JPH04294907A - Hard layer coated tungsten carbide group sintered hard alloy-made cutting tool - Google Patents

Abstract

PURPOSE:To provide a hard layer coated WC group sintered hard alloy-made cutting tool capable of exhibiting excellent performance in the case of using it for multiple cuttings such as high speed cutting, high speed feed and high speed notching. CONSTITUTION:In a hard layer coated WC group sintered hard alloy-made cutting tool, a WC group sintered hard alloy base substance contains free carbon, and the WC group sintered hard alloy base substance is also constituted of a surface layer part which is composed of the first hard dispersion phase forming component, a binding phase forming component and inevitable impurity and the internal part which is composed of the first hard dispersion phase forming component, the second hard dispersion phase forming component, a binding phase forming component and inevitable impurity, and the binding phase forming component of the WC group sintered hard alloy base substance forms density distribution such as having the maximum density in the internal part.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] This invention is based on hard layer coated tungsten carbide (hereinafter referred to as WC) that exhibits excellent performance when used as a cutting tool for high-speed cutting and heavy cutting such as high feed and high depth of cut. )-based cemented carbide cutting tools.

0002

[Prior Art] In general, a first hard dispersed phase forming component consisting of WC, one of metals from groups 4a, 5a, and 6a of the periodic table.
a second hard dispersed phase forming component consisting of a species or two or more carbides and/or carbonitrides; and one of the iron group metals.
On the surface of a WC-based cemented carbide substrate consisting of binder phase-forming components and unavoidable impurities, metals from groups 4a, 5a, and 6a of the periodic table, Al, and Si,
A single layer or a compound of one or more metal elements selected from the group consisting of carbon, nitrogen, boron, and oxygen, and one or more nonmetal elements selected from the group consisting of carbon, nitrogen, boron, and oxygen. 2. Description of the Related Art Hard layer-coated WC-based cemented carbide cutting tools are known, which are coated with a hard layer (hereinafter referred to as hard layer) composed of a plurality of layers. Since the service life of these hard layer-coated WC-based cemented carbide cutting tools is affected by the condition of the WC-based cemented carbide, various studies have been conducted on the condition of the WC-based cemented carbide. A patent application has also been filed for the same. For example, (A) "Japanese Journal of Metals, Vol. 45, No. 1, 1981, pages 95-99" describes commercially available WC, WC-30% TiC solid solution (
(hereinafter referred to as β), TiN and Co powders were used as raw material powders, and these raw material powders were mixed in a ball mill, molded in a press, and vacuum sintered to obtain WC-5.4% β-5. The 0% TiN-Co base is
The vertical axis is the normalized value of the X-ray intensity of W, Ti, and Co at the center of the substrate, and the horizontal axis is the depth from the substrate surface. The β-free layer (WC-Co layer) where the Co concentration peaks and the W,
This WC-
A hard layer-coated WC-based cemented carbide cutting tool is described in which the surface of a 5.4% β-5.0% TiN-Co based substrate is coated with a hard layer. Furthermore, (B) JP-A-61-3410
Publication No. 3 describes nitrides and carbonitrides of Ti and Ta.
W containing at least one species and one or more carbides of Ti and Ta
The C-based cemented carbide substrate is sintered by controlling the nitrogen partial pressure to 0.1 Torr or less, and after sintering is heated at 0.5 to 2.5° C./min. By cooling at a cooling rate of
Diffused into the C-Co layer, 200 to 600
% bond metal enrichment to increase hardness by 30-50% than the base material
A hard layer-coated WC-based cemented carbide cutting tool is described in which the surface of the WC-based cemented carbide substrate thus produced is coated with the above-mentioned hard layer.

0003

[Problem to be Solved by the Invention] However, in recent years, due to strong demands for labor saving and high efficiency, there has been a tendency to be forced to carry out heavy cutting under even more severe conditions than in the past. If heavy cutting is performed under harsher conditions using a hard layer-coated WC-based cemented carbide cutting tool, the base body will break in the early stages of use, resulting in an extremely short service life. Conventional hard layer coating WC described in (B)
When heavy cutting is performed under harsher conditions using cutting tools made of base cemented carbide, wear resistance, especially rake face wear resistance, is low.
It has reached the end of its life in a short period of time.

[0004] An analysis of the reasons for the short service life of these conventional hard layer-coated WC-based cemented carbide cutting tools revealed that (1) the conventional hard-layer-coated WC-based cemented carbide cutting tools described in (A) above; Regarding the lack of chipping resistance, the maximum peak value of the concentration of the bonding phase forming component is within a low range of 1.2 to 1.4 times the concentration of the bonding phase forming component in the center of the substrate.
2) Although the conventional hard layer-coated WC-based cemented carbide cutting tool described in (B) above has the bonding metal enriched by 200 to 600% from the inside of the base body, defects still occur, and these defects occur. Analysis of the cutting edge revealed that the origin of fracture was the WC.
- The reason is that the second hard dispersed phase has low wettability with the binder phase and does not have sufficient toughness, and that it generates heat. During heavy cutting with a large amount of material, the WC-Co layer on this surface tends to soften during cutting, resulting in extremely low wear resistance, especially on the rake face, and especially when the concentration of the components forming the binder phase reaches its maximum peak value on the outermost surface of the substrate. It was found that in cases where the adhesion area between the hard layer and the binder phase is large, the adhesion strength of the hard layer decreases and rake face wear grows even more rapidly.

[0005]

[Means for solving the problem] Therefore, the present inventors
As a result of research to solve the above-mentioned problems and obtain a hard layer-coated WC-based cemented carbide cutting tool that exhibits excellent performance even when used for heavy cutting under even harsher conditions, the first tool was developed. A surface portion (hereinafter referred to as surface layer portion) consisting of a hard dispersed phase forming component, a binder phase forming component and unavoidable impurities, and a first
Consisting of a hard dispersed phase forming component, a second hard dispersed phase forming component, a binder phase forming component, and a portion existing inside the surface layer portion (hereinafter referred to as inside) consisting of unavoidable impurities,
The binder phase forming component has a concentration distribution such that it has a maximum concentration in the interior of the WC containing free carbon.
A hard layer-coated WC-based cemented carbide cutting tool, which is made by coating the WC-based cemented carbide with a hard layer, simultaneously improves the originally contradictory properties of fracture resistance and wear resistance. They obtained the knowledge that it shows excellent performance even when used for heavy cutting under even harsher conditions.

The present invention was made based on this knowledge, and provides a WC-based cemented carbide substrate comprising a first hard dispersed phase forming component, a second hard dispersed phase forming component, a binder phase forming component and inevitable impurities. In the cutting tool, the WC-based cemented carbide substrate contains free carbon, and the WC-based cemented carbide substrate includes a first hard dispersed phase-forming component, a binder phase-forming component, and a hard layer. A surface layer portion consisting of unavoidable impurities, a first hard dispersed phase forming component, and a second hard dispersed phase forming component.
A hard layer comprising an interior composed of a hard dispersed phase-forming component, a binder phase-forming component, and unavoidable impurities, and having a concentration distribution such that the binder phase-forming component of the WC-based cemented carbide substrate has a maximum concentration in the interior. This is a cutting tool made of a coated WC-based cemented carbide.

The binder phase forming component of the WC-based cemented carbide substrate has a concentration distribution such that it has a maximum concentration in the interior, and is twice to 10 times the concentration of the binder phase forming component in the center of the substrate.
Preferably, it is within the range of 2 times. The reason for this is that if the maximum concentration is less than twice the concentration of the binder phase forming component in the center of the substrate, the toughness will not be sufficient during heavy cutting or interrupted cutting under severe conditions, which will cause defects. On the other hand, if the concentration of the binder phase forming components exceeds 10 times the concentration of the binder phase forming components in the inner center, wear and plastic deformation are likely to occur during heavy cutting under high feed conditions, which is undesirable. .

[0008] It is preferable that the minimum value of the hardness of the WC-based cemented carbide substrate exists within the above-mentioned interior.

Furthermore, the WC-based cemented carbide substrate of the hard layer-coated WC-based cemented carbide cutting tool of the present invention contains free carbon, and this free carbon increases crack propagation resistance and stabilizes toughness. Therefore, it is necessary for the WC-based cemented carbide base of the hard layer-coated WC-based cemented carbide cutting tool of the present invention used in heavy cutting. However, since the precipitation of free carbon on the surface layer of the cemented carbide substrate reduces the adhesion strength of the coating hard layer, it is better to have no free carbon precipitated on the surface layer of the WC-based cemented carbide substrate. preferable.

[0010] WC in which the binder phase forming component has the above concentration distribution
One of the methods for manufacturing a base cemented carbide substrate is the following manufacturing method.

First, a first hard dispersed phase forming component powder, a second hard dispersed phase forming component powder having a predetermined composition, and a binder phase forming component powder are prepared as raw material powders, and a predetermined amount of these powders are blended and mixed. to make a mixed powder, press-form this mixed powder to make a green compact, and sinter this green compact.
The temperature was maintained at 1380 to 1500°C for a predetermined time in a vacuum atmosphere, and the atmosphere was then switched from a vacuum atmosphere to a carburizing atmosphere while being maintained at this temperature, and the sintering was completed by maintaining this carburizing atmosphere for a predetermined time. Later, cooling rate: 0.3
Cool slowly at ~3.0°C/min.

[0012] When the green compact is sintered under such conditions and then slowly cooled, the surface layer portion consisting of the first hard dispersed phase forming component, the binder phase forming component and unavoidable impurities, as well as the first hard dispersed phase forming component and the first hard dispersed phase forming component, are formed. A WC-based cemented carbide substrate on which free carbon is precipitated is produced, which is composed of an interior consisting of two hard dispersed phase forming components, a binder phase forming component, and unavoidable impurities.

[0013] In the above method for producing a WC-based cemented carbide substrate, a surface portion containing no second hard phase forming component is obtained by holding the compact at 1380 to 1500°C for a predetermined time, and then placed in a carburizing atmosphere. By switching, the free carbon necessary for the WC-based cemented carbide substrate of this invention is precipitated, and by slow cooling at the following cooling rate: 0.3 to 3.0°C/min, the amount of components forming a binder phase inside the substrate is reduced. It is considered that a peak with the maximum is formed.

[0014] When a hard layer is formed on the surface of the WC-based cemented carbide substrate prepared in this manner by a normal chemical vapor deposition method, it exhibits excellent performance even in heavy cutting, which is even more severe than before. The hard layer-coated WC-based cemented carbide cutting tool of the present invention shown in FIG.

[0015]

EXAMPLES Next, the hard layer-coated WC-based cemented carbide cutting tool tip of the present invention and its manufacturing method will be specifically explained based on examples.

[0016] As raw material powder, average particle size: 1μ
m of (Ti0.32Ta0.33W0.35)C powder,
(Ti0.71W0.29) (C0.69N0.31)
Prepare powder, (Ta0.83Nb0.17)C powder, TiC powder, TiN powder, TaC powder, NbC powder, and furthermore, WC powder with average particle size: 3.5 μm, Co powder with average particle size: 1.2 μm. , and these raw material powders were blended so as to have the composition shown in Table 1, wet mixed in a ball mill for 72 hours, dried, and then heated at a pressure of 10 kg/mm2.
The powder compacts A to D having shapes conforming to SO standard SNMG120408 were press-molded. Then, these green compacts A
-D were sintered under the conditions shown in Table 2 to produce WC-based cemented carbide substrates (1) to (2). As shown in Table 2, the above-mentioned WC-based cemented carbide substrates ■ to Substrates (1) and (2) are sintered only in a vacuum atmosphere.

Regarding the WC-based cemented carbide substrates ① to ② thus obtained, the thickness of the surface layer mainly composed of WC and Co, the maximum Co concentration of the substrate: M, and the Co concentration of the center of the substrate: The values of N and M/N, and the distance from the substrate surface to the free carbon precipitation region were measured, and these measured values are shown in Table 3.

[0018]

[Table 1]

[0019]

[Table 2]

[0020]

[Table 3]

Furthermore, there are differences between the WC-based cemented carbide substrate used for producing the hard layer-coated WC-based cemented carbide chip of the present invention and the WC-based cemented carbide substrate used for producing the comparative hard-layer-coated WC-based cemented carbide chip. In order to clarify this, the Co amount and the second hard dispersed phase forming component were measured by X-ray diffraction on the polished surface parallel to the substrate surface of the WC-based cemented carbide substrates ■, ■, ■, ■, and ■. The amounts of Ti, Ta(Nb)](CN) and the micro-Vickers hardness measured using a 10° polished slope are shown in FIGS. 1 to 5.

From the results shown in FIGS. 1 to 5, it is clear that [Ti, Ta(Nb)] (CN), which is the second hard dispersed phase forming component,
does not exist in the basic surface layer, and the hard layer coating WC of the present invention
The WC-based cemented carbide substrates ■, ■, and ■ used for producing chips 1, 3, and 5 all have a Co content peak inside, whereas the comparative hard layer-coated WC-based It can be seen that in both of the WC-based cemented carbide substrates ① and ② used for producing the hard metal chips 3 and 4, the peak of the amount of Co exists in the surface layer portion.

After cleaning the surfaces of the above-mentioned WC-based cemented carbide substrates ① to ②, the compositions and average layer thicknesses shown in Table 4 were prepared using a normal chemical vapor deposition method with round honing of 0.06 mm. The present invention hard layer coated WC-based cemented carbide chips 1 to 5 and the comparative hard layer coated W
Chips 1 to 4 made of C-based cemented carbide were produced.

The following cutting tests were conducted on these various hard layer-coated WC-based cemented carbide chips.

Cutting test 1 The work material was SNCM439 (Brinell hardness: 290
) was prepared, and this square material was cut at a cutting speed of 100 m/min and a feed rate of 0.5 mm/rev. Intermittent cutting was performed under the conditions of , depth of cut: 4 mm, and the number of impacts until chipping occurred was measured, and the results are shown in Table 5.

Cutting test 2 As the work material, SCM440 (Brinell hardness: 250)
A round material is prepared, and this round material is cut at a cutting speed of 250 m/min and a feed rate of 0.5 mm/rev. , Depth of cut: 3mm, Cutting time: 15min. Continuous cutting was performed at high speed and high feed under the conditions of , and the rake face wear depth and flank wear amount of the insert were measured, and the results are shown in Table 5.
It was shown to.

Cutting Test 3 A round material of S55C (Brinell hardness: 320) was prepared as a work material, and this round material was cut at a cutting speed of 180 m/min and a feed rate of 1.0 mm/rev. , Depth of cut: 3mm, Cutting time: 2min. Continuous ultra-high feed cutting was carried out under the conditions of , and the amount of plastic deformation of the chip was measured, and the results are shown in Table 5.

[0028]

[Table 4]

[0029]

[Table 5]

[0030]

Effects of the Invention From the results shown in Tables 4 and 5, it can be seen that the hard layer-coated WC-based cemented carbide chips 1 of the present invention are obtained by coating WC-based cemented carbide substrates ■ to ■ with hard layers that meet the conditions of the present invention. ~5 is a comparative hard layer coated WC in which a hard layer is coated on a WC-based cemented carbide substrate ■~■ that does not meet the conditions of this invention.
Compared to the base cemented carbide tips 1 to 4, the number of impacts required for the tip to break during interrupted cutting is greater, so it has extremely superior fracture resistance, and its wear resistance and plastic deformation resistance are also approximately the same or It is clear that it is even better.

As mentioned above, the hard layer coating WC of the present invention
Cutting tools made of base cemented carbide have extremely excellent fracture resistance, wear resistance, and plastic deformation resistance, especially when used for heavy cutting, so they can demonstrate excellent performance over a long period of time in practical use. This brings about excellent industrial effects.

[Brief explanation of drawings]

FIG. 1: Co content and [T
i, Ta(Nb)](CN) concentration distribution curve and micro Vickers hardness distribution curve.

FIG. 2: Co content and [T
i, Ta(Nb)](CN) concentration distribution curve and micro Vickers hardness distribution curve.

FIG. 3: Co content and [T
i, Ta(Nb)](CN) concentration distribution curve and micro Vickers hardness distribution curve.

FIG. 4: Co content and [Ti
, Ta(Nb)](CN) concentration distribution curve, and micro-Vickers hardness distribution curve.

FIG. 5: Co content and [Ti
, Ta(Nb)](CN) concentration distribution curve, and micro-Vickers hardness distribution curve.

Claims (5)

[Claims] 1. A first hard dispersed phase forming component consisting of tungsten carbide, and a second hard dispersion consisting of one or more carbides and/or carbonitrides of metals from groups 4a, 5a, and 6a of the periodic table. 4a, 5a of the periodic table, and A compound of one or more metal elements selected from the group consisting of group 6a metals, Al, and Si, and one or more nonmetal elements selected from the group consisting of carbon, nitrogen, boron, and oxygen. In a cutting tool coated with a hard layer composed of one type of single layer or two or more types of multiple layers (hereinafter referred to as hard layer), the tungsten carbide-based cemented carbide base is coated with the first hard dispersed phase. a surface portion (hereinafter referred to as surface layer portion) consisting of a forming component, the above-mentioned binder phase forming component, and unavoidable impurities;
consisting of the first hard dispersed phase forming component, the second hard dispersed phase forming component, the binder phase forming component and unavoidable impurities, and a portion existing inside the surface layer portion (hereinafter referred to as the inside), Furthermore, the hard layer-coated tungsten carbide-based cemented carbide cutting tool is characterized in that the binder phase-forming component of the tungsten carbide-based cemented carbide base has a concentration distribution such that it has a maximum concentration in the interior. 2. The hard layer-coated tungsten carbide-based cemented carbide cutting tool according to claim 1, wherein the tungsten carbide-based cemented carbide substrate contains free carbon. 3. The hard layer-coated tungsten carbide-based cemented carbide according to claim 1 or 2, wherein the surface layer of the tungsten carbide-based cemented carbide base does not contain free carbon, and only the inside contains free carbon. manufactured cutting tools. 4. The maximum concentration of the binder phase forming component in the interior is 2 to 10 times the concentration of the binder phase forming component in the center of the tungsten carbide-based cemented carbide base. The hard layer-coated tungsten carbide-based cemented carbide cutting tool according to 2 or 3. 5. The hard layer coated tungsten carbide based cemented carbide according to claim 1, wherein the minimum value of hardness of the tungsten carbide based cemented carbide base body is present in the interior of the hard layer coated tungsten carbide based cemented carbide. Alloy cutting tool.