JP4849233B2 - Surface coated cutting tool with excellent chipping resistance due to hard coating layer - Google Patents

Description

  The present invention has an excellent hard coating layer even when cutting various steels and cast irons, especially under heavy cutting conditions such as high cutting and high feed that require a large mechanical load on the cutting edge. The present invention relates to a surface-coated cutting tool (hereinafter referred to as a coated tool) that exhibits chipping resistance and exhibits excellent wear resistance over a long period of time.

  Conventionally, generally on the surface of a substrate (hereinafter collectively referred to as a tool substrate) composed of a tungsten carbide (hereinafter referred to as WC) -based cemented carbide or titanium carbonitride (hereinafter referred to as TiCN) -based cermet. As a hard coating layer, a Ti carbide (hereinafter referred to as TiC) layer, a nitride (hereinafter also referred to as TiN) layer, a carbonitride (hereinafter referred to as TiCN) layer, a carbon oxide (hereinafter referred to as TiCO) And a coated tool (hereinafter referred to as a conventional coated tool) formed by vapor deposition of a Ti compound layer such as a layer and a carbonitride oxide (hereinafter referred to as TiCNO) layer, or further on the surface of the Ti compound layer Coated tools in which an aluminum oxide layer is formed by vapor deposition are known, and it is well known that these coated tools are used for continuous cutting and intermittent cutting of various steels and cast irons, for example. That.

Further, the Ti compound layer constituting the hard coating layer of the above conventional coated tool usually has a granular crystal structure, but the TiCN layer which is one of the Ti compound layers is intended to improve the strength of the layer itself. In a normal chemical vapor deposition apparatus, a TiCN having a vertically grown crystal structure (hereinafter referred to as a vertically long TiCN) is obtained by chemical vapor deposition in a medium temperature range of 700 to 950 ° C. using a mixed gas containing an organic carbonitride as a reaction gas. It is also known to form layers.
JP 58-157964 A JP 58-157965 A Japanese Patent Laid-Open No. 6-8010

  In recent years, the performance of cutting equipment has been remarkable. On the other hand, there is a strong demand for labor-saving and energy-saving in cutting, and further cost reduction. Although there is a tendency to be strongly demanded, in the above-mentioned conventional coated tool, there is no problem when this is used for continuous cutting or interrupted cutting under normal conditions such as steel or cast iron, but this is high-cut, When used for heavy cutting where a high mechanical load is applied to the cutting edge, such as high feed, the hard coating layer is not sufficiently strong at high temperature, so chipping is particularly likely to occur, and uneven wear rapidly occurs. The current situation is that it progresses and reaches the service life in a relatively short time.

Therefore, the present inventors, from the above viewpoint, paying attention to the Ti compound layer constituting the hard coating layer of the conventional coated tool, and as a result of conducting research to improve the chipping resistance of the hard coating layer,
The TiC layer having a granular crystal structure that is one of the Ti compound layers constituting the hard coating layer of the above-described conventional coated tool is generally a normal chemical vapor deposition apparatus.
Reaction gas composition (volume%): TiCl ₄ : 2 to 5%, CH ₄ : 4 to 20%, H ₂ : remaining reaction atmosphere temperature: 980 to 1100 ° C,
Reaction atmosphere pressure: 6-50 kPa,
(Hereinafter referred to as normal conditions)
(A) Using a normal chemical vapor deposition apparatus,
Reaction gas composition (volume%): TiCl ₄ : 2 to 5%, CrCl ₃ : 4 to 10%,
_{CH 4: 4~20%, Ar:} 5~15%, H 2: remainder,
Reaction atmosphere temperature: 1000 to 1050 ° C.
Reaction atmosphere pressure: 5 to 25 kPa,
Compared with the above normal conditions, the reaction gas composition was adjusted to a reaction gas composition different from the normal reaction gas composition (the temperature and pressure of the reaction atmosphere were almost the same as the above normal conditions). ), The resulting chemical vapor deposition layer is formed from a cubic Ti-rich TiCr composite carbide phase (hereinafter referred to as “(Ti, Cr) C phase”) as a matrix. Inside, a (Ti, Cr) C phase in which an orthorhombic Cr-rich CrTi composite carbide phase (hereinafter referred to as “(Cr, Ti) C phase”) is dispersed and distributed at a rate of 10 to 40 area%. And a (Cr, Ti) C phase mixed phase structured layer (hereinafter referred to as “(Ti: Cr) C layer”).

(B) The (Ti: Cr) C layer of (a) described above is used as an underlayer, and a conventional upper layer (ie, an internal layer comprising a TiN layer, a TiC layer or a vertically grown crystal) is formed thereon. When forming an intermediate layer composed of a TiCN (hereinafter referred to as “longitudinal TiCN”) layer of the structure, and an upper layer formed by laminating each surface layer composed of a TiN layer), and forming a hard coating layer with an underlayer and an upper layer, The tool base and the (Ti: Cr) C layer constituting the base layer have excellent adhesion, the bonding strength between the base layer and the tool base is improved, and the base layer has improved adhesion to the inner layer. Furthermore, since the mutual adhesion of each layer constituting the upper layer (inner layer-intermediate layer-surface layer) is also excellent, the adhesion between the hard coating layer itself and the hard coating layer and the tool substrate, Bond strength is very high, and as a result, the (Ti: Cr) C layer A coated tool provided with a hard coating layer as a layer has excellent high-temperature strength as a whole hard coating layer. For example, it has high heat generation, and has a large mechanical strength on the cutting edge such as high cutting and high feed. Demonstrate excellent chipping resistance even when used for heavy-duty machining with a load.
The research results shown in (a) and (b) have been obtained.

This invention was made based on the above research results,
“In a surface-coated cutting tool in which a hard coating layer composed of an underlayer and an upper layer is vapor-deposited on the surface of a tool base composed of tungsten carbide-based cemented carbide or titanium carbonitride-based cermet,
(A) the underlayer has a layer thickness of 0.1 to 2 μm, and
Composition formula: (Ti _1-X Cr _X ) C (where X is an atomic ratio of 0.05 to 0.30)
A cubic TiCr composite carbide phase that satisfies the following conditions: a cubic TiCr composite carbide in which an orthorhombic Cr-rich CrTi composite carbide phase is dispersed and distributed in a ratio of 10 to 40 area% in the matrix; It consists of a mixed phase texture layer of orthorhombic Cr-rich CrTi composite carbide phase,
(B) The upper layer is configured as a laminated structure of an inner layer, an intermediate layer, and a surface layer,
The inner layer is composed of a Ti nitride layer having a layer thickness of 0.5 to 2 μm,
The intermediate layer has a layer thickness of 0.5 to 5 μm, and consists of a Ti carbide layer having a granular crystal structure or a Ti carbonitride layer having a vertically long crystal structure,
The surface layer comprises a Ti nitride layer having a layer thickness of 0.3-2 μm;
The hard coating layer characterized by the above is characterized by a “coated tool (surface coated cutting tool) that exhibits excellent chipping resistance”.

  Below, the hard coating layer of this invention is demonstrated in detail.

(A) Underlayer ((Ti: Cr) C layer)
The underlayer composed of the (Ti: Cr) C layer has very good adhesion to the tool base, the bonding strength between the tool base and the underlayer is greatly improved, and (of the upper layer) Since the adhesion with the inner layer is also excellent, the bonding strength between the underlayer and the upper layer (the inner layer) is greatly improved.
As described above, the (Ti: Cr) C layer is formed by, for example, a normal chemical vapor deposition apparatus.
Reaction gas composition (volume%): TiCl ₄ : 2 to 5%, CrCl ₃ : 4 to 10%,
_{CH 4: 4~20%, Ar:} 5~15%, H 2: remainder,
Reaction atmosphere temperature: 1000 to 1050 ° C.
Reaction atmosphere pressure: 5 to 25 kPa,
It can be formed by chemical vapor deposition under the following conditions.
Then, the (Ti: Cr) C layer formed by vapor deposition under the above conditions has a 10 to 40 area% Cr-rich orthorhombic (Cr, Ti) C phase, and a Ti-rich cubic structure (Ti , Cr) has a mixed phase structure of a TiCr composite carbide phase and a CrTi composite carbide phase dispersed and distributed in a matrix composed of a C phase.
More specifically, the (Ti, Cr) C phase having a Ti-rich cubic structure constituting the matrix of the (Ti: Cr) C layer is expressed as follows:
_{Formula: (Ti 1-X Cr X} ) C
Is a composite carbide phase of Ti and Cr having a cubic structure in which the value of X (however, the atomic ratio) satisfies 0.05 ≦ X ≦ 0.30.
Further, the Cr-rich orthorhombic (Cr, Ti) C phase dispersed and distributed in the matrix composed of the (Ti, Cr) C phase is expressed by a composition formula,
Composition formula: (Cr _Y Ti _1-Y ) ₃ C ₂ (where Y is an atomic ratio, 0.55 ≦ Y ≦ 0.8), and / or
Composition _{formula: (Cr Z Ti 1-Z} ) 7 C 3 ( where, 0.85 ≦ Z ≦ 0.95 Z is atomic ratio)
Is a composite carbide phase of Cr and Ti having an orthorhombic structure mainly composed of.

When vapor deposition is performed under the vapor deposition conditions of (a) above, in the composition formula: (Ti _1-X Cr _X ) C, (Ti, Cr having a Cr content ratio satisfying 0.05 ≦ X (atomic ratio) ≦ 0.30. ) C phase is formed, and 0.55 ≦ Y (atomic ratio) in composition formula: (Cr _Y Ti _1-Y ) ₃ C ₂ and / or composition formula: (Cr _Z Ti _1-Z ) ₇ C ₃ ) ≦ 0.8, 0.85 ≦ Z (atomic ratio) ≦ 0.95, a Cr content ratio of (Cr, Ti) C phase is formed, and at the same time, 10 in the (Ti, Cr) C phase. A (Ti: Cr) C layer in which ˜40 area% of (Cr, Ti) C phase is dispersed and distributed is formed.
However, when vapor deposition is performed under conditions other than the vapor deposition conditions of (a), in the composition formula (Ti _1-X Cr _X ) C, the X value indicating the Cr content ratio of the (Ti, Cr) C phase is 5 The compositional formula: (Cr _Y Ti _1-Y ) ₃ C ₂ and / or the compositional formula: (Cr _Z Ti _1-Z ) is not only less than atomic%, or the X value exceeds 30 atomic%. _{In 7} C ₃ , the Y value is less than 55 atomic% or more than 80 atomic%, the Z value is less than 85 atomic% or more than 95 atomic%, and the (Cr, Ti) C phase The dispersion distribution ratio of is less than 10 area% or more than 40 area%, and the X value is less than 5 atomic%, the Y value is less than 55 atomic%, the Z value is less than 85 atomic% or (Cr, Ti ) When the C phase dispersion distribution ratio is less than 10% by area The effect of improving the adhesion between the underlayer ((Ti: Cr) C layer) and the tool substrate cannot be expected, and the improvement of the bonding strength between the underlayer and the tool substrate cannot be expected. When the Z value exceeds 30 atomic%, 80 atomic%, and 95 atomic%, or when the dispersion distribution ratio of the (Cr, Ti) C phase exceeds 40 area%, the distribution is distributed ( The (Ti: Cr) C layer itself, which is the underlying layer, becomes brittle due to the coarsening of the Cr, Ti) C phase, embrittlement due to changes in phase morphology, embrittlement at the interface between the matrix phase and the dispersed phase, etc. Alternatively, the adhesion and bonding strength with the inner layer (of the upper layer) are also deteriorated.
Therefore, the X value (atomic ratio) in the above composition formula is 0.05 to 0.30, the Y value (atomic ratio) is 0.55 to 0.8, and the Z value (atomic ratio) is 0.8 to 0.95. Furthermore, the dispersion distribution ratio of the (Cr, Ti) C phase was also determined to be 10 to 40 area%.
In addition, if the thickness of the underlayer ((Ti: Cr) C layer) is less than 0.1 μm, it is expected that the hard coating layer is closely bonded to the tool substrate by being interposed between the tool substrate and the upper layer. On the other hand, if the layer thickness exceeds 2 μm, chipping is likely to occur under severe cutting conditions such as heavy cutting such as high feed and high cutting, so the layer thickness of the underlayer is 0. .1 to 2 μm.

(B) Upper layer (laminated structure of inner layer-intermediate layer-surface layer)
The upper layer includes an inner layer made of a TiN layer having a thickness of 0.5 to 2 μm, an intermediate layer made of a TiC layer or a vertically long TiCN layer having a thickness of 0.5 to 5 μm, and a layer having a thickness of 0.3 to 2 μm It is formed as a laminated structure of a surface layer consisting of a thick TiN layer, but the TiN layer constituting the inner layer and the surface layer shows high chemical stability, especially against wear based on chemical reaction with the work material. Exhibits excellent wear resistance and contributes to improving the high-temperature strength of the hard coating layer, and the TiC layer that constitutes the intermediate layer is extremely hard, so wear caused by friction with the work material As is well known in the art, it exhibits excellent wear resistance with respect to, and further improves the high-temperature strength of the hard coating layer when the intermediate layer is composed of a vertically long TiCN layer. It is.
The thicknesses of the inner layer, the intermediate layer, and the surface layer constituting the upper layer were determined to be 0.5 to 2 μm, 0.5 to 5 μm, and 0.3 to 2 μm, respectively. When the value is less than the lower limit value, the characteristics (high-temperature hardness, high-temperature strength) of each layer cannot be fully exerted under the condition of heavy cutting in which a large mechanical load is applied to the cutting edge part. If the layer thickness exceeds the respective upper limit values, the bonding strength between the respective layers decreases, and chipping and uneven wear may occur.

  The coated tool of the present invention uses a hard coating layer as an underlayer, a cubic Ti-rich TiCr composite carbide phase ((Ti, Cr) C phase) as a matrix, and includes an orthorhombic Cr-rich layer. A mixed phase structure layer of cubic TiCr composite carbide and orthorhombic CrTi composite carbide phase in which a CrTi composite carbide phase ((Cr, Ti) C phase) is dispersed and distributed at a rate of 10 to 40 area% ( (Ti: Cr) C layer) to improve the adhesion and bonding strength between the underlayer and the tool base, and between the underlayer and the upper layer (inner layer thereof). For example, even hard cutting conditions such as high cutting and high feed with high mechanical loads, such as high-hardness and high-strength hard coating layers, have excellent joint strength along with high-temperature strength. This prevents chipping from occurring. The occurrence of uneven wear suppression while being, exhibit excellent wear resistance for a long time, and makes it possible to further life extension of service life.

  Next, the coated tool of the present invention will be specifically described with reference to examples.

As raw material powders, WC powder, TiC powder, ZrC powder, VC powder, TaC powder, NbC powder, Cr ₃ C ₂ powder, TiN powder, and Co powder each having an average particle diameter of 1 to 3 μm are prepared. The raw material powder is blended in the blending composition shown in Table 1, added with wax, ball mill mixed in acetone for 24 hours, dried under reduced pressure, and press-molded into a green compact of a predetermined shape at a pressure of 98 MPa. The green compact is vacuum-sintered in a vacuum of 5 Pa at a predetermined temperature within a range of 1370 to 1470 ° C. for 1 hour. After sintering, the cutting edge is subjected to a honing process of R: 0.07 mm. Thus, tool bases A to F made of WC-base cemented carbide having the insert shape specified in ISO · CNMG160612 were produced.

In addition, as raw material powders, TiCN (mass ratio TiC / TiN = 50/50) powder, Mo ₂ C powder, ZrC powder, NbC powder, TaC powder, WC powder, all having an average particle diameter of 0.5 to 2 μm. Co powder and Ni powder are prepared, and these raw material powders are blended in the blending composition shown in Table 2, wet mixed by a ball mill for 24 hours, dried, and pressed into a compact at a pressure of 98 MPa. The green compact was sintered in a nitrogen atmosphere of 1.3 kPa at a temperature of 1540 ° C. for 1 hour, and after the sintering, the cutting edge portion was subjected to a honing process of R: 0.07 mm. Tool bases a to f made of TiCN-based cermet having an insert shape of standard / CNMG160612 were formed.

Then, each of these tool bases A to F and tool bases a to f is charged into a normal chemical vapor deposition apparatus,
(A) First, under the conditions shown in Table 3 (underlayers (1) to (6)), the (Ti: Cr) C layer having the target layer thickness shown in Tables 4 and 5 is used as the underlayer of the hard coating layer. Formed as a vapor deposition
(B) Next, under the same conditions as shown in Table 3, the combinations shown in Tables 4 and 5, the target layer thickness, the inner layers (1) to (3), the intermediate layers (1) to (4), the surface The coated tools 1 to 13 of the present invention were manufactured by vapor-depositing an upper layer composed of the layers (1) to (3).
In addition, the longitudinal TiCN of the intermediate layer (4) in Table 3 indicates the conditions for forming a TiCN layer having a longitudinally grown crystal structure described in JP-A-6-8010. This shows the formation conditions of the crystal structure.

  For comparison purposes, the base layer of the hard coating layer is formed with the combinations and target layer thicknesses shown in Tables 6 and 7 under the formation conditions of the intermediate layers (1) to (3) shown in Table 3. Except for the above, conventionally coated tools 1 to 13 were produced under the same conditions as the above-described coated tools 1 to 13 of the present invention.

  Next, for the underlayers (1) to (6) constituting the underlayer of the hard coating layer of the present invention-coated tools 1 to 13, using an X-ray diffractometer and a scanning Auger electron spectrometer, (Cr , Ti) The existence form of the C phase was confirmed, and then the area ratio (five-point measurement of the five-point measurement) was performed by image analysis of the surface analysis result (photograph) of Cr at a magnification of 20,000 times using a scanning Auger electron spectrometer. (Average value) was measured. These measurement results are shown in Table 8. From Table 8, in the coated tools 1 to 13 of the present invention, the underlayer has a Ti-rich TiCr composite carbide ((Ti, Cr) C) phase as a matrix and a Cr-rich CrTi composite carbide ((Cr , Ti) C) phase is dispersed and distributed, and the area ratio occupied by the Cr-rich CrTi composite carbide ((Cr, Ti) C) phase is 10 to 40 area% of the whole.

  Moreover, when the thickness of each layer which comprises the hard coating layer of this invention coated tool 1-13 and the conventional coated tool 1-13 was measured using the scanning electron microscope (longitudinal section measurement), all were target layer thickness. The average layer thickness (average value of 5-point measurement) was substantially the same.

Next, for the above-described coated tools 1 to 13 of the present invention and the conventional coated tools 1 to 13, a cutting test was performed under the following cutting conditions in a state where each was fixed with a fixing jig to the tip of the tool steel tool. went.
[Cutting conditions A]
Work material: JIS / SUS316 (HB220) round bar,
Cutting speed: 100 m / min. ,
Cutting depth: 1.5 mm,
Feed: 0.6 mm / rev. ,
Cutting time: 10 minutes,
Wet continuous high feed cutting test of stainless steel under normal conditions (normal feed is 0.3 mm / rev.).
[Cutting conditions B]
Work material: JIS / FCD600 (tensile strength 610 MPa) round bar,
Cutting speed: 120 m / min. ,
Cutting depth: 7 mm,
Feed: 0.35 mm / rev. ,
Cutting time: 10 minutes,
Wet continuous high-cut cutting test of ductile cast iron under the conditions (normal cutting is 4 mm).
[Cutting conditions C]
Work material: JIS / SCM440 (HB260) 4-slotted round bar,
Cutting speed: 110 m / min. ,
Cutting depth: 7 mm,
Feed: 0.2 mm / rev. ,
Cutting time: 10 minutes,
Wet intermittent high-cut cutting test of alloy steel under the conditions (normal cutting is 3 mm).
The flank wear width of the cutting edge in the cutting test under the above cutting conditions A to C was measured. The measurement results are shown in Table 9.

  From the results shown in Tables 4 to 9, the coated tools 1 to 13 of the present invention have 10 to 40% by area of the hard coating layer in the Ti-rich (Ti, Cr) C phase matrix. It has a mixed phase structure layer ((Ti: Cr) layer) in which a Cr-rich (Cr, Ti) C phase is dispersed and distributed. As a result, the hard coating layer underlayer and tool substrate, and the underlayer (upper portion) The inner layer (with the inner layer) has excellent adhesion and bonding strength, and the upper layer of the hard coating layer consisting of a laminate structure of inner layer-intermediate layer-surface layer itself has excellent high temperature hardness. Because of its high-temperature strength and wear resistance, even when cutting steel and cast iron under heavy cutting conditions where a large mechanical load is applied to the cutting edge, chipping and uneven wear did not occur and it was excellent over a long period of time. TiC layer is used as the base layer for the hard coating layer while exhibiting wear resistance. In the conventional coated tools 1 to 13 thus configured, severe cutting called heavy cutting due to insufficient adhesion and bonding strength between the underlayer and the tool base, or between the underlayer and the TiN layer (provided thereon). Under the conditions, it is clear that chipping and uneven wear occur in the hard coating layer, and that the service life is reached in a relatively short time.

  As described above, the coated tool of the present invention is not only continuous cutting and interrupted cutting under normal conditions such as various steels and cast iron, but also severe cutting processing such as heavy cutting that requires a large mechanical load on the cutting edge. Even when used for conditions, the hard coating layer does not cause chipping or uneven wear, exhibits excellent wear resistance, and exhibits excellent cutting performance over a long period of time. It is possible to sufficiently satisfy the high performance of the machine, labor saving and energy saving of cutting, and cost reduction.

Claims (1)

In a surface-coated cutting tool in which a hard coating layer composed of an underlayer and an upper layer is vapor-deposited on the surface of a tool base composed of tungsten carbide-based cemented carbide or titanium carbonitride-based cermet,
(A) the underlayer has a layer thickness of 0.1 to 2 μm, and
Composition formula: (Ti _1-X Cr _X ) C (where X is an atomic ratio of 0.05 to 0.30)
A cubic TiCr composite carbide phase that satisfies the following conditions: a cubic TiCr composite carbide in which an orthorhombic Cr-rich CrTi composite carbide phase is dispersed and distributed in a ratio of 10 to 40 area% in the matrix; It consists of a mixed phase texture layer of orthorhombic Cr-rich CrTi composite carbide phase,
(B) The upper layer is configured as a laminated structure of an inner layer, an intermediate layer, and a surface layer,
The inner layer is composed of a Ti nitride layer having a layer thickness of 0.5 to 2 μm,
The intermediate layer has a layer thickness of 0.5 to 5 μm, and consists of a Ti carbide layer having a granular crystal structure or a Ti carbonitride layer having a vertically long crystal structure,
The surface layer comprises a Ti nitride layer having a layer thickness of 0.3-2 μm;
A surface-coated cutting tool that exhibits excellent chipping resistance due to its hard coating layer.