JPH06157135A - Surface-tempered sintered alloy and production thereof - Google Patents

Abstract

PURPOSE:To develop a surface-tempered sintered alloy superior in wear resistance, strength and toughness by forming and sintering rigid alumina by allowing a specific high M.P. metal to be a bond phase, and forming a specific metal compound contained layer on the surface. CONSTITUTION:In the production of the sintered alloy in which the rigid phase consisting of Al2O3 is a main component and the high M.P. metal is a bond phase, the sintered alloy consists of a matrix consisting of group IV, V, VI metals in periodic table and Ni, Co, Fe and Al or these alloys being incorporated in the 2-50vol.% ratio as the bond phase and the balance being the Al2O3 being >=50vol.% and the balance consisting of one or more kinds of ZrO2, partially stabilized ZrO2, HfO and Cr2O3, etc., or carbides of group IV-VI metals and nitride, etc. In the surface of the alloy, 0.01mm depth layer consists of Al2O3 and the high M.P. metallic compound of the carbides, nitrides and oxides, etc., of group IV-VI metals, and also average weight of the bond phase in the surface layer is smaller than the average value of the bond phase in the inside of the sintered alloy and the quantity of diffused elements of C, N and O2, etc., in the surface thickness decreases from the surface to the interior.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a surface heat-bonded material obtained by modifying the compositional components in the surface portion of a sintered alloy comprising a hard phase containing aluminum oxide as a main component and a binder phase containing a refractory metal. Regarding gold and its manufacturing method, specifically, for example, cutting tools such as turning tools, milling tools, drills and end mills, wear-resistant tools such as dies, punches and slitters,
The present invention relates to a surface-tempered sintered alloy most suitable for tools and parts represented by heat-resistant and oxidation-resistant parts such as high-temperature furnace jigs, parts for high-temperature equipment such as pipes, nozzles and bolts, and a manufacturing method thereof.

[0002]

2. Description of the Related Art As sintered alloy comprising a binding phase containing a hard phase and a refractory metal mainly composed of aluminum oxide, Al ₂ O ₃ -Cr sintered alloy, Al ₂ O ₃ -Mo-Cr sintered Bonded gold or Al ₂ O ₃ —W—Cr sintered alloy has been partially put into practical use as high temperature parts.

However, these high temperature parts have the problem that their strength and toughness are low and their applications are very limited.

Representatives proposed in order to solve this problem are Japanese Patent Laid-Open Nos. 54-4915 and 55-85653.

[0005]

As a prior art of a sintered alloy containing aluminum oxide and a refractory metal, Japanese Unexamined Patent Application Publication No. Sho.
No. 4-4915 discloses an oxide phase 10-9 composed of aluminum oxide, zirconium oxide or a mixture thereof.
An aluminum oxide-containing metal composition for tools is described which comprises 5% by weight and a metal phase consisting of a nickel alloy containing 30% by weight zirconium and 5 to 90% by weight.

Further, JP-A-55-85653 discloses a ceramic sinter for a cutting tool in which a matrix containing Al ₂ O ₃ and TiN as main components is dispersed and strengthened with metallic Ti.

The sintered alloys containing aluminum oxide and refractory metal described in both of these publications have improved fracture resistance during cutting for the purpose of improving strength and toughness, but are still satisfactory. However, if the fracture resistance is satisfactory, the wear resistance is conspicuously deteriorated.

The present invention has solved the above-mentioned problems. Specifically, the strength and toughness of the inside of the sintered alloy are increased, and the surface portion of the sintered alloy that is in direct contact with the workpiece is improved. An object of the present invention is to provide a surface-tempered sintered alloy in which the composition components are gradually and optimally modified to maintain wear resistance, strength, and toughness in a balanced manner, and a method for producing the same.

[0009]

DISCLOSURE OF THE INVENTION The inventors of the present invention have improved the strength and toughness by adjusting the binder phase component of a metal, as in the conventional sintered alloy containing aluminum oxide as the main component. Since wear resistance, heat resistance, oxidation resistance, and corrosion resistance are reduced, the study was conducted to find that in the interior of the sintered alloy, a binder phase that contributes to strength and toughness,
At the surface portion of the sintered alloy, a modified binder phase different from the binder phase inside the sintered alloy is used, and the concentration of the elements constituting the binder phase at the surface portion is changed to make the sintered alloy We obtained the knowledge that the characteristics of
The present invention has been completed.

That is, the sintered alloy of the present invention is a metal of group 4a, 5a, 6a of the periodic table, Ni, Co, Fe, Al.
And at least one binder phase in these mutual alloys 2
˜50% by volume with the balance being aluminum oxide in the hard phase, or 50% by volume or more of aluminum oxide with the remaining zirconium oxide, partially stabilized zirconium oxide, hafnium oxide,
From a hard phase consisting of chromium oxide, silicon oxide, silicon carbide, silicon nitride, carbides, nitrides of metals of groups 4a, 5a and 6a of the periodic table and at least one of these mutual solid solutions, and inevitable impurities A surface layer having a thickness of at least 0.01 mm from the surface is formed on a part or the whole surface of the sintered alloy consisting of aluminum oxide and a group 4a, 5a, 6a of the periodic table. At least one refractory metal compound among the above-mentioned metal carbides, nitrides, oxides, borides, silicides and mutual solid solutions thereof, or aluminum oxide, the refractory metal compound and the binder phase A sintered alloy having a surface layer consisting of: and the average amount of the binder phase in the surface layer is less than the average amount of the binder phase inside the sintered alloy, and is present in the surface layer. Playing carbon Nitrogen, oxygen, boron, and wherein at least one diffusing element in the silicon is gradually decreased toward the surface of the surface layer to the interior of said sintered alloy.

Specifically, the binder phase in the sintered alloy of the present invention is, for example, Ti, Zr, Hf, V, Nb, Ta, C.
r, Mo, W, Ni, Co, Fe, Al, ZrMo ₂ ,
TaCr ₂ , ZrW ₂ , TiAl, TiAl ₃ , Nb ₃ A
l, Ni ₃ Al, V ₃ Al, Mo ₃ Al, W ₃ Al, NiA
1, Fe ₃ Al, Co ₂ Al ₉ , Zr ₃ Al, Co ₃ Al,
Ni ₃ (Al, Ti) or carbon within the solid solution limit thereof,
The case where nitrogen and / or oxygen (for example, 0.01 atomic% or less) is contained can be given. Among these binder phases, particularly when the binder phase is a high melting point metal binder phase containing at least one of the metals of the 4a, 5a and 6a groups of the periodic table, the ease of forming the surface layer and the heat resistance, It is also preferable from the viewpoint of alloy characteristics such as oxidation resistance and corrosion resistance. If the amount of the binder phase is less than 2% by volume with respect to the entire sintered alloy, the strength and toughness are significantly deteriorated, and conversely, if it exceeds 50% by volume, the heat resistance,
Since the deterioration of the oxidation resistance and wear resistance becomes remarkable, 2-5
It is defined as 0% by volume.

The binder phase in the sintered alloy of the present invention consists of aluminum oxide alone, or 50% by volume or more of aluminum oxide (relative to the hard phase) and the rest, such as zirconium oxide, MgO, CaO, or Y ₂ O. Partially stabilized zirconium oxide, hafnium oxide, chromium oxide, containing rare earth element oxides including ₃ as a stabilizer
Silicon oxide, silicon carbide, silicon nitride, 4 of the periodic table
This is the case where it is made of one of carbides, nitrides, titanium carbonitride, titanium carbonitride / molybdenum, zirconium carbide / tungsten, sialon, and zirconium oxide / hafnium of a, 5a, and 6a group metals.

Inside the sintered alloy excluding the surface layer, so-called sintered alloy, the above-mentioned binder phase and hard phase are densely mixed, but inevitable impurities and production which are contained in trace amounts in the starting material. A small amount of unavoidable impurities that are mixed in the process, particularly when the starting materials are mixed and pulverized, may be included to the extent that the characteristics of the alloy are not significantly deteriorated.

The surface layer of the sintered alloy of the present invention is at least aluminum carbide and carbides, nitrides, oxides, borides, silicides of metals of groups 4a, 5a and 6a of the Periodic Table and their mutual solid solutions. In some cases, one refractory metal compound is contained, or in addition to aluminum oxide and the refractory metal compound, a binder phase contained in the sintered alloy is contained. As the refractory metal compound forming the surface layer, specifically, for example, TiC,
WC, Ti (C, N), (Ti, W), (Ti, Mo)
C, ZrN, TiN, (Ti, Nb) N, (Cr, A
l) ₂ O ₃ , Al ₂ TiO ₅ , TiB ₂ , WB, MoSi ₂ can be mentioned. When the binder phase is present in the surface layer, it is necessary to make the average amount of the binder phase in the surface layer smaller than the average amount of the binder phase present inside the sintered alloy in order to improve various properties of the sintered alloy. It plays an important role. The average amount of the binder phase in the surface layer is 50% of the average amount of the binder phase present inside the sintered alloy, depending on the use and shape.
The following is preferable, and particularly when importance is attached to abrasion resistance, it is preferable that the average amount of the binder phase in the surface layer is 1% by volume or less or zero.

In addition to the composition of the surface layer as described above, another important feature in the constitution of the surface layer is that the concentration distribution of the refractory metal compound as an essential component forming the surface layer is different. . Specifically, for example, when the content of the refractory metal compound present in the surface layer is large on the surface of the surface layer and gradually decreases toward the inside of the sintered alloy, or a carbide which is the refractory metal compound, The concentration of at least one diffusing element among carbon, nitrogen, oxygen, boron, and silicon forming the nitride, the oxide, the boride, the silicide, and the mutual solid solution thereof is high on the surface of the surface layer, It may be gradually decreasing toward the inside of the bond. Of these, in the latter case,
The concentration of one kind of diffusing element is high on the surface of the surface layer and gradually decreases toward the inside of the sintered alloy, while the concentration of another diffusing element is relatively lower than that inside the sintered alloy. High at the interface,
In some cases, the combination is gradually reduced toward the surface of the surface layer. When the thickness of this surface layer is less than 0.01 mm, the effect of improving wear resistance, heat resistance, oxidation resistance, and corrosion resistance is weak, and it varies depending on the above-mentioned structure and composition of the surface layer, but it is stable. In order to extend the life, it is particularly preferable that the thickness of the surface layer is 0.05 to 1 mm.

This surface layer is formed on a part of the surface of the sintered alloy, or on the entire surface, or on two or more surfaces, and one surface is different from the other surface layer. Configuration, specifically, if the thickness of the surface layer is different, the composition components of the surface layer may be different, in particular, according to the application and shape, the presence of different refractory metal compounds,
It is particularly preferable. As a specific application example, when used as a cutting tool, especially a throwaway tip, it is preferable to form different surface layers on the scooping surface and the flank surface. , Nitrides, oxides that enhance heat resistance and oxidation resistance,
It is preferable to use a surface layer containing a refractory metal compound made of a boride, and a flank surface to be a surface layer containing a refractory metal compound made of a carbide that enhances scraping abrasion resistance.

It is also preferable to further coat a part or all of the surface of the sintered alloy having the above-mentioned surface layer with a film of a metal, an alloy or an inorganic compound. Specifically, for example, the periodic table is used. 4a, 5a, 6a group metal carbides, nitrides, carbon oxides, oxynitrides, Al oxides, nitrides, Si carbides, nitrides and their mutual solid solutions, diamonds, diamond-like carbons, cubic crystals It is preferably composed of at least one single layer or multiple layers of boron nitride.

In order to produce the sintered alloy of the present invention, the conventional powder metallurgy method can be applied by additionally applying the dipping method, the diffusion method, the casting method, and the centrifugal molding method. Is a preferable method from the viewpoint of easy control of the surface layer, a simple manufacturing method, and quality control.

The method for producing a sintered alloy of the present invention is carried out by using metals of groups 4a, 5a and 6a of the periodic table, Ni, Co, Fe and Al.
And aluminum oxide or 50% by volume or more of aluminum oxide and the balance zirconium oxide in at least one binder phase forming powder among these mutual alloys or their precursors,
At least one of partially stabilized zirconium oxide, hafnium oxide, chromium oxide, silicon oxide, silicon carbide, silicon nitride, carbides and nitrides of metals of groups 4a, 5a and 6a of the periodic table and mutual solid solutions thereof. A first step of adding a hard phase forming powder consisting of
Second step of shaping the mixed powder into a predetermined shape to obtain a powder compact, contacting the powder compact with a compound containing at least one diffusing element among carbon, nitrogen, oxygen, boron and silicon Alternatively, it is a method comprising a third step of depositing or installing in a gas atmosphere containing the diffusing element and heating to 1400 to 1900 ° C.

As the binder phase forming powder in the production method of the present invention, for example, a fine metal or alloy powder having a particle size of 2 μm or less can be used, but a precursor which is thermally decomposed to produce a metal or alloy during the heating in the third step. , Specifically, for example, T
iH ₂ , ZrH ₂ , TaH ₂ , NbH ₂ , hydride, Cr
When N, Mo ₂ N, TiN, or Nitride is used, it is possible to obtain a dense and high-strength sintered alloy that tends to become fine during the mixing and pulverization in the first step and has little influence of adhesion and adsorbed oxygen. preferable. The hard phase forming powder used as a starting material for the binder phase forming powder may be a powder conventionally used in powder metallurgy, for example, a powder having a particle size of 10 μm or less, preferably a powder having a particle size of 3 μm or less, In the case of oxide powder, it is preferable to use a submicron particle size powder because a dense and high-strength sintered alloy can be obtained.

The first step of mixing and pulverizing the binder phase forming powder and the hard phase forming powder into a mixed powder is carried out by a mixing method which is carried out by a conventional powder metallurgy method to obtain the following powder green compact. Also in the second step, a method which is carried out by a conventional powder metallurgy method, for example, a method by die molding, extrusion molding, injection molding, casting molding, centrifugal molding may be carried out at appropriate times.

The third step in the production method of the present invention is to disperse a compound containing a diffusing element, such as carbon, graphite, metallic boron, silicon, boron carbide, silicon carbide, boron oxide or silicon nitride, in an organic solvent. And a slurry-like substance, a method of spraying or applying the slurry-like substance to the necessary surface of the above-mentioned powder compact,
In addition, a method of applying the above-mentioned slurry-like substance to a graphite plate, etc. and contacting the powder compact with it, and further, when molding the powder compact, the surface part is integrally molded with a layer of a compound containing a diffusion element. And the method of burying the powder compact in the powder of the compound containing the diffusing element, and then heating. Further, as another method of the third step, for example, CH ₄ , N ₂ , O ₂ , CO, CO ₂ , BCl ₄ , SiH _{4 are used.}
Alternatively, the powder compact may be placed and heated in a gas atmosphere containing the diffusing element. In this case, it is preferable to heat the powder compact in a vacuum or an inert gas up to a temperature at which the powder compact is sintered and become dense, and then switch to a gas atmosphere containing a diffusion element for sintering.

The control of the surface layer of the sintered alloy of the present invention, in particular, the control of the composition, thickness and concentration gradient of the diffusing element in the above-mentioned manufacturing method, is carried out in the amount of the compound containing the diffusing element and in the gas atmosphere. The diffusion element gas partial pressure, the sintering temperature and the time may be used.

It is preferable to further subject the sintered alloy obtained by the above manufacturing method to hot isostatic pressing (HIP treatment) in order to obtain a dense and high-strength sintered alloy. Also,
When the surface of the sintered alloy of the present invention is further coated with a film, it can be carried out by a conventional chemical vapor deposition method or physical vapor deposition method.

[0025]

In the sintered alloy of the present invention, the inside of the sintered alloy, specifically, the binder phase mainly constituting the inside of the sintered alloy acts to enhance strength and toughness, and forms a surface layer. The refractory metal compound and the binder phase concentration mainly act to enhance wear resistance, heat resistance, oxidation resistance, and corrosion resistance, and the concentration gradient of the diffusing element in the surface layer causes a difference between the surface layer and the inside of the sintered alloy. It has a function of enhancing thermal stress relaxation in the vicinity of the boundary surface.

[0026]

Example 1 α-alumina powder having an average particle size of 0.3 μm, 0.5 μm Mo, W, and WC powders, 1 to 3
μm Ti (C _0.5 , N _0.5 ), TiH ₂ , ZrH ₂ , Nb
H ₂ , TaH ₂ , CrN, Ni powder, A of 0.1 μm
1, ZrO ₂ (containing 3 mol% Y ₂ O ₃ ) powder was used.
Into a stainless steel pot lined with urethane and lined with methanol and alumina balls, mix and pulverize for 48 hours, mix and pulverize for 48 hours, then add and mix 6 wt% paraffin wax while heating to 80 ° C. To obtain a mixed powder. Next, each mixed powder was pressure-molded at ¹ ton / cm ² using a mold to prepare a powder compact. Then, after the powder compact was treated by the method for treating the surface of the powder compact described in Table 1, the sintering conditions also listed in Table 1 (provided that the sintering atmosphere was 10 ^{-3 at} all until 1500 ° C).
Sintered with a vacuum of Torr) and the shape is ISO
The product 1 of the present invention including a standard equivalent of SNMN120408
10 and comparative products 1 to 3 were obtained.

[0027]

[Table 1] The sintered alloys of the present invention products 1 to 10 and the comparative products 1 to 3 were cut, and the thickness of each surface layer, a point (surface layer) within 0.01 mm from the surface of the surface layer of the sintered alloy, and firing bonding At a point within 2.0 mm from the surface of the gold surface layer (inside of the sintered alloy), the minute component X-ray diffraction, the composition component by the metallographic microscope and the scanning electron microscope, and the micro Vickers hardness (500 g load) were measured. The results are shown in Table 2. (However, when there is no surface layer, 0.01 mm and 2.0 mm points were examined from the surface of the sintered alloy)

[0028]

[Table 2] Among the sintered alloys of Table 2 thus obtained, the products of the present invention 3, 5,
Work piece S48C, cutting speed 400 m / min, feed 0.2 mm using 7 and 10, comparative products 1 and 2 and commercially available pure alumina-based ceramics and alumina-titanium carbide-based ceramics manufactured in the same shape. / Rev, depth of cut 1.5 mm, chip shape SNMN120408 (with breaker, with 0.15 x -25 ° PH), cutting time 10
Min, dry turning test based on evaluation average flank wear width (V _B ) and work material S48C (4 grooves on outer circumference) cutting speed 10
0 m / min, feed 0.12 mm / rev, cut 1.
5 mm, same as chip shape, cutting time loss or life due to chipping, a dry interrupted turning test was carried out with an average life time of 3 corners evaluated, and the results are shown in Table 3.

[0029]

[Table 3]

[0030]

Example 2 Using the sintered alloys of the present invention products 3, 5, 7 and comparative products 1, 2 obtained in Example 1 and commercially available Al ₂ O ₃ based ceramics, Al ₂ O ₃ —TiC based ceramics , A 0.5 μm thick TiC film is formed on the surface of each sintered alloy or ceramic by a conventional chemical vapor deposition method.
1 μm thick Ti (C, N), 0.5 μm thick TiN
Are sequentially coated, and the products of the present invention 11, 12, 13,
Comparative products 4, 5 and coated Al ₂ O ₃ based ceramics and coated Al ₂ O ₃ —TiC based ceramics were obtained. The coated sintered alloy and the coated ceramics thus obtained were subjected to the turning test and the interrupted test conducted in Example 1, and as a result, the product 1 of the present invention was obtained.
1, 12 and 13 are the products 3 of the present invention of Example 1, respectively.
Compared with Nos. 5 and 7, the improvement was about 50 to 150%, while Comparatives Nos. 4 and 5 and the coated ceramics were each manufactured in Example 1.
It was almost the same as the comparative products 1 and 2 and the commercial ceramics.

[0031]

The hardness of the surface layer of the sintered alloy of the present invention is 4% to 34% higher than that of the inside of the sintered alloy, and the wear resistance is higher than that of the conventional aluminum oxide-based sintered alloy. Is 3.3 times or more, and the life due to fracture resistance is 5.6 times or more.
The effect of improving by 63 times, and the abrasion resistance is 7% to 7% compared with the conventional aluminum oxide ceramics.
52%, and the life due to fracture resistance is improved by 83% to 63 times.

Furthermore, the coated sintered alloy of the present invention coated with a hard coating has the effect of improving wear resistance and fracture resistance by 50 to 150% as compared with the sintered alloy of the present invention not coated with a coating. There is.

As described above, in the sintered alloy of the present invention, the surface layer exhibits the effects of enhancing wear resistance, oxidation resistance, heat resistance, corrosion resistance, welding resistance to iron-based materials, and adhesion with a hard coating. ,
The inside of the sintered alloy has the effect of enhancing strength and toughness, and is an industrially useful material that can be applied to tools and various mechanical parts.

Claims (4)

[Claims] 1. A metal of group 4a, 5a, 6a of the periodic table,
2 to 50% by volume of a binder phase of at least one of Ni, Co, Fe, Al and their mutual alloys, and a hard phase of the balance being aluminum oxide, or 50% by volume of aluminum oxide
Above and remaining zirconium oxide, partially stabilized zirconium oxide, hafnium oxide, chromium oxide, silicon oxide, silicon carbide, silicon nitride, carbides, nitrides of metals of groups 4a, 5a and 6a of the periodic table and mutual solid solutions thereof. A surface layer having a thickness of at least 0.01 mm from the surface is formed on a part or all of the surface of the sintered alloy composed of a hard phase composed of at least one of the above and unavoidable impurities. The layer is aluminum oxide and 4a of the periodic table,
A carbide, a nitride, an oxide, a boride, a silicide of a group 5a or 6a metal and at least one refractory metal compound among these mutual solid solutions, or aluminum oxide and the refractory metal compound. And a surface layer comprising the binder phase, wherein the average amount of the binder phase in the surface layer is less than the average amount of the binder phase inside the sintered alloy, and the surface At least one diffusing element among carbon, nitrogen, oxygen, boron, and silicon present in the layer is gradually reduced from the surface of the surface layer toward the inside of the sintered alloy. Sintered surface tempered alloy. 2. The surface layer is formed on at least two surfaces of the sintered alloy, and the surface layer formed on one surface of the sintered alloy and the surface formed on another surface of the sintered alloy. The surface-tempered sintered alloy according to claim 1, wherein different refractory metal compounds are present in the layer. 3. A carbide, a nitride, a carbonate, a nitrous oxide of a metal of group 4a, 5a, 6a of the periodic table on a part or all of the surface-tempered sintered alloy according to claim 1 or 2. A single layer or a multi-layer coating of at least one of the following: an oxide, an Al oxide, a nitride, a Si carbide, a nitride and their mutual solid solutions, diamond, diamond-like carbon, and cubic boron nitride. Surface refined sintered alloy characterized by. 4. A metal of group 4a, 5a, 6a of the periodic table,
Aluminum oxide, or 50% by volume or more of aluminum oxide and remaining zirconium oxide, partially stabilized zirconium oxide, in at least one binder phase forming powder of Ni, Co, Fe, Al and their mutual alloys or their precursors. Hard phase forming powder consisting of hafnium oxide, chromium oxide, silicon oxide, silicon carbide, silicon nitride, carbides and nitrides of metals of groups 4a, 5a and 6a of the periodic table, and at least one of these mutual solid solutions Is added and mixed and pulverized to form a mixed powder, a second step of forming the mixed powder into a predetermined shape to obtain a powder compact, and the powder compact is carbon, nitrogen, oxygen, boron, At least 1 in silicon
1400 to be placed in contact with or attached to a compound containing a diffusion element of a seed, or installed in a gas atmosphere containing the diffusion element
A method for producing a surface-tempered sintered alloy, comprising producing the surface-tempered sintered alloy according to claim 1 or 2 through a third step of heating to 1900 ° C.