression of entrained liquid droplets, can be used.

EXAMPLES Next, examples will be described, but the present invention is not limited to these examples.

As raw material powders, WC powder, VC powder, TaC powder, NbC powder, Cr ₃ C ₂ powder, and Co powder, all having an average particle size of 1 to 3 μm, were prepared. These raw material powders were compounded to the compounding composition shown in Table 1, wet-mixed in a ball mill for 72 hours, and dried. After that, the green compact was press molded at a pressure of 100 MPa, and the green compact was sintered in a vacuum of 6 Pa at a temperature of 1400° C. for 1 hour. Tool substrates 1 and 2 made of WC-based cemented carbide and having an insert shape conforming to ISO standard CNMG120408 were produced by honing No. 03. Next, tool substrates 3 and 4 made of WC-based cemented carbide and having an insert shape of ISO standard DCGT11T302M without honing on the cutting edge portion were produced in the same manner.

Subsequently, coating layers were formed on these tool substrates 1 to 4 according to the following procedures (a) to (c).

(a) Each of the tool substrates 1 to 4 is ultrasonically cleaned in acetone, dried, and placed radially at a predetermined distance from the central axis on a rotary table in a high-power pulse sputtering apparatus. On the other hand, sintered targets of Ti, Al, and Mo were arranged at four locations facing each other across the rotary table in the high-power pulse sputtering apparatus.

(b) While the inside of the device is evacuated and maintained at a vacuum of 0.1 Pa or less, the inside of the device is heated with a heater to 500 ° C., and then a direct current of −200 V is applied to the tool base that revolves while rotating on the rotary table. A bias voltage was applied. Thereafter, an argon (hereinafter referred to as Ar) gas was introduced into the apparatus as a discharge/sputtering gas to create an atmosphere of 2.0 Pa. Furthermore, Ar ions were excited by passing a current of 40 A through a tungsten filament provided in the apparatus, and the tool substrate was subjected to Ar bombardment treatment for 1 hour.

(c) Ar gas and nitrogen gas are introduced into the apparatus as sputtering gases, the atmosphere in the apparatus is set to 0.4 to 0.6 Pa, and the sintered target of Ti, Al and Mo is shown in Table 2. High power pulse sputtering was performed under predetermined pulse sputtering conditions for a time corresponding to the layer thickness. As a result, Example coated inserts 1 to 22 shown in Table 3 (hereinafter collectively referred to as Examples 1 to 22) were produced, respectively.

For the purpose of comparison, a coating layer was formed on these tool substrates 1 to 4 under the conditions shown in Table 4 according to the procedures (a) to (c) above, and the comparative coated tools shown in Table 5 were compared. Coated inserts 1-20 (hereinafter collectively referred to as Comparative Examples 1-20) were produced, respectively.

Next, the following cutting tests 1 and 2 were performed on Examples 1 to 22 and Comparative Examples 1 to 20, and the results are shown in Tables 6 and 7, respectively.

For Examples 1 to 11 and Comparative Examples 1 to 10, a dry high-speed continuous cutting test (cutting test 1) was performed under the following conditions while screwing the tip of the tool steel cutting tool with a fixing jig. carried out.

(Cutting conditions 1)
Work material: SUS304
Tool shape: ISO-CNMG120408
Cutting method: dry continuous turning
Cutting speed: 200m/min
Notch: 1.0 mm
Feed: 0.8mm
Cutting time: 25 minutes

After the cutting test was completed, the flank wear width was measured and the presence or absence of chipping was observed. However, when chipping occurred before the cutting time expired, the cutting was stopped and the time from the start of cutting was measured.

Next, for Examples 12 to 22 and Comparative Examples 11 to 20, a wet high-speed continuous cutting test (cutting test 2 ) was implemented.

Work material: SUS316
Tool shape: ISO-DCGT11T302M
Cutting method: Wet continuous lathe machining (turning)
Cutting speed: 60m/min
Notch: 1.0mm
Feed: 0.08mm
Cutting time: 180 minutes

After the cutting test was completed, the flank wear width was measured and the presence or absence of chipping was observed. However, when chipping occurred before the cutting time expired, the cutting was stopped and the time from the start of cutting was measured.

As is clear from the results of the cutting tests shown in Tables 6 and 7, all of Examples 1 to 22 have a small flank wear width even when subjected to high-speed continuous cutting, and have excellent wear resistance and chipping resistance. had On the other hand, in Comparative Examples 1 to 20, chipping occurred before the cutting test was completed, and the life was short.

Claims (2)

A surface-coated cutting tool having a tool substrate and a coating layer on the surface of the tool substrate,
The coating layer is
The average layer thickness is 0.5 to 10.0 μm,
When the average composition is represented by the composition formula: (Ti _1-x-y Al _x Mo _y )N, x is 0.50 to 0.65, y is more than 0.00 and 0.20 or less,
Containing crystal grains having an NaCl-type face-centered cubic structure with an average grain size of 20 to 100 nm,
And,
The area ratio occupied by large mixed droplets is 0.100% or less, and the area ratio occupied by small mixed droplets is 0.001 to 0.100%.
A surface-coated cutting tool characterized by: 2. The surface-coated cutting tool according to claim 1, wherein the coating layer has a nanoindentation hardness of 30 GPa or more.