JP3265885B2 - Surface coated tungsten carbide based cemented carbide cutting tool with excellent interlayer adhesion with hard coating layer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a hard coating layer having excellent interlayer adhesion and, therefore, exhibits excellent cutting performance over a long period of time when used for cutting, for example, mild steel having a large cutting resistance. The present invention relates to a surface-coated tungsten carbide based cemented carbide cutting tool (hereinafter referred to as a coated cemented carbide cutting tool).

[0002]

2. Description of the Related Art Conventionally, as described in, for example, JP-B-57-1585 and JP-B-59-52703, a tungsten carbide-based cemented carbide substrate as a whole, For example, a tungsten carbide-based cemented carbide substrate having a surface portion having a relatively high content of Co or the like as compared with the inside of the substrate, that is, a tungsten carbide-based cemented carbide substrate having a binder phase enriched zone on the surface portion (hereinafter, collectively referred to as a cemented carbide substrate) ), A first layer of titanium nitride (hereinafter referred to as TiN), a second layer of titanium carbonitride (hereinafter referred to as TiCN), and aluminum oxide ( A hard coating layer composed of a third layer of Al ₂ O ₃ ) and, if necessary, a fourth layer of TiN,
It is well known that coated carbide cutting tools formed with an average layer thickness of m are mainly used for cutting or milling alloy steel or cast iron.

[0003]

On the other hand, in recent years, the use of FA in cutting machines has been remarkable, and in conjunction with the demand for labor saving in cutting work, cutting tools tend to be required to be versatile. For carbide cutting tools, there is no problem if this is used for cutting alloy steel or cast iron, etc.
Particularly when used for cutting mild steel with high cutting resistance, the interlayer adhesion of the hard coating layer is not sufficient, so that the hard coating layer is liable to delamination and chipping, which causes a relatively short service life. At present.

[0004]

Means for Solving the Problems Accordingly, the present inventors have
From the above-mentioned viewpoint, the above-mentioned conventional coated carbide cutting tool was focused on, and a study was conducted to improve the interlayer adhesion of the hard coating layer constituting the cutting tool. In the hard coating layer constituting the cutting tool, the adhesion of the first TiN layer to the cemented carbide substrate is extremely high, but the second TiCN layer and the first TiN layer
A third TiN layer and a third Al ₂ O ₃ layer,
The adhesion between the Al ₂ O ₃ layer of the layer and the TiN layer of the fourth layer is insufficient, so that delamination and chipping tend to occur. (B) In the hard coating layer constituting the conventional coated carbide cutting tool, the first TiN layer and the second TiCN layer
Layer, further a fourth layer TiN layer that are formed as needed has the both granular crystal structure, although the third layer the Al ₂ O ₃ layer of with alpha-type crystal structure, TiCN layer of the second layer Is a vertically elongated crystal structure, and the third layer Al ₂
A structure in which the O ₃ layer is mainly composed of a kappa-type crystal, preferably a mixed structure in which the kappa-type crystal occupies 50% by volume or more and the remainder is composed of an alpha-type crystal, more preferably a structure substantially composed of a kappa-type crystal. Then, the adhesion of the first TiN layer and the third Al ₂ O ₃ layer to the _second TiCN layer and the adhesion of the fourth TiN layer to the _third Al ₂ O ₃ layer are remarkable. To improve. (C) After forming the second TiCN layer, 10 to 100 to
rr in a hydrogen atmosphere, temperature: 1 to 5 at 850 to 1100 ° C
When the heat treatment is performed under the condition of holding time, at least W and Co components among the components constituting the cemented carbide substrate diffuse and move to the grain boundaries of the first and second layers due to the capillary phenomenon. At least W and Co are contained in the grain boundaries, and as a result, the interlayer adhesion is further improved in combination with the improvement of the intercrystalline adhesion. The research results shown in (a) to (c) above were obtained.

The present invention has been made on the basis of the above research results, and includes a first TiN layer, a second TiCN layer, and a third Al ₂ O layer on the surface of a cemented carbide substrate. _Three
(A) the first layer and the fourth layer, wherein the coated hard cutting tool is formed by forming a hard coating layer composed of a layer and, if necessary, a fourth TiN layer with an average layer thickness of 3 to 30 μm. The layer has a granular crystal structure, the second layer has a vertically-grown crystal structure, the third layer has a structure mainly composed of a copper-type crystal, and (b) a crystal grain boundary of the first layer and the second layer. The coated cemented carbide cutting tool containing at least W and Co among the constituents of the cemented carbide substrate, and having the above-mentioned (a) and (b) to have excellent interlayer adhesion to the hard coating layer. It has features.

[0006] The TiCN layer having a vertically elongated crystal structure of the second layer of the hard coating layer constituting the coated carbide cutting tool of the present invention is, for example, as described in JP-A-6-8010. A) TiCl ₄ : 1 to ₄ in terms of reaction gas composition and volume%
_{%, CH 3 CN: 0.1~5%} , N 2: 0~35
%, H ₂ : remaining, (a) Reaction temperature: 850 to 950 ° C., (c) Atmospheric pressure: 30 to 200 torr. On the other hand, a TiCN layer having a granular crystal structure usually has (a) TiCl ₄ : 1 to 5
_{%, CH 4: 2~7%,} N 2: 15~30%,
H ₂ : remaining, (a) Reaction temperature: 950 to 1050 ° C., (c) Atmospheric pressure: 30 to 200 torr. Further, the Al ₂ O ₃ layer having a structure mainly composed of a copper-type crystal has the following characteristics.
0 minutes, AlCl ₃ : 1 to 20%, H ₂ : remaining, or AlCl ₃ : 1 to 20%, HCl: 1 to 20% and / or H ₂ S: 0.05 to 5%, H ₂ : After that, it is assumed that AlCl ₃ : 1 to 20%, CO ₂ : 0.
5~30%, H _2: remainder, or,, AlCl _3: 1~2
_{0%, CO 2: 0.5~30%} , HCl: 1~20
% And / or H ₂ S: 0.05 to 5%, H ₂ : remaining, (a) reaction temperature: 850 to 1000 ° C., (c) atmosphere pressure: 30 to 200 torr.

[0007] The hard coating layer constituting the coated cemented carbide cutting tool of the present invention is formed on the surface of the cemented carbide substrate by the chemical vapor deposition method and / or the physical vapor deposition method under the above-mentioned conditions and ordinary conditions. First, a first TiN layer is deposited, and then a second TiN layer is deposited.
The first layer is formed by sequentially depositing a TiCN layer as a layer, an Al ₂ O ₃ layer as a _third layer, and a TiN layer as a fourth layer, if necessary. In some cases, the C component in the cemented carbide substrate diffuses and forms a solid solution in the TiN layer. In this case, a part or the whole of the first layer becomes TiCN.

Further, the average thickness of the hard coating layer is 3 to
The reason why the thickness is set to 30 μm is that if the average layer thickness is less than 3 μm, it is not possible to secure desired excellent wear resistance, while if the average layer thickness exceeds 30 μm, the chipping resistance sharply decreases. The average thickness of the first TiN layer is 0.1 to 5 μm, that of the second TiCN layer is 3 to 20 μm, and that of the third layer is Al ₂ O _3.
The layer is 0.1 to 15 μm, and the fourth TiN layer is 0.1 μm.
It is desirable that the average layer thickness be 1 to 5 μm.

[0009]

Next, the coated carbide cutting tool of the present invention will be described in detail with reference to examples. As raw material powder, medium-grain WC powder having an average particle diameter of 3 μm, coarse WC powder having an average particle diameter of 5 μm
Powder, 1.5 μm (Ti, W) C (weight ratio, same hereafter, TiC / WC = 30/70) powder, 1.2 μm
(Ti, W) CN (TiC / TiN / WC = 24/2)
0/56) A powder and a Co powder of 1.2 μm were prepared, and these raw material powders were blended in the composition shown in Table 1, wet-mixed in a ball mill for 72 hours, dried, and dried.
SO ・ CNMG120408 (for cemented carbide substrates A to D)
And SEEN42AFTN1 (for cemented carbide substrate E)
Each of the compacts was press-molded into a green compact having the shape specified in Table 1, and the green compact was vacuum-sintered under the conditions shown in Table 1 to produce cemented carbide substrates A to E, respectively. Further, the cemented carbide substrate B was maintained at a temperature of 1400 ° C. for 1 hour in a CH ₄ gas atmosphere at 100 torr, and then subjected to slow cooling carburization. After the treatment, carbon and Co adhering to the substrate surface were removed. By removing with acid and barrel polishing, 1
Maximum Co content at 0 μm: 15% by weight, depth: 4
A 0 μm Co-enriched zone was formed on the substrate surface. Also,
In the cemented carbide substrates A and D, a Co-enriched zone having a maximum Co content of 9% by weight and a depth of 20 μm was formed on the surface portion at a position of 15 μm from the surface while being sintered, The remaining cemented carbide substrates C and E had no formation of the Co-enriched zone and had an overall homogeneous structure. Further, Table 1 shows the internal hardness (Rockwell hardness A scale) of each of the cemented carbide substrates A to E.

Next, the surfaces of these cemented carbide substrates A to E are honed, and the compositions and the compositions shown in Tables 3 to 6 are obtained by using an ordinary chemical vapor deposition apparatus under the conditions shown in Table 2. A hard coating layer having a crystal structure and an average layer thickness is formed. During the formation, the second layer is subjected to a heat treatment in a hydrogen atmosphere of 35 torr at a temperature of 1050 ° C. for a predetermined time within a range of 1 to 5 hours. Thus, the coated carbide cutting tools 1 to 7 of the present invention were manufactured, and the coated carbide cutting tools 1 to 7 of the related art were respectively manufactured without performing the heat treatment. As to the first and second hard coating layers constituting the various coated carbide cutting tools obtained as a result, the respective layers are observed with a transmission electron microscope (TEM) to identify five grain boundaries as appropriate for each layer. Then, the W and Co contents of this specific grain boundary were quantitatively analyzed by an energy dispersive X-ray measuring apparatus. These results are shown in Tables 3 to 6 as average values.

Further, the coated carbide cutting tools of the present invention 1 to 5
For the conventional coated carbide cutting tools 1 to 5, work material: mild steel round bar, cutting speed: 335 m / min., Feed: 0.26 mm / rev., Depth of cut: 2 mm, cutting time: 20 minutes. And continuous cutting test of mild steel, and work material: square bar of mild steel, cutting speed: 305 m / min., Feed: 0.26 mm / rev., Depth of cut: 1.5 mm, cutting time: 25 minutes. In each cutting test, the flank wear width of the cutting edge was measured. Tables 4 and 6 show the measurement results. Further, regarding the coated carbide cutting tools 6 and 7 of the present invention and the conventional coated carbide cutting tools 6 and 7, a work material: a square bar of mild steel, a cutting speed: 305 m / min., A feed: 0.36 mm / tooth, and a cutting depth : 2.5 mm, Cutting time: 30 minutes, Mild steel was milled, and the flank wear width of the cutting edge was measured. The measurement results are also shown in Tables 4 and 6.

[0012]

[Table 1]

[0013]

[Table 2]

[0014]

[Table 3]

[0015]

[Table 4]

[0016]

[Table 5]

[0017]

[Table 6]

[0018]

According to the results shown in Tables 3 to 6, the coated carbide cutting tools 1 to 7 according to the present invention show that delamination or chipping of the hard coating layer occurs in the hard coating layer despite the cutting of mild steel having high cutting resistance. While showing no abrasion and excellent wear resistance,
Conventionally, the coated carbide cutting tools 1 to 7 clearly show that the interlayer adhesion in the hard coating layer is insufficient, and delamination and chipping occur in the cutting of mild steel, resulting in a relatively short service life. is there. As described above, the coated cemented carbide cutting tool according to the present invention has a hard coating layer having excellent interlayer adhesion, so that it can cut not only alloy steel and cast iron, but also mild steel having a high cutting resistance. Even when used for cutting, excellent cutting performance is exhibited over a long period of time.

────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI C23C 16/40 C23C 16/40 (56) References JP-A-6-8010 (JP, A) JP-A 1-252306 (JP) , A) JP-A-63-195268 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B23B 27/14 B23P 15/28 C23C 16/30-16/40 C23C 14/06

Claims (2)

(57) [Claims] 1. A first layer of titanium nitride, titanium carbonitride on a surface of a generally homogeneous tungsten carbide based cemented carbide substrate or a tungsten carbide based cemented carbide substrate having a binder phase enriched zone on its surface. And a hard coating layer comprising an aluminum oxide third layer having an average layer thickness of 3 to 30 μm. Is a granular crystal structure, the second layer is a vertically elongated crystal structure, the third layer is a structure mainly composed of copper type crystals, and (b) the crystal grain boundaries of the first layer and the second layer are: A cutting tool made of a surface-coated tungsten carbide-based cemented carbide having a hard coating layer having excellent interlayer adhesion, wherein at least W and Co among components constituting the substrate are contained by diffusion. 2. A first layer of titanium nitride, titanium carbonitride on a surface of a tungsten carbide based cemented carbide substrate which is entirely homogeneous, or a tungsten carbide based cemented carbide substrate having a binder phase enriched zone on its surface. And a hard coating layer comprising a third layer of aluminum oxide and a fourth layer of titanium nitride with an average layer thickness of 3 to 30 μm. (A) the first layer and the fourth layer have a granular crystal structure, the second layer has a vertically-grown crystal structure, and the third layer has a structure mainly composed of copper-type crystals. the grain boundary layer and the second layer, the surface coating tungsten carbide group having at least W and Co may contain diffusing interlayer adhesion with excellent is hard layer, wherein one of the components constituting the base Super hard alloy Gold cutting tool.