JP3661503B2 - Surface coated tungsten carbide based cemented carbide cutting tool with excellent chipping resistance with hard coating layer in intermittent heavy cutting - Google Patents

Description

【００１６】
【表２】

【００１７】
【表３】

【００１８】
【表４】

【００１９】
【表５】

【００２０】
【発明の効果】
表２〜５に示される結果から、硬質被覆層中に構成層として存在するｌ−ＴｉＣＮ層が残留圧縮応力を有する上方部分層と残留引張応力を有する下方部分層からなる本発明被覆超硬工具１〜１０は、いずれも前記硬質被覆層がすぐれた耐チッピング性を具備することから、特に断続切削を高送りや高切り込みなどの重切削条件で行っても切刃に欠けやチッピングの発生なく、すぐれた耐摩耗性を長期に亘って発揮するのに対して、前記ｌ−ＴｉＣＮ層には残留引張応力のみが存在する従来被覆超硬工具１〜１０においては、いずれも前記ｌ−ＴｉＣＮ層以外の構成層も残留引張応力を具備することと相俟って高衝撃の加わる断続重切削ではチッピングが発生し、これが原因で比較的短時間で使用寿命に至ることが明らかである。
上述のように、この発明の被覆超硬工具は、例えば鋼や鋳鉄などの連続切削や断続切削は勿論のこと、高衝撃の加わる断続重切削にもすぐれた耐チッピング性を発揮し、長期に亘ってすぐれた切削性能を示すものであるから、切削加工の省力化および省エネ化、さらに低コスト化に十分満足に対応できるものである。[0001]
BACKGROUND OF THE INVENTION
The present invention provides a surface-coated tungsten carbide-based cemented carbide cutting tool that exhibits excellent chipping resistance when the intermittent cutting is performed under heavy cutting conditions such as high feed and high cutting. This is related to carbide tools.
[0002]
[Prior art]
Conventionally, in general, on the surface of a tungsten carbide base cemented carbide substrate (hereinafter referred to as a cemented carbide substrate),
(A) Titanium carbide (hereinafter referred to as TiC) layer, titanium nitride (hereinafter also referred to as TiN) layer, titanium carbonitride (hereinafter referred to as TiN) layer each having an average layer thickness and granular crystal structure of 0.1 to 3 μm. One or two of a TiCN layer, a titanium carbonate (hereinafter referred to as TiCO) layer, a titanium nitride oxide (hereinafter referred to as TiNO) layer, and a titanium carbonitride oxide (hereinafter referred to as TiCNO) layer A Ti compound layer comprising more than seeds;
(B) a titanium carbonitride (hereinafter referred to as 1-TiCN) layer having an average layer thickness of 2 to 10 μm and a vertically grown crystal structure;
(C) an aluminum oxide (hereinafter referred to as Al ₂ O ₃ ) layer having an average layer thickness of 0.5 to 5 μm and a granular crystal structure;
A coated carbide tool made by chemical vapor deposition of a hard coating layer composed of 3 to 15 μm in total thickness is known, and this coated carbide tool is used for continuous cutting and intermittent cutting of steel and cast iron. It is also known to be used.
It is also well known that generally Al ₂ O ₃ layers constituting the hard coating layer of the above-mentioned coated carbide tool are widely used in practical use, such as those having an α-type crystal structure and those having a κ-type crystal structure. Further, the l-TiCN layer is known, for example, from JP-A-6-8010 and JP-A-7-328808, and an organic carbonitride is used as a reaction gas in a normal chemical vapor deposition apparatus. It is formed by chemical vapor deposition at a medium temperature range of 700 to 950 ° C. using a mixed gas.
[0003]
[Problems to be solved by the invention]
On the other hand, there is a strong demand for labor saving and energy saving and cost reduction for cutting in recent years. With this, cutting tends to be performed under heavy cutting conditions such as high feed and high cutting. In conventional coated carbide tools, especially when this is used to perform intermittent cutting under heavy cutting conditions such as high feed and high cutting, chipping (microchips) is likely to occur in the hard coating layer, which The current situation is that the service life is reached in a short time.
[0004]
[Means for Solving the Problems]
Therefore, the present inventors conducted research to improve the chipping resistance of the hard coating layer in the above conventional coated carbide tool from the above viewpoint,
(A) In the hard coating layer of the above conventional coated carbide tool, when it is formed by the chemical vapor deposition method, there is a residual tensile stress of 30 to 70 kgf / mm ² in any of the constituent layers, which is high. It may cause chipping in intermittent heavy cutting with impact.
[0005]
(B) As described above, when the Ti compound layer and the Al ₂ O ₃ layer constituting the hard coating layer of the coated carbide tool are formed by chemical vapor deposition, tensile stress remains in both, and compression stress remains in this. In the case of the same l-TiCN layer, after forming the l-TiCN layer (lower partial layer) in which the tensile stress remains, the deposition condition is changed to change the lower partial layer. The 1-TiCN layer (upper portion) in which the compressive stress of 5 to ²⁰ kgf / mm ² remains without damaging the vertically grown crystal structure, that is, the vertically grown crystal structure continuous with the vertically grown crystal structure of the lower partial layer. Layer).
[0006]
(C) The 1-TiCN layer (upper partial layer) in which the compressive stress of 5 to ²⁰ kgf / mm ² remains is first subjected to normal conditions, that is,
Reaction gas composition (in% by volume, hereinafter the _{same) -TiCl 4: 1~3%, N2} : 20~40%, CH 3 CN: 0.1~1%, H2: rest,
Atmospheric temperature: 800-920 ° C
Atmospheric pressure: 50 to 150 Torr,
After forming the l-TiCN layer (lower partial layer) having a residual tensile stress of 30 to 70 kgf / mm ^{2 under} the conditions of
(By volume%, hereinafter the same) reaction gas composition _{-TiCl 4: 0.1~1%, N 2} : 30~50%, CH 4: 0.1~1%, H 2: remainder,
Atmospheric temperature: 940 to 1000 ° C.
Atmospheric pressure: 50 to 200 Torr,
And can be formed by performing chemical vapor deposition for a predetermined time.
(D) As described above, in the l-TiCN layer of the hard coating layer, the residual tensile stress is present in the lower part and the residual compressive stress is present in the upper part. When an l-TiCN layer in which stress and residual compressive stress coexist is present as a constituent layer of the hard coating layer, the resulting coated carbide tool can perform the above-described high-impact additional cutting that performs intermittent cutting under heavy cutting conditions. Since the hard coating layer has excellent chipping resistance, it should exhibit excellent cutting performance over a long period of time.
(D) The upper partial layer where the residual compressive stress is present in the l-TiCN layer constituting the hard coating layer has a layer thickness corresponding to 20 to 40% of the average layer thickness of the l-TiCN layer for the reason described later. It is necessary to have
The research results shown in (a) to (d) above were obtained.
[0007]
This invention was made based on the above research results,
On the surface of the carbide substrate,
(A) Of the TiC layer, TiN layer, TiCN layer, TiCO layer, TiNO layer, and TiCNO layer, all of which have an average layer thickness and granular crystal structure of 0.1 to 3 μm and have residual tensile stress A Ti compound layer comprising one or more of the following:
(B) It has an average layer thickness of 2 to 10 μm, and consists of an upper partial layer in which residual compressive stress exists and a lower partial layer in which residual tensile stress exists, and the upper partial layer and the lower partial layer are continuous with each other An l-TiCN layer having a vertically elongated crystal structure and the upper partial layer having a layer thickness corresponding to 20 to 40% of the average layer thickness of 3 to 10 μm;
(C) an Al ₂ O ₃ layer having an average layer thickness of 0.5 to 5 μm and a granular crystal structure and having residual tensile stress;
It is characterized by a coated carbide tool that exhibits excellent chipping resistance by intermittent heavy cutting, which is formed by chemical vapor deposition of a hard coating layer composed of 3 to 15 μm in total average layer thickness. .
[0008]
Note that the layer thickness of the upper partial layer in the l-TiCN layer constituting the hard coating layer of the coated carbide tool of the present invention is equivalent to 20 to 40% of the l-TiCN layer. If the thickness is less than 20% of the 1-TiCN layer, the residual compressive stress of the 1-TiCN layer is relatively small, and a sufficiently satisfactory chipping resistance cannot be ensured. If the ratio exceeds 50%, the granular crystal structure is mixed in the vertically grown crystal structure, and the excellent toughness provided by the vertically grown crystal structure is impaired.
[0009]
Furthermore, the average layer thickness of the constituent layers in the hard coating layer of the coated carbide tool of the present invention is determined for the following reason.
That is, each of the Ti compound layers has a common property of improving the interlayer adhesion between the constituent layers. Therefore, when the average layer thickness is less than 0.1 μm, the desired excellent interlayer adhesion is ensured. On the other hand, when the average layer thickness exceeds 3 μm, especially when a TiC layer is present as a constituent layer, chipping is likely to occur at the cutting edge during high-speed cutting, and a soft TiN layer is also present. In this case, since the wear of the hard coating layer is promoted, the average layer thickness is determined to be 0.1 to 3 μm.
[0010]
In addition, the Al ₂ O ₃ layer has the effect of improving the wear resistance of the hard coating layer, but if the average layer thickness is less than 0.5 μm, the desired excellent wear resistance cannot be ensured. On the other hand, if the average layer thickness exceeds 5 μm, chipping is likely to occur at the cutting edge, so the average layer thickness was set to 0.5 to 5 μm.
[0011]
Furthermore, the l-TiCN layer, as described above, imparts excellent toughness due to the vertically grown crystal structure to the hard coating layer, and the compression stress remains only after it is formed on the lower partial layer where residual tensile stress exists. The upper partial layer made possible has the effect of improving the chipping resistance of the hard coating layer, but if the average layer thickness is less than 2 μm, the desired effect cannot be obtained, while the average layer thickness is 10 μm. When the thickness exceeds 1, the cutting edge tends to be chipped or chipped, so the average layer thickness was determined to be 2 to 10 μm.
Also, the reason that the overall average layer thickness of the hard coating layer is 3 to 15 μm is that when the average layer thickness is less than 3 μm, the desired wear resistance cannot be ensured, while the average layer thickness exceeds 15 μm. This is because chipping and chipping are likely to occur in the cutting edge.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Next, the coated carbide tool of the present invention will be specifically described with reference to examples.
As raw material powder, average particle size: 1.5 μm fine WC powder, 3.0 μm medium WC powder, 1.2 μm (Ti, W) CN (weight ratio, the same below, TiC / TiN / WC) = 24/20/56) powder, 1.3 μm (Ta, Nb) C (TaC / NbC = 90/10) powder, 1.2 μm Cr ₃ C ₂ powder, and 1.2 μm Co powder These raw material powders are blended in the composition shown in Table 1, wet-mixed with a ball mill for 72 hours, dried, and then the mixed powder is formed into a throwaway chip shaped green compact in accordance with ISO standard CNMG120212. Cemented carbide substrates A to E are respectively formed by press molding and vacuum sintering the compact in a vacuum atmosphere of 10 ⁻³ torr at a predetermined temperature within the range of 1400 to 1460 ° C. for 1 hour. Manufactured.
Further, the carbide substrate E was subjected to carburizing treatment under a slow cooling condition after being kept at a temperature of 1400 ° C. for 1 hour in a CH ₄ gas atmosphere of 100 torr, and the carbon adhering to the surface of the carbide substrate after treatment. By removing Co by acid and barrel polishing, a Co-enriched zone having a maximum Co content of 15.9% by weight and a depth of 42 μm was formed on the surface of the substrate at a position of 11 μm from the surface.
In addition, in the above-mentioned cemented carbide substrate C, the Co substrate enriched zone having a maximum Co content of 10.5% by weight and a depth of 23 μm at the position of 17 μm from the surface on the surface of the cemented carbide substrate C, In the substrate D, a Co-enriched zone having a maximum Co content of 14.5% by weight and a depth of 29 μm is formed on the surface portion at a position of 22 μm from the surface, respectively. The Co-enriched zone was not formed, and the entire structure was uniform.
Further, Table 1 shows the internal hardness (Rockwell hardness A scale) of the above-mentioned carbide substrates A to E, respectively.
[0013]
Then, these carbide substrates A to E are processed and honed into a predetermined shape, and the surface thereof is subjected to Tables 3 and 4 under the conditions shown in Table 2 using a normal chemical vapor deposition apparatus. By forming a hard coating layer having the indicated target composition and target layer thickness (flank of the cutting edge), the l-TiCN layer among the constituent layers of the hard coating layer and the upper partial layer in which residual compressive stress exists and the residual tension The coated carbide tools 1 to 10 of the present invention constituted by the lower partial layer in which stress exists, and the conventional coated carbide tools 1 to 10 in which only the residual tensile stress exists in the l-TiCN layer were produced, respectively.
For the various coated carbide tools obtained as a result, the composition and average layer thickness of the constituent layers of the hard coating layer were measured using an electron probe microanalyzer and an optical microscope, and the residual stress of each constituent layer was measured. When calculated based on the measurement results of X-ray diffraction, all showed substantially the same composition and average layer thickness as the target composition and target layer thickness shown in Tables 3 and 4, and substantially the same as the target residual stress. Residual stress was shown.
[0014]
Next, for the present invention coated carbide tools 1-10 and conventional coated carbide tools 1-10,
Work material: JIS · SCM440 lengthwise equidistant 4 vertical grooved round bar,
Cutting speed: 200 m / min. ,
Incision: 4mm,
Feed: 0.3 mm / rev. ,
Cutting time: 10 minutes,
Dry intermittent high cutting test of alloy steel under the conditions of, and
Work material: JIS · SCr420H lengthwise equidistant 4 round bars with vertical grooves,
Cutting speed: 200 m / min. ,
Incision: 1.5mm,
Feed: 0.6 mm / rev. ,
Cutting time: 10 minutes,
The dry interrupted high feed cutting test was performed on the alloy steel under the above conditions, and the maximum flank wear width of the cutting edge was measured in any cutting test. The measurement results are shown in Table 5.
[0015]
[Table 1]

[0016]
[Table 2]

[0017]
[Table 3]

[0018]
[Table 4]

[0019]
[Table 5]

[0020]
【The invention's effect】
From the results shown in Tables 2 to 5, the coated carbide tool of the present invention in which the l-TiCN layer existing as a constituent layer in the hard coating layer is composed of an upper partial layer having a residual compressive stress and a lower partial layer having a residual tensile stress. Nos. 1 to 10 have no chipping or chipping even if the hard coating layer has excellent chipping resistance, especially when the intermittent cutting is performed under heavy cutting conditions such as high feed and high cutting. In the conventional coated cemented carbide tools 1 to 10, where only the residual tensile stress exists in the l-TiCN layer, the l-TiCN layer exhibits excellent wear resistance over a long period of time. In combination with the fact that the other constituent layers also have residual tensile stress, it is clear that intermittent cutting with high impact causes chipping, which leads to a service life in a relatively short time.
As described above, the coated carbide tool of the present invention exhibits excellent chipping resistance not only for continuous cutting and intermittent cutting of, for example, steel and cast iron, but also for intermittent heavy cutting with high impact. Since it shows excellent cutting performance over time, it can sufficiently satisfy the labor-saving and energy-saving of cutting, and further cost reduction.

Claims (1)

On the surface of the tungsten carbide base cemented carbide substrate,
(A) Titanium carbide layer, titanium nitride layer, titanium carbonitride layer, titanium carbonate layer, and charcoal, each having an average layer thickness of 0.1 to 3 μm and a granular crystal structure, and having residual tensile stress A Ti compound layer composed of one or more of the titanium nitride oxide layers;
(B) It has an average layer thickness of 2 to 10 μm, and consists of an upper partial layer in which residual compressive stress exists and a lower partial layer in which residual tensile stress exists, and the upper partial layer and the lower partial layer are continuous with each other A titanium carbonitride layer having a vertically elongated crystal structure and the upper partial layer having a layer thickness corresponding to 20 to 40% of the average layer thickness of 2 to 10 μm;
(C) an aluminum oxide layer having an average layer thickness of 0.5 to 5 μm and a granular crystal structure;
A surface-coated tungsten carbide-based cemented carbide cutting tool that exhibits excellent chipping resistance by intermittent heavy cutting, which is obtained by chemical vapor deposition of a hard coating layer composed of 3 to 15 μm in average thickness. .