JPH03197664A - High-toughness coated sintered hard alloy and its production - Google Patents

Abstract

PURPOSE:To produce the high-toughness coated sintered hard alloy which is enhanced in chipping resistance by allowing the lean layer of the hard phase of a B-1 type crystal structure and the enriched layer of a bond phase to exist on the surface of the sintered hard alloy and providing a core part contg. free carbon in the inside. CONSTITUTION:The coated sintered hard alloy is produced by forming the coated layer on the sintered hard alloy consisting of the hard phase which consists of the B-1 type crystal structure of 3 to 25wt.% bond phase essentially consisting of Co and Ni and the balance at least one kind of the phase of WC and the carbide, carbonitride, carbooxide and carbonitooxide of group 4a, 5a, 6a metals of periodic table and the inersolid solns. thereof, and unavoidable impurities. The sintered hard alloy consists of the core part which contains the tree carbon and the peripheral part which encloses the core part and does not contain the free carbon. The surface layer from the surface of the sintered hard alloy down to 5mum inside is so formed that the lean layer of the phase of the B-1 type crystal structure relatively decreased in the hard phase of the B-1 type crystal structure as compared to the core part and the enriched part of the bond phase relatively increased in the bond phase as compared with the core part.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention provides a high-toughness coating suitable for cutting tools such as turning tools, milling tools, end mills, and drills, and wear-resistant tools such as slitters, nozzles, and molds for gJ cans. This invention relates to cemented carbide and its manufacturing method.

(Prior art) Conventionally, TiC, TiN, Ti(C,
Nl.

A coated cemented carbide formed with a coating layer such as ^β203 has significantly improved wear resistance, and is therefore widely used in cutting tools, wear-resistant tools, and the like. However, this coated cemented carbide in practical use has a fragile coating layer, so when used as a cutting tool, for example, when used in applications that generate impact such as milling cutters and interrupted turning, or sharp cutting edges such as drills and end mills. The problem with shaped tools is that their range of application is limited. Representative examples of attempts to solve these problems include Japanese Patent Application Laid-Open No. 54-87719 and Japanese Patent Application Laid-open No. 134719-1987.

(Problem to be Solved by the Invention) JP-A No. 54-87719 discloses a hard phase consisting of a nitrogen-containing B-1 type crystal structure phase and a C phase, and a binder phase of the remaining iron group metal. In the cemented carbide consisting of, the phase with the B-1 type crystal structure in the surface layer is moved into the interior from the 5 to 200 μm surface layer of this cemented carbide, and the phase with the B-1 type crystal structure in the surface layer is mixed with another phase. A cemented carbide is disclosed in which the amount of the cemented carbide is reduced by less than 100%.

The coated cemented carbide disclosed in this publication, in which a hard coating layer is formed on the surface of the cemented carbide, has excellent fracture resistance due to the effect of the surface layer. Hard alloys and sintered hard materials J 1986.9a,
As shown in P2H4, the binder phase in the surface layer is poorer than that in the interior, so cracks that occur in the brittle coating layer are difficult to propagate inside the cemented carbide. The problem is that the suppressing effect of the layer is reduced, and as a result, the impact resistance effect is also reduced, and further expansion of the application has not been achieved.

JP-A-54-134719 discloses that in a coated cemented carbide formed by forming a hard coating layer on the surface of a cemented carbide, the cemented carbide has a surface portion that does not contain free carbon and has a layer thickness of 50 to 500 μm; It consists of a core containing 0.01 to 0.5% by weight of free carbon, and a softened layer whose hardness decreases by 10% or more continuously from the inside to the cemented carbide surface exists on the surface. A coated cemented carbide is disclosed.

The coated cemented carbide disclosed in this publication has improved chipping resistance and fracture resistance because the softened layer present on the surface of the cemented carbide suppresses the propagation of cracks that occur in the brittle coating layer. However, if you try to thicken the softened layer in order to improve chipping resistance and chipping resistance, there are problems in that it is extremely difficult to manufacture and the resulting products will vary widely. However, if the softened layer is made thinner, the effect of increasing chipping resistance and chipping resistance becomes weaker, so there is a problem in that the application is limited.

The present invention solves the above-mentioned problems,
Specifically, B is added to the surface of the cemented carbide used for the coated cemented carbide.
- Chipping resistance and plastic deformation resistance are significantly improved by the presence of both a depleted layer formed by depleting the hard phase of type 1 crystal structure and an enriched layer formed by enriching the binder phase. The purpose of the present invention is to provide a high-toughness coated cemented carbide that absorbs the internal propagation energy of cracks and increases II deficiency by providing a core portion in which free carbon exists inside the cemented carbide, and a method for producing the same. It is something to do.

(Means for Solving the Problems) The present inventors aim to improve the life of coated cemented carbide under severe cutting conditions such as higher speed cutting and higher feed cutting, among the areas in which coated cemented carbide is used. First, the chipping and fracture resistance of coated cemented carbide is to prevent cracks that occur in the coating layer from propagating inside the cemented carbide. In this case, it is best to prevent crack propagation at the initial stage of crack generation, and to do so, enrich the binder phase in the surface layer of the cemented carbide and increase the hard phase with the B-1 type crystal structure. This is based on the knowledge that it is most effective when people are poor.

Second, when coated cemented carbide is used as a cutting tool, it must have a certain degree of compressive strength to withstand the pressure applied to the cutting edge. In order to prevent cracks from propagating inside the cemented carbide and causing large defects or damage, if the binder phase concentration, hard phase composition, and grain size are the same, free carbon It was found that the presence of cracks makes it easier to absorb crack propagation energy.

Based on these first and second findings, we have completed the present invention.

That is, the high toughness coated cemented carbide of the present invention has C.

and/or 3 to 25% by weight of a binder phase mainly composed of Ni, and the remaining tungsten carbide phase and periodic table 4a, 5a.

At least one B-1 selected from group 6a metal carbides, carbonitrides, carbonates, carbonitrides, and mutual solid solutions thereof
A coated cemented carbide is formed by forming a single or multi-layer coating layer on the surface of a cemented carbide consisting of a hard phase having a type crystal structure and unavoidable impurities. A core portion containing B- a B-1 type crystal structure phase depletion layer in which the type 1 crystal structure hard phase is relatively reduced compared to the core; and the binder phase is relatively reduced compared to the core. The alloy is characterized by the presence of an increasing binder phase-enriched layer.

The binder phase in the cemented carbide in the high-toughness coated cemented carbide of the present invention has Co and/or Ni as its main components, and a portion of the hard phase components and inevitable impurities are dissolved therein. Among these, unavoidable impurities include those contained in the starting materials,
For example, Al1. These include Ca, Si, etc., and include, for example, Fe, Mn, etc., which are mixed in during the mixing and pulverizing process of the starting materials. Furthermore, the hard phase in the cemented carbide consists of a tungsten carbide phase and a B-1 type crystal structure phase, among which:
Specifically, the phase of the B-1 type crystal structure is 1, for example (TiJ
I.C.

(Ti, Ta1c, [Ti, Ta, W)C, (Ti
, Ta, Nb, W)C.

(Ti, W) (C, N1. (Ti, Tal (C
, N), (Ti, Ta, Wl (C, Nl.

(Ti, Ta, Nb, 'II) (C, Nl, (T
i, 1ll) (C101, [Ti, Ta) (C, 0
).

(Ti, Ta, Ill (C, 01, (Ti, Ta, N
b,w) (C,0).

(Ti, Ill (C,N, 01, (Ti,
Ta1(C,N,0).

(Ti, Ta, Wl (C, N, 0), (Ti, T
a, NbJl (C,N,0).

Cemented carbide made of such composition components consists of a core containing free carbon and a peripheral part surrounding this core and containing no free carbon. Especially, the peripheral part is made of cemented carbide. When the depth is 50 to 400 μm from the surface to the inside, it is preferable because the compressive strength as a cutting tool in a high feed region can be maintained. In addition, this cemented carbide has a layer depleted in the B-1 type crystal structure phase and a layer enriched in the binder phase in the inner surface layer up to at least 5 μm from the surface. It is particularly preferable that the depleted layer has a depth of 10 to 50 μm. Furthermore, with the intention of inhibiting crack propagation at an early stage, the binder phase enriched layer preferably has a maximum binder phase concentration on the surface of the cemented carbide, decreases toward the inside, and reaches a depth of 10 μm from the surface. It is further advantageous to increase the plastic deformation resistance from the minimum concentration at some point to the internal value.

The structure of the surface of this cemented carbide can be broadly classified and explained in more detail: ■ If the impoverished layer is the shallowest, then the enriched layer, and the peripheral area is the deepest, ■ the impoverished layer and the enriched layer. If the layers are almost the same depth, but the peripheral part is deeper than this,
■If the poor layer is shallow, the rich layer and the surrounding area are both deeper than it, and the rich layer and the surrounding area are almost the same depth, ■The poor layer, the enriched layer, and the surrounding area are at the same depth. When the depths are almost the same, the preferred configuration is that the impoverished layer is the shallowest, followed by the peripheral area, and the enriched layer is the deepest.It is preferable to use these layers depending on the purpose, especially when used as a cutting tool. In order to expand the usage area of , it is preferable to use the configurations of (1), (2), and (3).

When the amount of binder phase in this cemented carbide is less than 3wt%, the amount of hard phase increases relatively to more than 97wt%, so although it is a cemented carbide with poor and enriched layers, it has remarkable strength. On the other hand, if the amount of binder phase increases beyond 25 wt%, the amount of hard phase becomes relatively less than 75 wL%, and the wear of the cemented carbide after the coating layer disappears is severe, resulting in a shortened life. For this purpose, the amount of binder phase in cemented carbide is 3 to 25.
It is defined as wt%.

Specifically, the coating layer formed on the surface of such a cemented carbide includes, for example, carbides, nitrides, carbonates, nitroxides, +1 oxides of metals in groups 4a, 5a, and 6a of the periodic table, Examples include nitrides, Si carbides, nitrides, and mutual solid solutions thereof. Among these, a multilayer combination of coating layers of titanium carbide, titanium nitride, titanium carbonitride, and aluminum oxide is preferable because it is excellent as a cutting tool for steel and castings. Towards the surface, a titanium carbide layer, a titanium nitride layer, a titanium carbide layer, a titanium carbonitride layer, and an aluminum oxide layer.

It is even more preferable to use a multilayer structure in which titanium nitride layers are formed in this order. The optimal thickness of this coating layer varies depending on the application and tool shape, and when used as a cutting tool, the total thickness of the coating layer is 1-15 μm, and in particular, when it is multilayered, it is 5-1 μm.
The thickness is preferably 5 μm, and in the case of a single layer, about 1 to 10 μm.

When producing the high toughness coated cemented carbide of the present invention, several F[
Although there are two methods, the following method is preferable because it allows easy control of the surface of the cemented carbide and less variation.

That is, the method for producing a high toughness coated cemented carbide of the present invention is as follows:
Bonded phase 3 to z5r containing Co and/or Ni as main components
Mm%, remaining tungsten carbide phase and periodic table 4a,
5a, carbides, carbonitrides, carbonates of Ba group metals,
At least one of carbonitride oxides and mutual solid solutions thereof
This is a method for manufacturing a coated cemented carbide by forming a single or multilayer coating layer on the surface of a cemented carbide consisting of a hard phase consisting of a phase with an 8-1 type crystal structure and unavoidable impurities. hand,
After placing the cemented carbide in a reaction vessel, a first step of heating the reaction vessel in a carburizing atmosphere, cooling the reaction vessel with the atmosphere switched to a decarburizing atmosphere, and during the cooling. 1
A second step of passing the binder phase through a solid-liquid coexistence temperature range while slowly cooling at a rate of 0° C./min or less, and then forming the coating layer by physical vapor deposition or chemical vapor deposition. After the third step, the cemented carbide consists of a peripheral part that does not contain free carbon and a core part that contains free carbon inside the peripheral part, and from the surface of the cemented carbide. The hard phase of the B-1 type crystalline structure in the inner surface layer up to at least 5 μm is relatively reduced compared to the inside excluding the surface layer, resulting in poor phase of the B-1 type crystalline structure. This method is characterized in that a binder phase enriched layer is present in which the binder phase is relatively increased compared to the inside excluding the surface layer.

The first step, which is the treatment step of the cemented carbide in the method for producing a high-toughness coated cemented carbide of the present invention, includes a mixture of a hydrocarbon gas such as C114 and a) 13 gas or an inert gas as necessary. 12 in a carburizing atmosphere with a mixed gas of
The surface of the cemented carbide that has been carburized in the first step is then decarburized in the second step, which can also be done at a constant temperature. However, if it is slowly cooled while passing through the solid-liquid coexistence temperature range of the bonded phase, the surface layer can be easily controlled. The atmosphere during this slow cooling has a decarburizing effect even in vacuum, but for example, CO
If a decarburizing atmosphere such as x + lln or IIJ + IIs is used, the surface layer can be significantly controlled. Further, the cemented carbide produced in the first and second steps may be produced by using a substance containing a trace amount of N in the starting material of the cemented carbide, or
Alternatively, in the sintering process before the first step, it is preferable to nitridize the cemented carbide to contain a small amount of N in the cemented carbide because the surface layer can be easily formed. . The solid-liquid coexistence temperature range described here is, for example, as shown in FIG. This shows the temperature range indicated by diagonal lines in the (WC+γ+L) region of the Ic-Co cross-sectional view. By the way, - Book G! The second step can be carried out by taking out the cemented carbide from the sintering furnace after normal sintering, polishing it, etc., and then heating it again, but after sintering.

It is also possible to carry out the process continuously in the same furnace.

Following the first and second steps, the third step is to form a coating layer by physical vapor deposition or chemical vapor deposition.
This can be done by applying conventional methods.

(Function) The high-toughness coated cemented carbide of the present invention has the effect of suppressing microcracks generated in the brittle surface layer of the cemented carbide from propagating into the interior of the cemented carbide. Even if a crack propagates through the surface layer and the periphery and reaches the core of the cemented carbide, this core absorbs the energy of the crack and prevents damage to the entire alloy. The coating layer has the effect of increasing the compressive strength, and these effects allow the coating layer to fully demonstrate its excellent wear resistance and adhesion resistance, and as a result of these factors, chipping resistance and chipping resistance are improved. , it has extremely good breakage resistance and plastic deformation resistance.

The method for producing a high-toughness coated cemented carbide of the present invention has the effect that the combination of the first step and the second step facilitates control of the configuration of the peripheral portion and surface layer of the cemented carbide. It is something.

(Example) Example 1 Various commercially available powders (particle size 0.7 to 3.0 μm) were processed into WC-
3% TiC-0,5% TiN-6% TaC-6%C.

(wt%) according to the conventional manufacturing method, 1450
By vacuum sintering at ℃, lhr, TNIJN of JIS standard
A plurality of sintered bodies having a shape of 160408 were obtained. According to the observation of the cross-sectional structure at this time, no free carbon was observed from the surface to the inside. Then, we divided these sintered bodies into three groups. The group of 13 in the reaction vessel
After carburizing at 50°C for 30 minutes in a C114+TL gas mixture, the atmosphere was changed to COt+ll gas and slowly cooled to 1200°C at a rate of 5°C/min. It was then cooled to room temperature in vacuo. In the cross-sectional structure of this sample, no free carbon was observed up to 150 μm from the surface, and free carbon appeared in the interior. The surface part is an IC-Co alloy layer in which no B-1 crystal structure phase is observed from the surface to a depth of 20 μm, and the binder phase is enriched from the surface to a depth of 35 μm, with a 40 μm depth. It was observed that after the binder phase amount reached a minimum value at the position, which was smaller than the inside, it increased toward the inside to reach the inside value.

Furthermore, in the second group, during the same thermal cycle as the first group, no carburizing gas was used in the first step, and after holding in vacuum at 1350 ° C. for 30 minutes, CO, +l11
It was gradually cooled down to 1200°C in an atmosphere at a rate of 5°C/min. It was then cooled to room temperature in vacuo. In the cross-sectional structure at this time, a region where the B-1 type crystal structure phase was not observed was observed up to a depth of 20 μm from the surface, and a region of 45 μm from the surface was observed.
It was observed that the binder phase was enriched to a depth of m.
No free carbon was observed from the surface to the inside.

The remaining third group all had the same thermal history in vacuum. In the cross-sectional structure at this time, there was only a region where no B-1 type crystal structure phase was observed up to a depth of 20 μm from the surface. All of the above samples were coated with 2 μm TiC and 1 μm TiN by chemical vapor deposition.

2 μm TicN, 1 μm ARsrJ*,
A coated alloy was obtained by successively coating with 0.5 μm TiN (first group, inventive sample A: second group, comparative sample B: third group, comparative sample c).

For each of the above samples, the work material is 348C, which has four grooves parallel to each other at equal intervals in the longitudinal direction on the outer periphery of the cylindrical shape.
(11,250), cutting speed 150m/min
.

External turning is carried out under a constant depth of cut r:il of 5m1,
Set the feed amount to 0. 0.0 starting from I n+n+/rev
Raise it in 5m +++/rev increments (40 m + + + / rev increments)
After clearing 00 shocks, move on to the next feed) method,
Fracture resistance was evaluated based on the feed amount when the sample was fractured. As a result, on an average of 10 times for each sample, the present invention sample Δ was able to cut up to 0.45 mm/rev, whereas comparative sample B could cut 0.30 mm/rev and comparative sample C could cut 0.20 m1. /rev respectively deleted.

Example 2 Using various commercially available powders (particle size 0.9 to 2.5 μm), W
c -4%TiC-5%TaC-2%NbC-5%C.

-2% Ni (medium weight %) was blended and mixed, and press molding was performed to obtain a molded body in the shape of SNMN1240El according to the JIS standard. These were divided into three groups, and the first group was heated at 1IoO"c for 20 minutes during heating during sintering.

After nitriding in N1 atmosphere at 20 Torr, +4
Vacuum sintering was carried out at 20"C for lhr. After sintering, carburization was carried out in the same furnace at 1310℃ for 20 minutes in a C114+L atmosphere, and then the atmosphere was changed to nso+Ha and the temperature was increased to 3℃.
The mixture was slowly cooled to 1200° C./min, and then cooled in a vacuum to room temperature in a furnace. The cross-sectional structure of the alloy at this time is 18 mm from the surface.
No free carbon was observed up to 0 μm, and free carbon appeared in the inner part. In addition, the phase with the B-1 type crystal structure was significantly reduced from the surface to a depth of 32 μm compared to the inside, and furthermore, the binder phase was enriched from the inside to a depth of 45 μm from the surface. In the second group, vacuum sintering was performed without nitrogen treatment during the steps of the first group, and subsequent steps were performed under exactly the same conditions. The cross-sectional structure at this time is from the surface to
No free carbon was observed up to 200 μm, and free carbon appeared further inside. Furthermore, although a binder phase enriched region was observed up to 48 μm from the surface, the amount of the B-1 type crystalline structure phase did not change from the surface to the inside. Furthermore, in the third group, the nitriding treatment, carburizing treatment, and slow cooling treatment were not performed, and the furnace cooling was performed immediately after vacuum sintering. In the cross-sectional structure at this time, there was no free carbon at all from the surface to the inside, and no change was observed in the amount of the B-1 type crystal structure phase and the amount of the binder phase at the surface. Then, for all these samples, T
A coated alloy was obtained by coating iN with a thickness of 2 μm (first group, present invention sample D: second group, comparative sample E: third
Group, comparative sample F).

For each sample above, the cutting surface shape is 150mm x 8
0+am FC060f11e270) block,
Cutting speed 160m/min, depth of cut 2.0mm,
When face milling was performed under the conditions of a feed rate of 0.4 mm/blade, dry method, and -flute, the sample of the present invention had a through-surface wear t of 0.25 V+m after 20 bus cuts.
Comparative sample E was defective in 16 passes, and comparative sample F was defective in 7 passes.

(9. Effect of light) From the above results, the high toughness coated cemented carbide of the present invention has a higher toughness than the coated cemented carbide made by forming a coating layer on a cemented carbide with a conventional surface layer structure. Therefore, in terms of the feed size,
A coating formed by forming a coating layer on a cemented carbide that does not have a conventional surface layer. Compared to cemented carbide, it has a remarkable effect of improving fracture resistance by about 2.86 times.

Furthermore, the method for manufacturing a high-toughness coated cemented carbide of the present invention has the advantage that it is easy to control the core and peripheral portions as well as the surface layer.

[Brief explanation of drawings]

Figure 1 shows the cut +fj in the WC-16wL%CO composition.
This is a phase diagram. In Figure 1, WC is tungsten carbide, γ is Co phase, η is ■sco, c phase, C is carbon,
The shaded area indicates the solid-liquid coexistence temperature range of the bonded phase.

Claims (5)

[Claims] (1) Bonded phase 3 containing Co and/or Ni as a main component
25% by weight, remaining tungsten carbide phase and periodic table 4
Carbides, carbonitrides, carbonates of group a, 5a and 6a metals,
At least one of carbonitride oxides and mutual solid solutions thereof
In a coated cemented carbide formed by forming a single layer or multilayer coating layer on the surface of a cemented carbide consisting of a hard phase consisting of a phase with a B-1 type crystal structure and unavoidable impurities, the cemented carbide is , consisting of a core containing free carbon and a peripheral part surrounding the core and containing no free carbon, and an inner surface layer extending at least 5 μm from the surface of the cemented carbide,
The hard phase of the B-1 crystal structure is relatively reduced compared to the core, and the binder phase is A high-toughness coated cemented carbide characterized by the presence of an enriched layer of a binder phase. (2) The high-toughness coated cemented carbide according to claim 1, wherein the peripheral portion has a depth of 50 to 400 μm inward from the surface of the cemented carbide. (3) Claim 1, wherein the phase depletion layer having the B-1 type crystal structure has a depth of 10 to 50 μm from the surface of the cemented carbide toward the inside. or second
High-toughness coated cemented carbide as described in . (4) The binder phase enriched layer has a maximum binder phase concentration on the surface of the cemented carbide, and then decreases inward from the surface of the cemented carbide to at least 5 μm, and Claims 1 or 2, characterized in that the binder phase concentration reaches a minimum value at least 10 μm from the surface of the hard metal, and then increases again to reach an average binder phase concentration inside. High toughness coated cemented carbide according to item 3. (5) Bonded phase 3 containing Co and/or Ni as main components
25% by weight, remaining tungsten carbide phase and periodic table 4
Carbides, carbonitrides, carbonates of group a, 5a and 6a metals,
At least one of carbonitride oxides and mutual solid solutions thereof
A method for producing a coated cemented carbide comprising forming a single or multilayer coating layer on the surface of a cemented carbide comprising a hard phase consisting of a phase with a B-1 type crystal structure and unavoidable impurities. After placing the hard alloy in a reaction vessel, the first step is heating the reaction vessel in a carburizing atmosphere, cooling the reaction vessel in a decarburizing atmosphere, and heating the reaction vessel at 10°C during the cooling. /
a second step of passing the binder phase through a solid-liquid coexistence temperature range while slowly cooling at a rate of less than 10 minutes, and a third step of forming the coating layer by a physical vapor deposition method or a chemical vapor deposition method. The cemented carbide consists of a peripheral part that does not contain free carbon and a core part that contains free carbon outside the peripheral part, and at least 5 μm from the surface of the cemented carbide.
a phase depletion layer of the B-1 type crystal structure in which the hard phase of the B-1 type crystal structure in the inner surface layer up to m is relatively reduced compared to the inside excluding the surface layer; 1. A method for producing a high-toughness coated cemented carbide, characterized in that a binder phase-enriched layer is present in which the binder phase is relatively increased compared to the inside excluding the surface layer.