JPH0449510B2 - - Google Patents

Description

[Detailed description of the invention]

This invention relates to Si-Al-O-N type materials, and more particularly to dual-phase Si-Al-O-
This relates to N materials. There are numerous papers and patents describing relatively new Si-Al-O-N materials produced by adding aluminum and oxygen atoms to silicon nitride materials. Recently, these materials have found their way into the metalworking industry and have given rise to the possibility of processing cast iron and other similar materials. More specifically, Si-Al-O-N type materials made in accordance with U.S. Pat. No. 4,127,416 have proven useful in certain metal processing applications.
The material of the mold made by the above US patent is approximately
It is produced as a predominant single phase β-Si-Al-O-N material in which 10-20% of the glassy phase is present. This material is made essentially as described in that patent and includes the formation of a polytype material as an initial step in the process. The polytype material is then reacted with controlled amounts of silicon nitride and oxides of yttrium, lithium or calcium to form at least 80%, preferably 95%
forms a single-phase beta-type Si-Al-O-N ceramic. Such materials, when produced, have a 100,000-
It has a bending breaking strength in the range of 110000 psi and a soup hardness in the range of 1450-1800 Kg/mm ² at 100 g load. In accordance with the present invention, a dual phase Si-Al-O-N material is produced that is particularly useful as a cutting insert material. This double phase is α and β phase Si-Al-O-
Consists of N. It has been discovered that control of the amount of alumina in the mixture as well as the neutral medium for milling allows control of the composition of the final material such that α and β type Si-Al-O-N phases appear. As the amount of alumina decreases, the amount of α phase Si-Al-O-N increases. Control of other starting components also produces the same effect, e.g.
Less silica, more aluminum nitride, more polytype, more yttrium all result in more α-Si-Al-O in the final product.
- Generate N. Preferably, α phase Si-Al-O-
N is in the range 10-70% by weight and β in the composition
The phase Si-Al-O-N is in the range 20-90% by weight. A glassy phase in the range 0-10% by weight is also present. The added α-Si-Al-O-N in the composition increases the hardness without appreciably affecting the flexural rupture strength of the material. Although compounds of yttrium are used as sintering aids in the manufacture of the above products, it should be recognized that similar results are obtained with oxides of scandium, cerium, lanthanum and elements of the lanthanum series. The use of yttrium as a preferred sintering aid results in intergranular components consisting primarily of glassy phases;
It may also include other phases. As for other phases,
It is a cubic phase with the formula Y ₃ Al ₅ O ₁₂
YAG (yttrium aluminum garnet), which is the monoclinic phase of the formula YSiO ₂ N
N-α wollastonite, YAM, which is _a monoclinic phase with formula _{Y 4 Al 2} O _{9 ;} There is N-YAM, which is a clinic phase. The nature of the invention will become more apparent by reference to the following detailed description taken in conjunction with the accompanying drawings. The present invention relates to a dual-phase ceramic product and a method for manufacturing said product, which method comprises preparing a powder mixture consisting essentially of a first component consisting of a compound containing the elements silicon, aluminum, oxygen and nitrogen. and the proportions of the elements are such that the ratio of the total number of silicon and aluminum atoms to the total number of oxygen and nitrogen atoms is in the range of 0.735 to 0.77 and said compound is combined with the second component during the subsequent sintering process. react to form a dual phase ceramic material, the first phase having the general formula Si _6-z Al _z O _z N _6-z
According to the formula, Z is 0.38 to 1.5, the second phase is a hexagonal phase, and has the general formula (Si, Al) ₁₂ M _x (O,
N) ₁₆ , where M is lithium, calcium or yttrium, or any member of the lanthanum series, and X is from 0.1 to 0.2. The second component is based on the total weight of the first and second components.
Comprising 0.1-10%, the second component is further an oxide of the elements yttrium, scandium, cerium, lanthanum, and at least one of the metals of the lanthanum series. The mixture is then heated to 1600-2000°C in a protected environment with or without pressure.
sintered at a temperature of at least 10 minutes to at least 5 hours, decreasing with increasing temperature;
thereby producing a ceramic material containing at least 90% by volume of said dual phase ceramic material;
The second phase contains a portion of the second component. In the method described above, the first component compound is calculated by dividing the sum of all silicon and aluminum atoms in the compound by the sum of all oxygen and nitrogen atoms.
It is blended so that it becomes 0.735 to 0.77, preferably 0.745 to 0.76. The binary mixture is then prepared in a protected environment, preferably a non-oxidizing environment, more preferably a reducing environment, at a temperature of 1600-2000°C, at least 90% by volume.
is sintered for a sufficient time to produce a silicon aluminum oxynitride of the above formula. The required sintering time decreases with increasing temperature, with a sintering temperature of 2000°C the minimum time is only 10 minutes, while a temperature of 1600°C requires a sintering time of at least 5 hours. Ru. The compounds forming the first component of the raw mixture are conveniently silicon nitride, aluminum nitride, alumina and silica, present as inherent impurities on the silica and aluminum nitride. Alternatively, the first component may be defined by a ceramic intermediate containing silicon nitride and silicon aluminum oxynitride which does not follow the general formula Si _6-z Al _z O _z N _6-z . Such materials are called polytypes and are described in the aforementioned US Pat. No. 4,127,416. Example 7-17 utilizes the 21R polytype defined in the aforementioned US patent. Preferably, the ceramic intermediate silicon aluminum oxynitride has a rhombohedral structure and follows the approximate formula SiAl ₆ O ₂ N ₆ , and the ceramic intermediate preferably nitrides a powder mixture of alumina, aluminum and silicon. formed by heating in an atmosphere to a temperature of 1200-1400°C, the heating rate being controlled to substantially prevent exotherm;
Sinter the nitriding mixture at a temperature of 1500-1900 °C. Alternatively, the intermediate is a powder mixture of alumina, aluminum nitride and silicon nitride from 1200 to
a protected environment, preferably a non-oxidizing environment, at a temperature of 200°C;
More preferably, it is formed by heating in a reducing environment. In the method described above, the relative amounts of compounds present in the mixture are adjusted so that the general formula
A dual phase ceramic is produced having a first phase according to Si _6-z Al _z O _z N _6-z and a second phase according to the general formula (Si, Al) ₁₂ M _x (O, N) ₁₆ . In the above formula, Z is 0.38~
1.5, because having Z values within these limits has been found to produce a complete product with high strength even when sintering is carried out without applying pressure. . On the other hand, the Z value is 0.38
If the Z value is lower than 1.5, the material becomes difficult to sinter without applying pressure, and if the Z value is higher than 1.5, the strength of the product deteriorates. Furthermore, the relative amounts of compounds in the first component are
Adjusted to give said atomic ratio between 0.735 and 0.77. That is, it has been found that when the ratio is lower than 0.735, the mixture becomes oxygen rich and slippery. This results in the production of too much glass during sintering, which has been found not only to have an adverse effect on the high temperature strength properties of the product, but also to have an adverse effect on the low temperature strength properties. Furthermore, it has been found that glass cannot be removed by the heat treatment process detailed below. On the other hand, the atomic ratio is
It has been found that if it exceeds 0.77, there is insufficient oxygen to form the glass necessary to achieve the toughening of the product. The tolerance range of 0.1 to 10% by weight for the second component of the starting mixture is again selected on the basis that it provides a satisfactory oxygen content in the sintered product. The element selected for the second component is cerium, yttrium, scandium, lanthanum or one of the lanthanum series. That is, they have highly refractory oxides, and these oxides, together with the silica and alumina present, produce a high melting point glass, so the product can be heated at higher temperatures than would be the case with a low melting point glass. can be used. The second component is also α-Si-Al- of the first component.
Necessary for the formation of the O-N phase. Thus, by definition, α-Si-Al-O-N contains one of the yttrium or lanthanum series. Among the elements selected for the second component, yttrium is preferred. That is, the presence of ittria in the sintering mixture has been found to result in a high strength product without the application of pressure. By carrying out the method described above, a dual phase silicon aluminum oxynitride of at least 90% by volume is formed, with which it consists primarily of a glassy phase, but also possibly YAG, YAM, N-
An intergranular component is formed containing YAM and other phases such as Y-N-α-wollastonite. The presence of glass helps strengthen the product during sintering, but tends to result in a reduction in the high temperature properties of the final component. However, it has been found that the amount of glass phase in the sintered product can be reduced by subjecting the product to a final heat treatment step. In this final heat treatment step, the temperature of the product is reduced to within 200°C of the melting point of the glass (i.e.
(approximately 1400°C in the case of yttrium glass) and then cooling the product to convert at least a portion of the glass into YAG, YAM, N-YAM and Y-N-
It crystallizes into intergranular components containing other phases such as α-wollastonite. EXAMPLES The starting materials used in this invention are as listed below, but the starting materials shown in the aforementioned US Pat. No. 4,127,416, or the known conditions for the production of Si-Al-O-N materials. It may be any other known material that satisfies the requirements. Silicon (Elkem Metals) Fe < 1.0% C 0.1-0.4% typical Ca < 0.07% typical Al < 0.53% -200 mesh grain Yttrium (Molycorp, Division of Union 76) 99.99% purity -325 mesh grain aluminum (Alcan Aluminum Corporation ) 99.3% purity 16 micron average particle size alumina (Reynolds) Rc-172DBM 99,7% Al ₂ O ₃ 0.04% Na ₂ O 0.07% SiO ₂ 0.03% Fe ₂ O ₃ particle size < 1 micron alumina (Alcoa) A-16 SG 99.5% Al ₂ O ₃ 0.05-0.09% Na ₂ O 0.02-0.04% SiO ₂ 0.01-0.02% Fe ₂ O ₃ Particle size < 1 micron In Table 2, percent α-Si-Al-O
-N and β-Si-Al-O-N were based on 100% from the beginning. This is because it ignored the 10 percent glass where no other crystalline phase was present and which could not be quantified by X-ray diffraction. This percentage was changed to include 10% glass and therefore α-Si-Al
The percentages of -O-N and β-Si-Al-O-N totaled 90 percent and are shown in Table 2 (continued). Example 1 92 parts by weight of silicon nitride powder (containing about 4% by weight surface silica), 5 parts by weight aluminum nitride (containing about 6% by weight surface alumina), 5 parts by weight alumina, 7 parts by weight parts by weight of yttrium oxide in isopropanol.
0.96 milled for 96 hours using Al-O-N media
It was made to have an average particle size of microns. After drying, the powder was sieved through a 50 mesh sieve and isostatically compacted at a pressure of 30,000 psi. Pieces of raw material were cut from the isostatically compacted slag and embedded in a 50/50 weight ratio boron nitride and silicon nitride powder mixture in a graphite crucible. The crucible was placed in a graphite element low resistance furnace and heated to 500°C in vacuum, then to 1830°C under 1 atmosphere of nitrogen and held at this temperature for 40 minutes. After cooling, a 0.2 x 0.2 x 0.8 inch bar of sintered material was ground using a 600 grit abrasive wheel and, after die checking, a 0.56 inch outer span.
Broken at a point bend. The fragments were used for density and hardness measurements and phase determination by X-ray fracture. The properties of the materials are shown in Table 1. Example 2 Similar to Example 1, but sintering was carried out at 1830° C. for 60 minutes. Example 3 92 parts by weight of silicon nitride powder (containing about 4% by weight surface silica), 5 parts by weight aluminum nitride (containing about 6% by weight surface alumina), 3 parts by weight alumina, 7 parts by weight parts by weight of yttrium oxide were milled in isopropanol using alumina abrasive media for 48 hours. Attrition from such media amounted to 1.9 parts by weight, which was incorporated into the overall composition. The average particle size of the ground powder was 1.49 microns. The powder was processed as in Example 1, but sintering was carried out at 1780°C for 49 minutes and at 1830°C for 15 minutes. The properties are shown in Table 1. Example 4 92 parts by weight of silicon nitride powder (containing about 4% by weight of surface silica), 8 parts by weight of aluminum nitride (containing about 6% by weight of surface alumina), and 7 parts by weight of yttrium oxide. A composition consisting of was milled in isopropanol using high density Si-Al-O-N media for 168 hours to an average particle size of 0.63 microns. The subsequent treatment was the same as in Example 1. Example 5 Materials similar to Example 4 were tested in a static nitrogen atmosphere.
It was heat treated at a temperature of 1400°C for 5 hours. The results are shown in Table 1. Example 6 92 parts by weight of silicon nitride powder (containing approximately 4% by weight surface silica), 8 parts by weight aluminum nitride (containing approximately 6% by weight surface alumina), and 5 parts by weight yttrium oxide. using alumina abrasive media in isopropanol
Milled for 48 hours. Attrition from this media amounted to 2.0 parts by weight, which was incorporated into the overall composition. The average particle size of the ground powder is
It was 1.47 microns. It was then processed as in Example 1, but sintering was carried out at 1850°C for 60 minutes. The results are shown in Table 1. Polytype Example Example 7 86.9% by weight silicon nitride and 6.59% by weight
A powder mixture was constructed consisting of the 21R polytype and 6.54% by weight of Ittria. The powder mixture was then milled for 2 days using a Si-Al-O-N cycloid as the medium, and the average particle size obtained was
1.07 microns and 90% were smaller than 2.21 microns. This powder was then cold isostatically compacted at a pressure of 30,000 psi and the green slag was then sintered at 1830° C. for 50 minutes under the same conditions as in the previous example. The sintered material was then analyzed and its properties are shown in Table 2. Example 8 Powders were processed as described in Example 7, but the starting powder mixture consisted of 81.3% by weight silicon nitride, 12.1% by weight 21R polytype, and 6.54% by weight Ittria. It was hot. The sintered material was analyzed and its properties are shown in Table 2. Example 9 The processing of this powder was the same as that of Examples 7 and 8, but the ball milling media was an alumina cycloid. The raw powder consisted of 86.9% by weight silicon nitride, 6.54% by weight 21R polytype, and 6.54% by weight ittria. The powder is
Milled to an average particle size of 0.91 microns, 90% of which
It was smaller than 1.72 microns. The powder mixture was found to have an additional 3.55% by weight friction pick-up from the alumina cycloid. The mixture was then heated at 1780°C for 40 minutes and at 1830°C.
Sintered for 25 minutes. The sintered material was analyzed and its properties are shown in Table 2. Example 10 82.2% by weight silicon nitride and 11.2% by weight
21R polytype and 6.54% by weight of Ittria,
A powder mixture consisting of an additional 3.57% by weight alumina from alumina cycloid attrition during ball milling was processed. The average particle size was 0.93 microns, with 90% smaller than 1.77 microns. This composition is Example 9
sintered similarly to that of The sintered material was analyzed and its properties are shown in Table 2. Example 11 85% by weight silicon nitride and 8.4% by weight
21R polytype and 6.54% by weight of Ittria,
A powder mixture consisting of directly added 2.51% by weight alumina and 0.1% by weight silica was processed.
The mixture was milled to an average particle size of 1.0 micron using Si-Al-O-N media. The sintered material was analyzed and its properties are shown in Table 2. Example 12 Composition consisting of 83 parts by weight of Si ₃ N ₄ (containing 1.0% by weight O as a surface layer), 17 parts by weight of 21R polytype, 7 parts by weight of ittria, and 3 parts by weight of alumina is Si-Al-O- in isopropanol.
Milled for 72 hours using N media to an average particle size of 0.71 microns. After drying, the powder is sifted through a 50 mesh sieve and
Isometrically compressed at a pressure of 30000psi. Pieces of raw material were cut from the isostatically compacted slag and embedded in a 25/75 weight ratio silicon nitride and boron nitride powder mixture in a graphite crucible. The crucible was placed in a graphite element resistance heating furnace and heated to 900 °C under vacuum.
°C and then 40 °C to 1780 °C in 1 atm nitrogen.
heated for 25 minutes, then heated at 1830°C for 25 minutes,
It was then cooled to 1000°C in approximately 30 minutes. Its properties are shown in Table 2. Example 13 77 parts by weight of silicon nitride (1.09 parts by weight as surface layer)
% O), 23 parts by weight of 21R polytype, and 7
A composition consisting of parts by weight of ittria and 3 parts by weight of alumina was processed identically to Example 12. The average particle size of the ground powder was 0.84 microns. Its properties are shown in Table 2. Example 14 75 parts by weight of silicon nitride (1.09 parts by weight as surface layer)
A composition consisting of 25 parts by weight of 21R polytype, 7 parts by weight of ittria, and 3 parts by weight of alumina was processed identically to Example 12. The average particle size of the ground powder was 0.92 microns. Its properties are shown in Table 2. Example 15 75 parts by weight of silicon nitride (0.77 parts by weight as surface layer)
A composition consisting of 25 parts by weight of 21R polytype, 7 parts by weight of ittria, and 9 parts by weight of aluminum oxide was processed in the same manner as in Example 12. The average particle size of the ground powder was 0.82 microns. Its properties are shown in Table 2. Example 16 85 parts by weight of silicon nitride and 15 parts by weight of 21R
A composition consisting of Polytype, 7 parts by weight of Ittria, and 1.0 parts by weight of alumina was processed in the same manner as in Example 12. The average particle size of the ground powder was 0.95 microns. Its properties are shown in Table 2. Example 17 A composition consisting of 85 parts by weight of silicon nitride, 15 parts by weight of polytype, 7 parts by weight of ittria, and 8 parts by weight of alumina was processed in the same manner as in Example 12. The average particle size of the ground powder was 1.09 microns. Its properties are shown in Table 2. The composite materials produced in each of the above examples showed excellent metal cutting results when used as cutting inserts. Excellent results have been obtained when machining cast iron and nickel-based alloys. first 11
The test results reported in the table for the example are:
The flexural fracture stiffness of the material was reported as determined by the method described in Lucas Industries, US Pat. No. 4,127,416 and with the dimensions specified in Example 1 above. It was subsequently determined that a material's fracture toughness is a much better indicator of a material's metal cutting ability than its flexural fracture strength. In new Examples 12-17, these values are reported instead of flexural breaking strength. A Vickers diamond indentation with a load of 18 kg was used in the fracture toughness test. Fracture toughness is determined by the dimensions of the indentation and related cracks, as well as the load and
Journal of the American Ceramic Society
Using the method described in Vol 59 (1976) p.371
Calculated from Young's modulus value of 305 GPa. Examples 10, 12, 13, and 14 show that the percent α-Si-Al-O-N increases with increasing polytype. Examples 16, 17, 14, and 15 show that α-Si-Al-O-N content and hardness decrease with alumina content. The invention is further defined with respect to FIG.
No. 4,127,416 and 4,113,503 to Lucas Industries, a Si-Al-O-N phase diagram is shown. The rectangular composition area claimed by Lucas is shown schematically in the accompanying drawings. The boundaries are set at Z values of 0.38 and 1.5, where Z is β-Si-Al-O-
It is found in the formula of N Si _6-z Al _z O _z N _8-z .
The upper and lower boundaries are 0.735 and 0.770 cation to anion ratio (c/a). Lucas is c/
The s ratio was defined as molar silicon plus molar aluminum divided by molar oxygen plus molar nitrogen. Ittria's contribution was not included. Exceeding the upper limit c/a ratio results in too much glass, which is detrimental to the properties of the single phase β-Si-Al-O-N. Single phase β-Si-Al-O-N sintered body is
Ratios higher than 0.770 are difficult. Compositional regions overlapping with the Lucas region were defined with clear differences. Z is 0.38 and Z=
The border set to 1.5 is the same as Lucas, but
The upper and lower boundaries are two-phase ceramic, α-Si
-Al-O-N plus β-Si-Al-O-N. The c/a ratio is defined as molar silicon plus molar aluminum plus molythtrium divided by molar oxygen plus molar nitrogen. Yttrium is included in the c/a ratio, which is appropriate since yttrium is an integral part of α-Si-Al-O-N. Second, the equivalent calculated by Lucas is Y ₂
Only Si, Al, O, and N are considered, excluding _O3 . The composition of the present invention has an equivalent weight calculated by including itria, and as a result, the composition point is located slightly higher than the ground plane on the phase diagram. This composition point is then projected onto the ground plane, yielding effective equivalents for silicon and aluminum. Oxygen and nitrogen are unaffected. The effective equivalent weight is plotted in FIG. The table below shows the differences between Lucas for Example 9 and the method of the invention.

[Table] In this way, the compositional region is defined on the ground plane, but this indirectly explains the influence of itria, and the composition region is defined on the base plane.
This is important because it enters the O-N structure. The upper boundary segment with a constant c/a ratio of 0.739 represents the effective equivalent composition of the final composition between 0-10% α-Si-Al-O-N. Example 17,
15 defines the line O effective equivalent = 0.1644 (Al effective equivalent) + 0.0865, which line is equal to the constant c/a line of 0.739 at (0.1143, 0.1053) and also (0.2084,
0.1208) intersects the line of Z=1.5.
The combination of the c/a ratio 0.739 line segment and the segment between intersections described above has a final α- of 0-10%.
represents a composition having an effective equivalent percent yielding Si-Al-O-N content. The bottom border is
It represents a constant c/a ratio of 0.794. European Research Office United States
For Army Grant No. DAERO-78-G-012, “The Role of Additives in the
Densification of Nitrogen Ceramics” (1979)
α−Si− proposed by KHJack in October)
The general formula for Al-O-N is Y _x Si ₁₂ -(m+n)Alm+n
OnN _16-o , where X=0-2, m=1-
4, n=0-2.5. Phase definition 1 β ¹ is the general formula Si _6-z Al _z O _z with O<Z<4.2
It is a hexagonal phase with N _8-z and is detected by the X-ray diffraction characteristic pattern for Z=0 and Z=4β ¹ . 2 α ¹ is the general formula (Si, Al) ₁₂ Mx (O, N) ₁₆ where M=Li, Ca, Y or other lanthanum series
It has a hexagonal crystal phase. The theoretical maximum value is X=2
, which is approached in the case of Ca, but Y
For , the actual maximum value is about 0.7. Detected by X-ray diffraction. 3 α-Si ₃ N ₄ is an unsubstituted allotrope of Si ₃ N ₄ . 4N _- YAM is a monoclinic phase with the formula _Y4Si2O7N2 , which has _the same _{structure as} YAM- _Y4Al2O9 and forms _a perfect solid solution with it. 5 Y-N-α-wollastonite is a monoclinic phase with the formula YSiO ₂ N. 6 YAG is a cubic phase with the formula Y ₃ Al ₅ O ₁₂ . Some substitution of Al by Si and simultaneous substitution of O by N can occur.

【table】

【table】

【table】

【table】 [Brief explanation of the drawing]

Figure 1 shows the Si-Al-O-N defined in the present invention.
The silicon nitride corner of the ground plane of the phase diagram is shown.

Claims (1)

[Scope of Claims] 1 Compounds containing the elements silicon, aluminum, oxygen and nitrogen in proportions such that the ratio of the total number of silicon and aluminum atoms to the total number of oxygen and nitrogen atoms is in the range 0.735-0.77. and said compound reacts with a second component during a subsequent sintering step to form a dual phase ceramic material;
Its first phase follows the general formula Si _6-z Al _z O _z N _6-z , where z is 0.38−1.5, and the second phase follows the general formula (Si, Al) ₁₂ M _x (O, N) ₁₆
Powder consisting essentially of a first component in accordance with the invention and not more than 10% by weight of a second component in the form of an oxide of at least one of the elements ythtrium, scandium, cerium, lanthanum and metals of the lanthanum series. forming a mixture and heating said mixture in a protected environment for 1600°C with or without pressure;
sintering at a temperature of 2000° C. for a period of at least 10 minutes to at least 5 hours, decreasing with increasing temperature, at least 90% by volume of said dual phase ceramic material and said at least one part being in a glassy phase during sintering; 1. A method for producing a ceramic product, characterized in that the method produces a ceramic material containing a second phase containing two elements.