JPH06298568A - Whisker-reinforced sialon-based sintered compact and sintered and coated material - Google Patents

Abstract

PURPOSE:To obtain a whisker-reinforced beta-sialon-based sintered compact having remarkably improved high-temperature strength and hardness and excellent abrasion resistance and chipping resistance by using a specific double oxide as the grain boundary phase material. CONSTITUTION:The whisker-reinforced sialon-based sintered compact is composed of <=35wt.% of ceramic and/or carbon whiskers, 1-20wt.% of a grain boundary phase composed mainly of the double oxide of formula (R is at least one kind of rare earth element including Sc and Y; M is Hf or Zr; -1<x<1; O is oxygen) and the remaining part of a matrix phase composed mainly of beta-sialon. The whisker to be used in the above process is e.g. silicon carbide whisker, silicon nitride whisker, aluminum oxide whisker and carbon whisker. Silicon carbide whisker is especially preferable among the above whiskers owing to its excellent tensile strength.

Description

Detailed Description of the Invention

[0001]

The present invention relates to ceramics and / or
Further, the present invention relates to a β-sialon-based sintered body containing carbon whiskers and a coated sialon-based sintered body obtained by coating the surface thereof with a coating film. Or a whisker reinforced sialon-based sintered body which is optimal as a wear-resistant tool such as a can forming die, a slitter, a bush, a guide, a nozzle, a valve, a ball, etc. The present invention relates to a coated sialon-based sintered body having a surface coated with a coating.

[0002]

2. Description of the Related Art Generally, β-sialon (compositional formula: Si
_6-Z-Al zO zN_8-Z, 0 <z ≦ 4.2) is silicon nitride.
Easier to sinter and smaller coefficient of thermal expansion than plain
High thermal shock resistance, corrosion resistance to steel and cast iron
Although it is rich (has poor affinity) and has high strength,
Reach satisfactory wear resistance and fracture resistance
There is a problem of not doing.

In order to solve this problem, a whisker-reinforced sialon-based ceramics sintered body, in which SiC whiskers are dispersed, has been proposed. Typical examples thereof are Japanese Patent Publication No. 3-51669 and Japanese Patent Publication No. 3-51669. Kaisho 6
There is a publication of 3-112471.

[0004]

[Problems to be Solved by the Invention] Japanese Patent Publication No. 3-51669
In the publication, SiC whiskers, B_FourC whiskers and
And TiB₂One or more of whiskers 10
~ 30 wt% of Y, Mg, Ca and rare earth elements
A compound of one or more of Al, Si, O and N
Vitreous phase composed of and unavoidable impurities 7-20w
t%, composition formula Si_6-Z-Al zO zN_8-Z(However, 0 <z
≦ 4) β-sialon phase
Described the cutting tool parts made of earlon-based ceramics.
Has been.

The sintered body described in the above publication is intended to improve the toughness of the sintered body by the whiskers and the glassy phase, but it contains a large amount of the low melting point glassy phase. There is a problem that the strength is remarkably reduced at high temperatures, and when it is used as a cutting tool in which the cutting edge has high temperature, the fracture resistance is lowered and the life is remarkably shortened.

Further, in Japanese Patent Laid-Open No. 63-112471.
Is the formula Si_6-Z-Al zO zN_8-Z(However, 0 <z ≦ 4.
The main component is β-sialon represented by 2), and 0.1
~ 15wt% oxide of Group 3a element, and 1-35wt%
Including silicon carbide whiskers, the grain boundary phase is crystallized
Silicon nitride ceramics characterized by
Has been.

The sintered body described in the above publication is intended to improve the strength at high temperature by making the grain boundary phase a crystalline phase having a higher melting point than the glassy phase.

That is, Y ₂ added as a sintering aid
Oxides of Group 3a elements such as O _{3 and} CeO ₂ react with Si, Al, O and N which are the main components and form a grain boundary phase mainly composed of a glassy phase after sintering. Is crystallized by performing heat treatment at 1200 to 1600 ° C. in a non-oxidizing atmosphere. In this case, as the crystalline grain boundary phase produced, for example, an oxide of a 3a group element is Y ₂ O ₃
In the case of, Y ₂ Si ₃ N ₄ O ₃ (Merilite), Y ₈ Si ₄ N ₄
O ₁₄ (J _{phase), Y 2 Si 2 O 7} , Y 20 N 4 Si 12 O 48 and the like. Although these crystalline phases have a higher melting point than the vitreous phase, their heat resistance is far inferior to that of Sialon, which is the main component, and they are inadequate. When used, there is a problem that the life is shortened due to deterioration in fracture resistance and wear resistance.

The present invention has solved the above-mentioned problems. Specifically, in a β-sialon-based sintered body reinforced with whiskers, its grain boundary phase is a complex oxide having high hardness and high melting point. The purpose of the present invention is to provide a whisker-reinforced sialon-based sintered body and a coated sintered body thereof, which are excellent in wear resistance, fracture resistance, oxidation resistance, and thermal shock resistance, in which hardness and strength at high temperature are remarkably improved. To do.

[0010]

Means for Solving the Problems In order to be able to use a whisker-reinforced sialon-based sintered body as a cutting tool for Ni-based superheat-resistant alloys such as Wasparloy, which is a difficult-to-cut material, As a result of studying the properties of the boundary phase, when an oxide of a rare earth element is used as a sintering aid and HfO ₂ and / or ZrO ₂ is added thereto, the rare earth element and Si, Al, O, N Is suppressed, the rare earth element oxide reacts with HfO ₂ and / or ZrO ₂ to form a composite oxide, and the composite oxide has an extremely high melting point and a high hardness, The present invention has been completed on the basis of the finding that the strength and hardness at high temperature are remarkably improved and a sintered body having excellent wear resistance and fracture resistance is obtained.

That is, the whisker-reinforced sialon-based sintered body of the present invention contains ceramics and / or carbon whiskers in an amount of 35% by weight or less and R ₂ M _2-X O _7-2X (where R is Sc, Y Represents at least one of rare earth elements including M, M represents Hf and / or Zr, -1 <x <1, and O represents oxygen.) The grain boundary phase is 1 to 20% by weight, and the balance is a matrix containing β-sialon as a main component.

Specific examples of whiskers in the sintered body of the present invention include silicon carbide whiskers, silicon nitride whiskers, aluminum oxide whiskers, and carbon whiskers, and silicon carbide whiskers having particularly excellent tensile strength are preferable. The size of the whiskers has an average diameter of 0.1 to 1.5 μm, particularly preferably 0.3 to 1 μm, and an average length of 5 to 100 μm.
Particularly, those having an average length of 10 to 50 μm are preferable. If the content of this whisker exceeds 35% by weight,
It is difficult to sinter, it becomes difficult to obtain a dense sintered body, and the wear resistance is significantly reduced. In particular, the content of whiskers is preferably 10 to 30% by weight.

The complex oxide as the grain boundary phase in the sintered body of the present invention is specifically, for example, Y ₂ ZrO ₅ , Dy.
₂ (Zr, Hf) O ₅ , (Y, Dy) ₂ HfO ₅ , Dy ₂ H
fO ₅ , Y ₂ HfO ₅ , Sc ₂ ZrO ₅ , Er ₂ ZrO ₅ , L
a ₂ HfO ₅ , and other grain boundary phases include Si
Oxide or glassy (amorphous) containing a rare earth element
The substance can be mentioned. This grain boundary phase is 1% by weight
If it is less than 20% by weight, the strength and toughness are significantly deteriorated. On the contrary, if it exceeds 20% by weight, the thermal shock resistance is significantly decreased. It is preferable that the grain boundary phase has more complex oxides forming the grain boundary phase, and 50% by weight or more of the grain boundary phase is composed of the complex oxide, so that the amount of the glassy substance can be suppressed as much as possible. preferable.

In addition to the whiskers and the grain boundary phase, at least one of nitrides, carbides, oxynitrides, and carbonates of metals of Group 4a in the periodic table and their mutual solid solution or silicon carbide is used. The presence of the dispersed phase in an amount of 20% by weight or less is preferable because it improves wear resistance and welding resistance.

The matrix in the sintered body of the present invention is
More than 50% by weight in the matrix is traditionally defined
Β-sialon (Si_6-Z-Al zO zN_8-Z,
0 <z ≦ 4.2), and the rest is α-silicon nitride, β
-Silicon nitride, α-sialon [My (Si, Al)₁₂
(O, N)₁₆, M = Li, Mg, Ca, Y, etc., 0.3 ≦
y <1.0]
It Β-sialon in this matrix is wear resistant
And to improve toughness, Z is 0.5 ≦ z ≦ 3.0
It is particularly preferable that it is in the range.

On the whole surface or a part of the surface of the sintered body of the present invention having the above-mentioned constitution, for example, on a partial surface such as a flank or a scooping surface in a cutting tool, 4a, 5a, 6 of the periodic table.
Group a metal, Al carbide, nitride, oxide and their mutual solid solution or diamond, diamond-like carbon, cubic boron nitride, hard boron nitride, and at least one single layer or two or more multiple layers Become 0.5
It is preferable to form a coating film having a thickness of up to 20 μm because it has the effect of enhancing wear resistance and welding resistance.

The sintered body of the present invention can be produced by a conventional powder metallurgy method. For example, it can be obtained by mixing, molding and sintering desired starting material powder and whiskers which are commercially available. In particular, it is preferable to mix the whiskers by adding the whiskers at the time of finishing and mixing them for a short time after sufficiently mixing and crushing the other starting material powders in order to prevent the aspect ratio from being decreased by over-milling. In the sintering step, under a non-oxidizing gas atmosphere such as nitrogen gas or an inert gas, at a temperature of 1600 to 1900 ° C. and atmospheric pressure,
Pressurization, depressurization or hot press sintering may be performed. Also,
It is also preferable to perform hot isostatic pressure treatment (HIP treatment), if necessary.

When a film is formed on the surface of the thus obtained sintered body, the conventional chemical vapor deposition method (CVD
Method) or physical vapor deposition method (PVD method).

[0019]

[Function] Whiskers in the sintered body of the present invention have crack deflection, pullout and bridging effects which are interpreted as the strengthening mechanism of whiskers, and the effects are toughness, strength, abrasive wear resistance and high temperature strength. , The thermal shock resistance is enhanced, the grain boundary phase acts to assist the action effect of the whiskers and the matrix, and the strength and toughness at room temperature and high temperature are enhanced, and the matrix enhances the wear resistance. It is a thing.

[0020]

Example 1 Si ₃ N _{4 having} an average particle size of 0.7 μm
, 0.2 μm Al ₂ O ₃ , 0.3 μm AlN, 0.
5 μm Y ₂ O ₃ , 0.5 μm Dy ₂ O ₃ , 0.4 μm HfO ₂ , 0.5 μm ZrO ₂ , 0.5 μm TiN,
0.5 μm TiC, 0.5 μm Ti (C, N) powders, and Si with an average diameter of 0.6 μm and an average length of 30 μm
Each was compounded as shown in Table 1 using C whiskers.

[0021]

[Table 1] In Table 1, other compounded powders except for whiskers were charged into a container together with Si ₃ N ₄ balls and an ethanol solvent, ball mill mixed and pulverized for 64 hours, then whiskers were added, and further mixed and dried for 8 hours. A mixed powder was obtained. This mixed powder was inserted into a carbon mold coated with a release agent, and 300 kg for 1 hour at 1700 ° C. in a normal pressure N ₂ gas atmosphere.
Hot press sintering was performed at a pressure of / cm ² to obtain sintered products of the present invention products 1 to 8 and comparative products 1 to 5.

The compositions of the sintered bodies of the products 1 to 8 of the present invention and the comparative products 1 to 5 thus obtained were analyzed by X-ray diffraction, TEM (transmission electron microscope) and EPMA (electron probe microanalysis). The results are shown in Table 2. In particular, the value of Z in β-sialon is a value converted by the lattice constant obtained from the X-ray diffraction line.

[0023]

[Table 2] In addition, the room temperature and high temperature (130
The hardness and bending strength in 0 ° C.-argon atmosphere) were measured, and the results are shown in Table 3.

Further, each sintered body shown in Table 2 was subjected to a cutting test under the following conditions (A) and (B), and the results are also shown in Table 3. (A) Wet continuous turning test conditions Work material: Waspiro Cutting speed: 125 m / min Cutting depth: 1.0 mm Feed: 0.15 mm / rev Cutting time: 3 min Cutting oil: Water-soluble cutting oil Chip shape: SNGN120408 Evaluation: Average flank wear (V _B) and boundary wear amount (V _N) (B) milling test conditions workpiece by dry: FCD600 (45 × 200 mm surface) cutting speed: 150 meters / min cut: 1.5 mm initial feed: 0.20 mm / rev Chip shape: SNGN120408 Evaluation: Maximum feed leading to chip loss (0.03 mm / rev feed increased if chipping is not lost at 1 Pass)

[0025]

[Table 3]

[0026]

Example 2 Using the products 2, 3 and 8 of the present invention and the comparative products 2 and 4 obtained in Example 1, CV was applied to the surface of each sintered body.
A film was formed by the D method. The coating is formed on the surface of each sintered body as shown in Table 4 with the layer formed on the surface of the sintered body as the first layer, the second layer next, and the third layer next. Thus, coated sintered bodies No. 9 to 11 of the present invention and comparative coated sintered bodies No. 6 and 7 were obtained.

Using the obtained sintered body, a cutting test was conducted under the conditions (A) and (B) of Example 1, and the results are shown in Table 4.

[0028]

[Table 4]

[0029]

The sintered body of the present invention has an equivalent room temperature hardness of 13 to 13 as compared with the conventional whisker-containing sialon-based sintered body.
%, The high temperature hardness is improved by 40%, the room temperature bending strength is improved by 19%, and the high temperature bending strength is about 45-10%.
0% improvement, the flank wear amount in the cutting test is equivalent to 4
It has a remarkable effect that the boundary wear amount is reduced by 7%, the boundary wear amount is reduced by about 25 to 49%, and the fracture resistance is also improved by 3 to 4 ranks (feed of 0.09 to 0.12).

Claims (3)

[Claims] 1. A whisker of ceramics and / or carbon in an amount of 35% by weight or less and R ₂ M _2-X O _7-2X (where R is at least one of rare earth elements including Sc and Y). Where M represents Hf and / or Zr, -1 <x <1, and O represents oxygen.) 1 to 20% by weight of a grain boundary phase containing a composite oxide as a main component. The balance consists of a matrix whose main component is β-sialon, and a whisker-reinforced sialon-based sintered body. 2. A ceramic and / or carbon whisker of 35% by weight or less and R ₂ M _2-X O _7-2X (where R is at least one of rare earth elements including Sc and Y). Where M represents Hf and / or Zr, -1 <x <1, and O represents oxygen.) 1 to 20% by weight of a grain boundary phase containing a composite oxide as a main component. 20% by weight or less of at least one disperse phase in a nitride, a carbide, a nitride oxide, a carbonate of a metal of Group 4a of the Periodic Table and their mutual solid solution or silicon carbide, and the balance being β-sialon A whisker-reinforced sialon-based sintered body comprising a matrix containing as a main component. 3. The whole or a part of the surface of the sintered body according to claim 1 or 2, wherein a metal of group 4a, 5a, 6a of the periodic table, a carbide of Al, a nitride, an oxide and a mutual thereof are included. 0.5 to 2 consisting of a solid solution or diamond, diamond-like carbon, cubic boron nitride, hard boron nitride, at least one single layer or two or more multiple layers
A coated sialon-based sintered body, wherein a coating having a film thickness of 0 μm is formed.