JPH11236269A - Silicon nitride sintered body and cutting tool using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the silicon nitride sintered body consisting of a composite material which is formed by dispersing a Ti compound-based reinforcing phase in a silicon nitride matrix and in which the dispersed reinforcing phase exhibits its maximum material property improvement effect through enhancement of wettability of the reinforcing phase by the matrix, and accordingly, which has high strength, high toughness, high hardness and excellent wear resistance. SOLUTION: This sintered body consists of a composite material that is formed by dispersing a reinforcing phase 2 in a matrix phase 1 in a 10 to 40 vol.% ratio of the reinforcing phase 2 based on the total volume of these phases 1 and 2, wherein the matrix phase 1 comprises a main phase consisting of β-silicon nitride crystals and a grain boundary phase contg. at least one group 3a element of the Periodic Table; and the reinforcing phase 2 comprises particles or whiskers of at least one Ti compound selected from nitride, carbide-nitride and carbide-oxide-nitride of Ti, and at least one transition metal selected from Ni, Fe, Co, Cu, Mo, W and Mn and more specifically, consists of core parts 2a each consisting of such a Ti compound(s) and a shell parts 2b each of which is formed on the periphery of one of the core parts 2a and contains such a transition metal(s).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to wear-resistant parts, sliding parts, corrosion-resistant parts, heat-resistant parts, decorative parts, and the like. The present invention relates to an excellent silicon nitride sintered body and a cutting tool using the same.

[0002]

2. Description of the Related Art In general, since ceramics have a lower specific gravity than metals, they are lighter in weight, have higher hardness than metals, and are excellent in wear resistance, oxidation resistance, corrosion resistance and heat resistance. , Wear-resistant cutting tools, sliding parts such as balls for bearings, heat-resistant parts such as valves, headliners, heating elements, firing tubes, etc., decorative parts such as watch case, fishing reel guides, etc. Is used in a wide range of fields.

[0003] Ceramic materials mainly used for such applications are mainly alumina, silicon carbide, aluminum nitride, graphite or silicon nitride, but have a lower fracture toughness and strength than metals. Various studies on ceramic composite materials are under way.

Among them, attempts have been made to improve the toughness or strength by dispersing hard particles or fibrous crystal particles (whiskers, fibers) in the above-mentioned main components. For example, as the dispersed phase, in addition to oxide particles such as zirconia, carbon fibers, silicon carbide, titanium carbide, carbides such as titanium carbonitride, particles such as carbonitrides, or whiskers thereof are known. .

[0005]

For example, alumina-silicon carbide whisker-based composite materials can greatly improve toughness and strength as compared with alumina ceramics, but have low properties such as strength, toughness and high-temperature strength of alumina itself. Therefore, its effect is also limited, and its usable applications are limited.

[0006] On the other hand, the silicon nitride sintered body has a structure in which the needle-like crystals are entangled because the crystals grow into needles at the stage of firing. Although it is a material with excellent thermal shock resistance,
There is an attempt to further improve toughness and strength by dispersing silicon carbide whiskers because they are not practically sufficient. However, both silicon nitride and silicon carbide have a problem that their adhesion to metal and adhesion are higher than that of alumina, and their hardness is low, so that their wear resistance is low.

Accordingly, the present inventor has proposed that, in addition to improving the toughness and strength of the silicon nitride based sintered body, improving the wear resistance.
TiC or Ti with high hardness and excellent wear resistance
An attempt was made to disperse whisker of titanium compound such as N, but the expected effect was not obtained. It has been found that the titanium compound has poor wettability with silicon nitride, so that the titanium compound has low adhesion and affinity with a silicon nitride matrix, and mutual compatibility is not sufficient.

Accordingly, an object of the present invention is to improve the wettability between the reinforcing phase and the matrix in a composite material in which a silicon compound is used as a matrix and a Ti compound-based reinforcing phase is dispersed, thereby improving the properties by the reinforcing phase. To provide a silicon nitride sintered body having high strength, high toughness and high hardness and excellent wear resistance.

[0009]

The present inventors have conducted various studies on a specific structure for improving the wettability between a silicon nitride-based matrix phase and a Ti compound-based reinforcing phase.
The present inventors have found that the presence of a specific transition metal in the Ti compound-based reinforcing phase improves the wettability with the silicon nitride matrix, leading to the present invention.

That is, the silicon nitride sintered body of the present invention has a β-
A main phase made of silicon nitride crystal and at least
In a matrix phase including a grain boundary phase containing a group a element, particles or whiskers of at least one Ti compound of Ti nitride, carbonitride, and carbonitride, and Ni, Fe, Co, Cu, Mo, W and Mn
Characterized in that the reinforcing phase containing at least one transition metal selected from the group of is dispersed at a rate of 10 to 40% by volume.

Further, the strengthening phase includes a core portion made of particles or whiskers made of at least one kind of Ti compound of Ti nitride, carbonitride, and carbonitride, and the transition around the core portion. A metal-containing shell portion, wherein the transition metal is contained at a ratio of 0.01 to 8% by weight in terms of metal, with 100% by weight of all components other than the Ti compound; In the total amount of the matrix, 70 to 95% by weight of silicon nitride, 1 to 15% by weight of Group 3a element of the periodic table in terms of oxide, 7% by weight or less of aluminum in terms of oxide, and oxidation of impurity oxygen Contained in a proportion of 10% by weight or less in terms of silicon,
The sintered body has a relative density of 95% or more, a porosity of 3% or less, an average void diameter of 5 μm or less, and a peak intensity of 206 cm ⁻¹ of silicon nitride detected by Raman spectroscopy of the sintered body. X ₁ and the peak intensity X of Si at 521 cm ⁻¹
_It has various features such as a ratio of (X ₂ / X ₁ ) to ₂ being 0.2 to 3.

Further, according to the present invention, the above-mentioned silicon nitride based sintered body is used as a cutting tool.

[0013]

In order to improve the toughness, strength and hardness of a silicon nitride sintered body, it is effective to disperse a ceramic whisker or the like as a reinforcing phase. Among them, among them, the hardness is high and the wear resistance is excellent. By selecting a Ti compound such as TiC, improvement in mechanical properties can be expected. Moreover,
In the sintered body obtained by adding a Ti compound to silicon nitride and firing, a certain effect was observed in the strength and toughness, but the wear resistance was not significantly improved, but rather deteriorated. There was a tendency to.

This is because the Ti compound has poor wettability, adhesion and affinity with silicon nitride, and is not sufficiently compatible with each other. For this reason, the shape and the amount of the Ti compound to be controlled are finely controlled. There must be. In other words, when a substance having poor mutual compatibility is dispersed, toughness and strength are improved due to the bridging effect of cracks depending on the amount and shape of addition, but sinterability is deteriorated, or the dispersion strengthening substance and the silicon nitride matrix are mixed. It is presumed that the abrasion resistance was degraded because the mutual bonding force was reduced due to poor wettability, adhesion, and affinity, and the dispersion strengthening phase on the sintered body surface was dropped (degranulated).

On the other hand, according to the present invention, Ni, Fe, Co, Cu, M
When at least one transition metal selected from the group consisting of o, W and Mn is contained, the transition metal becomes a so-called T
By forming a shell part around the core part made of the i-compound, the effect of improving the wettability of the reinforcing phase to the silicon nitride matrix and improving the mutual compatibility is achieved. The wear resistance can be significantly improved.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The silicon nitride based sintered body of the present invention is composed of a silicon nitride based matrix phase 1 and a Ti compound based reinforcing phase 2 as shown in the schematic structure diagram of FIG. The silicon nitride matrix phase 1 has a main phase composed of β-silicon nitride crystal and a grain boundary phase containing at least an element of Group 3a of the periodic table. On the other hand, the Ti compound-based strengthening phase 2
It is mainly composed of at least one kind of particles or whiskers of the nitride, carbonitride and carbonitride of i.

The Ti compound in the Ti compound-based reinforcing phase 2 is a particle or whisker (fibrous substance) made of at least one of Ti nitride, carbonitride, and carbonitride. , TiC, TiCN,
TiCO, TiNO, TiCNO and the like can be mentioned. These particles and whiskers have a stoichiometric composition,
Alternatively, it may be composed of a non-stoichiometric composition.

The Ti compound is preferably a whisker. In this case, the whisker may be in the form of long fibers or short fibers, or a mixture thereof. 0.1 to 2μ
m, preferably 0.5 to 1.5 μm, and an average aspect ratio of 2 to 50, preferably 4 to 30. This is because if the average particle size exceeds 2 μm, the sinterability is hindered, the bonding force between the matrix and the whiskers is reduced, and the toughness, strength and wear resistance of the sintered body are reduced.
The average aspect ratio is for the same reason.

When a Ti compound in the form of particles is used, the average particle size is 0.2 to 3 μm, preferably 0.4 to 3 μm.
It is desirable that the thickness be 1.5 μm. This is because, in the case of a particle shape, if the average particle size exceeds 3 μm, the bonding force with the matrix decreases, and the toughness, strength and wear resistance of the sintered body decrease.

According to the present invention, it is important that the Ti compound based reinforcing phase 2 contains at least one transition metal selected from the group consisting of Ni, Fe, Co, Cu, Mo, W and Mn. . Due to the presence of these transition metals, Ti
The wettability of the compound-based reinforcing phase 2 with the silicon nitride matrix phase 1 can be improved, and the mutual compatibility can be improved.

When the transition metal is contained in the Ti compound-based reinforced phase 2 as described above, the Ti compound-based reinforced phase 2 generally has a central part (FIG. 1) composed of a Ti compound. A core portion 2a and a shell portion 2b containing the transition metal around the core portion 2a are formed. This transition metal desirably exists as an oxide, nitride, oxynitride or silicide, in which case the transition metal forms a solid solution with the Ti compound in the core portion 2a. However, the transition metal is mainly contained more in the shell part 2b than in the core part 2a.

As described above, since the transition metal is largely contained in the shell portion 2b in the core-shell structure, it is possible to contribute to improvement in wettability between the reinforcing phase 2 and the silicon nitride matrix phase 1. Note that the shell portion 2b is not necessarily formed on the entire periphery, but may be formed around the core portion 2a.
%, The effect is exhibited.

The thickness of the shell portion 2b is not particularly limited, but is preferably 0.1 to 0.5 μm on average.
m is desirable.

In the present invention, the Ti compound is desirably contained in a total amount of 10 to 40% by volume, particularly 15 to 30% by volume. The above content is 10
If the content is less than 30% by volume, the effect of improving the mechanical properties by the Ti compound cannot be expected, and if the content exceeds 40% by volume, the sinterability and the bonding force with the matrix decrease, and the strength and wear resistance decrease. There are cases. In addition, the said transition metal contained in the said Ti compound type | system | group reinforcement | strengthening phase 2 is 0.01-0.0% when the total amount of all the components other than a Ti compound is 100 weight%.
It is contained at a ratio of 8% by weight, and in particular, from 0.1 to 5% by weight and from 0.5 to 4% by weight in terms of improvement in strength and wear resistance, wear resistance can be further improved.

On the other hand, in terms of composition, the silicon nitride matrix phase contains 75 to 95% by weight, preferably 8% by weight of silicon nitride when the total amount of all components other than the Ti compound is 100% by weight.
0-90% by weight. The silicon nitride crystal phase is composed of acicular β-silicon nitride particles having an average particle diameter (minor axis diameter) of 0.5 to 2 μm and an average aspect ratio of 3 or more, and has a structure in which they are entangled with each other. It contributes to the improvement of fracture toughness and strength of the sintered body.

Further, the silicon nitride-based sintered body contains a Group 3a element of the periodic table as a sintering aid component, and its content is 1 to 15% by weight in terms of oxide, preferably 3% by weight. -10
% By weight. Other sintering aids include aluminum in an amount of 7% by weight or less, preferably 5% by weight or less in terms of oxide, and 10% by weight or less, preferably 8% by weight or less in terms of silicon oxide in terms of silicon oxide. It is desirable to include each in the ratio of. Examples of the Group 3a element of the periodic table include Y, Er, Yb, Lu, and Sm, and among them, Y, Yb, and Er are preferable.

Here, the impurity oxygen refers to the amount of Y or rare earth element (RE) in the sintered body based on the total amount of oxygen in the sintered body.
Stoichiometric composition (RE ₂ O ₃ and A
l ₂ O ₃ ), which is the remaining oxygen content after subtracting the oxygen content assumed to be bound by the reaction, and most of the remaining oxygen content is composed of unavoidable oxygen in the silicon nitride powder or SiO ₂ component added intentionally. You.

The group 3a element of the periodic table, aluminum and impurity oxygen form a glass phase at the grain boundary of the silicon nitride crystal phase, or form a rare earth element—Si ₃ N ₄ —Si
It may exist as an O ₂ -based crystal phase. Note that aluminum may be partially dissolved in the β-silicon nitride crystal phase.

In order to obtain excellent mechanical properties, the silicon nitride sintered body of the present invention has a relative density of 95% or more, preferably 98% or more, and a porosity of 3% or less. Is preferably 1.5% or less in order to achieve excellent wear resistance.

Further, it is desirable that substantially no voids exist in the silicon nitride sintered body. However, if voids are inevitably generated, the voids are uniformly dispersed to be a source of destruction. When cracks occur, even if breakage, breakage and breakage occur due to crack propagation,
Cracks can be prevented from developing. The average diameter of the voids is desirably 5 μm or less. This is because, when the average void diameter exceeds 5 μm, minute shedding and chipping occur at the same time, shedding increases, and wear increases.

In order to uniformly disperse such voids, the silicon nitride raw material is mixed and pulverized, molded and fired without granulation, or once the mixed powder is granulated, and then the granulated powder is mixed. Can be uniformly scattered by sufficiently increasing the molding pressure during molding to crush the granulated powder. The void diameter distribution can be controlled by the raw material powder used, the pressure at the time of molding, and the degree of densification by firing conditions.

Further, according to the present invention, when such a sintered body is analyzed by Raman spectroscopy, it is desirable that minute Si is detected. This Si is at a level that cannot be observed even with a scanning electron microscope (SEM), and is detected by Raman spectroscopy. Although this Si cannot be detected by SEM observation, it is presumed that it is probably dispersed in silicon nitride crystal grain boundaries in the silicon nitride matrix or in silicon nitride grains.

The presence of such Si in the matrix can enhance the strength and toughness. The reason for this is not clear, but is presumed to be because Si dispersed at the grain boundaries acts to hinder the progress of cracks.

However, the Si particles present at the grain boundaries need to be very small. For example, if the Si particles are present at a level detected by X-ray diffraction measurement, they become sources of destruction and cause sintering. It degrades the strength of the body. On the other hand, the sintered body of the present invention needs to be present at a specific level according to Raman spectroscopy in which even a trace amount of Si can be detected. Specifically, the intensity of the peak existing near 206 cm ^{−1 of} β-silicon nitride is X ₁ ,
When the intensity of the peak near 521 cm ^{−1 of} Si is X ₂ , the peak ratio represented by X ₂ / X ₁ is desirably 0.2 to 3, preferably 0.5 to 2. If the peak ratio is lower than 0.2, the effect of improving the strength and toughness is low, and desired characteristics cannot be obtained. If the peak ratio exceeds 3, the precipitated Si itself becomes a source of destruction and deteriorates the strength. .

Next, the method for producing the silicon nitride sintered body of the present invention will be described. As the silicon nitride raw material, a silicon nitride powder, in particular, a powder having an α-rate of 90% or more is used.
Alternatively, when the equivalent of 0 to 80% by weight of the silicon nitride raw material is replaced with silicon powder and the silicon powder is nitrided at a low temperature, α-Si ₃
N ₄ is likely to be generated, and the α-Si
It is possible to increase the content of ₃ N _4. Such α-
Firing a compact having a high Si ₃ N ₄ content can increase the generation of needle-like β-silicon nitride crystal phases,
The strength and toughness of the sintered body can be increased. The average particle size of the silicon nitride powder is 0.4 to 1.2 μm,
An appropriate amount of impurity oxygen is 0.5 to 1.5% by weight.

Next, for such silicon nitride powder,
Group 3a element oxide of the periodic table, and in some cases, Al ₂
The O ₃ powder, and further the SiO ₂ powder, the composition of the molded body before firing has a rare earth element oxide equivalent of 1 to 15 wt%, particularly 3 to 10 wt%, and Al ₂ O ₃ of 7 wt% or less, Especially 5
% By weight or less, and the remaining oxygen content obtained by subtracting the oxygen content in the Group 3a element oxide powder and the Al ₂ O ₃ powder from the total oxygen content in the molded body is 10 weight in terms of SiO _2. %, Especially 8% by weight or less.

In addition to the above components, Ni, Co,
At least one of W, Mo, Mn, Cu and Fe
Oxides, nitrides, oxynitrides or silicide powders of various kinds of transition metals are added at a ratio of 0.01 to 8% by weight in terms of metal, and a nitride of Ti is added to the above components. , A carbonitride or a carbonitride, and at least one kind of particles or whiskers are added and mixed at a ratio of 10 to 40% by volume.

After forming a granulated body having a size of 30 to 300 μm from the obtained mixed powder by mesh pass granulation, spray granulation, dry granulation or the like, a known molding method such as press molding, cast molding, It is formed into a desired shape by extrusion molding, injection molding, cold isostatic pressing or the like.

Next, this molded product was used for 1650 to 1850
C, especially 1700-1800 C in a nitrogen atmosphere, especially S
By a known firing method in an iO-containing atmosphere, the sintered body is densified by firing under the condition that the density of the sintered body is 95% or more of the theoretical density.
As the firing method, a well-known firing method such as normal pressure firing, nitrogen gas pressure firing, and hot isostatic pressure firing method is employed. SiO
Atmosphere is SiO ₂ + Si or SiO ₂ + Si
The mixed powder of ₃ N ₄ can be molded article is formed by firing put together in a firing bowl to be accommodated.

In order to leave Si in the matrix of the sintered body, the sintering temperature should be set within a range of about 30 ° C. lower than the equilibrium temperature at which silicon nitride decomposes into silicon and nitrogen gas at normal pressure. By firing, a very small amount of Si ₃ N ₄ is decomposed, and the Si generated by the decomposition is present in the grain boundaries of the silicon nitride crystal particles in the matrix. In addition,
The amount of Si can be arbitrarily controlled by, for example, the holding time in the above temperature range.

Further, the sintered body fired as described above is further subjected to hot isostatic pressure firing at 1600 to 1800 ° C.
At a temperature of 1000 to 1000 in nitrogen gas or argon gas.
It can be further densified by firing under a pressure of 2000 atm.

[0042]

EXAMPLE A silicon nitride (Si ₃ N ₄ ) powder having an average particle diameter of 1 μm, an alpha conversion of 98% and an oxygen content of 1.2% by weight, a silicon powder having an average particle diameter of 0.7 μm, and an average particle diameter Is 3 μm or less, oxides of the elements of Group 3a of the periodic table (RE ₂ O ₃ ), aluminum oxide (Al ₂ O ₃ ), and silicon oxide (SiO ₂ )
The powder of ₂ ), and further, the transition metal compound and the Ti compound were mixed so that the composition of the molded body had the ratio shown in Tables 1 and 2. The Ti compound has an average particle size of 0.5 to 1
A Ti compound whisker having a particle size of μm, an average particle diameter (minor axis diameter) of 0.8 μm, and an average aspect ratio of 10 to 20 was used.

The resulting mixture was spray-dried to form granules having a particle size of 40 to 200 μm. afterwards,
Rubber press (isostatic press) molding was performed at a pressure of 0.3 to 3 t / cm ² .

When no Si powder was contained in the compact, the compact was fired in a nitrogen atmosphere at a nitrogen pressure of 9 atm at the firing temperature shown in Table 1 for 5 hours and then cooled in a furnace to obtain a sintered body. In addition, Si
When the powder was included, the powder was heated at 1150 ° C. for 5 hours to be nitrided, then fired at the firing temperature shown in Table 1 for 5 hours, and subsequently cooled in a furnace to obtain a sintered body. The size of the void was controlled by the pressure during molding.

In the firing, each molded body was subjected to 5% of the weight of the molded body.
% SiO ₂ + Si (1: 1 by weight) mixed powder was placed, placed in a silicon carbide sagger, and fired. The sample N
For O.22, they were fired without placing a SiO ₂ + Si powder mixture.

The relative density, porosity, strength, toughness, hardness and average void diameter of each of the sintered bodies thus obtained were measured by the following methods. The results are shown in Table 4. The relative density and the porosity were obtained by processing to a shape defined by JISR1601 and measuring the specific gravity based on the Archimedes method. The strength was determined by performing a four-point bending strength test at room temperature based on JISR1601. The toughness of the mirror-finished sample was measured according to JIS-R160.
The fracture toughness at room temperature based on No. 7 was measured. Hardness was measured by Vickers hardness (load 1 kg). Further, the average void diameter was examined using a SEM or a stereomicroscope.

Further, by Raman spectroscopy, the peak intensity X ₁ of silicon nitride at 206 cm ^{-1 and} the peak intensity X of Si at 521 cm ^-1 were measured.
The X ₂ / X ₁ ratio with the peak intensity X _{2 of} ⁻¹ was determined. In addition,
FIG. 2 is a Raman spectroscopic analysis chart of Sample No. 3.
It was shown to.

Further, a cutting test was performed using the sintered bodies having the respective compositions under the conditions shown in Table 3 below, and the wear amount after the test was measured.

[0049]

[Table 1]

[0050]

[Table 2]

[0051]

[Table 3]

[0052]

[Table 4]

As is clear from the results in Tables 1 and 4,
Samples Nos. 7 and 25 to which no transition metal was added had a large abrasion amount of 3 mm or more and low abrasion resistance properties. However, according to the present invention, the sample of the present invention to which a predetermined amount of transition metal was added was used. All have mechanical properties of a strength of 800 MPa or more, a toughness of 7.0 MPa · m ^1/2 or more, and a hardness of 15.0 GPa or more.
And a cutting test 2 having excellent wear resistance of 0.5 mm or less.

According to the results shown in Table 1, in Samples Nos. 1 and 23 in which the amount of the Ti compound was smaller than the range of the present invention, the effect of the abrasion resistance was not sufficient, and in Samples Nos.
In No. 4, the sinterability was reduced and the wear resistance was significantly deteriorated.

Among the products of the present invention, the samples having an intensity ratio of 0.2 to 3 by Raman spectroscopy show characteristics superior to those of samples No. 20, 21, and 22 which deviate from this range. Strength of 900 MPa or more, toughness of 8.0 MPa · m
Excellent characteristics of 0.4 mm or less in cutting test 1 at ^1/2 or more and 0.3 mm or less in cutting test 2.

[0056]

As described above, according to the silicon nitride sintered body of the present invention, a nitride of Ti with a silicon nitride matrix phase,
Particles made of at least one Ti compound of carbonitrides and carbonitrides or their whiskers have improved wettability, and have excellent strength, toughness and wear resistance, and are suitable for cutting tools and the like. Can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic structural diagram of a silicon nitride based sintered body of the present invention.

FIG. 2 shows an example of a Raman spectroscopic analysis chart of the silicon nitride based sintered body (sample No. 3) of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Matrix phase 2 Reinforcement phase 3 Core part 4 Shell part

Claims (7)

[Claims] 1. A matrix phase comprising a main phase composed of β-silicon nitride crystal and a grain boundary phase containing at least an element belonging to Group 3a of the periodic table. Made of at least one kind of Ti compound among the materials, or whiskers thereof, and Ni, Fe, Co, C
at least one selected from the group consisting of u, Mo, W and Mn
A silicon nitride based sintered body characterized in that a reinforcing phase containing a kind of transition metal is dispersed at a ratio of 10 to 40% by volume. 2. The method according to claim 1, wherein the reinforcing phase is Ti nitride, carbonitride,
The silicon nitride according to claim 1, further comprising a core portion made of particles or whiskers of at least one Ti compound of carbonitrides, and a shell portion containing the transition metal around the core portion. Quality sintered body. 3. A method according to claim 1, wherein said transition metal is 0.01% in terms of metal, with 100% by weight of all components other than said Ti compound.
2. The composition according to claim 1, which is contained in a proportion of about 8% by weight.
The silicon nitride based sintered body according to the above. 4. A peak intensity X ₁ at 206 cm ⁻¹ of silicon nitride detected by Raman spectroscopy, and 521c of Si.
The ratio (X ₂ / X ₁ ) to the peak intensity X _{2 at} m ⁻¹ is 0.2 to 0.2
3. The silicon nitride sintered body according to claim 1, wherein 5. The matrix phase comprises 70 to 95% by weight of silicon nitride, 1 to 15% by weight of a Group 3a element of the periodic table in terms of oxide, and 100% by weight of all components other than the Ti compound. The silicon nitride-based sintered body according to claim 1, wherein the silicon nitride-based sintered body contains 7% by weight or less in terms of oxide and 10% by weight or less in terms of silicon oxide in terms of silicon oxide. 6. The silicon nitride sintered body according to claim 1, wherein the relative density is 95% or more, the porosity is 3% or less, and the average void diameter is 5 μm or less. 7. A cutting tool comprising the silicon nitride-based sintered body according to any one of claims 1 to 6.