KR100457658B1 - Method to improve wear resistance and toughness of coated cutting tools - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coated cemented carbide tool, and to coating a hard ceramic on a cutting tool such as cemented carbide to be laminated by medium and high temperature chemical vapor deposition to improve the wear resistance and toughness of the coated cemented carbide cutting tool. It is about manufacture.

According to the present invention, a tungsten carbide-based cemented carbide substrate has an average film thickness of 0.1 to 5 µm and a Ti compound layer such as a TiC layer, a TiN layer, a TiCN layer, and a grain thickness and columnar growth crystal structure of 2 to 15 µm. In the surface-coated cemented carbide cutting tool formed by chemically and physically depositing a crystal coating layer composed of a TiBCN layer of granular crystal structure, an average thickness of 0.5 to 8 µm and an Al 2 O 3 layer of granular crystal structure, as an average layer of 3 to 25 µm. The TiBCN layer of the columnar growth crystallographic structure and granular crystallographic structure constituting the hard coat layer is expressed _by the composition formula of the upper and lower portions thereof: TiBC _x N _Y (X + Y ≒ 1, B: 0.01 to 1% by volume). At its own expense, the upper surface is Y: 0.05-0.35, B: 0.08-1% by volume. The lower surface is Y: 0.65-0.95, B: 0-0.08% by volume. Cemented carbide consisting of a gradient gradient TiBCN layer in which the concentrations of C and N are stepless or stepwise Cutting tools are provided.

Description

Coated cemented carbide cutting tool with improved wear resistance and toughness {Method to improve wear resistance and toughness of coated cutting tools}

The present invention has excellent chipping resistance and abrasion resistance of Titanium-Borocarbonitride (hereinafter referred to as TiBCN) of the columnar crystal structure or granular crystal structure constituting the hard coat layer, and particularly, the high speed and high speed of intermittent cutting such as steel or cast iron Even if the cutting is performed under heavy cutting conditions such as cutting and high feed, the cutting tool made of surface-coated cemented carbide (hereinafter referred to as cemented carbide tool) exhibits no chipping (micro-breakage) during pickling and shows excellent cutting performance without change for a long time. It is about.

Generally, a layer of titanium carbide (hereinafter referred to as TiC) and titanium nitride (hereinafter referred to as " TiC ") having an average thickness of 0.1 to 5 [mu] m and a granular crystal structure on the surface of the tungsten carbide carbide substrate (hereinafter referred to as a cemented carbide). , TiN) layer, titanium carbonitride (hereinafter referred to as TiCN) layer, titanium oxide (hereinafter referred to as TiCO) layer, titanium nitride (hereinafter referred to as TiNO) layer and titanium carbonitride (hereinafter referred to as TiCNO) layer Aluminum oxide having a Ti compound composed of one or two or more kinds above, (b) an MT-TiCN layer having an average film thickness of 2 to 15 µm, and (c) an average thickness and granular crystal structure of 0.5 to 8 µm (hereinafter Al). Coated carbide tools consisting of chemical vapor deposition and / or physical vapor deposition with a total average thickness of 3 to 25 μm in a hard coat layer composed of ₂ O ₃ layers are known, and this coated carbide tool is used for continuous cutting of steel or cast iron. It is also known to be used for interrupted cutting. In general, as the Al ₂ O ₃ layer constituting the hard coat layer of the coated carbide tool, one having an α-type crystal structure or a κ-type crystal structure is widely used. Moreover, the MT-TiCN layer is a matter known by, for example, Japanese Patent Laid-Open No. 6-8015, Japanese Patent Laid-Open No. 7-328808, and the like. In these chemical vapor deposition apparatuses, chemical vapor deposition is carried out using a mixed gas containing organic carbonitride as a reaction gas in a medium temperature region of 700 to 950 ° C.

On the other hand, the recent cutting process has a high speed and tends to make heavy cutting such as high cutting, high feed, etc., but in the conventional coated carbide tool, the MT-TiCN constituting such a hard coated layer has a relatively good toughness and thus high-speed cutting. No chipping, no chipping, and excellent cutting performance. However, if cutting conditions are severe, intermittent cutting at high speed, and high cutting, high feed, and heavy cutting conditions have not yet been achieved, It is not possible to prevent chipping at pickling, and the tool life occurs in a relatively short time.

In order to solve this problem, Japanese Patent Laid-Open No. 2000-158204 focuses on TiCN constituting the hard coat layer of the conventional coated carbide tool, and improves its toughness. For example, by changing the content of CH ₃ CN and / or CH ₄ steplessly or stepwise, the concentration gradient is given to the lower C component with higher C component from the lower surface to the upper surface of the MT-TiCN layer. When the gradient is expressed by the surface portion and the lower surface portion by the composition formula: TIC _1-x N _x , the technique has been disclosed in which the upper surface portion satisfies X: 0.05-0.35, and the lower surface portion satisfies X: 0.65-0.95. In this case (in this case, C and N are gradient concentration gradients, and C and N concentrations change steplessly or stepwise). The resulting TiCN layer (hereinafter referred to as concentration gradient TiCN) is C from the lower surface to the upper surface. Compared with the conventional TiCN layer having no concentration gradient of N, excellent toughness is provided first, and thus, the coated carbide tool in which the concentration gradient TiCN layer constitutes a hard coating layer has the hard coating layer itself according to the concentration gradient TiCN layer. Once it has excellent toughness, it is known that intermittent cutting is performed by heavy cutting at high speed while exerts excellent cutting performance without occurrence of chipping on edges even under extreme cutting conditions.

However, various cutting conditions require the cutting tool to be suitable for each cutting condition. For example, in the case of severe interrupted cutting, excellent toughness and adhesion between thin films are required, while the wear mechanism is tough when frictional wear is dominant. Rather than improving wear resistance. Therefore, it is necessary to simultaneously improve chipping resistance and wear resistance in cutting tools, but it is very difficult to improve both endurance and wear resistance of tools at the same time, and commercially produced cutting tools should be optimized according to the wear mechanism of each grade.

The present invention is to solve the above-mentioned problems, to optimize the TiBC _x N _Y (X + Y ≒ 1, B: 0.01 ~ 1% by volume) coating conditions to improve the wear resistance and toughness at the same time to extend the tool life The purpose is to provide a cutting tool that can be used.

1 is a graph for the micro hardness (Micro Hardness) according to the addition of MT-TiBCN boron,

2 is a wear resistance comparison test graph, and

Figure 3 is a graph showing the increase in wear resistance and toughness by the concentration gradient TiBC _X N _Y (X + Y ≒ 1, B: 0.01 to 1% by volume) according to the present invention.

In order to achieve the above object, according to the present invention, in manufacturing a coated cemented carbide tool, a surface coated cemented carbide tool comprising sequentially coating a titanium chemical and a ceramic layer using mesophilic chemical vapor deposition on the surface of a tool base material is provided. do.

Here, (a) TiC layer, TiN layer, TiCN layer, TiCO layer, TiNO layer, or TiCNO layer having one or more kinds of (A) average film thickness and granular crystal structure on the surface of the superhard gas. Ti compound layer, (b) TiBC _x N _Y (X + Y ≒ 1, B: 0.01 to 1% by volume) layer after average thickness of 2 to 15 µm and (c) average thickness and granular crystal structure of 0.5 to 8 µm In the coated cemented carbide tool comprising a hard coat layer composed of an aluminum oxide layer (hereinafter referred to as Al ₂ O ₃ ) having chemical vapor deposition and / or physical vapor deposition after a total average thickness of 3 to 25 μm, the TiBC constituting the hard coat layer _x N _Y (X + Y ≒ 1, B: 0.01 ~ 1% by volume) When the layer is expressed _by the composition formula of its upper and lower parts: TiBC _x N _Y (X + Y ≒ 1, B: 0.01 ~ 1% by volume) In terms of atomic ratio, the upper surface portion is Y: 0.05-0.35, B: 0.08-1 volume%, and the lower surface portion is Y: 0.65-0.95, B: 0-0.08 volume%, and the film thickness concentration gradient of B, C and N is And concentration stages in which B, C and N concentrations change steplessly _{TiBC x N Y (X + Y} ≒ 1, B: 0.01 ~ 1vol%) it is preferable to configure.

Composition formula of the concentration gradient TiBC _x N _Y (X + Y # 1, B: 0.01 to 1% by volume) constituting the hard coat layer of the coated carbide tool of the present invention: TiBC _x N _Y (X + Y # 1, B: 0.01 to 1% by volume), the Y value of the upper surface portion is 0.05 to 0.35, preferably 0.15 to 0.30, the Y value of the lower surface portion is 0.65 to 0.95, preferably 0.7 to 0.85. In other words, if the Y value of the lower surface portion is less than 0.65, the concentration gradient of C and N in the rear film direction becomes small, so that the toughness improvement cannot be obtained. As a result, it is impossible to secure the excellent chipping resistance as desired for the hard coat layer. On the other hand, if the Y value of the upper surface portion is less than 0.05 or if the Y value of the lower surface portion exceeds 0.95, the concentration gradient of C and N becomes too large to prevent the deterioration of toughness, and thus the chipping is likely to occur. In addition, the B value of the upper surface portion is 0.08 to 1% by volume, preferably 0.08 to 0.5 volume%, and the B value of the lower surface portion is 0 to 0.08% by volume, preferably 0 to 0.05% by volume. When the volume% is exceeded, the film adversely affects the thin film, resulting in a significant decrease in hardness. The desired wear resistance improvement cannot be obtained. When the lower B value is 0.05 volume% or more, the concentration gradient of B becomes small, which adversely affects toughness. This is because chipping resistance is lowered. Figure 1 is a graph for the microhardness (Micro Hardness) according to the addition of boron in MT-TiBCN. The addition of a small amount of boron shows a rapid increase in hardness of MT-TiBCN in some ranges.

In addition, the Ti compound layer constituting the hard coat layer has an effect of improving the adhesion between the thin films between the constituent layers. Therefore, when the average thickness is less than 0.1 µm, it is impossible to ensure the good inter-film adhesion between the thin films. When the average film thickness exceeds 5 mu m, the wear progress of the hard coat layer is promoted, so the average film thickness is preferably 0.1 to 5 mu m. In addition, the Al ₂ O ₃ layer has the effect of improving the wear resistance of the hard coat layer, but if the average thickness is less than 0.5 μm, it is impossible to secure the desired excellent wear resistance. On the other hand, if the average thickness exceeds 8 μm, chipping is likely to occur. Therefore, it is preferable to make the average film thickness into 0.5-8 micrometers. In addition, as described above, the concentration gradient TiBC _x N _Y (X + Y ≒ 1, B: 0.01 to 1 vol%) layer has the effect of simultaneously improving the chipping resistance and the abrasion resistance of the hard coat layer. The improvement effect desired for the chipping resistance and the abrasion resistance cannot be obtained. On the other hand, if the average thickness exceeds 15 µm, the wear resistance decreases rapidly, so the average thickness is set to 2 to 15 µm. If the average thickness of the hard coat layer is set to 3 to 25 µm, the desired abrasion resistance is not secured if the average thickness is less than 3 µm. On the other hand, if the average thickness exceeds 25 µm, defects or chippings are more likely to occur in pickling. Therefore, the total average film thickness is preferably 25 µm or less.

The base material used in the present invention can be used for other cemented carbides composed of WC, TaC, TiC, Co, etc., as long as the base material can be coated on the surface of the base material.

Therefore, the base material composition is not limited to any one.

Hereinafter, the present invention will be described through preferred embodiments.

Cemented carbide base material of CNMG120408 for the lathe cutting tool was composed of 8.3wt% Co, 3.5wt% TaC, and the rest, WC and WTiCN. The initial and outer lamination coatings were omitted and only TiBC _x N _Y (X + Y ≒ 1, B: 0.01 to 1% by volume) coating conditions were shown in the table.

Example

TABLE 1

TiB _x C _y N _z (x + y + z = 1) Formation Conditions Temperature (℃) Torr Reaction gas composition (% by volume) H ₂ TiCl ₄ CH ₃ CN BCl ₃ Existing Coating Condition One 800 50 balance 5 0.5 0.45 2 800 75 balance 4 One 2.0 3 880 80 balance 3 2 0.08 4 880 130 balance 10 5 0.01 5 900 100 balance 5 4 3.5 6 850 200 balance 10 3 1.0 7 880 80 balance 2 2 0.4 8 950 50 balance One 0.8 0.7

TABLE 2

TiBC _x N _y (X + Y ≒ 1, B: 0.001 to 1% by volume) Temperature (℃) Torr Reaction gas composition (% by volume) H ₂ TiCl ₄ CH ₃ CN BCl ₃ Invention coating condition One 900 90 balance 2 Top 0.2 Top 0.3 if 0.1 if 0.01 2 850 85 balance 2 Top 0.8 Top 0.5 if 0.1 if 0.02 3 900 100 balance 2 Top 1.5 Top 0.2 if 0.2 if 0.03 4 800 70 balance 2 Top 1.0 Top 1.0 if 0.1 if 0.08 5 950 90 balance 2 Top 1.0 Top 0.08 if 0.4 if 0.01 6 880 85 balance 2 Top 1.5 Top 0.25 if 1.0 if 0.04 7 800 80 balance 2 Top 2.0 Top 0.18 if 1.0 if 0.02 8 900 75 balance 2 Top 4.0 Top 0.8 if 0.5 if 0.03

The coated samples were subjected to abrasion and endurance tests. Performance comparisons were tested by general turning operations.

[Abrasion Resistance Test]

The criterion for tool life was 0.2mm wear based on the tool life, based on the flank wear caused by cutting the workpiece.

The graph of FIG. 2 shows a result of abrasion resistance comparison test. As can be seen from the graph, specimen B shows improved abrasion resistance compared to A and a conventional sample. Specimen A is assumed to be boron-free (Boron) concentration gradient MT-TiCN and specimen B is boron-added TiBC _x N _Y (X + Y ≒ 1, B: 0.01 to 1% by volume).

As shown in the graph of micro-hardness according to the MT-TiBCN boron addition of Figure 1 shows that the hardness of MT-TiBCN increases rapidly within a certain range of boron addition by a small amount of boron addition This increase in hardness can be seen to improve wear resistance.

The following shows the wear-resistant cutting test conditions, and the test was conducted twice under the same conditions to increase reliability.

-> Wear Resistance Cutting Test Condition

Cutting condition: V = 200m / min, f = 0.25mm / rev, d = 2.0mm, dry cutting

Workpiece: SCM440 (Diameter: 300mm, Length: 600mm)

[Impact Resistance Test]

The impact resistance test was carried out by cutting cylindrical grooves with four grooves in the longitudinal direction to severely impact the tool.

In general, cutting tools have a general tendency that the toughness decreases when the wear resistance is improved, but at the same time, the wear resistance and the toughness are simultaneously controlled by the concentration gradient TiBC _x N _Y (X + Y ≒ 1, B: 0.01 ~ 1% by volume). The results were improved. (See Figure 3)

-> Impact resistant cutting test conditions

Cutting condition: V = 200m / min, f = 0.45mm / rev, d = 2.0mm, dry cutting

Workpiece: SCM440 (Diameter: 300mm, Length: 600mm) 4-hole Groove Outer Diameter Machining

As described above, according to the present invention, the TiBCN layer of the columnar growth crystallographic structure and the granular crystallographic structure constituting the hard coat layer is the upper and lower compositional formulas, and the concentration of B, C, and N in the film direction is also increased. The cemented carbide cutting tool with abrasion resistance and impact resistance significantly improved compared to the conventional one by constructing a TiBCN layer of stepless or stepwise concentration gradient.

Although the present invention has been described above through the preferred embodiments of the present invention, those skilled in the art will understand that various modifications and changes can be made within the scope of the present invention as set forth in the claims below.

Claims (1)

(Correction) 1 or 2 types of titanium carbide layer, titanium carbonitride layer, titanium oxide layer, titanium nitrate layer or titanium carbonitride layer having an average film thickness and granular crystal structure of 0.1 to 5 탆 on the tungsten carbide carbide surface The hard coat layer comprised of the compound layer formed from the above, the TiBCN layer which has columnar crystal structure and granular crystal structure of 2-15 micrometers, and the aluminum oxide layer which has the average thickness and granular crystal structure of 0.5-8 micrometers is 3 In the surface coated cemented carbide cutting tool subjected to chemical vapor deposition and / or physical vapor deposition with a total average thickness of ˜25 μm, The TiBCN layer of columnar crystal structure and granular crystal structure constituting the hard coat layer is expressed _by the composition formula of the upper and lower portions thereof: TiBC _x N _Y (X + Y ≒ 1, B: 0.08 to 0.5 % by volume). At its own expense, the upper surface is Y: 0.15 to 0.30 , B: 0.08 to 0.5 % by volume. The lower surface is Y: 0.7 to 0.85 , B: 0.001 to 0.05 % by volume. The surface-coated cemented carbide tool comprising a concentration gradient TiBCN layer in which the concentrations of C and N are changed steplessly or stepwise.