JPS5952703B2 - Surface coated cemented carbide parts - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a cutting tool that has excellent wear resistance and plastic deformation resistance, and is rich in toughness, and is particularly effective in the area of cutting where heavy loads are applied when used as a cutting tool. The present invention relates to a surface-coated cemented carbide member that exhibits excellent performance.

Conventionally, for example, carbides, nitrides, and oxides of metals of groups 4a, 5a, and 6a of the periodic table, Al, Si, and B have been coated on the surface of a tungsten carbide (hereinafter referred to as WC)-based cemented carbide member. Surface-coated cemented carbide members in which a coating layer consisting of a single layer or a multilayer of two or more of solid solutions of two or more of these solid solutions are well known, and some of them include is widely used in practice.

However, in the above-mentioned conventional surface-coated cemented carbide member, although the coating layer is harder than the cemented carbide base, it is brittle, so the stress is much lower than in the case of only the cemented carbide base 5. Cracks are likely to occur in the coating layer, and when a chemical vapor deposition method, which is widely used as a surface coating method, is applied to form a coating layer on the surface of a cemented carbide substrate, a temperature of 1000 to 1100°C is required. Since the vapor deposition process is carried out at high temperatures, cracks may occur as tensile stress is applied to the coating layer due to the difference in thermal expansion coefficient between the cemented carbide substrate and the coating layer during the cooling process. Once a crack occurs in the coating layer, for example, when used as a cutting tool, the crack rapidly propagates inside the cemented carbide base because cutting stress is concentrated at the tip of the crack. Eventually, there was a problem in that the cutting edge was damaged.

Therefore, it has been considered to prevent the propagation of cracks by making the composition of the cemented carbide base in the conventional surface-coated cemented carbide member rich in toughness. On the other hand, if the surface-coated cemented carbide parts are used in a heavy-load cutting area, it is unavoidable that the plastic deformation resistance and wear resistance deteriorate. When used in this case, there was a problem in that, although the coating layer was hardly worn, the cemented carbide base material underwent plastic deformation, making it impossible to obtain the desired performance.

From the above-mentioned viewpoints, the present inventors have solved the problems of the conventional surface-coated cemented carbide members, and achieved excellent wear resistance and plastic deformation resistance. As a result of conducting research to obtain a surface-coated cemented carbide member with high toughness, we found that (a) the surface of the cemented carbide base was coated with WC monoiron group material, which is softer and more tough than the inside of the cemented carbide base; A softened layer made of a metal alloy (hereinafter referred to as a "surface softened layer") suppresses propagation of cracks from the coating layer and significantly improves toughness.

(b) The above effects of the surface softening layer are closely related to the amount of binder phase in the cemented carbide base, and the amount of binder phase constituting the surface softening layer is the amount of binder phase in the cemented carbide base. If the amount is increased compared to , the effect will be amplified.

(C) When nitrogen is dissolved as a solid solution in the binder phase of the surface softening layer, the surface softening layer is strengthened; As a result, the plastic deformation resistance of the member is improved.

The findings shown in (a) to (c) above were obtained.

This invention was made based on the above findings, and includes metals from groups 4a, 5a, and 6a of the periodic table, Al. A coating layer with a thickness of 1 to 20 μm consisting of a single layer or a multilayer of two or more of the carbides, nitrides, and oxides of Si and B, and solid solutions of two or more of these. In the surface-coated cemented carbide member, the interior of the cemented carbide base is made of 40 to 95% tungsten carbide, one of nitrides and carbonitrides of metals from groups 4a, 5a, and 6a of the periodic table. Na consisting of one or more types of
Cl type crystal structure compound: 2 to 30%, one or more iron group metals, and unavoidable impurities: the remainder, and the surface portion of the cemented carbide substrate is Over a depth of 2 to 100 μm, tungsten carbide: 65 to 95%, solid solution nitrogen: 0.01 to 2.0%, one or more iron group metals and unavoidable impurities: the remainder, and is 5 to 50% softer in terms of Bitkers hardness than the hardness inside the cemented carbide base,
In addition, the surface softening layer has an amount of binder phase that is 10 to 200% larger than the amount of binder phase inside the cemented carbide substrate (the above is volume %, the below % is volume %), which provides an excellent surface softening layer. It is characterized by a surface-coated cemented carbide member that has toughness, wear resistance, and plastic deformation resistance.

Next, the surface softening layer and the inside of the cemented carbide substrate in the surface-coated cemented carbide member of the present invention will be described in detail.

(a) Surface Softening Layer As mentioned above, it is believed that cracks in surface-coated cemented carbide members are usually caused by propagation of cracks from the coating layer into the interior of the cemented carbide base. ,
Immediately below the coating layer, that is, on the surface of the cemented carbide base, 2 to
WC: 65-95%, solid solution nitrogen: 0.01-2.0%, iron group metals and unavoidable impurities: remainder, softened by 5-50% in terms of Vickers hardness from the inside of the substrate over a depth of 100 μm. By forming a surface softening layer with a high toughness of the composition, it suppresses the propagation of cracks from the hard coating layer, and improves strength, toughness, and plastic deformation resistance. It is.

In this case, if the WC content is less than 65%, the iron group metal content becomes relatively too large and wear resistance decreases, whereas if the WC content exceeds 95%, the relative In general, the content of iron group metals becomes too low and the desired toughness improvement effect cannot be obtained, so the WC content is increased from 65 to 65%.
It was set at 95%.

In addition, when nitrogen is dissolved in iron group metals, the binder phase composed of the iron group metals is strengthened, and the plastic deformation resistance is greatly improved without decreasing toughness. If the content of The content of solid solution nitrogen was determined to be 0.01 to 2.0% because the functions of nitrogen would be impaired.

Furthermore, if the softening is less than 5% in terms of Bitkers hardness compared to the inside of the base, the desired toughness improvement effect cannot be secured, while if it is softened by more than 50%, the plastic deformation resistance and wear resistance will be reduced. The hardness of the surface softening layer was set to be 5 to 50% softer in terms of Vickers hardness than the internal hardness of the base.

In addition, if the depth (layer thickness) is less than 2 μm, the desired toughness improvement effect cannot be obtained, while if the layer thickness exceeds 100 μm, the plastic deformation resistance will be significantly reduced. The depth (layer thickness) of the layer was determined to be 2 to 100 μm.

Furthermore, if the amount of the binder phase is increased by less than 10% in proportion to the amount of the binder phase in the cemented carbide constituting the inside of the base, even if the Vickers hardness is softened by 5 to 50% compared to the inside of the base. However, if the amount is increased by more than 200% (doubling), the wear resistance and plastic deformation resistance will be significantly reduced. The amount of the binder phase was increased by 10 to 200% relative to the amount of the binder phase inside the substrate.

(b) Inside of the cemented carbide base The inside of the cemented carbide base must have a certain level of wear resistance even after the coating layer and the surface softening layer are worn away by abrasion, and together with the surface softening layer, It must impart toughness to the member.

However, the content of WC, which is a hard phase forming component, is 4
If it is less than 0%, the content of iron group metals, which are binder phase forming components, will be relatively too high, and even if a coating layer and a surface softening layer are present, the cutting resistance applied during cutting will not be able to be resisted.
Significant plastic deformation began to occur on the cutting edge, while 95%
If the WC content exceeds 20%, the iron group metal content becomes relatively too low, making it impossible to secure the desired toughness. Therefore, the WC content was set at 40% to 95%.

In addition, the NaCl-type crystal structure compound is a chemically stable component, and even after the coating layer and the surface softening layer are worn away due to wear, the component maintains the desired wear resistance, and the characteristics of the surface softening layer. It is a component that is contained so that the properties of the surface softening layer can be sufficiently exhibited, but if the content is less than 2%, the desired effect of improving wear resistance and the effect of fully exhibiting the characteristics of the surface softening layer cannot be obtained. On the other hand, if the content exceeds 30%, the toughness of the member will decrease significantly, so the content was set at 2 to 30%.

Regarding the thickness of the coating layer, if the layer thickness is less than 1 μm, the desired effect of improving wear resistance cannot be secured;
If the layer thickness exceeds m, the toughness decreases significantly, so
It was determined to be 1 to 20 μm. Further, the coating layer in the surface-coated cemented carbide member of the present invention can be formed by a coating layer forming method such as a usual chemical vapor deposition method, ion plating method, or sputtering method.

Furthermore, the cemented carbide substrate having the surface softening layer in the surface-coated cemented carbide member of the present invention has (a) a hardness of Bitkers after sintering compared to the cemented carbide constituting the interior of the cemented carbide substrate; 5 to 50% soft hardness and a binder phase amount of 1
In order to form a 0-100% more surface softening layer, WC powder and iron group metal are mixed by a conventional powder metallurgy method, then made into a slurry, and then conventionally processed to form the inside of the cemented carbide substrate. The above slurry is sprayed in a nitrogen atmosphere onto the surface of a green compact separately formed by the powder metallurgy method to adhere to a thickness of 2 to 100 μm, and then dried under reduced pressure.
When the whole is finally sintered by the usual powder metallurgy method, for example, nitrogen gas is introduced at a predetermined constant pressure at a temperature higher than the liquid phase appearance temperature of cemented carbide to form a surface softening layer on the iron. (b) A cemented carbide base material of a predetermined composition, which has been sintered in advance by a normal powder metallurgy method, is first sintered in a CO gas atmosphere.
Re-sintering is carried out by holding at a temperature higher than the liquid phase appearance temperature of the cemented carbide for a predetermined time, and then held again at a temperature higher than the liquid phase appearance temperature of the cemented carbide for a predetermined time in a nitrogen gas atmosphere. Method.

In this case, the composition of the surface softening layer, the amount of solid solution of nitrogen in the binder phase, the layer thickness, and the hardness are determined by the PcO partial pressure, the PN2 partial pressure,
A desired result can be obtained by adjusting the resintering temperature and the like. In this case, the sintering and resintering may be performed continuously at a temperature higher than the liquid phase appearance temperature of the cemented carbide. It can be manufactured by the methods shown in (a) and (b) above.

Next, the surface-coated cemented carbide member of the present invention will be explained using examples.

Example 1 The final component composition inside the cemented carbide base was WC-1.
5%CO-10%TaC-2%NbC-10%TiC-
Commercially available raw material powders were blended to give 5% TiN, wet mixed in a ball mill for 48 hours, and dried. -After, 1
A green compact was formed by pressing at a pressure of 5 kg/ml.

Next, this green compact was sintered by holding it in a vacuum at a temperature of 1400°C for 1 hour, and then only the atmosphere was changed to a CO gas atmosphere of 20t0rr (under reduced pressure) and held for 2 hours, and then the temperature was changed to a CO gas atmosphere of 20t0rr (under reduced pressure). in N2 gas atmosphere, j temperature 1320℃
By holding the sample for 0.2 hours, an SNU432 type throwaway chip A, which is a cemented carbide base according to the present invention, was manufactured. This throw-away chip A has a Vickers hardness H over a depth of 30 μm from the surface.
V: 1150, a surface softening layer having a composition consisting of WC, 0.15% solid solution nitrogen, and 26% CO is formed, and the internal roughness of the substrate is Vickers hardness Hv: 142.
It had a value of 0. Next, the throw-away chip A was placed in a chemical vapor processing furnace, and treated with TiCl4:4% and CH4:
The surface of the present invention was coated with a TiC layer with a layer thickness of 5 μm by maintaining the temperature at 1050° C. for 2 hours while introducing a gas having a composition of 4% H2 and 92% H2 (volume %). A coated throw-away tip A was manufactured.

In addition, for the purpose of comparison, a green compact molded under the same conditions as in the above green compact molding was heated to 1400°C in vacuum for 1 hour.
A comparative surface-coated throwaway chip A was produced by directly coating the TiC layer under the same conditions on the surface of a comparative throwaway chip A, which had been produced by holding for a period of time and had no surface softening layer formed.

Next, regarding the surface-coated throwaway chip A of the present invention and the comparative surface-coated throwaway chip A, workpiece material: SNCM-8 (hardness HB: 260), cutting speed:
150m/Min, feed: 0.35mm/Rev. Continuous cutting tests were conducted under the conditions of , depth of cut: 4 mm, and flank wear and rake face wear with respect to cutting time were measured, respectively.

The measurement results are shown in FIGS. 1 and 2. As shown in the figure, the surface-coated throw-away tip A of the present invention exhibits excellent wear resistance, whereas the comparative surface-coated throw-away tip A exhibits inferior toughness and plastic deformation resistance after 75 minutes after the start of cutting. It was something that was missing. moreover,
For the purpose of evaluating toughness, as shown in the front and side views of FIGS. 3 and 4, respectively, prismatic coatings were placed on the outer peripheral surface of the rotating drum 1 at opposite positions along its length. Insert and fix the cutting material 2, apply the above-mentioned double-surface coated throw-away tip 3 to the position shown in the figure, and cut the material: SCM.
-4 (hardness HB: 250), cutting speed: 100m/Mi
n, Feed: 0.45mm/Rev. An intermittent cutting test was conducted under the following conditions: depth of cut: 3 mm, cutting time: 3 min, and the defect rate (number of defective chips/number of test chips x 100) of 20 test chips was measured.

As a result, the surface-coated throw-away chip A of the present invention showed a chipping rate of 10% and had excellent toughness, whereas the comparative surface-coated throw-away chip A had a chipping rate of 10%.
The defect rate was 80%, and the toughness was poor. Example 2 The final component composition inside the cemented carbide substrate was LWC-
15%CO-5%TiC-5%TiN-3%TaCl%
Commercially available raw material powders were blended to give NbC-2% TaN, wet mixed in a ball mill for 48 hours, dried, and pressed to form a green compact. WC powder prepared separately in advance: 80%, C
A mixed slurry consisting of 20% O powder was uniformly sprayed to a thickness of 30 μm in an N2 gas atmosphere and dried under reduced pressure.

The compacted powder having a double structure in this way was heated in a vacuum at a temperature of 14°C.
After sintering by holding at 00°C for 1 hour, the pressure: 3
In a nitrogen gas atmosphere of 0 atm, the temperature was maintained at 1400°C for 0.1 hour, 0.2 hour, and 0.4 hour, respectively (
SNU432 type throwaway chip B, which is a cemented carbide base according to the present invention, is
, C, and D, respectively. The two throwaway tips B-D obtained as a result each contain 0.15
%, 0.25%, and 0.37% of solid solution nitrogen, and a surface softening layer having a Vickers hardness of Hv: 1150 is formed at a depth of 30 μm from the surface of each layer, and All of them had internal hardness of 1480 bits hardness Hv. Next, Example 1 was applied to each surface of the throwaway chips B-D.
Surface-coated throwaway chips B to D of the present invention were manufactured by forming a coating layer of 5 μm thick (7) TiC under the same conditions as in Example 1. Further, for comparison purposes, a comparative surface-coated throw-away chip B was manufactured under the same conditions except that the nitrogen solution treatment was not performed. Regarding the surface-coated throwaway tip B-D of the present invention and the comparative surface-coated throwaway tip B manufactured in this way, workpiece material: SNCM-8 (Hardness HB: 270)
, Cutting speed: 170m/Min, Feed: 0.45mm
/Rev. A continuous cutting test was conducted under the following conditions: depth of cut: 4 mm, cutting time: 30 min1, and blank wear and crater wear were measured.

The measurement results are shown in Table 1. Note that Table 1 also shows the solid solution nitrogen content in the surface softening layer. As shown in Table 1, the surface-coated throw-away tips B-D of the present invention both exhibit superior cutting performance compared to the comparative surface-coated throw-away tip B, which does not contain solid solution nitrogen in the surface softening layer. It's obvious.

Example 3 The composition inside the cemented carbide base was WC-15%CO-5%T.
A surface-coated throwaway chip E of the present invention was manufactured under the same conditions as those for the surface-coated throwaway chip B of the present invention in Example 2, except for iC-5%TiN-5%TaC-1%NbC. .

For comparison purposes, a comparative surface-coated throwaway chip E was manufactured under the same manufacturing conditions as the surface-coated throwaway chip E of the present invention, except that the surface softening layer was not subjected to nitrogen solid solution treatment. .

Furthermore, for the purpose of comparison, a comparative surface-coated throwaway chip (hereinafter referred to as a conventional surface-coated throwaway chip) was manufactured under the same manufacturing conditions as the surface-coated throwaway chip E of the present invention, except that no surface softening layer was formed. )
was manufactured.

Continuous cutting tests were conducted on these surface-coated throw-away chips under the same conditions as in Example 2.

The test results are shown in Table 2. As shown in Table 2, the surface-coated throwaway chip E of the present invention is different from the comparative surface-coated throwaway chip E in which the surface softening layer does not contain solid solution nitrogen, and the conventional surface-coated throwaway chip E in which no surface softening layer is formed. It is clear that it has significantly superior cutting characteristics compared to throw-away tips. As mentioned above, the surface-coated cemented carbide member of the present invention has excellent toughness, wear resistance, and
It also has plastic deformation resistance, so it exhibits extremely good cutting performance especially when used as a cutting tool.

[Brief explanation of drawings]

FIGS. 1 and 2 are curve diagrams showing the relationship between cutting time, flank wear, and rake face wear in continuous cutting tests for the surface-coated throw-away chip of the present invention and a comparative surface-coated throw-away chip; FIG. and FIG. 4 are a front view and a side view showing an interrupted cutting test mode.

Claims (1)

[Scope of Claims] 1. On the surface of the cemented carbide substrate, metals of Groups 4a, 5a, and 6a of the periodic table, carbides, nitrides, and oxides of Al, Si, and B, and two or more of these metals are present. In a surface-coated cemented carbide member in which a coating layer of 1 to 20 μm thick is formed from a single layer of one type or a multilayer of two or more types from the group consisting of solid solutions, the interior of the cemented carbide base is Tungsten carbide: 40-95%, Na consisting of one or more of nitrides and carbonitrides of metals in groups 4a, 5a, and 6a of the periodic table
Cl type crystal structure compound: 2 to 30%, one or more iron group metals, and unavoidable impurities: the remainder, and the surface portion of the cemented carbide substrate is Over a depth of 2 to 100 μm, tungsten carbide: 65 to 95%, solid solution nitrogen: 0.01 to 2.0%, one or more iron group metals and unavoidable impurities: the remainder, and is 5 to 50% softer in terms of Vickers hardness than the hardness inside the cemented carbide base,
Furthermore, the surface softening layer has a binder phase amount that is 10 to 200% larger than the binder phase amount inside the cemented carbide substrate.
1. A surface-coated cemented carbide member characterized in that: