JPH05170520A - Fiber-reinforced ceramics - Google Patents

Abstract

PURPOSE:To provide the subject fiber-reinforced ceramics having high toughness and sufficiently applicable to cutting of an iron-based material. CONSTITUTION:One or two or more kinds of titanium carbide, nitride and carbonitride and one or two or more kinds of silicon carbide, nitride and carbonitride are contained in an amount of 10 to 60vol.% in total and the remainder components are aluminum oxide and unavoidable impurities. Based on the above-mentioned carbides, nitrides and carbonitrides of titanium and silicon, whisker is used in an amount of 10 to 95vol.%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fiber reinforced ceramic containing a fibrous substance such as whiskers, and more particularly to a fiber reinforced ceramic excellent in high toughness and particularly suitable as a tool material.

[0002]

2. Description of the Related Art Conventionally used alumina (hereinafter,
Al ₂ O ₃ and referred to) whereas quality sintered body excellent in wear resistance, various proposals have been made because of the inferior toughness.

One of them is to improve the toughness by blending Al ₂ O ₃ with a fibrous substance typified by silicon carbide (hereinafter referred to as SiC) whiskers. JP-A-61-28671 And JP-A-62-41776.

All of these fiber-reinforced ceramics are mainly composed of Al ₂ O ₃ , SiC whiskers are added to the mixture, and the mixture is fired by hot pressing or the like.

Since fiber-reinforced ceramics containing such SiC whiskers has high hardness of SiC itself and good thermal conductivity, when used as a cutting tool, some superheat-resistant alloys are cut (rough cutting of Inconel 718). ) Shows excellent cutting performance.

Further, it has been proposed to use titanium carbide (hereinafter referred to as TiC) whiskers as the fibrous material in addition to the SiC whiskers (JP-A-2-13336).
9).

[0007]

[Problems to be Solved by the Invention] However, Si
Since C easily reacts with iron, especially iron oxide, Al ₂ O ₃
-SiC whisker-based tools often use other Al ₂
The amount of wear tends to increase as compared with tools mainly containing O ₃ . For example, when SUS304 is cut, conventional A
If it is an l ₂ O ₃ system tool, even if it is under a condition where it can be sufficiently cut, a tool containing SiC whiskers may rapidly wear and become uncut. Further, it has been confirmed that the amount of wear is larger than that of an Al ₂ O ₃ system tool when cutting cast iron.

Further, although the Al ₂ O ₃ -TiC whisker-based tool shows an improvement in toughness, it is not sufficient, and it has a drawback that it tends to be broken when an excessive load is generated during cutting.

[0009]

[Means for Solving the Problems] The inventors of the present invention have made extensive studies on the above problems, and as a result, in the composite material containing Al ₂ O ₃ as a main component, Ti carbide and nitriding It is high if one or two or more kinds of a metal and a carbonitride and one or two or more of a Si carbide, a nitride and a carbonitride are contained, and a part of them is used as a whisker. It has been found that a fiber-reinforced ceramic having toughness and sufficiently applicable to the cutting of iron-based materials can be obtained.

Further, the inventors of the present invention have found that the optimum sintering aid for ceramics in which the above Al ₂ O ₃ is mixed with carbides and nitrides of Ti and Si and whiskers such as carbides and nitrides of Ti and Si. By finding the agent, conventional Al
_It has been found that a material having mechanical properties such as toughness superior to that of the ₂ O ₃ -SiC whisker addition system can be obtained.

That is, according to the present invention, one or more of Ti carbides, nitrides and carbonitrides and one or more of Si carbides, nitrides and carbonitrides are added together. 10 to 60% by volume, the balance consisting of aluminum oxide and unavoidable impurities, and the above Ti and Si
10 to 95% by volume of the carbides, nitrides, and carbonitrides of 1. have a composition composed of whiskers. This fiber-reinforced ceramic contains 0.1 to 1 kind or 2 or more kinds of oxides of Mg, Ti, Si, Zr and rare earth elements as a sintering aid.
It is desirable to contain 10% by weight.

The present invention will be described in detail below.

According to the fiber-reinforced ceramics of the present invention,
10 to 60% by volume of one or more of Ti carbide, nitride and carbonitride and one or more of Si carbide, nitride and carbonitride, especially 20
~ 45 volume% dispersedly contained, and particles having an aspect ratio of 1.5 or more as whiskers are present in 10 to 95 volume%, particularly 20 to 90 volume% of Ti and Si carbides, nitrides and carbonitrides. Let

Here, the reason why the amounts of the carbides, nitrides and carbonitrides of Ti and Si are limited to the above range is that when the amount is less than 10% by volume, the grain growth of Al ₂ O ₃ is suppressed. Is weakened, and if it exceeds 60% by volume, the sinterability is lowered, and the fracture toughness and the bending strength are also lowered.
Further, the amount of whiskers is limited to 10 to 95% by volume of the carbides, nitrides and carbonitrides of Ti and Si, because if the amount is less than 10% by volume, the toughness of the sintered body is not improved. This is because if it is more than 95% by volume, the sinterability is lowered and the bending strength is lowered.

According to the present invention, the above Al ₂ O _{3 is also used.}
-A sintering aid is added to improve the sinterability in Ti and Si-based materials. As the sintering aid used, Mg,
At least one kind of oxides of Si, Ti, Zr and rare earth elements is mentioned, and specifically, Yb, Nd, E
r, Ce, Sm, Y, Gd, Dy and La are mentioned. These sintering aids are 0.1 to 10% by weight in the total amount,
In particular, it is contained in a proportion of 0.3 to 7% by weight. If the amount of the auxiliary agent is less than 0.1% by weight, the sinterability is poor and a dense material cannot be obtained, and the toughness in the whisker addition system cannot be improved. Further, even if it exceeds 10% by weight, it does not contribute to the improvement of the toughness, and the hardness and the bending strength decrease.

In the production of the fiber reinforced ceramics of the present invention, Al ₂ O ₃ as a raw material, one or more of Ti carbide, nitride and carbonitride, and Si carbide, nitride and carbonitride. One or more of these materials are used, and a sintering aid is added and mixed thereto.

The whiskers used in the present invention are composed of a single crystal or a polycrystal, and have an average diameter (minor axis length) of 2 μm or less, particularly 0.2 to 0.7 μm.
m is preferable, and those having an average aspect ratio represented by major axis / minor axis of 3 to 100, particularly 10 to 30, are used. If the average diameter is 2 μm or less, the grain growth during sintering does not become excessive and high bending strength can be maintained, whereas if the average diameter is larger than 2 μm, the grain growth of crystal particles during sintering is remarkable, and the grain size is large. Becomes difficult to control, the strength decreases, and the toughness varies. Further, when used as a cutting tool, the boundary wear of the flank tends to increase.

On the other hand, if the average aspect ratio is less than 3, the effect of fiber reinforcement is reduced and the toughness is reduced, and if it is more than 100, the raw material is difficult to handle and it is difficult to disperse it uniformly, so that the toughness tends to be reduced. Even in this case, if a part of them is pulverized and mixed, they can be used without problems.

The Ti and Si carbides, nitrides and carbonitrides can be arbitrarily selected in size and shape, but in order to increase the grain growth suppressing effect, the average grain size is 3 μm.
m or less is good.

According to the present invention, the TiC component and Al ₂
In the mixing with the O ₃ component, whiskers tend to have a small aspect ratio due to firing, and therefore it is desirable to mix the whiskers in an amount slightly larger than the amount to be present in the sintered body.

Whiskers are uniformly dispersed in the mixture of the above raw materials by granulation and drying. Further, the structure may be controlled by agglomerating the whiskers by spray-drying the slurry. Then, this mixture is molded by a desired molding means, for example, a die press, a cold isostatic press, an extrusion molding or the like, and then fired. Normal firing, hot pressing, hot isostatic firing, etc. are applied for firing.

The firing is carried out at a temperature of 1450 to 1950 ° C. with Ar,
In a reducing atmosphere in which an inert gas such as He or carbon is present, and in a pressurized or depressurized atmosphere thereof, a pressure of 0.
It may be carried out for 5 to 6.0 hours. To obtain a particularly high density sintered body, a sintered body having a theoretical density ratio of 96% or more is prepared by ordinary firing and hot pressing, and further hot isostatic pressure is applied. 500 to 2000 atm, 1450 to 1950 ° C by firing
It can be baked in.

[0023]

In the fiber-reinforced ceramics of the present invention, whiskers are added to improve the toughness and wear resistance of the sintered body while maintaining the characteristics of Al ₂ O ₃ itself. It is possible to suppress grain growth of Al ₂ O ₃ and improve properties such as strength of the sintered body.
That is, it has high toughness and can be sufficiently applied to the cutting of iron-based materials.

Further, by adding an optimum sintering aid, the sinterability can be improved and the characteristics such as toughness can be improved.

[0025]

EXAMPLES Al ₂ O ₃ powder having an average particle size of 1 μm or less and a purity of 99.9% or more, and one or more kinds of Ti carbide, nitride and carbonitride powders having an average particle size of 1 μm or less, The composition of one or more of Si carbide, nitride, and carbonitride powders having an average particle diameter of 1 μm or less and a sintering aid powder is shown in Table 1.
And, after weighing so as to be in Table 2, they were mixed and pulverized by an attrition mill for 12 hours. A predetermined amount of whiskers having an aspect ratio of 10 to 60 was added to this mixed powder, and the whiskers were sealed together with nylon balls in a nylon pot and mixed in a rotary mill for 12 hours. The mixed slurry was dried to obtain a raw material for hot pressing.

[0026]

[Table 1]

[0027]

[Table 2]

A carbon mold was filled with this raw material, and 1700
K1c was measured by IM method by hot press firing at a pressure of 300 kg / mm ² for 1 hour at ˜1920 ° C., three-point bending bending strength based on JIS1601, Vickers hardness, and polishing to a mirror surface state by IM method. The whiskers with an aspect ratio of 1.5 or more in the sintered body were obtained by surface analysis from electron micrographs.

A cutting test for investigating the tool wear life was conducted under the following conditions.

Work Material: Inconel 718 Cutting Speed (V): 300 m / min Feed Speed (f): 0.1 mm / rev Depth of Cut (t): 2.0 mm Cutting Oil: Water-soluble Life Judgment (mm): Defect Cutting time until Tool shape: RNGN 120416 Table 3 shows the test results.

[0031]

[Table 3]

According to Table 3, all the samples (No. 3, 4, 6-12 and 14-19) of the sintered material of the present invention are comparative examples (No. 1, 2, 5, 13, 20). It has a longer life than that of, and is superior in toughness, strength, hardness, etc.,
It has been revealed that excellent cutting performance is exhibited over a long period of time.

[0033]

The fiber-reinforced ceramics of the present invention are made of Ti
One or more of the above carbides, nitrides and carbonitrides and one of the Si carbides, nitrides and carbonitrides
Content of 10 to 60% by volume in total, and the balance consisting of aluminum oxide and inevitable impurities, and
Since 10 to 95% by volume of the above carbides, nitrides, and carbonitrides of Ti and Si are composed of whiskers, they have high toughness and excellent characteristics that are sufficiently applicable to cutting of iron-based materials. Fiber-reinforced ceramics can be obtained.

Claims (2)

[Claims] 1. A total of 10 to 60 of one or more of Ti carbides, nitrides and carbonitrides and one or more of Si carbides, nitrides and carbonitrides.
It is characterized in that it contains 10% by volume of 10% to 95% by volume of the above carbides, nitrides, and carbonitrides of Ti and Si containing whiskers. Fiber reinforced ceramics. 2. Mg, Ti, Si, Zr as a sintering aid
2. The fiber-reinforced ceramics according to claim 1, which contains 0.1 to 10% by weight of one or more oxides of rare earth elements.