JP2016113347A - Si3nN4-BASED CERAMIC LESS IN HEAT RELEASING PROPERTY, AND TIP EXCHANGE TYPE CUTTING TIP, END MILL AND ANTIFRICTION TOOL USING THE SAME - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide SiNceramic less in heat releasing property and excellent in abrasion resistance at high temperature, a tip exchange type cutting tip and an end mill containing the same and a roll for plastic processing.SOLUTION: In a SiNceramic, WOof 1 mass% to 7.9 mass% is blended with a raw material powder, set in a carbon case and filled in a vacuum sintering furnace using a carbon heater and sintered under nitrogen atmosphere. WOis reduced and carbonated to W, WC and WC by sintering, and a cutting tool for Inconel processing excellent in durability can be made by setting WC at 50 mass% in the same, WC amount in the sintered body at 0.44 mass% to 3.85 mass%.SELECTED DRAWING: Figure 5

Description

The present invention relates to a cutting edge replaceable cutting tip, an end mill, a general cutting tool, a general wear-resistant tool, and a material thereof, which are manufactured by Inconel (registered trademark, the same shall apply hereinafter) by cutting an aircraft part or the like. This relates to the Si ₃ N ₄ ceramics.

  Inconel parts are often used for aircraft engine parts. However, Inconel is a difficult-to-cut material, and a cutting tool used for forming a part usually uses an exchangeable cutting tip or end mill made of an expensive cBN sintered body. Therefore, a cheaper and higher performance tool material is desired.

JP 61-091065 A JP 05-105518 A

B. D. Cullity (translated by Gentaro Matsumura): X-ray diffraction theory, Agne Inc., 1961 International Center for Diffraction Data: Powder Diffraction File (TM), Alphabetic Index for Experimental Patterns, Organic Phases, Sets 1-60, 2010 Daido Special Metal Co., Ltd. Catalog: INCONEL (registered trademark) alloy 718

In this technical field, there is Si ₃ N ₄ ceramics as an alternative to the cBN sintered body. Inconel cutting with recent Si ₃ N ₄ ceramic cutting edge-changing cutting tips and end mills increases the cutting temperature by increasing the cutting speed from 500 m / min to 1100 m / min, and increases the tensile strength of Inconel. High-efficiency machining is aimed at by cutting in a state where the thickness is reduced. However, satisfactory life Si ₃ N ₄ ceramics that can be used for this purpose have not yet been obtained, and improvements are desired. Therefore, the present inventors decided to develop Si ₃ N ₄ ceramics suitable for Inconel cutting.

Most Si ₃ N ₄ ceramics are added with Al ₂ O ₃ , Y ₂ O ₃ , AlN, and / or MgO. Furthermore, what is commonly called Si ₃ N ₄ includes those that are α or β-sialon (SiAlON, where the ratio of each element is not 1: 1: 1: 1), and vice versa. Therefore, unless otherwise specified, α or β-Si ₃ N ₄ is also included in the description below.

For Si ₃ N ₄ ceramics, various sintering techniques have been disclosed from old times to recent years. As a result of investigations by the present inventors, according to Patent Document 1, a preferable sintering temperature is 1700 ° C. to 1850 ° C., and a preferable sintering time is 1 h to 2 h. It was found that it was sintered. According to Patent Document 2, although low-temperature sintering is disclosed, long-time sintering such as sintering at 1550 ° C. for 6 hours and further sintering at 1650 ° C. for 3 hours is performed.

As is well known, Si ₃ N ₄ is a covalently-bonded crystal, and since the bonding force between Si atoms and N atoms is strong, both Si and N are based on the fact that each atom cannot easily diffuse. Since the diffusion rate of atoms is slow, it does not sinter easily. Therefore, 1 mass% to 5 mass% of Al ₂ O ₃ , Y ₂ O ₃ , MgO, AlN or the like is added as a sintering aid to cause a chemical reaction with each other to lower the melting point of Si ₃ N ₄ lower than 1900 ° C. It is widely practiced to make the above material, generate a liquid phase at a sintering temperature, and promote sintering densification by a so-called “sintering method in the presence of a liquid phase”.

Therefore, the _{Si 3 N 4 -2mass% Al 2} O 3 -5mass% Y 2 O 3 -3mass% MgO-1mass% AlN ceramic is present inventors have typical _Si 3 _{N 4} ceramics First, raw material powder As an average particle size manufactured by Ube Industries, Ltd. (D50 value of particle size distribution measured by laser diffraction / scattering method using MT3300EXII manufactured by Microtrack, the same applies hereinafter) 0.6 μm Si ₃ N ₄ (Si ₃ N ₄ is 98%) remainder _SiO 2, _Si 3 95% or more of _{N 4} is _alpha-Si 3 _{N 4} in rest _beta-Si 3 _{N 4.} shapes particulate. This sialon does not include so raw materials), Denki Kagaku Kogyo Co., Ltd. the average particle size of 1μm of _Al 2 _{O 3,} and an average particle size of 5μm manufactured by Shin-Etsu chemical Co., Ltd. _Y 2 _{O 3,} an average particle size of 1μm manufactured by Junsei chemical Co., Ltd. MgO, AlN having an average particle size of 1.0 μm manufactured by Denki Kagaku Kogyo Co., Ltd., blended into a predetermined composition, wet-ground for 24 h, dried powder was cold compression molded at a pressure of 98 MPa, and vacuum sintered After evacuating (less than 6.5 Pa) using a furnace (a type that can be made into a nitrogen atmosphere to less than 1 MPa after evacuating to 6.5 Pa or less, the same applies below), the sintering temperature is set as a nitrogen atmosphere of 0.5 MPa. A sintered body was obtained by sintering at 1650 ° C., 1700 ° C. or 1750 ° C. for 3 hours, and the structure of the sintered body was examined to obtain FIG.

  FIG. 1 shows the result of observing the mirror surface with an SEM. The reason why sintering was performed at a relatively low temperature is that the structure after sintering is more likely to be fine particles (higher strength can be obtained by making fine particles) and the sintering cost is low.

As a result of X-ray diffraction, α-Si ₃ N ₄ was not detected and was all β-Si ₃ N ₄ . Therefore, what appears to be columnar in FIG. 1 is β-Si ₃ N ₄ like the fine grains. That is, all of _α-Si 3 _{N 4} raw material powder is that it has a phase transformation to _β-Si 3 _{N 4} by sintering. Needless to say, since the α → β transformation temperature is about 1400 to 1550 ° C., the β phase is a stable phase at any of the three types of sintering temperatures used.

The higher the sintering temperature, the larger the size of β-Si ₃ N ₄ particles. This is because, based on the fact that the smaller particles have higher solubility in the liquid phase, the dissolution of small particles into the liquid phase → diffusion of the same solute into the liquid phase → precipitation of the solute onto the large particles results in β -Si ₃ N ₄ grains grow (so-called Ostwald growth), because the diffusion of atoms in the liquid phase becomes more active as the temperature increases, so that the grain growth rate increases. In this precipitation stage, α-Si ₃ N ₄ becomes β-Si ₃ N ₄ .

  The arrows in FIG. 1 are pores, and pores were generated at any temperature, and the number and size of pores increased as the sintering temperature increased. This is because MgO added as described above reacts with other components to locally produce a low-melting-point material, and the inside of the furnace is carburizing as described later, so that part of it is reduced and CO gas is reduced. This is thought to be due to the occurrence of residual impurities in the ceramics. This is the first finding.

  As described above, in the first composition, it was thought that there was too much sintering aid, so MgO, which is considered to be the main glass component, was reduced and the sintering temperature was lowered. Regarding MgO, the initial mass was reduced from 3 mass% to 2 mass% to 0 mass%, and the sintering temperature was set to 1650 ° C., the lowest among the three types.

  However, with 0 mass% MgO, densification was insufficient at 1650 ° C. for 3 h. Even at 1% by mass MgO, 1650 ° C. for 3 h sintering resulted in considerable densification but slight pores. The structure of each sintered body is shown in FIG. Although 1 mass% of MgO is necessary, it has been found that improvement in sinterability is necessary.

Therefore, as a result of careful consideration, an increase in the amount of AlN added was considered. AlN combines with α-Si ₃ N ₄ as a raw material and SiO ₂ which is the surface oxide of the powder particles to form α-sialon, thereby suppressing generation and growth of β-Si ₃ N _4. It is well known that α-sialonization acts as a driving force for sintering and, as a result, sintering densification at a low temperature results in a finer structure. Here, since Al ₂ O ₃ acts on the formation of α-sialon in the reverse direction, it was not added.

From the above, Si ₃ N ₄ -5 mass% Y ₂ O ₃ -1 mass% MgO-0 mass% to 6 mass% AlN ceramics were produced by sintering at 1650 ° C. for 3 h. The ceramics thus obtained were subjected to X-ray diffraction. From the obtained X-ray diffraction pattern, α-Si ₃ N ₄ ICDD (International Center for Diffraction Data) data is regarded as equivalent to α-sialon data, and α-sialon ({210} plane peak, 2θ = 35 .3 °) and β-Si ₃ N ₄ ({200} plane peak, 27.0 °) reference peak (reference peak hereinafter referred to as SP) area is defined as I / Ic of the ICDD data (α -Al ₂ O ₃ (Corundum) 50 mass% mixed α α-Al ₂ O ₃ {113} intensity Ic and the ratio of the intensity I of the strongest line of the sample) was corrected, respectively, From the intensity (area), α-sialon SP / (SP of α-sialon + SP of β-Si ₃ N ₄ ) × 100 was taken as α rate, and FIG. 3 was obtained.

Although the observation structure photograph is omitted, as the amount of AlN added increases, the granular α-sialon increases, the formation and growth of β-Si ₃ N ₄ is suppressed, and pores are not recognized. And when it added to 6 mass%, since alpha-sialon coarsened, 4 mass% seemed to be good as an AlN addition amount.

From the above, it was discovered that Si ₃ N ₄ -5 mass% Y ₂ O ₃ -1 mass% MgO-4 mass% AlN ceramics sintered at 1650 ° C. for ₃ h is a structurally excellent ceramic at the test piece level. This is the second finding.

When this Si ₃ N ₄ -5 mass% Y ₂ O ₃ -1 mass% MgO-4 mass% AlN ceramic was mass-produced, it showed an off-white appearance color, but a part of the ceramic color became lighter or darker. Produced part. This is because the material has a grayish white appearance from the raw material stage, so heat, that is, electromagnetic waves (mainly infrared rays) are not sufficiently absorbed, it is difficult to uniformly heat, and Si ₃ N ₄ ceramics has a relatively low temperature and short time at 1650 ° C. Since the sintering was performed for 3 hours, it was considered that the composition and amount of the liquid phase generated by the chemical reaction between Si ₃ N ₄ and the sintering aid varied.

  Therefore, mass production of this ceramic in a short time at a low temperature seemed difficult. However, the present inventors considered to make the grayish white overall black. This is because black easily absorbs electromagnetic waves and is easily heated uniformly.

At first, a commercially available carbide powder such as WC was tried as a blackening method, but the addition of the carbide powder was stopped because the aggregated particles of the carbide were relatively difficult to grind and the sinterability was poor. Next, by adding WO ₃ which is yellow but relatively easily pulverized, it can be colored to some extent (for example, yellow gray) and can be uniformly finely dispersed, so that Si ₃ N ₄ -5 mass% Y ₂ O ₃ -1 mass To 3% MgO-4 mass% AlN, WO _{3 having} an average particle size of 0.6 μm manufactured by Nippon Shin Metals Co., Ltd. (as observed by SEM, the particles were approximately 0.2 μm to 1.0 μm) was added up to 5 mass%.

Then, contrary to expectation, the appearance from addition of 0.2 mass% WO _{3 started} from gray to dark gray instead of yellow-gray, and became uniform black from the addition of 1 mass% WO ₃ to the appearance and the inside. In order to investigate this cause, not an optical image generated depending on the SEM texture of the mirror surface, that is, the reflectance of visible light, but an image generated depending on the amount of secondary electrons knocked out by the incident electron beam (secondary electron). As a result of observing the electronic image, FIG. 4 was obtained.

Particles that appear white from 1 mass% WO ₃ addition were observed, and increased as WO ₃ addition increased, as well as the average atomic number that determines the brightness of the secondary electron image (the higher this is, the more In view of the fact that WO ₃ has a higher average atomic number than other constituent phases, this was initially thought to be WO ₃ . The size of the particles is at most about 1 μm, and most are as small as 0.2 μm or less. This is probably because WO ₃ was crushed as expected.

As a precaution, ceramics added with WO ₃ up to 5 mass% so as to be easily understood by X-ray diffraction were produced, and as a result of X-ray diffraction, FIG. 5 was obtained. Even when WO _{3 was} added up to 10 mass%, almost no pore was observed under the SEM structure. In the upper part of FIG. 5, the results of identification using ICDD data are indicated by arrows with α-sialon peak as α and β-Si ₃ N ₄ peak as β.

In the figure, the highest α-sialon peak in the angle range of the figure is indicated by αmax, and the same β-Si ₃ N ₄ peak is indicated by βmax. Here, it was investigated in detail, but the peak of WO ₃ was observed. The peak indicated by a broken line was a peak of W ₂ C, W ₂ C + α-sialon or W ₂ C + β-Si ₃ N ₄ . That is, the added WO ₃ was changed to W ₂ C.

This is supported by the following WO ₃ addition amount and peak change. The first peak from the left shown by the broken line shows a decrease in peak height less than other α-sialon peaks even when the amount of WO ₃ added is increased, but this is an increase in the W ₂ C peak. It is because it is doing. The same applies to the first and second peaks from the right indicated by broken lines. Furthermore, the second peak from the left indicated by a broken line is a single peak of W ₂ C, and becomes higher as the amount of addition of WO ₃ increases.

Then, the X-ray diffraction results are abbreviated by 10 mass% WO ₃ is added, after the sintering, was found to contain a large amount of W as well as _{W 2} C. FIG. 6 shows the relationship between the added amount of WO ₃ and the weight ratios of W, W ₂ C, and WC with respect to W and the entire carbide thereof.

From this, it is understood that in the carbonization range of the present inventors, not only W ₂ C (including X2 described later) but also W ₂ C + WC or W + W ₂ C may be obtained. This is because WO ₃ is reduced and carbonized during sintering, WO ₃ by the strength of the _{carbonization, WO 3 → W → W 2} C → indicates that it has been reduced and carbonized in the order of WC, Si ₃ This phenomenon was first discovered by the present inventors during the sintering of N ₄ . This will be described in detail below.

The quantification method of the ratio of each phase in WC, W ₂ C, and W was based on the following method. Since there is no independent peak for WC, first, WC {101} (2θ = 48.3 °), β-Si ₃ N ₄ {220} (47.8 °) and {211} (48.0 °) ) And the area of β-Si ₃ N ₄ {200} (27.0 °). According to the ICDD data, the sum of the areas of β-Si ₃ N ₄ {220} and {211} is 11.8 / 100 times the area of β-Si ₃ N ₄ {200}. the sum of the areas of ₃ N ₄ {220} and {211} was calculated, and the area of overlap of the peak of WC {101} and _{β-Si 3 N 4 {220} } and _{{211}, β-Si 3} N 4 The area of WC {101} was determined from the difference from the sum of the areas of {220} and {211}. According to the ICDD data, since the area of WC {101} is 83/100 times the area of WC {100}, the area of WC {100} was calculated.

For W ₂ C, this area was determined because W ₂ C {002} (38.0 °) is the only independent peak. According to the ICDD data, since the area of W ₂ C {002} is 22/100 times the area of W ₂ C {101}, the area of W ₂ C {101} was calculated.

  For W, since W {110} (40.3 °) is the only large peak and this overlaps with α-sialon {300}, the area of this peak is determined, and then α-sialon { 101} (20.6 °) was determined. According to the ICDD data, the area of α-sialon {300} is 2.4 / 88.7 times the area of α-sialon {101}, so the area of α-sialon {300} is calculated and W The area of W {110} was calculated from the difference between the peak overlap area of {110} and α-sialon {300} and the area of α-sialon {300}.

From the area values of the peaks of WC {100}, W ₂ C {101}, and W {110} obtained in this way, the volume fraction of each phase is calculated according to Equation 1, and from this and the specific gravity. The weight fraction was calculated. Equation 1 is the p. It is quoted from 396.

In addition, the carbon analysis (high frequency combustion-infrared absorption method) of each ceramics added with 1, ₃ , 5 mass% WO ₃ was performed, and it was confirmed that the entire sintered body contained a carbon amount corresponding to W ₂ C and WC. .

By the way, it is thermodynamically impossible to reduce and carbonize WO ₃ in a nitrogen atmosphere. Nevertheless, W ₂ C and WC were produced when using a vacuum sintering furnace, using carbon equipment such as a carbon case, carbon insulation, carbon heater (hereinafter referred to as carbon case). It was thought that there was a trace amount of water in the N ₂ gas. That is, WO ₃ is exposed to a reducing atmosphere for some reason and is reduced to W, and then carbon such as a carbon case reacts with the moisture to become CO gas and the like, and these carbonize W. It was.

The reason why W ₂ C and WC looked white in the SEM structure is that, like WO ₃ described above, the average atomic number is larger than that of the other components, so that the amount of secondary electrons emitted is large. ₂ C and WC are not optically (white) optically white. Since W ₂ C and WC have an optically gray-black appearance, Si ₃ N ₄ ceramics are blackened by containing a predetermined amount of W ₂ C and WC.

As described above, WO ₃ is added in advance, sintered in a nitrogen atmosphere of 0.5 MPa using a carbon case or the like, and the contained WO ₃ is reduced and carbonized, whereby Si ₃ N ₄ -based ceramics We succeeded in dispersing fine W ₂ C (and WC, W) in the inside (maximum of about 1 μm and most of 0.2 μm or less). This is the first time for the inventors. This is the third finding.

In addition, the addition of WO ₃ slightly loses the effect of suppressing the grain growth of β-Si ₃ N ₄ and the improvement of the sinterability due to the formation of α-sialon of AlN, but the sinterability is slightly reduced by the addition of 10 mass% WO ₃ (It produced some pores). There are two reasons for this.

(1) WO ₃ is first reduced to W at 500 ° C. to 800 ° C. in a reducing atmosphere. This is an endothermic reaction and is not strongly related to densification. Next, in a carburizing atmosphere, W reacts with C from 800 ° C. to become W ₂ C, and if there is sufficient C and time, it becomes WC at 1400 ° C. (Because there is little C under the conditions of the present invention, W ₂ C is mainly used. These are exothermic reactions. From this, it is considered that a new sintering driving force is generated by the carbonization of W, and that stronger sintering is performed.

(2) As shown in FIG. 6, when the amount of added WO ₃ exceeds approximately 7.9 mass%, a large amount of simple W is formed, and as a result, endothermic reaction at low temperature increases during sintering, and at high temperature. This reduces the exothermic reaction, and sinterability begins to deteriorate.

From these viewpoints of sinterability, it can be said that the addition of WO ₃ under the sintering conditions (the carburizing atmosphere in the present invention) is preferably 1 mass% or more and 7.9 mass% or less. This is the fourth finding.

In addition, in FIG. 5, there are two arrow peaks indicated as X. However, since X1 can be seen even without addition of WO ₃ , it seems to be a kind of sialon, but there is only one independent peak. Could not be identified. X2 is the total of Si ₃ N ₄ , SiAlON, Y—SiAlON, Mg—SiAlON, WO _X , Mg—Y—Al—O, and Mg—Y—Al—W—O described in Non-Patent Document 2. (There are many types of X). From this and the increase in the peak with increasing WO ₃ , X2 is presumed to be an unknown phase based on W ₂ C. Therefore, thought to substances having substantially the same effect as W 2 _C, it may be considered included in the above W _{2 C.}

As described above, Si ₃ N ₄ -5 mass% Y ₂ O ₃ -1 mass% MgO containing 1 mass% to 7.9 mass% of W ₂ C in terms of WO _{3 in a} state in which pores are hardly generated and having no structure unevenness. Since mass production of Si ₃ N ₄ -based ceramics blended with -4 mass% AlN became possible, when applied to a cutting tip, W ₂ C was 50 mass% or more and the amount of W ₂ C in the sintered body was 0 if .46Mass% or more 3.85Mass% or less, exhibited a more excellent cutting life prior the _Si 3 _{N 4} ceramics. There are two reasons why cutting performance is excellent.

(1) In addition to having a structure that hardly generates pores, WO ₃ is added (mixed) in an amount of 1 mass% to 7.9 mass%, of which 50 mass% or more is set to W ₂ C, and the amount of W ₂ C in the sintered body is By producing 0.46 mass% or more and 3.85 mass% or less to blacken, the sinterability was enhanced and uniform sintering was possible, and essentially high strength was achieved.

(2) Here, as a result of examining the thermal conductivity of each sintered body of FIG. 4, it is as shown in Table 1. Even when WO _{3 is} added, the thermal conductivity is only slightly increased and the thermal conductivity is low. It was. As a result, the temperature rise during cutting tends to be constant. In addition, since the sinterability is improved, it is a uniform ceramic, so that stable cutting is easy. As described above, in the cutting of Inconel, the cutting temperature is increased, and cutting is performed in a state where the tensile strength of Inconel is reduced, thereby aiming at high-efficiency production. FIG. 7 shows the high-temperature tensile strength of Inconel 718 (registered trademark, the same applies hereinafter) according to Non-Patent Document 3. When the temperature is 800 ° C. or higher, the temperature is reduced from ½ to 1/8 compared with normal temperature. Therefore, it is important to 1) keep the temperature at the time of cutting high, 2) to perform stable cutting, and for that purpose, 1) heat dissipation is not required, and 2) ceramics are sintered uniformly. Is important, and the Si ₃ N ₄ ceramic of the present invention satisfies both of them.

As described above, the Si ₃ N ₄ based ceramic of the present invention was able to obtain good cutting performance for Inconel. These are the fifth findings. The above are the research results based on the sintering condition of 1650 ° C.-3 h.

The hardness of this ceramic, including the high temperature hardness, was not strongly related to the cutting performance for Inconel. Moreover, the cutting performance with respect to gray cast iron was excellent at 1400 HV or more. Normally, 1900HV or higher is required, but it seems that high hardness W ₂ C is finely dispersed as described later.

From this, 1 mass% to 7.9 mass% of WO ₃ which is a new discovery is added, of which 50 mass% or more becomes W ₂ C, and the amount of W ₂ C in the sintered body is 0.46 mass% or more. In the case of 85 mass% or less, three points of 1) blackening, 2) sintering driving force due to exothermic reaction, and 3) fine dispersion of W ₂ C with high hardness are excellent in cutting performance of the above-mentioned Inconel. It is obvious that the present invention can be applied not only to the composition but also to a wider range of Si ₃ N ₄ based ceramic compositions.

That is, other than the above-mentioned WO ₃ -added Si ₃ N ₄ -5 mass% Y ₂ O ₃ -1 mass% MgO-4 mass% AlN ceramics, Al ₂ O ₃ is 0 mass% to 15 mass% and Y ₂ O ₃ is 0 mass%. above 15 mass% or less, AlN is less 0Mass% or more 20 mass%, MgO is less 0Mass% or more 1 mass%, the sum and the Y of the _Y 2 _{O 3} in terms of content (AlN compounded amount of the raw material powder) AlN converted content of Al 5mass % And above, WO ₃ is 1 mass% or more and 7.9 mass% or less, the remainder is compounded and sintered as Si ₃ N ₄ , and 50 mass% or more of W after sintering and its carbide is W ₂ C, sintering _Si 3 _{N 4} ceramic _{W 2} C amount is less 0.46Mass% or more 3.85Mass% of the body a similar WO ₃ added Results can be expected.

This production is performed as follows. Each powder of Si ₃ N ₄ , Al ₂ O ₃ , Y ₂ O ₃ , AlN, MgO, and WO ₃ is prepared in a predetermined amount, wet mixed and pulverized, and if necessary, powder molding aids such as paraffin are added. Then, after being dried, cold compression molded and if necessary molded into a predetermined shape is filled into a vacuum sintering furnace using a carbon case or the like, and 1600 ° C. in a nitrogen atmosphere of 0.2 MPa or more and less than 1 MPa. above 1800 ° C. to sinter the holding of the following temperatures below 3h more at 6h, making _Si 3 _{N 4} ceramic having a W or a carbide by reducing and carbonization of WO _3.

Here, the reason why Al ₂ O ₃ is set to 0 mass% or more and 15 mass% or less is that when the content exceeds 15 mass%, the oxygen content increases, causing unevenness in the components in the glass phase and unstable characteristics. . The reason why Y ₂ O ₃ is set to 0 mass% or more and 15 mass% or less is that if it exceeds 15 mass%, the glass phase becomes excessive and the strength decreases. The reason why AlN is set to 0 mass% or more and 20 mass% or less is that when it exceeds 20 mass%, α-sialon becomes coarse and the hardness decreases. MgO may be 0 mass% or more and 1 mass% or less, but may be 0 mass%, but is added up to 1 mass% in order to improve sinterability when the glass phase is small. However, pores are generated when it exceeds 1 mass%.

The reason why the total amount of Al in terms of AlN (the amount of AlN in the raw material powder) and Y in terms of Y ₂ O ₃ is set to 5 mass% or more is that if it is less than this, sintering becomes difficult. The reason why W or its carbide is set to 1 mass% or more and 7.9 mass% or less in terms of WO ₃ is that if it is less than 1 mass%, the blackening becomes insufficient and the wear resistance does not increase, and if it exceeds 7.9 mass%, FIG. The added WO ₃ is not completely carbonized, W ₂ C is less than 50 mass%, and a large amount of W is generated and softens, so the wear resistance is not sufficiently increased and the sinterability is reduced. This is because the strength becomes low.

The reason why the amount of W ₂ C in the sintered body is set to 0.46 mass% or more and 3.85 mass% or less is that when the W ₂ C amount is less than 0.46 mass%, the W ₂ C amount is not blackened and is increased to more than 3.85 mass%. This is because it is not economical because the sintering atmosphere needs to be controlled.

  The reason why the sintering temperature is set to 1600 ° C. or more and 1800 ° C. or less is that the sintering is not sufficiently performed at a temperature lower than 1600 ° C., and if the temperature exceeds 1800 ° C., coarse grains are formed and the hardness is reduced. The reason why the holding time of sintering is set to 3 h or more and 6 h or less is that when the sintering time is less than 3 h, the sintering is not sufficiently performed, and when it exceeds 6 h, coarse particles are formed and the hardness and / or strength is excessively lowered. The reason why the pressure of nitrogen during sintering is set to 0.2 MPa or more and less than 1 MPa is that if the pressure is less than 0.2 MPa, evaporation of nitrogen from the sintered body increases and a dense sintered body is not obtained. This is because it is an uneconomical furnace.

If the sintering temperature is increased and / or the sintering time is long, the composition may be such that the glass component is reduced, and one kind of Al ₂ O ₃ , Y ₂ O ₃ , AlN, and MgO may be used. Useful ceramics can be made by adding more than a plurality of types.

If the sintering temperature is lowered and / or the sintering time is shortened, it is useful to add more than one kind or more kinds of Al ₂ O ₃ , Y ₂ O ₃ , AlN, MgO. Ceramics can be made.

Regarding the reduction and carbonization of WO ₃ during sintering to W ₂ C or the like, the compact is filled in a carbon case and once vacuumed (6.5 Pa or less using a vacuum sintering furnace using the carbon case) ), The sintering temperature is set to 1600 ° C. or higher and 1800 ° C. or lower and held for 3 hours or longer and 6 hours or shorter as a nitrogen atmosphere of 0.2 MPa or higher and lower than 1 MPa.

Among these _conditions, Y 2 _{O 3} to 5 mass%, AlN and 4 mass%, MgO and 1 mass%, the WO ₃ 1 mass% or more 7.9Mass% or less, and contain inevitable impurities, the balance in _Si 3 _{N 4} A carbon case that is blended into a certain composition, wet-mixed and pulverized, added with powder molding aids such as paraffin, if necessary, dried, cold-compressed, and molded into a predetermined shape if necessary. Set inside, filled in a vacuum sintering furnace using a carbon heat insulating material and a carbon heater, exhausted to 6.5 MPa, and then sintered at 1650 ° C. for 3 h under a nitrogen atmosphere of 0.2 MPa or more and less than 1.0 MPa, W or its carbide contained after sintering is produced by reducing and carbonizing WO _{3 of} the raw material powder during sintering, of which 50 mass% or more is W ₂ C. The Si ₃ N ₄ ceramics having a W ₂ C content of 0.46 mass% or more and 3.85 mass% or less in the sintered body are particularly useful as cutting tools and general wear-resistant tools for Inconel as shown in the examples. High performance.

Further, part or all of Y ₂ O ₃ may be substituted with at least one of R ₂ O ₃ (R is an element of Sc or lanthanum series). This also shows the same characteristics as the Si ₃ N ₄ ceramics. These are the sixth findings.

It is possible to carbonize WO ₃ by introducing a carburizing gas, that is, a hydrocarbon such as CH ₄ or CO at the time of sintering, but it requires special equipment and is uneconomical.

In the Si ₃ N ₄ ceramics of the present invention, W ₂ C in the ceramic is a hard substance (3000 HV) next to B ₄ C, SiC and TiC in carbides, and it is very finely dispersed. Therefore, it is obvious that it has characteristics useful as a wear-resistant tool. That is, it can also be used as molten aluminum parts, abrasive cloth dressing plates, induction hardening jigs, plastic working rolls, nozzles, nozzle covers, and bearing balls. This is the seventh finding.

The reason why the method of directly adding the W ₂ C powder to the raw material is not adopted in the present invention is based on the following circumstances. 1) A sintering driving force generated by heat generation due to carbonization cannot be obtained, and the degree of freedom in composition is reduced. 2) Since commercially available W ₂ C is hard, it will not be sufficiently refined under normal ceramic mixing and grinding conditions (balls in grinding are ceramics), so mixing and grinding conditions in cemented carbide (balls in grinding are cemented carbide) ) Is previously prepared and added for use, which increases costs. 3) Since the oxidized pulverized, it becomes the same as the addition of virtually WO _3. 4) From these 1) to 3), the method of adding W ₂ C powder to the raw material is not industrially useful.

  Also, powder molding aids such as paraffin did not particularly affect carburization in the sintering of the present invention. These are considered to evaporate below 600 ° C., disappear from the green compact, and move from the furnace to a wax trap or the like.

When carbonization at the sintering temperature is extremely insufficient, W ₅ Si ₃ or the like may be generated in addition to W. Thus, the present invention has been completed.

The Si ₃ N ₄ ceramics containing WO ₃ in the material powder of 1 mass% or more and 7.9 mass% or less of the present invention has low heat dissipation and excellent wear resistance at high temperatures. When used as a type cutting tip or end mill, it has excellent durability. Similarly, it has excellent characteristics as wear-resistant tools such as molten aluminum parts, polishing cloth dressing plates, induction hardening jigs, plastic working rolls, nozzles, nozzle covers, bearing balls and the like.

This is the influence of the sintering temperature on the mirror surface SEM structure of Si ₃ N ₄ ceramics blended with the composition of Si ₃ N ₄ -2 mass% Al ₂ O ₃ -5 mass% Y ₂ O ₃ -3 mass% MgO-1 mass% AlN. A white arrow indicates a pore. The high-magnification photograph (top) is a photograph of a part with few pores. Effect of MgO addition amount on mirror SEM structure of Si ₃ N ₄ ceramics blended with Si ₃ N ₄ -2 mass% Al ₂ O ₃ -5 mass% Y ₂ O ₃ -1 mass% to ₂ mass% MgO-1 mass% AlN composition It is. A white arrow indicates a pore. The high-magnification photograph (top) is a photograph of a part with few pores. This is the influence of the added amount of AlN on the α rate of Si ₃ N ₄ -based ceramics blended in a composition of Si ₃ N ₄ -5 mass% Y ₂ O ₃ -1 mass% MgO-0 mass% to 6 mass% AlN. Si ₃ is the effect of _{N 4 -5mass% Y 2 O 3} -1mass% WO 3 Addition on MgO-4mass% _Si 3 _{N 4} ceramic mirror SEM tissues formulated to AlN composition. White particles in the ceramic added with WO ₃ are phases containing W such as W ₂ C. The maximum dimension was about 1 μm, and many particles were 0.2 μm or less. FIG. 5 is an X-ray diffraction diagram (target: CuKα) of each ceramic of FIG. 4. FIG. 5 shows the relationship between the amount of WO ₃ added to the total amount of ceramic and the weight ratio of W, W ₂ C, and WC to the entire W and W carbides. In addition to the composition of FIG. 5, the addition of 10 mass% of WO ₃ is added. It is the influence of the measurement temperature on the tensile strength of Inconel 718 (part of the diagram in Non-Patent Document 3 is modified). Inconel 718 with a diameter of 12.7 mm, which was solvated at 982 ° C.-1 h and cooled in the furnace to 621 ° C. after 718 ° C.-8 h and kept at 621 ° C. so that the total aging time was 18 h. According to the test piece.

As raw material powder, Si ₃ N ₄ with an average particle size of 0.6 μm manufactured by Ube Industries, Ltd., Y ₂ O ₃ with an average particle size of 5 μm manufactured by Shin-Etsu Chemical Co., Ltd., MgO with an average particle size of 1 μm manufactured by Junsei Chemical Co., Ltd. Using AlN manufactured by Chemical Industry Co., Ltd. with an average particle size of 1.0 μm and WO ₃ manufactured by Nippon Shin Metal Co., Ltd. with an average particle size of 0.6 μm, they are blended into the composition shown in Table 2 and dried after wet mixing and grinding for 24 hours. Compressed and molded at a pressure of 98 MPa, filled in a carbon case, evacuated to a vacuum (6.5 Pa or less) once using a vacuum sintering furnace using a carbon case, etc., and then sintered as a 0.5 MPa nitrogen atmosphere. The temperature was set to 1650 ° C. and held for ₃ hours to produce Si ₃ N ₄ -based ceramics (sample numbers No. 1 to No. 17 in Table 2).

  Using this ceramic, a cutting edge exchangeable cutting tip for turning was prepared, and the performance when Inconel 718 was cut at a cutting speed of 1000 m / min is shown in Table 2. It was written together with the phase composition. Inventive ceramics No. 9-No. 11 and no. 14-No. The cutting performance of 17 was 1.2 times longer than that of commercially available conventional ceramics.

  The raw material powder is not limited to the above product, and the same result can be obtained even if the manufacturer is different as long as it has a quality equivalent to the above.

  Table 3 shows the results of verifying the wear resistance performance. The reference ceramics could not be used due to insufficient strength, but the inventive ceramics could be used. Moreover, it turns out that the outstanding long life is shown in comparison with the existing material. Sample No. 5, no. 9-No. 12 and no. 17 is common to Table 2.

  The ceramic cutting tool of the present invention is frequently used in the field of cutting Inconel aircraft parts and the like, and improves productivity and economy. Moreover, it is not limited to this and is frequently used as a wear-resistant tool to improve productivity and economy. Therefore, the utility value is great.

From the above, Si ₃ N ₄ -5 mass% Y ₂ O ₃ -1 mass% MgO- 1 mass% to 6 mass% AlN ceramics were produced by sintering at 1650 ° C. for 3 h. The ceramics thus obtained were subjected to X-ray diffraction. From the obtained X-ray diffraction pattern, α-Si ₃ N ₄ ICDD (International Center for Diffraction Data) data is regarded as equivalent to α-sialon data, and α-sialon ({210} plane peak, 2θ = 35 .3 °) and β-Si ₃ N ₄ ({200} plane peak, 27.0 °) reference peak (reference peak hereinafter referred to as SP) area is defined as I / Ic of the ICDD data (α -Al ₂ O ₃ (Corundum) 50 mass% mixed α α-Al ₂ O ₃ {113} intensity Ic and the ratio of the intensity I of the strongest line of the sample) was corrected, respectively, From the intensity (area), α-sialon SP / (SP of α-sialon + SP of β-Si ₃ N ₄ ) × 100 was taken as α rate, and FIG. 3 was obtained.

As described above, Si ₃ N ₄ -5 mass% Y ₂ O ₃ -1 mass% MgO containing 1 mass% to 7.9 mass% of W ₂ C in terms of WO _{3 in a} state in which pores are hardly generated and having no structure unevenness. Since mass production of Si ₃ N ₄ -based ceramics blended with -4 mass% AlN became possible, when applied to a cutting tip, W ₂ C was 50 mass% or more and the amount of W ₂ C in the sintered body was 0 if less .44 mass% or more 3.85mass%, exhibited a more excellent cutting life prior the _Si 3 _{N 4} ceramics. There are two reasons why cutting performance is excellent.

(1) In addition to having a structure that hardly generates pores, WO ₃ is added (mixed) in an amount of 1 mass% to 7.9 mass%, and 50 mass% or more of W generated by reduction and carbonization during sintering and its carbides By making it W ₂ C and blackening the W ₂ C content in the sintered body by producing 0.44 mass% to 3.85 mass%, it is possible to enhance the sinterability and sinter uniformly. And essentially high strength.

From this, WO ₃ is added by 1 mass% to 7.9 mass%, which is a new discovery, and 50 mass% or more of W and its carbide produced by reduction and carbonization during sintering become W ₂ C, and sintering. When the amount of W ₂ C in the body is 0.44 mass% or more and 3.85 mass% or less, 1) blackening, 2) sintering driving force due to exothermic reaction, 3) high hardness W ₂ C is finely dispersed It is obvious that the above three points are not limited to the composition with excellent cutting performance of the above-mentioned Inconel, but can be applied to a wider range of Si ₃ N ₄ ceramic compositions.

That is, other than the above-mentioned WO ₃ -added Si ₃ N ₄ -5 mass% Y ₂ O ₃ -1 mass% MgO-4 mass% AlN ceramics, Al ₂ O ₃ is 0 mass% to 15 mass% and Y ₂ O ₃ is 0 mass%. above 15 mass% or less, AlN is 1 mass% or more 20 mass% or less, MgO is less 0Mass% or more 1 mass%, the sum and the Y of the _Y 2 _{O 3} in terms of content (AlN compounded amount of the raw material powder) AlN converted content of Al 5 mass% or more, WO ₃ is 1 mass% or more and 7.9 mass% or less, the remainder is blended and sintered as Si ₃ N ₄ , and 50 mass% or more of sintered W and its carbides are W ₂ C and sintered. The amount of W ₂ C in the combined body is 0.44 mass% to 3.85 mass% , and the amount of W is 0.01 mass% to 0.16 mass. %, And Si ₃ N ₄ -based ceramics having a WC amount of 0.08 mass% or more and 0.37 mass% or less can be expected to have the same WO ₃ addition effect.

This production is performed as follows. Each powder of Si ₃ N ₄ , Al ₂ O ₃ , Y ₂ O ₃ , AlN, MgO, and WO ₃ is prepared in a predetermined amount, wet mixed and pulverized, and if necessary, powder molding aids such as paraffin are added. Then, after being dried, cold compression molded and if necessary molded into a predetermined shape is filled into a vacuum sintering furnace using a carbon case or the like, and 1600 ° C. in a nitrogen atmosphere of 0.2 MPa or more and less than 1 MPa. Sintering is performed at a temperature of 1800 ° C. or less for 3 hours or more and 6 hours or less, and WO ₃ is reduced and carbonized to produce W 3 and its carbide Si ₃ N ₄ ceramics.

Here, the reason why Al ₂ O ₃ is set to 0 mass% or more and 15 mass% or less is that when the content exceeds 15 mass%, the oxygen content increases, causing unevenness in the components in the glass phase and unstable characteristics. . The reason why Y ₂ O ₃ is set to 0 mass% or more and 15 mass% or less is that if it exceeds 15 mass%, the glass phase becomes excessive and the strength decreases. The reason why AlN is 1 mass% or more and 20 mass% or less is that when it exceeds 20 mass%, α-sialon becomes coarse and the hardness decreases. MgO may be 0 mass% or more and 1 mass% or less, but may be 0 mass%, but is added up to 1 mass% in order to improve sinterability when the glass phase is small. However, pores are generated when it exceeds 1 mass%.

The reason why the total amount of Al in terms of AlN (the amount of AlN in the raw material powder) and Y in terms of Y ₂ O ₃ is set to 5 mass% or more is that if it is less than this, sintering becomes difficult. The reason why W and its carbides are set to 1 mass% or more and 7.9 mass% or less in terms of WO ₃ is that if the content is less than 1 mass%, blackening becomes insufficient and the wear resistance does not increase, and if it exceeds 7.9 mass%, FIG. The added WO ₃ is not completely carbonized, W ₂ C is less than 50 mass%, and a large amount of W is generated and softens, so the wear resistance is not sufficiently increased and the sinterability is reduced. This is because the strength becomes low.

The reason why the amount of W ₂ C in the sintered body is set to 0.44 mass% or more and 3.85 mass% or less is that when the W ₂ C amount is less than 0.44 mass%, blackening does not occur and the amount is increased to more than 3.85 mass%. This is because it is not economical because the sintering atmosphere needs to be controlled. When the amount of W ₂ C in the sintered body is 0.44 mass% or more and 3.85 mass% or less, the W amount is 0.01 mass% or more and 0.16 mass% or less, and the WC amount is 0.08 mass% or more and 0. .37 mass% or less.

Among these _conditions, Y 2 _{O 3} to 5 mass%, AlN and 4 mass%, MgO and 1 mass%, the WO ₃ 1 mass% or more 7.9Mass% or less, and contain inevitable impurities, the balance in _Si 3 _{N 4} A carbon case that is blended into a certain composition, wet-mixed and pulverized, added with powder molding aids such as paraffin, if necessary, dried, cold-compressed, and molded into a predetermined shape if necessary. Set inside, filled in a vacuum sintering furnace using a carbon heat insulating material and a carbon heater, exhausted to 6.5 MPa, and then sintered at 1650 ° C. for 3 h under a nitrogen atmosphere of 0.2 MPa or more and less than 1.0 MPa, W and its carbides contained after sintering are produced by reducing and carbonizing WO _{3 of} the raw material powder during sintering, of which 50 mass% or more is W ₂ C. The Si ₃ N ₄ ceramics having a W ₂ C content of 0.44 mass% or more and 3.85 mass% or less in the sintered body are particularly cutting tools for inconel and general wear-resistant tools as shown in the examples. As a high performance.

This is the influence of the sintering temperature on the mirror surface SEM structure of Si ₃ N ₄ ceramics blended with the composition of Si ₃ N ₄ -2 mass% Al ₂ O ₃ -5 mass% Y ₂ O ₃ -3 mass% MgO-1 mass% AlN. A white arrow indicates a pore. The high-magnification photograph (top) is a photograph of a part with few pores. Effect of MgO addition amount on mirror SEM structure of Si ₃ N ₄ ceramics blended with Si ₃ N ₄ -2 mass% Al ₂ O ₃ -5 mass% Y ₂ O ₃ -1 mass% to ₂ mass% MgO-1 mass% AlN composition It is. A white arrow indicates a pore. The high-magnification photograph (top) is a photograph of a part with few pores. This is the influence of the added amount of AlN on the α rate of Si ₃ N ₄ ceramics blended in the composition of Si ₃ N ₄ -5 mass% Y ₂ O ₃ -1 mass% MgO- 1 mass% to 6 mass% AlN. Si ₃ is the effect of _{N 4 -5mass% Y 2 O 3} -1mass% WO 3 Addition on MgO-4mass% _Si 3 _{N 4} ceramic mirror SEM tissues formulated to AlN composition. White particles in the ceramic added with WO ₃ are phases containing W such as W ₂ C. The maximum dimension was about 1 μm, and many particles were 0.2 μm or less. FIG. 5 is an X-ray diffraction diagram (target: CuKα) of each ceramic of FIG. 4. FIG. 5 shows the relationship between the amount of WO ₃ added to the total amount of ceramic and the weight ratio of W, W ₂ C, and WC to the entire W and W carbides. In addition to the composition of FIG. 5, the addition of 10 mass% of WO ₃ is added. It is the influence of the measurement temperature on the tensile strength of Inconel 718 (part of the diagram in Non-Patent Document 3 is modified). Inconel 718 with a diameter of 12.7 mm, which was solvated at 982 ° C.-1 h and cooled in the furnace to 621 ° C. after 718 ° C.-8 h and kept at 621 ° C. so that the total aging time was 18 h. According to the test piece.

Claims (9)

Al is 0 mass% or more and 15 mass% or less in terms of Al ₂ O ₃ (Al ₂ O ₃ content in raw material powder) and 0 mass% or more and 20 mass% or less in terms of AlN (AlN content in raw material powder), Y is Y ₂ O ₃ 15mass% or more 0Mass% in terms of the following, a Mg 1 mass% or more 0Mass% in terms of MgO below, W, or 1 mass% or more 7.9Mass% less the carbide in terms _of WO _3, and contains inevitable impurities, The balance is Si ₃ N ₄ , and the total amount of Al in terms of AlN (AlN content in the raw material powder) and the amount of Y in terms of Y ₂ O ₃ is 5 mass% or more. WO ₃ is used as a raw material powder, and it is produced by reduction and carbonization during sintering, of which 50 mass% or more is W ₂ C, and a sintered body Si ₃ N ₄ -based ceramics in which the amount of W ₂ C is 0.46 mass% or more and 3.85 mass% or less. Each powder of Si ₃ N ₄ , Al ₂ O ₃ , Y ₂ O ₃ , AlN, MgO, and WO ₃ is prepared in a predetermined amount, wet-mixed and pulverized, and if necessary, a molding aid is added. After the intermediate compression molding, if necessary molded into a predetermined shape, set in a carbon case, filled in a vacuum sintering furnace using a carbon heat insulating material and a carbon heater, exhausted to 6.5 Pa or less, Sintering by holding at a temperature of 1600 ° C or higher and 1800 ° C or lower for 3h or more and 6h or less under a nitrogen atmosphere of 0.2MPa or more and less than 1MPa to reduce and carbonize WO ₃ to obtain W or a carbide thereof. 1. A method of producing a Si ₃ N ₄ ceramic. A Si ₃ N ₄ based ceramic in which a part or all of Y ₂ O ₃ of claim 1 is substituted with at least one of R ₂ O ₃ (R is an element of the Sc or lanthanum series). The Si ₃ N ₄ ceramics according to claim _{3, wherein} a part or all of Y ₂ O _{3 according to} claim 2 is substituted with at least one of R ₂ O ₃ (R is an element of Sc or lanthanum series). how to. Y is 5 mass% in terms of Y ₂ O ₃ , Al is 4 mass% in terms of AlN, Mg is 1 mass% in terms of MgO, W or its carbide is 1 mass% to 7.9 mass% in terms of WO ₃ , and contains inevitable impurities However, the balance is Si ₃ N ₄ , and the contained W or carbide thereof is produced by reducing and carbonizing during sintering using WO ₃ as a raw material powder, of which 50 mass% or more is W Si ₃ N ₄ -based ceramics that are ₂ C and have a W ₂ C content of 0.46 mass% or more and 3.85 mass% or less in the sintered body. Y ₂ O ₃ is 5 mass%, AlN is 4 mass%, MgO is 1 mass%, WO ₃ is 1 mass% to 7.9 mass%, the remainder is Si ₃ N ₄ and the raw material powder is prepared, wet mixed and pulverized, necessary Add a molding aid, and after drying, cold compression molding, and if necessary molded into a predetermined shape, set it in a carbon case and place it in a vacuum sintering furnace using a carbon heat insulating material and a carbon heater. After filling and evacuating to 6.5 Pa or less, sintering is performed by holding at a temperature of 1650 ° C. for 3 hours under a nitrogen atmosphere of 0.2 MPa or more and less than 1 MPa, and WO ₃ is reduced and carbonized to form W or a carbide thereof. A method for producing the Si ₃ N ₄ ceramics according to claim 5.   A blade-tip-exchangeable cutting tip or an end mill produced using the ceramic according to claim 1, claim 3 or claim 5.   A method for cutting Inconel (registered trademark) at a cutting speed of 500 m / min or more and 1100 m / min or less with the cutting edge exchangeable cutting tip or end mill of claim 7.   A molten aluminum part, a polishing cloth dressing plate, an induction hardening jig, a roll for plastic working, a nozzle, a nozzle cover, or a bearing ball, produced using the ceramic according to claim 1, claim 3 or claim 5.