JPS5935435B2 - 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, is rich in toughness, and has excellent cutting ability in the range from semi-finishing to rough cutting, especially when used as a cutting tool. Surface-coated cemented carbide showing performance 1 This relates to a member.

Conventionally, for example, on the surface of a tungsten carbide (hereinafter referred to as WC)-based cemented carbide member, 4a, 5a, and 6 of the periodic table were applied.
A single layer or two of a group consisting of carbides, nitrides, carbonitrides, carbonates, and carbonitrides of group A metals, aluminum oxides and oxides, and solid solutions of two or more of these. BACKGROUND ART Surface-coated cemented carbide members having a coating layer composed of multiple layers or more are known, and some of them are widely used in practical use.

However, in the above-mentioned conventional surface-coated cemented carbide member, the coating layer is harder than the cemented carbide base but is brittle, so the stress is much lower than in the case of only the cemented carbide base. 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 high temperature of 1000 to 1100°C is applied. During the cooling process, 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, which may cause cracks. Once a crack occurs in the coating layer, for example, when used as a cutting tool, the cutting stress is concentrated at the tip of the crack, so the crack rapidly propagates inside the cemented carbide base, and finally There was a problem that the cutting edge could be 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 such conditions, it is impossible to avoid deterioration in plastic deformation resistance and wear resistance. If the desired performance cannot be obtained in the cutting area where the There is a problem in that the inferior cemented carbide substrate is exposed and its wear progresses rapidly.

That is, when the surface-coated cemented carbide member is used, for example, as a cutting tool for cutting steel, the crater wear formed on the rake face of the tool disappears due to wear of the coating layer, then rapidly develops, and finally the cutting edge The phenomenon of reaching the ridge and causing the cutting edge to break, as well as the roughness of the finished surface formed by turning, are closely related to the boundary wear on the front flank of the tool.On the other hand, this boundary wear It is thought that there is a close relationship with the oxidation reaction of the tool, abrasive wear, and the diffusion phenomenon between the tool and the workpiece in the boundary area of the surface-coated cemented carbide member. When the coating layer, which has excellent oxidation resistance, welding resistance, and hardness (excellent abrasive wear resistance) is worn away, the cemented carbide base, which is also inferior in these properties, is exposed, and boundary wear rapidly progresses. This can be seen in the phenomenon that, despite low blank wear and crater wear, the tool life is shortened due to deterioration of the finished surface roughness. On the other hand, in the above-mentioned conventional surface-coated cemented carbide members, it is possible to increase the thickness of the coating layer for the purpose of improving wear resistance, but if the coating layer is made too thick, the toughness will drop sharply. As described above, the thickness of the coating layer is limited in terms of toughness.

Therefore, from the above-mentioned viewpoint, the present inventors solved the problems of the conventional surface-coated cemented carbide members and created a material that has excellent wear resistance and plastic deformation resistance, and is also rich in toughness. As a result of research to obtain surface-coated cemented carbide members, (
a) When the hardness of the surface portion of the cemented carbide substrate immediately below the coating layer is a hardened layer having an intermediate curvature between the covering property and the inside of the cemented carbide substrate, a decrease in toughness of the cemented carbide substrate is suppressed. Furthermore, it is possible to significantly improve wear resistance and plastic deformation resistance.

(b) Immediately below the hardened layer on the surface of the cemented carbide base (hereinafter referred to as the hardened surface layer), a softened layer made of a WC-iron group metal alloy that is softer and more tough than the inside of the cemented carbide base { By forming an intermediate softening layer (hereinafter referred to as an intermediate softening layer), propagation of cracks from the coating layer can be suppressed, and the toughness can be significantly improved.

The findings shown in (a) and (b) above were obtained. This invention was made based on the above knowledge, and it is possible to coat the surface of the cemented carbide base with 4a, 5a,
and carbides, nitrides, carbonitrides, carbonates, and carbonitrides of group 6a metals, aluminum oxide, and a single layer or two or more of the group consisting of solid solutions of two or more of these metals. Layer thickness 1-20μ consisting of multiple layers of
In a surface-coated cemented carbide member in which a coating layer of m is formed,
The inside of the cemented carbide base is made of tungsten carbide: 40 to 95%, carbides of metals from groups 4a, 5a, and 6a of the periodic table,
A composition consisting of a NaCl-type crystal structure compound consisting of one or more types of nitrides and carbonitrides: 5 to 30%, and one or more types of iron group metals: 5 to 30%. 4a of the periodic table, and the surface part of the cemented carbide base is covered with 4a of the periodic table to a depth of 1 to 30 μm from the surface.
, 5a, and 6a group metal carbonitrides: NaCl type crystal structure compound consisting of one or more types of metal carbonitrides: 70
~98%, one or more iron group metals: 2~
The hardened surface layer has a composition of 30% and is 5 to 50% harder in terms of Vickers hardness than the hardness inside the base, and further, between the inside of the base and the hardened surface layer, directly below the hardened surface layer. At a depth of 2 to 50 μm, 70 to 95% of tungsten carbide, 5 to 30% of one or more iron group metals, (
or more (by volume%), and has an intermediate softened layer that is 5 to 50% softer in terms of Vickers hardness than the internal hardness of the base, resulting in excellent toughness, abrasion resistance, and It is characterized by a surface-coated cemented carbide member that has been given plastic deformation resistance h.

Next, the surface hardening layer, intermediate softening layer, and internal composition of the cemented carbide substrate in the surface-coated cemented carbide member of the present invention will be described in detail below.

(a) Hardened surface layer As mentioned above, the hardened surface layer is made of one or more chemically stable metal carbonitrides of Groups 4a, 5a, and 6a of the periodic table. By using a cemented carbide made of a NaCl-type crystal structure compound (hereinafter referred to as a NaCl-type compound) and one or more iron group metals, a decrease in toughness is suppressed, and the coating layer is Even after being worn out, it has excellent wear resistance.

That is, for example, when a cemented carbide member is used as a cutting tool to cut steel, crater wear that occurs on the cutting tool is mainly attributable to wear due to adhesion, diffusion, corrosion (oxidation), etc. that cause tool damage. However, the amount of binder phase in cemented carbide and the amount of binder phase in cemented carbide constitute the same. For example WC, TlC, TaC, and Nb
It has a close relationship with the chemical stability of hard phases such as C,
For example, WC-C with a hard phase of WC with a hexagonal crystal structure
In O-based cemented carbide, crater wear develops significantly when cutting steel, making it unsuitable for use as a cutting tool, whereas O-based cemented carbide contains TiC, TaC, and NbC with an NaCl-type crystal structure as hard phase-forming components. WC-TaC
- It is a well-known fact that NbC-CO based cemented carbide exhibits excellent crater abrasion resistance, is suitable as a steel cutting tool, and is widely used; Due to the well-known fact that WC has superior crater abrasion resistance, it has a hard phase consisting of a NaCl-type compound that has superior chemical stability compared to WC with a hexagonal crystal structure, and a hard phase consisting of an iron group metal. If a layer consisting of a binder phase is formed on the surface of a cemented carbide base,
Abrasion resistance of surface-coated cemented carbide parts (crater abrasion resistance)
It is understood that this will result in a significant improvement. Regarding the component composition range in the surface hardening layer, if the content of iron group metal, which is a binder phase forming component, is less than 2%,
If the content of the NaCl type compound, which is a relatively hard phase-forming component, exceeds 98%, it is impossible to secure the desired toughness, and on the other hand, if the content exceeds 30% of the iron group metal, Since the content of the NaCl-type compound is relatively too small (less than 70%) and it becomes impossible to secure the desired wear resistance, the component composition range of the surface hardening layer is changed to NaCl-type compound: 70 to 98%. %, iron group metal: 2-3
It was set at 0% (capacity %).

In addition, as mentioned above, surface-coated cemented carbide cutting tools with a coating layer are significantly more effective in cutting areas with high heat generation, such as high feed and high depth of cut, compared to cemented carbide cutting tools without a coating layer. Although it shows improved plastic deformation resistance, it is impossible to avoid a decrease in toughness due to the formation of a coating layer made of a hard material. As mentioned above, it is necessary to select a material with a high quality of material, and as a result, the plastic deformation resistance of the cemented carbide substrate is currently unsatisfactory.

On the other hand, in the case of cutting tools, tool damage caused by wear due to the scratching action of hard particles in the work material and wear due to plastic deformation of the cutting edge is generally closely related to the hardness of the cutting tool. Particularly, the latter type of tool damage is caused by the fact that the cemented carbide base is softened by the heat generated during cutting, and deforms without being able to withstand the stress applied to the cutting edge during cutting. In this way, the plastic deformation of a surface-coated cemented carbide member is closely related to the hardness and thermal conductivity of the cemented carbide base. 1 to 3 from the surface of the cemented carbide base in the alloy member
If the depth of 0 μm is hardened by 5 to 50% to the Bitkers hardness than the part hardness within the base, the plastic deformation resistance of the cemented carbide base can be significantly improved while suppressing a decrease in toughness of the base. The conclusion was that it is possible. In this case, if the hardness is less than 5% in terms of Bitkers hardness compared to the inside of the base, the desired improvement effect will not be obtained, while if it is hardened to more than 50%, the toughness will be significantly reduced. It was hardened by 5 to 50% to the Bitkers hardness, and the depth (layer thickness) was 1 μm.
If it is less than 30μ, the desired improvement effect will not be achieved.
The depth (layer thickness) was determined to be 1 to 30 Itm because a layer thickness exceeding m would cause a decrease in toughness.

(b) Intermediate Softened Layer As mentioned above, it is thought that cracks in a surface-coated cemented carbide tool are usually caused by propagation of cracks from the coating layer into the interior of the cemented carbide base. ,
Immediately below the surface hardening layer, over a depth of 2 to 501 tm, a layer made of WC: 70 to 95% and iron group metal: 5 to 30%, softened by 5 to 50% in terms of Ribbickas hardness from the inside of the base. By forming a softened layer with a high component composition, it suppresses the propagation of cracks from the hard coating layer, and
The aim was to improve strength and toughness.

In this case, if the ferrous metal content is less than 5%, the WC content will be relatively too high, exceeding 95%, and the desired toughness improvement effect cannot be obtained; When iron group metals are included, the WC content becomes relatively too low (less than 70%), resulting in a decrease in wear resistance and plastic deformation resistance.
: 70-95%, iron group metal: 5-30% (capacity%)
It was established that In addition, 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, whereas if it is softened by more than 50%,
Due to the significant decrease in plastic deformation resistance and wear resistance,
The hardness of the intermediate softened layer was set to be 5 to 50% softer in terms of Vickers hardness than the internal hardness of the base. Furthermore, if the depth (layer thickness) is less than 2 μm, the desired toughness improvement effect cannot be obtained, while if the layer thickness exceeds 50 μm, the plastic deformation resistance will be significantly reduced. The depth (layer thickness) of the layer was determined to be 2 to 501 tm. -) Internal composition of cemented carbide substrate The interior of the cemented carbide substrate must have a specified wear resistance even after the coating layer and surface hardening layer are worn away by wear, and together with the intermediate softening layer, It must impart toughness to the member.

However, if the content of the iron group metal, which is a binder phase-forming component, is less than 5%, the desired toughness cannot be secured in the member, while if the content exceeds 30%, the coating layer and hardened surface layer will deteriorate. Even if it were present, it would not be able to withstand the cutting resistance applied during cutting, resulting in significant plastic deformation of the cutting edge, so its content was set at 5 to 30% by volume.

In addition, the NaCl type compound is a chemically stable component, and is a component that is contained so that the member has a predetermined wear resistance even after the coating layer and the hardened surface layer are worn away due to wear. If the content is less than 5%, the desired effect of improving wear resistance cannot be obtained, while if the content exceeds 30%, the toughness of the member will be significantly reduced. Therefore, the content is set at 5 to 30% by volume. Ta.

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 set as 1 to 201 tm.

Further, the coating layer in the surface-coated cemented carbide member of the present invention can be formed by conventional coating layer forming methods such as chemical vapor deposition, ion plating, and sputtering.

Furthermore, the cemented carbide substrate having the surface hardening layer and the intermediate softening layer in the surface-coated cemented carbide member of the present invention has (a
) In order to form an intermediate softened layer having a hardness that is 5 to 50% softer in terms of Vickers hardness after sintering than the cemented carbide constituting the interior of the cemented carbide substrate, for example, NaCl type compounds are used. WC powder and iron group metal are mixed by a normal powder metallurgy method, then made into a slurry, and a hardened surface layer having a hardness of 5 to 50% of the Vickers hardness after sintering is also formed separately. In order to achieve this, NaCl-type compound powder and iron group metal were mixed together to form a slurry using a normal powder metallurgy method (
In this case, the hardness is determined by the relationship between the particle size of the NaCl-type compound powder and the amount of iron group metal powder), and then the inside of the cemented carbide base is formed separately by a normal powder metallurgy method. First, a slurry for forming an intermediate softened layer among the slurries prepared as described above was sprayed onto the surface of the formed green compact in an N2 atmosphere.
After depositing to a thickness of 50 μm, the slurry was dried under reduced pressure, and then 1 to 301 tons of slurry was deposited in the same manner to form a surface hardening layer.
A method of depositing the material to a thickness of m and drying it, and finally sintering the entire product using a conventional powder metallurgy method.

(b) If the cemented carbide constituting the inside of the base body contains nitrides or carbonitrides of metals in Groups 4a, 5a, and 6a of the periodic table that have an NaCl type crystal structure, conventional powder metallurgy is used in advance. A cemented carbide base material of a predetermined composition sintered and formed by the method is first re-sintered by holding it at a temperature equal to or higher than the liquid phase appearance temperature of the cemented carbide in a CO gas atmosphere for a predetermined time, Next, N2 gas is introduced to change the atmosphere to CO gas and N.
A method in which a mixed gas atmosphere of two gases is maintained at a temperature higher than the liquid phase appearance temperature of the cemented carbide for a predetermined period of time. In this case, the composition, layer thickness, and hardness of the surface hardening layer and the intermediate softening layer are PcO partial pressure, PcO + PN25 + pressure J) N2/
A desired result can be obtained by adjusting the PCO+PN2 ratio and the resintering temperature. It can be manufactured by a method such as. 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 is WC-15.
%CO-10%TaC-2%NbClO%TiC-5%
Commercially available raw material powders were blended to give TiN (volume %), wet mixed in a ball mill for 48 hours, and dried.
SNP432 with a Vickers hardness of 1420 was formed by pressing at a pressure of 15 kg/m to form a compact, and by holding the compact in a vacuum at a temperature of 1400°C for 1 hour and sintering it. Manufactured throw-away tip material.

Next, the upper and lower surfaces and outer periphery of the resulting throw-away tip material were polished, and the cutting edge was prehoned to a desired shape.
Re-sintering was performed by holding the temperature at 1400°C for 2 hours in a CO gas atmosphere under a reduced pressure of
O gas partial pressure: 30t0rr, N2 gas partial pressure: 270t0
A throw-away chip, which is a cemented carbide base according to the present invention, was manufactured by re-sintering the product in a reduced pressure mixed gas atmosphere of RR and holding the temperature at 1400° C. for 2 hours. In this throw-away tip, 10
Vickers hardness: Hv: 16 over a depth of 1 J, m
20 and 57%TiClO%TiN-10%T
aC-2%NbC-3%CO-18%WC (capacity%
A hard surface layer having a composition of
An intermediate softened layer having a composition of %CO (volume %) was formed. Next, the throw-away chip was placed in a chemical vapor deposition furnace, and TiC24:4 was heated under atmospheric pressure.
%, CH4: 4%, H2: 92% (volume %) while introducing a gas at a temperature of 1050°C.
By holding for a period of time, a surface-coated throw-away chip according to the invention was produced which was coated with a TLC layer with a layer thickness of 5 μm.

For the purpose of comparison, a TiC layer was directly coated on the surface of the above throwaway chip material under the same conditions without forming a surface hardening layer and an intermediate softening layer as described above. A coated throw-away tip was manufactured.

Next, regarding the above-mentioned surface-coated throw-away chip of the present invention and comparative surface-coated throw-away chip) Work material: SNCM-8 (hardness: HB25O), Cutting speed: 200 m/Minl Feed: 0.5 No./Rev.) Continuous cutting tests were conducted under conditions of depth of cut: 2 mm1, and flank wear and crater wear were determined as a function of cutting time.

The measurement results are shown in FIG. 1 and FIG. 2, respectively.
As shown in the figure, the surface-coated throw-away chip of the present invention does not show the rapid progression of wear seen in the comparative surface-coated throw-away chip, and it is clear that it exhibits excellent wear resistance. Furthermore, for the purpose of evaluating toughness, as shown in FIGS. 3 and 4 in front and side views, respectively, angles are placed at opposite positions on the outer peripheral surface of the rotating drum 1 along the length direction. Insert and fix the columnar work material 2, apply the chip 3 to the position shown in the figure, work material: SNCM-8 (hardness: HB25O), cutting speed: 100 m/Minl feed: 0.365 m71/Re
v. An intermittent cutting test was conducted under the following conditions: depth of cut: 2 mm1 cutting time: 3 min1, and the defect rate (number of defective chips/number of test chips XlOO) of 50 test chips was measured.

As a result, the surface-coated throw-away chip of the present invention showed a chipping rate of 4% and had excellent toughness, whereas the comparative surface-coated throwaway chip showed a chipping rate of 8% and had excellent toughness. It was inferior. Example 2 The final component composition inside the cemented carbide base is WC-15
%CO - 10% TaC - 2% NbC - 15% TiC (volume %) by blending commercially available raw material powders, wet mixing in a ball mill for 48 hours, drying, and pressing. The powder was molded, and then WC powder: 75% and CO powder: 2, which were separately prepared in advance, were applied to the surface of the green compact.
A mixed slurry consisting of 5% (volume %) was uniformly sprayed to a thickness of 30 μm in a N2 gas atmosphere and dried under reduced pressure.
Subsequently, TiC powder: 55%, TiN powder: 20%, T
aC powder: 5%, NbC powder: 5%, CO powder: 5% (
A mixed powder slurry consisting of % by volume) was similarly uniformly sprayed to a thickness of 30 μm in a N2 gas atmosphere and dried under reduced pressure.

Then, the green compact having the triple structure was uniformly sprayed in a vacuum atmosphere IZ and dried under reduced pressure.

Next, the powder compact having the triple structure was sintered by holding it at a temperature of 1400° C. for 1 hour in a vacuum atmosphere to obtain SNU432, which is the cemented carbide substrate according to the present invention.
Manufactured a throw-away chip. In the throwaway chip according to the present invention obtained as a result, the Vickers hardness: Hv
156O and TiC-16%TiN-5%Ta
A surface hardening layer having a composition consisting of C-5%NbC7%CO (volume %) is formed, and furthermore, from just below this surface hardening layer to a depth of 26 μm, the surface hardness has a Vickers hardness: Hll.
An intermediate softened layer was formed having a composition of 2O and WC-21%CO (volume %), and had an internal hardness of Hvl45O. In addition, for the purpose of comparison, the composition of the slurry for forming the surface hardening layer was changed to one containing no TiN powder, that is, TiC powder: 85
%, TaC powder: 5%, NbC powder: 5%, CO powder:
A comparative throw-away chip was manufactured under the same conditions as in the manufacture of the throw-away chip of the present invention, except that a mixed powder slurry consisting of 5% (volume %) was used.

The comparative throwaway chip obtained as a result showed the same values as the above-mentioned throwaway chip of the present invention in terms of the composition, Vickers hardness, and layer thickness of the intermediate softening layer, as well as the internal composition and internal hardness, but the surface As for the hardened layer, the layer thickness is the same, but its composition is TiC-5%.
It was made of TaC-5%NbC7%CO (volume %), did not contain carbonitrides defined in the present invention, and exhibited a Vickers hardness: Hvl 59O. next,
After performing prehoning to a thickness of 0.05 mm on the surfaces of the throwaway chips of the present invention and comparative throwaway chips, a layer thickness of 5 μM was applied under the same conditions as in Example 1.
O) A surface-coated throwaway chip according to the invention and a comparative surface-coated throwaway chip were prepared by coating with a TiC layer.

For both throwaway tips, work material: S4
5C (Hardness: HB25O) Cutting speed: 160 m/Minl Feed: 0.35 mm/ReV 1 Depth of cut: 2 mm 1 Continuous cutting tests were conducted under the following conditions, and flank wear and crater wear with respect to cutting time were measured.

The measurement results are shown in FIGS. 5 and 6. As shown in the figure, it is clear that the surface-coated throw-away tip of the present invention has superior cutting characteristics as compared to the comparative surface-coated throw-away tip. Example 3 The final component composition inside the cemented carbide base is WC-15
%CO-10%TaC-2%NbCl5%TiC (volume%) Except for blending the raw material powder, Example 2
A surface-coated throw-away chip of the present invention having an internal hardness of Hvl45O was manufactured under the same conditions as those used to manufacture the surface-coated throw-away chip of the present invention.

For comparison purposes, the internal hardness: Hvl was measured under the same conditions except that the final component composition inside the cemented carbide base was WC-15% CO by volume, which is outside the scope of the present invention.
A comparative surface coated throwaway chip with 23O was prepared.

Next, using both of the throw-away tips obtained as a result, cutting speed: 80 m/Minl feed: 1.3 mm/Rev.) Depth of cut: 8 mm Cutting tool shape: SNU644 When cutting HB28O), the comparison surface-coated throw-away tip reached the end of its life in 30 minutes due to the cutting edge falling off, whereas the surface-coated throw-away tip of the present invention reached the end of its life 50 minutes after the start of cutting. The life span was reached when normal wear reached 0.35 mm on the flank surface.

As mentioned above, the surface-coated cemented carbide member of the present invention has extremely excellent toughness, wear resistance, and plastic deformation resistance by forming a surface hardening layer and an intermediate softening layer on the cemented carbide base. It is durable and exhibits excellent properties especially when used as a cutting tool.

[Brief explanation of drawings]

Figures 1 and 5 are curve diagrams showing the relationship between cutting time and flank wear in continuous cutting tests for the surface-coated throw-away chip of the present invention and a comparative throw-away chip, and Figures 2 and 6 are the same. A curve diagram showing the relationship between cutting time and crater wear, and FIGS. 3 and 4 are a front view and a side view showing an intermittent cutting test and a test mode.

Claims (1)

[Scope of Claims] 1. On the surface of the cemented carbide substrate, carbides, nitrides, carbonitrides, carbonates, and carbonitrides of metals of groups 4a, 5a, and 6a of the periodic table, as well as aluminum oxide, Furthermore, a layer thickness of 1 to 20 μm consisting of a single layer of one type or a multilayer of two or more types of solid solutions from the group consisting of two or more types of solid solutions.
In a surface-coated cemented carbide member having a coating layer formed thereon, the interior of the cemented carbide base is made of: tungsten carbide: 40 to 95%, carbides of metals from groups 4a, 5a, and 6a of the periodic table;
NaCl-type crystal structure compound consisting of one or more types of nitrides and carbonitrides: 5 to 30%, and a composition consisting of 5 to 30% of one or more types of iron group metals. 4a of the circumferential law table,
NaCl-type crystal structure compound consisting of one or more carbonitrides of group 5a and 6a metals: 70-
98%, one or more iron group metals: 2-3
0%, and is composed of a surface hardened layer that is 5 to 50% harder in terms of Vickers hardness than the hardness inside the base, and further between the inside of the base and the hardened surface layer. Over a depth of 2 to 50 μm from directly below, tungsten carbide: 70 to 95%, one or more iron group metals: 5 to 30%, (
1. A surface-coated cemented carbide member characterized in that it has a composition consisting of 5% to 50% less hardness in terms of Vickers hardness than the internal hardness of the base body, with an intermediate softened layer interposed therebetween.