JP2000143350A - Abrasion resistant member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an abrasion resistant member having excellent abrasion resistance and excellent impact resistance. SOLUTION: This abrasion resistant member contains a β-silicon nitride crystal phase as a main component, Y and/or a rare earth element in an amount of 1-15 wt.% expressed in terms of an oxide, aluminum in an amount of 0.01-5 wt.% expressed in terms of an oxide and impure oxygen in an amount of <=10 wt.% expressed in terms of silicon oxide and has a higher peak intensity ratio represented by H1/H2 in the interior of the sintered compact than that on the surface of the sintered compact when the peak intensity of Si indicated at 521 cm-1 is H1 and the peak intensity of silicon nitride indicated at 206 cm-1 is H2 in a Raman spectrochemical analytical chart and >=3.20 g/cm2 density and more specifically has <=0.1 peak intensity ratio represented by H1/H2 on the surface of the sintered compact and >0.1 and <=3 peak intensity ratio in the interior of the sintered compact. Furthermore, the silicon nitride-based sintered compact contains at least one kind of compound of Mg, W, Mo, Mn, Cu and Fe in an amount of <=8 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wear-resistant member such as a tool, a sliding agent, a container, a lining material, a crushing media, etc., which require wear resistance.

[0002]

2. Description of the Related Art Conventionally, wear-resistant members have been constituted by metal wear-resistant members having excellent impact resistance. However, in recent years, wear-resistant members have been highly purified and the wear-resistant members have been reduced in weight. The request was not satisfactory.

[0003] That is, a metal wear-resistant member is excellent in impact resistance, but on the other hand, the wear resistance is insufficient, and there is a case where Fe wear powder which is a metal component is mixed, resulting in a high pulverized material. Purification could not be expected. Therefore, a member coated with a metal body is used, but since the metal has a high density, the weight of the crusher and the crusher member increases,
This occupies a large weight with respect to the capacity of the wear member.

In order to solve such problems, there has been proposed a wear-resistant member which achieves wear resistance and weight reduction by using ceramics such as alumina, zirconia, and silicon nitride.

[0005]

However, the wear-resistant member made of alumina ceramics has a problem that the strength and the fracture toughness are insufficient and the product is cracked or peeled off. Further, although the wear-resistant member made of zirconia ceramics has higher strength and fracture toughness than alumina ceramics, there has been a problem that thermal shock resistance is insufficient due to a rise in temperature and chipping is likely to occur.

Accordingly, wear-resistant members having a metal coating on the surface of these ceramics have been proposed.
In such a coating technique, abrasion or abrasion of the coating layer causes rapid abrasion and lacks stability.

A wear-resistant member made of a silicon nitride-based sintered body has also been proposed in Japanese Patent Application Laid-Open No. 5-301775. However, while having excellent impact resistance, it is practically sufficient in terms of wear resistance. Is not satisfactory.

Therefore, an object of the present invention is to provide a wear-resistant member having excellent wear resistance and excellent impact resistance.

[0009]

The present inventors, when employing a silicon nitride sintered body as a wear-resistant member, control the component composition in the sintered body within a predetermined range, and at the same time, Contains fine Si at a level detected by fine Raman spectroscopy, and S and S on the surface and inside of the sintered body are contained.
It has been found that by controlling the amount of i finely, an excellent wear-resistant member with little wear can be obtained, and the present invention has been achieved.

That is, the wear-resistant member of the present invention comprises a β-silicon nitride crystal phase as a main component, contains Y and / or a rare earth element in an amount of 1 to 15% by weight in terms of oxide, and contains aluminum in an amount of 0 to 0% in terms of oxide. .01～5 wt%, the impurity oxygen comprises in a proportion of 10 wt% or less of silicon oxide in terms of weight, in a Raman spectroscopic analysis chart, H ₁ peak intensity of Si shown in 521 cm ^-1, the silicon nitride 206cm ^-1 when the peak intensity was H _2, H ₁ / H ₂ in the peak intensity ratio represented sintered body interior is greater than the sintered body surface and density 3.
It is characterized by being at least 20 g / cm ² .

More specifically, the peak intensity ratio represented by H ₁ / H ₂ is 0.1 or less on the surface of the sintered body, and is larger than 0.1 and 3 or less on the inside of the sintered body. That the sintered body has a porosity of 3% or less, an average void diameter of 5 μm or less, and a void diameter of 5 to 30 μm of 30% or less; a void diameter of 30 μm or more of 5% or less; In addition, the silicon nitride-based sintered body contains at least one of Mg, W, Mo, Mn, Cu and Fe in an amount of 8% by weight as oxide, nitride, oxynitride or silicide. % Is desirable.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION A wear-resistant member of the present invention comprises a silicon nitride-based sintered body comprising a β-silicon nitride crystal phase and a grain boundary phase containing silicon, Y and / or a rare earth element, aluminum, oxygen and nitrogen. It is composed of union. The β-silicon nitride crystal phase exists as a columnar crystal having an average aspect ratio of 3 or more and an average minor axis diameter of 0.5 to 2 μm.

Further, in terms of composition, silicon nitride is used in an amount of 75 to 9%.
It contains 5% by weight, preferably 80-90% by weight. Further, the silicon nitride crystal phase is needle-like β-silicon nitride particles, and by having a structure in which they are entangled, the fracture toughness and the strength are improved, and the pulverization characteristics are also improved. If the amount of silicon nitride is less than 75% by weight, hardness and wear resistance deteriorate,
If the content is more than 95% by weight, the sinterability is reduced and the wear resistance is deteriorated.

Further, the silicon nitride-based sintered body includes
And / or contains a rare earth element in an amount of 1 to 15% by weight, preferably 3 to 10% by weight in terms of oxide, and contains aluminum in an amount of 0.01 to 5% by weight as oxide, preferably 1 to 3%.
% By weight, and further contains 10% by weight or less, preferably 8% by weight or less of impurity oxygen in terms of silicon oxide. Within these ranges, high wear resistance is obtained. Further, Y and / or rare earth elements, aluminum may exist as to form a glass phase, or Y and / or rare earth elements -Si ₃ N ₄ -SiO ₂ based crystal phase in the grain boundary phase. Note that aluminum may be partially dissolved in the β-silicon nitride crystal phase.

The amount of Y and / or the rare earth element is 1% by weight
If it is less than this, the amount of glass produced during sintering will be insufficient, and denseness with a density of 3.20 g / cm ² or more will not be obtained. If it is more than 15% by weight, the amount of glass produced will be excessive, and The grain boundary phase increases, and the wear resistance deteriorates. If the aluminum content is less than 0.01% by weight,
This is because densification is insufficient, and when it is more than 5% by weight, thermal shock resistance is reduced. Furthermore, the amount of impurity oxygen is 10
If the content is more than 10% by weight, abrasion resistance is degraded due to softening of the grain boundary phase and a decrease in thermal shock resistance.

As the Y and / or rare earth element, at least one selected from the group consisting of Y, Er, Yb, Lu and Sm is particularly preferably used.

Here, the above-mentioned impurity oxygen refers to the stoichiometric composition (RE ₂ O ₃ ) of Y and / or rare earth element (RE) and Al in the sintered body based on the total oxygen amount in the sintered body.
And the amount of oxygen remaining after subtracting the amount of oxygen assumed to be bound by Al ₂ O ₃ ), most of which is composed of unavoidable oxygen in the silicon nitride powder or SiO ₂ components intentionally added. Is done.

Further, in addition to the above components, at least one of Mg, W, Mo, Mn, Cu and Fe is added to the silicon nitride sintered body as an oxide, nitride, oxynitride or silicide. By containing it at a ratio of 8% by weight or less, sinterability can be enhanced, densification can be promoted, and characteristics can be further improved. If the amount is more than 8% by weight, the strength may be reduced due to excessive uneven distribution, and the wear resistance may be deteriorated.

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

For example, if this Si is present at a level detected by the X-ray diffraction measurement method, the Si induces abrasion and deteriorates the abrasion resistance of the sintered body. Due to the presence of this minute amount of Si, wear resistance can be maintained and abnormal wear can be suppressed. The reason for this is not clear, but it is presumed that Si dispersed at the grain boundaries probably acts to hinder the propagation of cracks, improves impact resistance, and suppresses chipping, chipping, and delamination wear that induce abnormal wear. .

Further, when according to the present invention, the intensity of the peak near 521 cm ^-1 specific to the beta-H ₂ the intensity of a peak existing near 206cm ^-1 of silicon nitride, Si was H ₁ , H ₁ / H ₂ is a big feature that the inside of the sintered body is larger than the surface of the sintered body. As described above, when the peak ratio is larger inside, the wear resistance can be stabilized by the effect of suppressing abnormal wear such as chipping, chipping, and peeling.

Here, the surface portion indicates a portion having a depth of 200 μm from the burning surface of the sintered body after firing, and the inside means a portion deeper than 200 μm from the burning surface of the sintered body. . Specifically, by setting the peak ratio of the surface portion to 0.1 or less, preferably 0.05 or less, the progress of normal wear on the surface portion can be suppressed. Further, the intensity of the internal peaks is greater than 0.1 and 3 or less, preferably 0.
Desirably, it is 2 to 2.5. If the peak ratio in the inside is 0.1 or less, the effect of suppressing abnormal wear is low, and desired characteristics cannot be obtained.
This is because i itself becomes a wear source and deteriorates wear resistance.

The silicon nitride sintered body of the present invention has a density of 3.20 g / cm ³ or more, preferably 3.23 g / cm ³ or more.
g / cm ³ or more and a porosity of 3% or less, and preferably 1.5% or less, in order to achieve excellent wear resistance.

Further, by uniformly dispersing voids within a predetermined range in the silicon nitride sintered body, when a crack which is a fracture source occurs, breakage, chipping, and breakage are caused by the progress of the crack. Even if it occurs, it is possible to prevent the crack from developing. Regarding the distribution state of the voids, the average void diameter was 5 μm or less, and the diameter was 5 to 5 μm.
It is desirable that the voids of 30 μm have a void diameter distribution of 30% or less of the total number of voids, the void diameter of 30 μm or more 5% or less, and the remainder having a void diameter of 5 μm or less.

This is because, when the average void diameter exceeds 5 μm, small voids are uniformly scattered and cracks selectively propagate to the crystal grain boundaries, thereby causing minute shedding wear and chipping. , Mixed into the pulverized media, making it difficult to purify the pulverized material. In the void diameter distribution, if the void diameter is 30 μm or more and exceeds 5%, local chipping or shedding occurs to promote abrasion.
If the number of voids of 0 μm exceeds 30%, minute chipping, grain shedding increases, and wear increases.

In order to uniformly disperse such voids, a silicon nitride raw material is mixed and pulverized, and formed without granulation.
After firing or once granulating the mixed powder, the granulated powder can be evenly scattered by sufficiently increasing the molding pressure during molding to crush the granulated powder. In addition,
The void diameter distribution can be controlled by the raw material powder used, the pressure during molding, and the degree of densification by firing conditions.

Specifically, in order to produce the wear-resistant member of the present invention, the silicon nitride raw material having an average particle size of 0.4 to
Use a silicon nitride powder having a thickness of 1.2 μm and an impurity oxygen amount of 0.5 to 1.5% by weight, in particular, a powder having an α conversion of 90% or more. If the silicon powder is replaced with a 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 ₃ N ₄ content of the compact after nitriding can be increased. By firing such a compact having a large content of α-Si ₃ N ₄ , the generation of needle-like β-silicon nitride crystal phase can be increased, and the strength and toughness of the sintered compact can be increased. it can.

Next, a Y ₂ O ₃ powder and / or a rare earth element oxide powder, an Al ₂ O ₃ powder, and in some cases, a SiO ₂ powder,
The composition of the molded body before firing is such that the amount of oxides of Y and / or rare earth elements is 1 to 15% by weight, particularly 3 to 8% by weight,
l ₂ O ₃ is 0.01 to 5 mol%, particularly 1 to 3 wt%, and further, based on the total oxygen content in the compact, Y ₂ O ₃ or rare earth oxide powder, Al ₂ O ₃ powder It is added so that the amount of oxygen remaining after subtracting the oxygen content therein is 10% by weight or less, especially 8% by weight or less in terms of SiO ₂ .

The content of these sintering aid components is limited as described above. If each component is lower than the above-mentioned values, the liquid phase becomes insufficient during the firing process, a dense body cannot be obtained, and the strength decreases. As a result, if each component is more than the above value, the liquid phase during firing increases,
This is because silicon nitride tends to cause abnormal grain growth, and the abnormal grains serve as a fracture source to lower the strength. In addition, silicon nitride is strongly decomposed in the surface layer and the strength is reduced.

Further, in addition to the above, Mg, W,
At least one oxide, nitride, oxynitride or silicate powder of Mo, Mn, Cu and Fe is added and mixed at a ratio of 8% by weight or less.

After the obtained mixed powder is formed into a granule having a size of 30 to 300 μm 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 1950
By a known sintering in a nitrogen atmosphere at ℃, the sintered body is densified under the condition that the sintered body density becomes 3.20 g / cm ³ or more.
Next, as a sintering method, the obtained molded body is heated in a nitrogen atmosphere containing SiO at 1700 to 1800 ° C., particularly 1750 ° C.
Normal pressure firing at a temperature of １1800 ° C. Atmosphere SiO can be formed by baking SiO ₂ + Si, or a mixed powder of SiO ₂ + Si ₃ N ₄ put together in a baking pot shaped body is housed.

More specifically [0033] The baking temperature at this, silicon nitride and fired in a Si ₃ N ₄ silicon and nitrogen gas at about 30 ° C. lower temperature range decomposes equilibrium temperature under normal pressure, A very small amount of Si ₃ N ₄ is decomposed. This decomposition causes the generated Si to exist as particles in the grain boundaries. The amount of Si can be arbitrarily controlled by, for example, the holding time in the above temperature range.

At this time, in order to reduce the amount of Si detected by Raman spectroscopy between the surface of the sintered body and the inside of the sintered body to be smaller than that of the inside, the SiO gas concentration in the sintering atmosphere must be adjusted. It can be formed by suppressing the concentration of SiO contained therein to be lower. In addition, Si
When O is not contained, or at a sintering temperature exceeding 1800 ° C., the decomposition of silicon nitride is intense, and it is difficult to perform detailed control to decompose only a small amount of silicon nitride. Also 17
When the temperature is lower than 00 ° C., the sinterability is reduced and Si
Cannot be expected, and improvement in strength and toughness cannot be expected.

[0035]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Silicon nitride (Si ₃ N ₄ ) powder having an average particle size of 0.7 μm, an oxygen content of 1.2% by weight and an α rate of 98%, various rare earth element oxides (RE ₂ O ₃ ), Using each powder of aluminum oxide (Al ₂ O ₃ ) and silicon oxide (SiO ₂ ), each component was blended so as to have the composition shown in Tables 1 and 2, and the particle size was 40 to 2 by spray drying.
A granule of 00 μm was produced. After that, 1-3 tons / c
Rubber press (isostatic press) molding was performed at a pressure of m ² . The amount of SiO ₂ is Si ₃
It also includes those obtained by converting impurity oxygen in N ₄ powder into SiO ₂ . Each compact was placed in a silicon carbide sagger, and 5% of the weight of the compact was mixed with SiO ₂ + Si (1: 1 by weight) using a carbon heater under the conditions shown in Tables 1 and 2. 5
Firing was carried out at normal pressure for a time. For sample No. 24,
It was fired without disposing the SiO ₂ + Si mixed powder.

For each of the thus obtained sintered bodies, the density, porosity, strength, toughness, hardness and void distribution were measured by the following methods, and the results are shown in Tables 3 and 4.
The density and the porosity were obtained by processing to a shape under the conditions specified 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 is determined by JIS-R16
It was determined by measuring the fracture toughness at room temperature based on No. 07.

Further, regarding the state of the voids, the distribution state of the voids was examined using an SEM or a stereomicroscope. The obtained sintered body was subjected to Raman spectroscopy to obtain 206c of silicon nitride.
a peak intensity of H ₂ m ^-1, was determined H ₁ / H ₂ ratio of the peak intensity H ₁ of Si 521 cm ^-1. In addition, the peak intensity of the surface part measured the peak intensity ratio of 100 micrometer depth from the baked surface after baking, and measured the peak intensity ratio of 300 micrometer depth from the baked surface inside. FIG. 1 shows a Raman spectroscopic analysis chart of the sample No.

As a wear test, a test for determining a wear rate was performed as follows. For the wear rate, 60 mm x 3
A sample plate of 0 mm × 6 mm was prepared, and the surface was smoothed and used as an evaluation surface. A SiC GC # 240 (80 to 130 μm) containing water was used as a medium against the surface, and the injection pressure was 2.5 kg / The sample was placed at a right angle (90 °) to the sample plate for 3 minutes in cm ² , and the change in weight of the sample plate was measured, and this was defined as the wear rate. In addition, the nozzle diameter of the above injection was 7.6 mm, and the collision distance was 10 mm.

As a tool wear test, a test for obtaining the following wear amount was performed. Sample shape CNGN120408 Work material FC-25 Cutting speed 500m / min Cutting depth 2mm Feeding 0.5mm / rev Cutting time 30min

[0040]

[Table 1]

[0041]

[Table 2]

[0042]

[Table 3]

[0043]

[Table 4]

As is clear from the results in Tables 1 to 4, the sample of the present invention had a strength of 600 MPa or more and a toughness of 6.
Mechanical properties of 0 MPa · m ^1/2 or more, hardness of 13.0 GPa or more, wear rate of 1.0% or less, tool wear rate of 1.0
mm was achieved.

On the other hand, in the samples No. 13 to No. 17 whose composition ranges deviate from the range of the present invention, the wear rate is remarkably increased, and the media wear rate is also increased. 3.0 density
Sample No. 18 of 9 g / cm ³ and density of 3.20 g / cm ³
In the sample No. 19 of cm ² or less, both the wear rate and the media wear rate were significantly increased. Samples Nos. 22 and 24 having Raman peak intensities equal to or less than the central part from the surface part were not satisfactory because of insufficient wear rate and medium wear.

[0046]

As described above, according to the wear-resistant member of the present invention, while controlling to a specific composition, a small amount of Si is appropriately precipitated in the sintered body, and the amount is adjusted from the surface to the central portion from the surface. By increasing the wear resistance, and by controlling the density, it is possible to have excellent mechanical properties and to improve the wear resistance as a wear-resistant member. Practical use and long life of the member can be achieved.

[Brief description of the drawings]

FIG. 1 shows a silicon nitride sintered body (sample No.
9 shows an example of a Raman spectroscopic analysis chart on the surface of 9).

FIG. 2 shows a silicon nitride sintered body (Sample No.
9 shows an example of a Raman spectroscopic analysis chart inside 9).

Continued on the front page F-term (reference) 4G001 BA01 BA03 BA04 BA06 BA08 BA09 BA12 BA31 BA32 BA37 BA48 BA49 BA51 BA53 BB01 BB03 BB06 BB08 BB09 BB12 BB31 BB32 BB37 BB48 BB49 BB51 BB53 BB62 BB73 BC12 BE16 BD18 BD14

Claims (4)

[Claims] 1. A composition comprising a β-silicon nitride crystal phase as a main component, Y and / or a rare earth element in an amount of 1 to 15% by weight in terms of oxide, and aluminum in an amount of 0.01 to 5% by weight in terms of oxide.
It contains impurity oxygen in a proportion of 10% by weight or less in terms of silicon oxide, and in the Raman spectroscopic analysis chart, 521c
The peak intensity of Si shown in m ^-1 is H ₁ , and the peak intensity of silicon nitride is 20
When the peak intensity of 6 cm ^-1 was H _2, the peak intensity ratio represented by H ₁ / H ₂ is a sintered body interior is greater than the sintered body surface and density of 3.20 g / cm ² or more A wear-resistant member characterized by the following. 2. The sintered product according to claim 1, wherein the peak intensity ratio represented by H ₁ / H ₂ is 0.1 or less on the surface of the sintered body and 3 or less on the inside of the sintered body. The wear-resistant member according to claim 1, wherein 3. The sintered body has a porosity of 3% or less, an average void diameter of 5 μm or less, a void diameter of 5 to 30 μm of 30% or less, a void diameter of 30 μm or more of 5% or less, and a remainder of void diameter. 2. The wear-resistant member according to claim 1, having a void diameter distribution of 5 [mu] m or less. 4. The method according to claim 1, wherein the silicon nitride sintered body includes Mg, W, M
8% by weight of at least one of o, Mn, Cu and Fe as oxide, nitride, oxynitride or silicide
The wear-resistant member according to claim 1, wherein the wear-resistant member is contained in the following ratio.