JPH04187739A - Hard sintered alloy having gradient compositional structure and its manufacture - Google Patents

Abstract

PURPOSE:To improve the wear resistance, plastic deformation resistance, toughness or the like of a sintered alloy by allowing diffusion elements to exist on the surface layer of a sintered alloy in such a manner that they are gradually reduced in the direction to the inner part and gradually increasing the relative concn. of a bonding phase and the average grain size of a hard phase in the surface layer in the direction to the inner part. CONSTITUTION:A sintered alloy is formed of 5 to 50vol.% bonding phase essentially consisting of an iron group and a hard phase essentially consisting of the carbides and nitrides of 4a, 5a and 6a group metals and mutual solid soln. therebetween. In the surface layer of 0.1 to 5mm from the surface of the above sintered alloy, at least one kind of diffusion elements among Cr, Mo, V, Ta, Al, Zr, Nb, Hf, W, Si, B, P and C are allowed to exist in such a manner that they are gradually reduced in the direction to the inner part. Furthermore, either or both of the relative concn. of the bonding phase and the average grain size of the hard phase are gradually increased or enlarged in the direction to the inner part. Because this hard sintered alloy having a gradient compositional structure is excellent in chipping resistance, the effect of a long service life can be obtd. when it is used for cutting tools and wear resistant tools.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to cutting tools such as turning tools, milling tools, and drill 2 end mills, dies, and punches.

Wear-resistant tools such as slitters, liners, stirring bars, civil engineering construction tools such as cutter bits, or chemical nozzles,
A hard sintered alloy with a gradient composition structure suitable for various tools or tool parts, including corrosion-resistant tools such as watch exterior parts, and the like! ! This relates to the 8i manufacturing method.

(Prior art) A hard phase containing titanium carbide or titanium nitride as a product and Co
Sintered alloys consisting of a binder phase mainly composed of N1 and/or N1 are used in various tools. The type and amount of these materials are adjusted to maintain a balance between wear resistance and toughness. However, since the wear resistance and toughness of sintered alloys tend to be antinomic in that improving one will reduce the other, it is extremely difficult to improve both at the same time.

An attempt has been made to solve this problem by creating an alloy in which the compositional structure near the surface and inside the sintered alloy are different.
Representative examples include JP-A-54-139815, JP-A-2-15139, and JP-A-2-9.
This is proposed in Publication No. 3036.

(Problems to be Solved by the Invention) Among the prior art techniques in which the compositional structures near the surface and inside of the sintered alloy are made different, the sintered alloy disclosed in JP-A-54-139815 has It is an alloy that has a hardness distribution that decreases continuously toward the inside up to a depth of 1 mm, and has a hard surface layer with a surface hardness that is 5 to 30% higher than the internal hardness. The hard surface layer of the sintered alloy disclosed in this publication was formed by carburizing atmosphere treatment below the liquid phase appearance temperature and vacuum sintering, and was formed simply by the amount of bonded carbon in the hard phase of the hard surface layer. Because of the hardness distribution, there is a problem that the effect of increasing both wear resistance and toughness is weak, and the range of applications is ultimately limited.

Furthermore, Japanese Patent Application Laid-open No. 2-15139 discloses that the surface part of the alloy up to 1000 μm from the surface has higher toughness than the inside.

A T1CN-based cermet with high hardness is disclosed,
JP-A-2-93036 discloses a T1CN-based cermet in which a portion having a Vickers hardness of 2000 or more is present between the surface of a sintered alloy and a surface area of 50 μm. The surface part of the T1CN-based cermet disclosed in these publications is produced by introducing N2 gas into the furnace from the temperature at which the liquid phase appears and before the maximum sintering temperature is reached, and after the maximum sintering temperature is reached, the furnace is heated. It is formed by lowering the internal pressure, and is formed by the formation of nitrides in the hard phase near the surface and the reduction of the binder phase 1.

Although these T1CN-based cermets disclosed in the same publication have improved surface toughness, they still have insufficient fracture resistance and plastic deformation resistance, and it is difficult to improve all of these properties at the same time as wear resistance. However, there is a problem in that its practical use is limited.

The present invention solves the above-mentioned problems. Specifically, the present invention has been made to gradually reduce the diffusion elements in the surface layer from the surface of the sintered alloy to the inside of 0.1 to 5 mm.
By gradually increasing and/or increasing the relative concentration of the binder phase in the surface layer and/or the average particle size of the hard phase, wear resistance, plastic deformation resistance, toughness, corrosion resistance, and oxidation resistance can be improved. Another object of the present invention is to provide a hard sintered alloy having a gradient composition structure with excellent wear resistance and fracture resistance at high temperatures.

(Means for Solving the Problems) The present inventor has investigated the problem that when conventional sintered alloys have improved wear resistance, their toughness decreases, and when their toughness is improved, their wear resistance decreases. However, during the sintering of the powder compact in the manufacturing process of sintered alloy, elements that are easy to diffuse and can harden the surface layer are diffused in a gradient over the surface region, and We found that by further hardening the surface layer by controlling the concentration of the binder phase and/or the distribution of the average particle size of the hard phase, the wear resistance, toughness, and plastic deformation resistance of the sintered alloy itself can be significantly improved. It is something. Based on this knowledge, we have completed the present invention.

That is, the hard sintered alloy with a gradient composition structure of the present invention contains 5 to 50% by volume of a binder phase mainly composed of iron group metals, and the remainder carbides and nitrides of metals of groups 4a, 5a, and 6a of the periodic table, and these. A sintered alloy consisting of a hard phase whose main component is at least one kind of mutual solid solution of (however, a hard phase whose main component is a metal carbide containing tungsten carbide) and inevitable impurities, The surface layer from a part of the surface or the entire surface to the inside of 0.1 to 5 mm is:
Cr, Mo, V.

Ta, ^A, Zr, Nb, Hf, *, Si
, B, P, C (7) gradually decreases from the surface toward the inside, and one or both of the relative concentration of the binder phase and the average particle size of the hard phase decreases from the surface. It is characterized by a gradual increase or increase towards the inside.

The binder phase in the hard sintered alloy with a gradient composition structure of the present invention is composed of at least one of Co, Ni, and Fe or a mutual alloy thereof, or when 50% by volume or more of the binder phase is composed of Co, Ni, or Fe. At least one species of
The remainder is, for example, Ti, Nb, Cr, Mo, V,
^β.

This is the case of Cu and Mn. Among these, Go and /
Or Ni with 10% by volume or less of Ti, V, Cr, M
o, Al2. Preferably, the binder phase is an alloy consisting of at least one of the following.

In addition to this binder phase, the hard phase constituting the hard sintered alloy of the present invention includes at least one of carbides, nitrides, and mutual solid solutions of metals in groups 4a, 5a, and 6a of the periodic table.
It consists of a hard phase whose main component is seeds (excluding cases where the main component is metal carbide containing tungsten carbide),
These hard phases may coexist as carbonates, oxynitrides, and oxycarbonitrides with oxygen contained to the extent of inevitable impurities. These hard phases consist of a core and an outer periphery surrounding the core, and the core and the outer periphery have a structure in which the type or content of metallic elements and/or non-metallic elements is different. There is also.

The surface layer constituting the hard sintered alloy of the present invention is hardened compared to the inside by the presence of a diffusion element solid-solved in the hard phase and/or the binder phase, and as a result of sintering. The wear resistance of the alloy itself is increased, and if the thickness is less than 7 mm, the improvement in wear resistance will be weak;
If the thickness exceeds m, the toughness will decrease and manufacturing difficulties will occur, so the thickness is set at 0.1 to 5 mm.

The diffusing element present in this surface layer is, for example, Co-Cr or Ni-Mo, which is solid-solved in the binder phase in the surface layer.

Ni-Cr, Co-V, N1-V, Co-Z
r, Co--Ti, optionally in the bonded phase, e.g. Co5Si, CoTi5. N
It exists in the form of intermetallic compounds such as iz^A, N15P, and Al2Ti5, or is solidly dissolved in the hard phase in the surface layer, such as (Ti, Mo1C, etc.).

(Ti, Mo) CN, (V, W) C, (Ti, W)
C, (TaJ)C(7)J:') It exists in a hard phase structure. Among these diffusion elements, Cr, B,
Al, Si, and P are mainly dissolved in the bonded phase and V,
Zr, Nb, Mo, Hf, Ta, and 'R are mainly dissolved in the hard phase to harden the surface layer, and further improve the hardness by reducing the amount of binder phase in the surface layer. Also, among the diffusive elements, Mo.

W, C, and N have the effect of hardening the five surface layers and suppressing the grain growth of the hard phase in the first surface layer.

Further, among the diffusing elements, W and Mo are particularly preferable because they have a large effect of suppressing particle growth of the hard phase and greatly improve hardness.

The hard phase present in this surface layer is represented by 4a and 5 of the periodic table.
a. It has a volunteer structure in which at least one of carbides, nitrides, and mutual solid solutions of group 6a metals is used as a core, and the above-mentioned diffusive element is dissolved in solid solution in the outer periphery surrounding the core. It is particularly preferable that the core of this hard phase is made of titanium carbide or titanium carbonitride, and that the above-mentioned diffusive element dissolved in solid solution in the outer periphery is made of Mo or W.

In particular, regarding the concentration of the diffusing element in the surface layer and the concentration of the hard phase particle size 7 binder phase, the average concentration of the diffusing element in the surface layer from the surface of the sintered alloy to 0.1 mm inward (Cs) and the average concentration of the diffusing element inside (C
I), the ratio of Cs/Ci = 2.0 or more -F, and the average concentration of the binder phase in the surface layer (bs), the average particle size of the hard phase (ds), and the average binder phase in the interior target concentration (
bi) and the average particle diameter fdi) of the hard phase is bs/bi
= 0.9 or less and/or ds/di = 0.9 or less is preferable in order to improve both wear resistance and toughness.

Furthermore, regarding the hardness of this surface layer, the average Vickers hardness fHVs from the surface of the sintered alloy to the inside of the sintered alloy and the average Vickers hardness in the interior (HVilt(D ratio HVs/ )IVi=1.
2 [1 or more is preferable.

The hard sintered alloy with a gradient composition structure of the present invention can be obtained by diffusing a diffusive element from the surface of the powder green compact during or after sintering. solids containing.

Although there is a method of diffusing from a liquid or gas, it is particularly preferable to use the following method because it is easy to control the thickness of the surface layer and the degree of inclination of the diffusing element.

That is, the method for producing a hard sintered alloy with a graded composition structure according to the present invention uses 5 to 50% by volume of powder mainly composed of iron group metals and the remaining carbides and nitrides of metals of groups 4a, 5a, and 6a of the periodic table. and a powder mainly composed of at least one of these mutual solid solutions, and a step of pulverizing and mixing to obtain a mixed powder;
A step of pressure-molding the mixed powder into a predetermined shape to obtain a powder compact, bringing a solid substance of metal 1 alloy or compound containing a diffusive element into contact with the powder compact, and heating at 1250 °C in a vacuum or non-oxidizing atmosphere. This method is characterized by a step of heating to ~1600°C or +250 to 160[1"C] in a gas atmosphere containing a diffusing element. Among the steps in this method, Contacting the powder compact with a solid substance containing powder means, for example, a method of integrally molding the powder solid substance on the surface of the powder compact, a method of applying the powder solid substance to the surface of the powder compact, or a method of applying the powder solid substance to the surface of the powder compact. Examples include a method of placing a powder compact on a sintering plate, or a method of embedding a powder compact in a solid material.In addition, solid materials include metals and alloys containing diffusive elements. For example, Mo=C, Cr5Ci, VC, l
lIC, A9aCs, IIIB.

Compounds such as MoB and NbN can be used, and in particular when they are composed of diffusive elements of metals in groups 4a, 5a, and 6a of the periodic table, when their carbides are used as solid substances, solid solution in the binder phase can be reduced from low temperatures. This is preferable because the diffusion effect is large because of this phenomenon, and the amount of carbon in the hard phase in the surface layer is difficult to decrease.

The amount of diffusing elements in the surface layer or the thickness of the surface layer is.

Although it can also be adjusted by the amount of solid material brought into contact with the powder compact, it is preferable to control it by the diffusion coefficient of the diffusing element in the binder phase, the heating temperature for sintering, and the holding time.

In addition, when diffusing the diffusing element onto the surface of the sintered alloy using a gas atmosphere containing the diffusing element, for example, VOCl25
．． Cr0xCjlL,, Nb0Cn,, Mo
Fs, TaCl2s.

It is preferable to carry out in a mixed gas atmosphere of a chloride or acid chloride such as Bla, Aβ Cβ, SiC flood, P[43, and H2 and CH.

(Function) The hard sintered alloy with the gradient composition structure of the present invention mainly has the function of increasing wear resistance and plastic deformation resistance in the surface layer, and increasing toughness in the interior, and the diffusion elements in the surface layer and the binder phase. Among the diffusing elements, V, Cr,
Mo, C, B.

In the case of Ar2, Si, and P, they have the effect of lowering the temperature at which a liquid phase appears, and as a result, a liquid phase appears preferentially on the surface during sintering (heating), and this liquid phase enters the interior through capillary action. Cr, B, Ar2. In the case of Si and P, they are solid solution dispersed in the bonded phase, and in the case of V, Zr, Nb, and Mo.

Hf, Ta, Il! In the case of Mo and VJ diffusion elements, they act to suppress the growth of hard phase particles during sintering, resulting in a decrease in the hard phase particle size in the surface layer. It has the effect of making the inside smaller than the inside.

(Example) Commercially available TiC powders with average particle diameters of 0.2 μm and 1.5 μm, 1. sum T1Co, yNo, s powder,
1.5 gm carbonyl Ni powder, 1.2 μm CO powder, 1. lum TiC/WC/TaC=
50/20/30 solid solution powder and 1-2 μm VC,
MozC, ZrC, NbC, Cr, C, TaC, II
C.

TiN, TiH, and powder were weighed and blended into the composition shown in Table 1, and placed in a cemented carbide pot with an acetone solvent and
The mixture was charged together with cemented carbide balls, mixed and ground for 48 hours, dried, and then heated to 80° C. while adding and mixing 3.0 wt % paraffin wax to obtain a mixed powder.

Next, a 20φ press mold was used, and MoxC, VC, Tic, TaC, An, and C were placed on the press surface of the lower bottle.
, or a mixture of these powders as shown in Table 1, and then set the lower bottle in a mold and fill it with each mixed powder of the composition shown in Table 1 to make I ton/ 20φX 25 with a thin film of each diffusion element integrally molded on the bottom surface by pressurizing it with a pressure of 1.5 cm.
A molded body of mm was produced. The obtained compact was placed on a carbon plate covered with carbon powder, and placed in a vacuum furnace for about 10 minutes.
The product was sintered in an atmosphere of "" Torr at a predetermined temperature for 9 hours to obtain product 1-10 of the present invention.

In addition, using each mixed powder with the composition shown in Table 1, 2
A molded body of 0φ x 25 mm was prepared, and a predetermined amount of MoxC powder or NbC powder mixed in paraffin wax and hexane was applied to one side of the molded body, and then sintered in vacuum in the same manner to obtain the product of the present invention II,! I got 2. Meanwhile, the molded body is 20. It was embedded in a mixed powder of powder and Cr5Cx or 84C powder and vacuum sintered to obtain products 13 and 14 of the present invention.

Furthermore, a compact of the mixed powder having the composition shown in Table 1 was prepared as Ar-1.
Product 15 of the present invention was obtained by sintering in a mixed gas consisting of MoFs (0voI2%)la-0.5vofi%MoFs.

A cylindrical sintered body (approximately 20
φX 20 mm) was cut, and the concentration of the diffusing element, amount of binder phase, hard phase particle size, and Vickers hardness were measured for the surface layer and inside. The results are shown in Table 2 in comparison with a normally sintered sintered alloy that has not been subjected to diffusion treatment. In addition, the invention product I
Diffusing element concentration from the surface to the inside, bonding phase Ni1
1. Hard phase grain size.

The measured values of the Vickers hardness distribution are shown in FIGS. 1 and 2.

The margin comparison product 1 below is a commercially available TiC-Mo-Ni smet comparison product 2 is a commercially available TiC-TiN4C-TiC-TiN.
4C-TaC-based cermet comparison product 3 was a commercially available TiN4C-TaC-Ni-Co based cermet.Measurements of each factor shown in Table 2 were as follows: Concentration of diffusive element: 0.0% from the surface by EPM 8 minutes.
The average density Cs up to 1 mm and the internal value Ci were measured.

Amount of bonded phase: According to EPMA analysis, 0.0% from the surface.
The average density bs up to 1 mm and the internal value b1 were measured.

WC particle size: From the SEM composition image, 0 from the surface
．． Calculate the average particle size ds up to 1 mm and the internal particle size d1 (Fulman's formula) Vickers hardness: O, I from the surface using a microhardness tester at a load of 200g.
The Vickers hardness HVs up to mm and the internal hardness Hv1 were measured.

Next, practical test results of the product of the present invention will be described.

First, a solid drill with an outer diameter of 10 mm, a cutting edge length of 60 mm+, and a handle of 30 mm was manufactured using the invention product I+ and comparative product 2 in Table 2, and a plate material of carbon steel 348C (thickness 3
0 mm), a cutting speed of room/min, and a feed rate of O1 to 0.3 mm/rev were used to conduct the test. Partial wear amount of corner after drilling 200 holes is 3rd
Shown in the table.

Table 3 As is clear from the results, the product of the present invention has excellent wear resistance at the outer peripheral cutting edge and high toughness at the axial center, making it difficult to break.

Next, using the invention product 1 and comparative product 1 in Table 2, IS
O standard SNMNI20408 (Removal allowance for scooping surface 0.0
A wear resistance test (A) and a chipping resistance test (old) were performed using a lathe and the cutting conditions shown in Table 4.

Margin below Table 5 shows the results obtained under the conditions shown in Table 4.

Table 5 (Effects of the Invention) The hard sintered alloy with a gradient composition structure of the present invention has excellent wear resistance, as well as toughness, impact resistance, and plastic deformation resistance, so it has excellent fracture resistance and It has excellent breakability, and as a result, when used as cutting tools, wear-resistant tools, or tool parts, it has the effect of long life, and when used as rotating tools, such as parts for drills and cutters, it has the effect of increasing the lifespan. Significantly longer life compared to bonded metals2

[Brief explanation of drawings]

FIG. 1 is a curve diagram showing the distribution state of the concentration of the binder phase and the concentration of MO, which is a diffusing element, from the surface to the inside of the product 2 of the present invention of Example. FIG. 2 is a curve diagram showing the distribution state of the average particle diameter of the hard phase and the Vickers hardness from the surface to the inside of the invention product 2 of Example. In the figure, 1: Bonded phase concentration curve 2: Mo diffusion element concentration curve 3: Average particle size of hard phase 4: Vickers hardness Patent applicant Toshiba Tungaloy Corporation

Claims (7)

[Claims] (1) 5 to 50% by volume of a binder phase mainly composed of iron group metals, and the remaining main components are at least one of carbides, nitrides, and mutual solid solutions of metals of groups 4a, 5a, and 6a of the periodic table. In a sintered alloy consisting of a hard phase (however, a hard phase whose main component is a metal carbide containing tungsten carbide is excluded) and inevitable impurities, a part of the surface or the entire surface of the sintered alloy The surface layer from 0.1 to 5 mm inside is made of Cr, Mo, V, Ta, Al, Zr, Nb
, Hf, W, Si, B, P, and C gradually decrease from the surface toward the inside, and one of the relative concentration of the binder phase and the average particle size of the hard phase, or A hard sintered alloy with a graded composition structure, characterized in that both gradually increase or increase from the surface toward the inside. (2) 0.1 mm from the surface of the above sintered alloy toward the inside
The average concentration of the above diffusing element in the surface layer up to (Cs
) and the average concentration (Ci
) is Cs/Ci=2.0 or more, and the average concentration (bs) of the binder phase in the surface layer, the average particle size (ds) of the hard phase, and the ratio of the binder phase in the interior The ratio between the average concentration (bi) and the average particle diameter (di) of the hard phase is bs/bi=0.9 or less and/or ds/di=0.
9 or less, the hard sintered alloy having a gradient composition structure according to claim 1. (3) 0.1 mm inward from the surface of the sintered alloy
Claim 1, characterized in that the ratio of the average Vickers hardness (HVs) in the surface layer up to the average Vickers hardness (HVi) in the interior is HVs/HVi=1.20 or more. A hard sintered alloy with a gradient composition structure as described. (4) The hard phase in the surface layer of the sintered alloy has a core made of at least one of carbides, nitrides, and mutual solid solutions of metals from groups 4a, 5a, and 6a of the periodic table, and the core is surrounded by A hard sintered alloy with a gradient composition structure according to claim 1, characterized in that the alloy has a volunteer structure in which the above-mentioned diffusive element is solidly dissolved in the outer periphery of the alloy. (5) The inclination according to claim 4, wherein the core of the hard phase is made of titanium carbide or titanium carbonitride, and the diffusive element dissolved in solid solution in the outer periphery is made of Mo or W. A hard sintered alloy with a compositional structure. (6) 5 to 50% by volume of powder containing iron group metal as the main component;
Powder whose main component is at least one of carbides, nitrides, and mutual solid solutions of metals from Groups 4a, 5a, and 6a of the periodic table (however, only powder whose main component is metal carbide including tungsten carbide) Cr, Mo, V, T
a, Al, Zr, Nb, Hf, W, Si, B, P, and C. A solid substance of a metal, alloy, or compound containing at least one diffusing element among a, Al, Zr, Nb, Hf, W, Si, B, P, and C is brought into contact with the powder compact and heated in a vacuum or in a Heating to 1250-1550°C in an oxidizing atmosphere, or heating to 1250-1550°C in a gas atmosphere containing the diffusion element.
A method for producing a hard sintered alloy with a gradient composition structure, comprising the step of heating to 50°C. (7) The mixed powder is made of Co and/or Ni, titanium carbide or titanium carbonitride, and at least one of tantalum carbide, niobium carbide, vanadium carbide, tungsten carbide, and titanium nitride, and the solid substance is 7. The method for producing a hard sintered alloy with a gradient composition structure according to claim 6, wherein said powder is made of molybdenum or molybdenum carbide powder.