JPH0328172A - High toughness-and high hardness-sintered material - Google Patents

Abstract

PURPOSE:To produce the subject high toughness- and high hardness-sintered material excellent in cutting force, detect resistance and chipping resistance by blending a high pressure phase form boron nitride having a specified average particle diameter with a heat-resistant and high hardness ceramics fiber and a transition metal ceramics as binders. CONSTITUTION:An objective high toughness- and high hardness-sintered material is composed of (A) 20-80V% pressure phase form boron nitride (<=1mum average particle size), (B) 3-30V% heat-resistant and high hardeness ceramics fiber (e.g. preferably SiC fiber having 0.2-1mum average fiber diameter, 5-20mum average fiber length and 10-50 aspect ratio) and (C) a carbide, a nitride, a borate of a transition metal (e.g. Ti, Zr, Hf, V, Nb, Ta, Cr or Mo) belonging to IVA, VA or VIA group, an oxide or a nitride of Al, a mixture thereof or a solid solution thereof (<=1mum average particle diameter) and having 5-50 ratio of the average length of (B) component to the average particle size of (A) and (C) components.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sintered body having high hardness, excellent wear resistance, and excellent toughness. It is useful as a material for cutting tools such as base or Co-base cemented carbide, or wear-resistant tools such as bearings and wire drawing dies. [Prior art] Materials for cutting tools and wear-resistant tools such as those mentioned above include:
Traditionally, tungsten carbide (WC)-based superhard materials have been used. However, as the demands of users become more stringent, the development of tool materials superior to the above-mentioned WC-based carbide materials is awaited. As tool materials that meet these demands, cubic boron nitride sintered bodies containing small amounts of AI and iron group metals in cubic boron nitride (Japanese Unexamined Patent Publication No. 17503/1983), or ceramics as a binder, are available. A cubic boron nitride sintered body using the same method was proposed in Japanese Patent Publication No. 57-3631. However, cutting tools made from these materials exhibit excellent cutting performance under relatively light cutting conditions, such as continuous cutting with a small depth of cut, but they exhibit excellent cutting performance under relatively low load cutting conditions, such as continuous cutting with a small depth of cut, but when cutting with a large depth of cut or repeated cutting, such as with interrupted cutting. Under severe cutting conditions where impact force is applied, satisfactory performance is not necessarily obtained, and there are problems with fracture resistance and chipping resistance.

[Problem to be solved by the invention] The present invention solves the above-mentioned circumstances. The purpose was to create a fracture-resistant material that exhibits excellent cutting performance even under cutting conditions where large loads are applied, or where even small loads are repeatedly applied. The purpose of the present invention is to provide a high-toughness, high-strength sintered body with excellent toughness, chipping resistance, and wear resistance. [Means for solving the cm problem] The structure of the sintered body according to the present invention that can solve the above problems is: ■ High-pressure phase type boron nitride with an average grain size of 1 μm or less: 20 to 80
Volume % ■Fibrous heat-resistant high-hardness ceramics ■average particle size of 1 μm or less, periodic table No. 4a, 5a,
Group 6a lm fiber metal carbides, nitrides, borides or A
1f selected from the group consisting of oxides and nitrides of I! ,
or a mixture of two or more thereof or a mutual solid solution compound: the remainder, and the ratio of the average length of the above component (1) to the average particle diameter of the above component (1) and the precepts (2) is 5 to 50. It is something that you have. [Function] The present inventors conducted various studies in order to elucidate the reason why the boron nitride sintered body using ceramic as a binder lacks fracture resistance and chipping resistance, and found that the cause of the above defects is as follows. It is believed that this is due to the lack of toughness of the ceramics that constitute the bonding part.
) carbides, nitrides, borides, and oxides, nitrides of A1 1ff! Or 2f selected from them! A mixture or mutual solid solution of the above (hereinafter collectively referred to as transition metal ceramics) ■ and a fibrous heat-resistant high-hardness ceramic (hereinafter referred to as fibrous ceramics) ■ are used together, and the fibrous ceramics ■ By specifying the ratio between the average length and the average particle diameter of the transition metal ceramics ■ and high-pressure phase boron nitride ■, and setting the blending ratio of these ■, ■, and ■ within a specific range, chipping resistance and resistance can be improved. I learned that a sintered body with excellent chipping resistance and high wear resistance can be obtained. The high-pressure phase type boron nitride used in the present invention as component (■) is as follows:
A general term for cubic boron nitride and Wurtz type boron nitride, which have a hardness second only to diamond.
Cut. It is a precept that is the main component of cutting or polishing, and it is a sintered body (in order to give the specified cutting and polishing performance, the blending amount should be adjusted so that the content in the sintered body is 20 to 80% by volume. In addition, the average grain size of the sintering raw material must be 1 μm or less.However, if the content of high-pressure phase boron nitride is less than 20% by volume, the hardness of the sintered body On the other hand, if it exceeds 80% by volume, the amount of transition metal ceramics ■ and fibrous ceramics ■ that make up the binder phase is insufficient. As a result, the toughness decreases, and the chipping resistance and chipping resistance as intended by the present invention cannot be obtained.

The more preferable content of high-pressure phase boron nitride ■ is 30 to 70.
It is volume %. In addition, this high-pressure phase type boron nitride ■ is in powder form as described later! It is mixed with a fibrous ceramic ■ and transition metal powder ■, and then sintered after being pressed and shaped. However, if the particle size of high-pressure phase boron nitride ■ is too large, the fibrous ceramic ■ will break during pressing. Therefore, as high-pressure phase type boron nitride (2), a fine powder with an average particle size of 1 μm or less must be used. Next, the fibrous ceramics (■) mainly has the effect of inhibiting the growth of cracks that may occur in the binder phase of the sintered body and increasing the toughness, and its average fiber length (L) is different from that of the high-pressure phase type boron nitride (■). Average particle diameter (d) of transition metal ceramics ■
It must be in the range of 5 to 50 times [5d≦L≦50d]. However, if [L<5d], the expected toughness improvement effect of the fibrous ceramics (■) will not be fully exhibited, while if [L>50dl], the fibrous ceramics (■) will become intertwined with each other and the dispersion state will deteriorate. This is because the sintering becomes uneven and sintering becomes uneven, making it impossible to obtain a sintered body of stable quality. The absolute value of the IAM diameter and LAI length of the fibrous ceramic (■) is not particularly limited as long as it satisfies the above requirements. Diameter is 0.2~
1 μm, average fiber length is 5 to 20 μm, and asvect ratio is 1.
It is preferable to use fibrous Serayox (IA) having an IA of 0 to 50. The IA fibrous ceramics (■) should be blended in the sintering raw material so that it accounts for 3 to 30% by volume; if it is less than 3% by volume, the toughness improvement effect will not be sufficiently exhibited, and if it exceeds 30% by volume, In the mixed state, the fibrous ceramics (■) tend to segregate, making sintering uneven or defective in this area. A more preferable amount of fibrous ceramics (2) is in the range of 10 to 25% by volume. Next, the transition metal ceramic (2) is the main component of the binder phase, and its average grain size is preferably 1 μm or less for the same reason as stated in the explanation of the high-pressure phase type boron nitride (2). The types are as shown above, and these transition metal ceramics not only have excellent heat resistance and strength, but also have strong sintering properties with the high-pressure phase boron nitride powder and fibrous ceramics. They have the property of binding together, and by using them alone or in combination as a binding material, a strong sintered body can be obtained. This transition metal ceramic (■) is blended as the remaining component of the high-pressure phase type boron nitride (■) and the fibrous ceramic (■), so the amount blended will vary depending on the blended amounts of components (■) and (■), but it will be used as a binder phase. In order to effectively exhibit the function of molten metal and obtain a uniform and strong sintered body, it is preferable to set the blending ratio in the range of 20 to 40% by volume. ■ above,
A particularly preferable combination among the components (2) and (2) is cubic boron nitride as the component (2), fibrous silicon carbide (including silicon carbide whiskers) as the component (2), A1203 or A1203 and TIC as the component (2), This makes it possible to obtain a sintered body with outstanding performance, high toughness, and high hardness. The method for manufacturing a sintered body using the above raw materials is not particularly limited, and for example, the ingredients ①, ②, and ② may be blended in predetermined amounts, mixed uniformly, and filled into a mold in the state of mixed powder, or pre-embossed. After forming, sintering at high temperature and pressure yields a hard and highly tough sintered body. The sintering conditions at this time can be freely selected so that the raw material components, especially high-pressure phase boron nitride, can be sintered and integrated without thermally altering them. is 1300~1700
°C and pressure ranges from 30 to 70 kbar. [Example] A cubic boron nitride powder with an average particle size of 1 μm or less, a transition metal ceramics powder with an average particle size of 1 μm or less, and an average particle size of about O. Silicon carbide fibers having an average length of 1 to 20 μm in S μm were used in the proportions shown in Table 1 C. 3f above! The raw materials No. 1 were thoroughly mixed using ethyl alcohol as a dispersion medium, and dried to form a mixed powder. Furthermore, code J'
For (comparative example), cubic boron nitride with an average particle size of 3 μm and transition metal powder with an average particle size of 1 μm were used. After the obtained mixed powder was pressed and molded, it was heated in a vacuum furnace for 10''
It was degassed by holding it at 1000°C for 1 hour at a vacuum level of 'mmHH. This degassed compact was fired for 15 minutes at 1600° C. and 60 kbar using a belt-type ultra-high pressure and high temperature generator to obtain a sintered compact. Cutting chips were prepared from each of the obtained sintered bodies, and an interrupted cutting test was performed in the longitudinal direction of the outer circumference using a grooved cylindrical SCM435 (HRe60) material as the work material, and the time required for the cutting chips to break was measured. was measured. However, the cutting conditions are: speed: 100 m/win, depth of cut: 0.3 mm, feed: 0. IS am/rev. The results are summarized in Table 1. However, the breakage life of the cutting tip is expressed as the time ratio with respect to the time taken for the cutting tip with code c'<comparative example to break off, with the time taken as 1. From Table 1, it can be considered as follows.

(!) Codes A-H are examples that satisfy the requirements defined by the present invention, and the lifespan until breakage is 3 of the comparative example (code C').
This is more than twice as long, and the lifespan of each cutting member is extremely excellent.

(2) Symbols A° to J° are comparative examples that lack any of the requirements specified by the present invention as shown below, and the lifespan until breakage is significantly inferior to that of the present invention. Symbol A°: The length ratio of the silicon carbide fibers is less than 5.

~E゜　: Silicon carbide fiber is not blended. :The blending amount of silicon carbide fiber is 30% by volume. exceeds. :Length ratio of silicon carbide fiber exceeds 50 ing. Contains 90 units of dicubic boron nitride More than product%, transition metal ceramics There seems to be a shortage in the amount of

Code B゜ Code F゜ Code G゜ Code H゛ Code I゛: The amount of cubic boron nitride is insufficient. Code J゜: The average particle size of cubic boron nitride exceeds 1 μm. [Effects of the Invention] The present invention is constructed as described above, in which a specific transition metal ceramic is used as a binder phase for high-pressure phase boron nitride, and a specific amount of fibrous ceramics with a specific shape is used as a reinforcing material. This makes it possible to increase the toughness of the high-pressure phase type boron nitride sintered body without impairing its wear resistance.
The lifespan of the material for wear-resistant tools such as cutting tools, bearings, and wire drawing dies can be significantly extended.

Claims (1)

[Claims] (1) [a] High-pressure phase type boron nitride with an average particle size of 1 μm or less:
20 to 80 volume% [b] Fibrous heat-resistant high-hardness ceramics: 3 to 30 volume% [c] Periodic table No. 4a and 5 with an average particle size of 1 μm or less
one selected from the group consisting of carbides, nitrides, and borides of Group A and VIA fiber metals, or oxides and nitrides of Al, or a mixture or mutual solid solution compound of two or more thereof: the remainder; and the average length of the component [b] above, and the average length of the component [a] above.
] A high-toughness, high-hardness sintered body characterized in that the ratio of component [c] to the average particle diameter is 5 to 50.