JP2766661B2 - Boron treated hard metal - Google Patents

Abstract

A hard, relatively non-brittle, cemented carbide body is made by sintering pressed grade carbide powders in the presence of a boron-containing material such as boron nitride. During sintering, appreciable quantities of boron migrate or diffuse into the body to become incorporated throughout the microstructure of the carbide resulting in the formation of a third quarternary phase comprised of tungsten, cobalt, boron and carbon.

Description

Description: FIELD OF THE INVENTION The present invention relates to a cemented carbonized body, and more particularly to a boronized carbonized body.

2. Description of the Related Art In the cutting industry, there is an increasing demand for a cutting tool having a sharper blade and a longer life. A cutting tool provided with a conventional cemented carbide cutting tip is made of tungsten carbide (wc) as a hard metal phase and cobalt (Co) as a binder phase. The WC and Co powders are sintered to form a WC / Co sintered carbonized body. As is known, many improvements have been made to simple WC / Co bodies to improve properties for various applications.
Generally, there is a reciprocity between fragility and hardness. Choosing a harder metal to improve cutting performance and maintain a sharp blade,
Metals tend to be more brittle and therefore will undergo brittle fracture faster than less rigid materials.

To solve the problem of increased brittleness due to increased hardness, attempts have been made to add a thin coating or layer of boron to the surface of the carbonized body. The surface coating or layer can be applied by thermal spraying, physical vapor deposition, chemical vapor deposition, and other known methods. It is also known that boron diffuses from the surface of the sintered carbonized body to form a thin, hard layer.

A major problem that has always been encountered in forming boronide coatings or layers on WC / Co and other carbides is that once the thin layer has been worn, its hardness and other improvements are lost. The tool no longer withstands satisfactory use. If the blade with the coating is first brazed to the sawing plate and then sharpened, the coating or surface layer may be lost at that point. Continued sharpening will almost certainly be lost to the surface. Another problem is the fact that such layers have different properties, such as coefficient of thermal expansion, from the matrix, and tend to separate from the matrix during use. It is also difficult to braze the layered or coated pieces.

This application is related to U.S. application Ser.
(Partial continuation of US application Ser. No. 07 / 167,000, filed 988.3.11).

Means for Solving the Problems a. General The present invention solves the problems related to the coatings or layers that have conventionally been present in sintered carbide, or the problem of increased brittleness, and provides a longer wear than the conventional technology. It is intended to provide a sintered carbonized object that becomes a good cutting blade that can withstand the heat.

Surprisingly, according to the present invention, boron can be added to a sintered carbonized body such as WC / Co from a surface to an extremely deep position.

Even if boron is added according to the present invention, the standard characteristic values such as hardness and coercive force change only slightly, so that no significant improvement has been made to the standard WC / Co body. It is. However, WC / Co manufactured based on the present invention
In practical tests of carbonized objects such as WC / Co tools, the results are superior to conventional WC / Co tools. Such improvement may be due to several factors.

Recent analysis of the present invention shows that boron forms a third phase. This third phase contains cobalt, small amounts of boron and carbon, and substantially higher amounts of tungsten than in the standard binder phase, and appears to serve as another binder phase. This third phase is thought to be the cause of the improvement, and appears to primarily improve the fracture toughness of the material, thereby making it difficult for cracks to propagate through the material and lead to fracture. The corrosion resistance also appears to be improved. It is also possible that the improved microstructure has enabled the formation of sharper blades than in the prior art.

As described above, an object of the present invention is to provide an improved boron-added carbide tool suitable for cutting, drilling, grinding, and the like.

It is another object of the present invention to provide a method for adding boron deep into the structure of a sintered carbonized body such as WC / Co.

It is another object of the present invention to provide an improved sintered carbonized body that can be polished, polished and reused without losing initial properties.

Another object of the present invention is to provide a sintered carbonized body having improved corrosion resistance.

Another object of the present invention is to provide a sintered carbonized body having improved fracture toughness.

It is another object of the present invention to provide a sintered carbonized body comprising a carbide phase, a binder phase, and a third phase including a binder and boron.

Another object of the invention is to provide a carbide phase comprising a carbide-forming element and carbon, a binder phase, and a sintering comprising a binder, boron and a third phase comprising at least 40% by weight (wt.%) Of the carbide-forming element. The purpose is to provide a carbonized body.

It is another object of the present invention to provide a sintered carbonized body comprising a carbide phase, a binder phase, and a third phase that improves toughness without adversely affecting hardness.

The details are described below in order to facilitate understanding of these improvements.

b. Details The sintered carbonized object of the present invention is obtained from a multi-disciplinary study result taught by past knowledge. In general,
The sintered carbonized body is manufactured by the following steps. Carbide materials, such as tungsten carbide (WC), and binders, such as cobalt (Co), are ground to obtain well-controlled components and particle sizes (called "grades") followed by, for example, It is dried by such means as spray drying. Dried carbide / binder (eg WC / Co)
The powder is then pressed into a predetermined shape in the presence of a lubricant.

When sintering is performed in a continuous firing (stalking) furnace, the compact is placed in a graphite boat filled with sintered sand such as AI ₂ O particles. The compact is surrounded by the sand and is usually placed in layers in a boat. Several layers are stacked in a graphite boat, such as placing a layer of sand in a graphite boat, then a layer of compact, then sand, and then another layer of compact. The sand prevents sintering and destruction of the compacts and also acts as a separator when the boat is passed through different temperature zones in the furnace for liquid phase sintering of the compacts. In one embodiment of the present invention, the boron-containing powder is mixed with the sand before the compact is immersed in the sand.

The inventor has used boron nitride, boron powder, boron carbide, and boron oxide as the boron-containing powder, but believes that other boron-containing powders are also effective. When using boron nitride as an additive to sintered sand, the semiconductor products division of the Standard Oil Engineered Materials company (address 2050 Corv Road, Special Fibers
Building, Sanborn, NY 14132 US), commercially available under the registered trademark of COMBAT, boron nitride powder CAS No. 10043-11.
I tried using -5 and found it to be satisfactory. This BN powder has a particle size of −325 mesh. The amount of BN used below is based on the powder of this particle size. According to basic chemical and physical principles, if powders with different particle sizes, that is, powders with different surface areas are used, it is necessary to adjust the addition amount so as to have the same effective surface area. In a valid other containing boron material present _{invention: AlB 2, AlB 12, CrB} , CrB 2, Cr 3 B 5, MoB, NbB 6, NbB 2, B 3 Si, B 4
Si, B ₆ Si, TaB, TaB ₂ , TiB ₂ , WB, W ₂ B ₅ , W ₂ B, VB ₂ , and ZrB ₂ . Since the transfer of boron to cemented carbide is likely to be in the gas phase, other boron-containing organometallic compounds with relatively low vaporization temperatures can be other sources of boron: B ₃ N ₃ H ₆ , B
₁₀ H ₁₄ , B ₂ H ₇ N, B ₁₀ H ₁₀ C ₂ H ₂ , B (OCH ₃ ) ₃ , C ₆ H ₅ BCI ₂ , C ₅ H ₅ NBH
Such as _{3, B (C 2 H 5} ) 3. Other inorganic compounds, such as CoB, FeB, MnB, NiB and boron halides, have promised satisfactory results, but were not tested this time.

By the way, the graphite boat containing the sand and the compact enters a sintering furnace, and is heated or pre-sintered to remove a lubricant, and then heated to a sintering temperature.

If the sintering takes place in a vacuum furnace, the compact is placed in a saucer. To prevent the compact from sticking to the pan,
Also, in order to prevent carbon migration between the graphite float and the compact, some paint or coating is usually applied to the pan before placing the compact. The coating is preferably dried in a vacuum drying oven. In the present invention, some form of boron is added to the paint or film. Mixing the boron nitride powder with water and / or alcohol to a paint concentration and simply applying it to a saucer gave good or completely satisfactory test results. In this test, boron penetrated into the compact but was not as uniform as when sand was used. It seems that a more uniform distribution was obtained when the composition was applied to all the molded bodies. Other forms of boron-containing powders and other solvents or bases could be used. The pan is then placed in a furnace, raised to a pre-sintering temperature for lubricant removal, and then to a sintering temperature.

The resintering of the green body can also be performed in the presence of boron-containing sand or paint, but again the boron will be distributed to the depth of the compact as well. Of course, in this case, since there is no lubricant to be removed, pre-sintering is unnecessary.

When the compact is sintered in boron-added sand or paint,
Some form of boron diffuses or migrates into the compact or sintered body and at least 3.18 mm (0.12 mm)
Disperse fairly even to a depth of 5 inches). 12.7m thickness
Preliminary testing with a material as thick as 0.5 inches (m) showed a boron concentration gradient that was higher toward the surface and lower toward the interior. By controlling the amount of surrounding boron-containing material and controlling the time and temperature of the sintering (or re-sintering) process, it is possible to produce a relatively uniform dispersion of boron or a sintered body having a desired concentration gradient. It is considered possible. Further, by re-sintering the sintered body treated according to the present invention in a controlled atmosphere without using a boron-containing material,
It would also be possible to obtain the desired concentration gradient or uniformity. However, what is formed by the present invention is not a surface layer or film. Since the surface layers formed by various known methods are on the order of 0.0254 mm (0.001 inch) thick, there is at least a two-digit difference between the substantially uniform boron distribution depth and the coating thickness in the present invention. There will be.

Surprisingly, the various properties of the sintered bodies obtained according to the invention do not seem to change much compared to the same sintered bodies sintered without the presence of boron. Hardness, lateral cracking strength, coercive force, etc. are substantially the same. Fracture toughness is improved over the same sintered body except for the absence of boron. The corrosion resistance also appears to be improved. And
As will be shown later in the test results, saw blades with a cutting edge made according to the present invention show much better performance than the boron-free target.

Observation of the microstructure of the carbonized bodies obtained according to the present invention reveals some interesting facts: First, it appears that the presence of boron removes free carbon. When presintered without boron is resintered according to the present invention, the porosity due to free carbon is greatly reduced or eliminated.

Secondly, when the sintered bodies according to the present invention are corroded with Murakami's reagent, they show a rapid corrosion phase, which is called "η
Similar to the defect known as the (eta) phase, but much finer than the "eta phase" shape, it is usually formed in a spiral or feather uniform throughout the sintered body. Also, unlike a sintered body having an “η phase”, the sintered body of the present invention is less brittle than a sintered body having no rapid corrosion phase. As will be described in detail later, analysis of the carbonized body indicates that boron exists in a feather-like structure.

Thirdly, the tenth and higher magnifications taken from other photographs and
According to FIG. 11, the swirl or feather is actually the third phase, the average size of which is larger than the average size of the standard resultant material phase. The third phase fills the gaps between the tungsten carbide grains so as to connect the gaps. According to FIG. 11, the tungsten carbide grains have straight sides, cubic, box-shaped,
Or have a square shape. However, in the third phase region, the tungsten carbide grains are more rounded, and some are shrunk and rounded. It appears that these tungsten carbide grains have undergone some reaction and some of the particle components have been lost and become part of the third phase. In fact, analysis of these samples shows that a significant amount of tungsten is present in the third phase. In addition, boron is present in this phase, and carbon and cobalt are also found.

Fourth, when described later, white spots are observed in the microstructure after corrosion, but the amount is unknown.

For the present invention, several different carbonized bodies were tested under various conditions. 1 to 5 and 10 to 11 show the microstructures of the above-mentioned objects obtained as a result of the test.

The samples for microstructure observation in FIGS. 1 to 5 are prepared by a standard method. A typical procedure for preparing a sample is as follows.
The sample is embedded in a thermosetting epoxy resin. The sintered sample is coarsely polished with a 220-mesh diamond grindstone while cooling with water, and then finely polished with a 45μ diamond grindstone while also cooling with water. Subsequently, a rough buffing is performed on a rigid flat cloth turntable such as nylon or silk, and then on a paper turntable. At this time, a 15 or 30 μm diamond paste may be used. During polishing, oil or water may or may not be used as a lubricant depending on the solubility of the diamond retaining agent. Thereafter, the sample is ultrasonically cleaned in a soap solution. Next, the intermediate buffing is performed by using a cloth or a paper rotating table in the same manner as described above. Here, a 6 or 9 μm diamond paste is used, and ultrasonic cleaning is performed again in a soap solution.
Finish buffing is performed on a cloth turntable using a short fiber cloth (for example, rayon) or a paper turntable. During polishing, a 1 or 3μ diamond paste may be used, and ultrasonic cleaning is performed in a soap solution using a lubricant in the same manner as above. Additional polishing with a short fiber cloth may be performed using diamond of 0.25 to 1 μm. Polishing is performed until a mirror surface free of polishing scratches is obtained.
The polished sample is ultrasonically washed in soap, washed with water, washed with alcohol, and dried.

Next, corrosion is performed for feather-like structure observation. Two chemical corrosives have been found to manifest this texture. Murakami's reagent (10% KOH, 10% K ₃ Fe (CN) ₆ , and
80% H ₂ O) for 2 minutes, dry with water and alcohol. Murakami's reagent rapidly dissolves the components of the carbides treated according to the invention (typically 2-4 seconds). Alternatively, 30 ml H ₂ O + 10 ml HCI + 10 ml HNO
_The surface is eroded with an acid corrosive, which is a mixture of step ₃ , until the delayed foaming reaction is completed. The sample is first washed with water, then with alcohol and dried. The acid corrosive is less active than Murakami's reagent, but is suitable for detailed microstructure observation.

In the present invention, another type of sample was prepared as follows. That is, the sample was embedded in the resin, and the hard component was slightly polished until it slightly protruded from the soft component, so that the conductive material was placed in the resin. This type of sample is applied to analysis using an electron beam. FIG. 11 shows a photograph obtained by observing the sample thus manufactured at a magnification of about 2.000. As shown in FIGS. 11 and 12, from the observation result of the sample subjected to the post-polishing corrosion and the sample not subjected to the polishing at a magnification of 2.000 times by the scanning electron microscope, the feather-like structure certainly has the third phase functioning as another bonding phase. It turns out that it is. The analysis of the third phase will be described later.

Generally speaking, the higher the amount of binder phase relative to the amount of carbide particles, the softer and tougher the material. However, a peculiar phenomenon in this case is that the third phase plays a role in improving the toughness without adversely affecting the hardness.

 The following example shows details of the tests performed.

Example 1: One sample of intermediate grains of 91% WC and 9% Co in a continuous stalking furnace at 1450 ° C for 1 hour in a decomposed ammonia atmosphere.
Sintered in alumina sand containing supersaturated carbon and 1% boron nitride. A new phase 3 was discovered at high magnification (5.200x) and the sample was analyzed.

 The analysis results are as follows.

(1) Undervalues (2) Probably overvalues This novel third phase appears with tungsten and cobalt reacting in a wide composition range, as long as carbon and boron are present in a sufficient ratio suitable for the formation of the third phase. Should be. It is considered that the third phase can be formed in the following composition range.
Tungsten in the range of 60-95 wt.% (Probably 50-95 wt.
%), 13-35 wt.% Cobalt (probably 5-50 wt.%),
0.5-2.0 wt.% Carbon (probably 0.1-6.5 wt.%) And 2.0-6.0 wt.% Boron (probably 0.5-10.0 wt.%). Third
Within the phase, the weight ratio of tungsten to cobalt should always exceed 1.0. Also, the weight ratio of boron to carbon in the third phase should always exceed 1.0.

Example 2: Ultra fine tungsten carbide (wc) powder 94.5% WC / 5.5%
After mixing at a Co ratio, the lubricant was mixed, followed by pressure molding. The compact was surrounded by Al ₂ O ₃ particles mixed with 2.5 wt.% BN powder, placed in a graphite boat, and pre-sintered and fully sintered in a continuous stalking furnace. The sintering temperature was kept at 1410 ° C. for about 70 minutes. During sintering, decomposed ammonia was flowed into the furnace.

FIG. 2 shows the micro composition (prepared and corroded as described above) of the completed sample. Comparison of the micro-composition after treatment shown in FIG. 2 with that of FIG. 1 (micro-composition of a sample prepared in the same manner except that boron nitride was not contained in the sintered sand) shows that the treatment in the presence of bomen The presence of an unusual feather-like or lace-like corrosive phase is observed in the sample obtained. This corrosive phase is fairly evenly distributed throughout the sample. Feathers or split ends look darker and thicker than the rest.
According to the analysis described below, some form of boron is present in this feathered tissue.

Example 3: A medium WC powder sample is mixed at a ratio of 87% WC / 13% Co,
After mixing the lubricant, press molding was performed.
Sintered in sand containing BN.

The corroded sample was corroded by the above-mentioned acid corrosive agent after polishing. The microstructure after corrosion is shown in FIG. Again, comparing the microcomposition of FIG. 4 with FIG. 3, which is the microstructure of the same material sintered without BN, a branched microstructure is observed in the microstructure of FIG. Again, the tips of the branches are thicker and darker than the rest.

Example 4: An intermediate sample of 87% WC / 13% Co composition was prepared as in Example 1, except that 0.5% BN was added to the sand. In this case as well, a branching phenomenon is observed, and at high magnification, white spots appear as indicated by arrows.

The reason for emphasizing this abnormal structure is that seeing this structure is the starting point of the present invention, and is the easiest to show that boron has actually migrated into the sintered body.

Example 5: Vermont American OM1 grade, i.e. medium grain W
Prepare a mixture of C powder and Co binder at a ratio of 91% WC / 9% Co, and use Vermont American C-3110-
It was press-formed into a saw blade designed in the shape of a 1-type blade.
A coating of boron nitride (BN) and water is applied to the cutting edge, vacuum-dried so that only BN remains on the cutting edge, placed in a standard graphite pan for vacuum sintering, pre-sintered in vacuum and Sintering was performed. The vacuum furnace was purged with an inert gas before sintering, and kept in vacuum during pre-sintering and main sintering. The sample was kept at a sintering temperature of 1410 ° C. for 60 minutes and then cooled. Rockwell hardness (A scale) of the sample is 90.7,
The coercive force Hc was 80. The cutting edge of this saw also showed a fan-like or feather-like pattern throughout the tissue after corrosion, as described above.

Example 6: The saw blade was adjusted in the same manner as in Example 5 (91% wc / 9% Co intermediate particles), but the molded body coated with the paint was pre-sintered and then sintered in a continuous stalking furnace. The coated samples were dried in fresh air, surrounded with boron-free alumina (Al ₂ O ₃ ) sand, and placed in graphite boats. The furnace was maintained at a sintering temperature of 1410 ° C. for about 70 minutes while flowing decomposed ammonia into the furnace.

Coated and uncoated samples were sintered simultaneously and the following test results were obtained.

Also in this example, in the coated sample, boron migrated throughout the sample, and in the final sample, the above-mentioned feather-like fast corrosive phase was observed in the whole structure, but was not observed in the sample without the film. This final sample is a uniform sintered body and has no film or layer on the surface.
No substantial change in specific gravity, hardness, and coercivity is observed.

Example 7: Vermont Americ mixing 91% WC intermediate flour with 9% Co powder
An an-shaped C-31701-1 saw blade was pre-sintered without boron, and then placed in a graphite boat with alumina sand mixed with 0.5 wt.% BN and re-fired in a continuous stalking furnace. Tied. The sintering time, sintering temperature and gas flow are the same as in Example 2. Again, a characteristic feathery tissue appeared.

This saw blade was brazed to a 254 mm (10 inch), 40 tooth saw plate. The brazing joint strength is determined by the drop impact test.
Tested compared to a standard WC blade. The drop weight test results are 166 inches-ounce for boron-treated cutting tips, normal WC
136 inches-ounce for the tip piece, 22
% Has been improved.

Using these saw plates, cut a 19.1 mm (3/4 inch) medium density particle board (particle board) to 15.3 mm
(50 feet) The power consumption was recorded for each cutting length. In this test, the comparison was the same except for the cutting edge (1).
Untreated and (2) "Boro fuse (Boro
fuse) ”method (this method is considered to form a boronide layer on the surface). The test results are shown in the graph of FIG. 6, where the saw blade with the cutting edge according to the invention is clearly improved over the other two. The saw blade according to the invention shows significantly less power consumption than the others at all stages of the test. Since the power consumption is directly related to the sharpness of the cutting edge, this test result shows that the saw blade according to the present invention is superior in both initial sharpness and maintaining sharpness to others. It is.

Example 8: A WC / Co compact was sintered in alumina sand in a continuous stalking furnace at a sintering temperature of 1410 ° C. for about 70 minutes.
This sample is made of various WC / Co, that is, 6% Co fine granules,
13% Co intermediate grains and 6.5% CO extremely coarse grains were used. The amount of BN in the alumina sand was increased by 0.5% in the range of 0% to 2.5%. Specific gravity, Rockwell hardness, lateral cracking strength,
The coercive force, shrinkage, and weight loss were measured for each sample and the results showed that the boron nitride content in the sand did not change these characteristic values beyond normal manufacturing variations. In the sample in which BN was present in the sand, a characteristic feather-like structure appeared in the microstructure.

Example 9: 91% WC / 9% Co intermediate grain 5.08mm × 6.35mm × 19.0
A 5 mm (0.2 inch × 0.25 inch × 0.75 inch) carbide test rod was sintered in boron-free alumina sand. Further, the test rod was placed in alumina mixed with various boron-containing powders, and resintered in a continuous stalking furnace at 1410 ° C. for about 70 minutes in a decomposed ammonia atmosphere. In each sample, a clear microstructure was obtained indicating that boron diffused into the carbonized body due to corrosion. The boron source, hardness (Rockwell A), and coercive force (HC) are as follows.

Example 10: A. Many grades of composite carbides were also tested. Vermont American 170H280 type metal cutting saw blade with 77.1% wc, 11.4% Co, 4% Tic, 5.25% TaC, 2.25% NbC composition re-sintered in 1.0% BN alumina sand with MC115 grade did. A characteristic microstructure also appeared, indicating that boron had diffused throughout the structure.

B. MC85 grade single-edged blade with the composition of 72.0% WC, 8.5% Co, 8% TiC, 11.5% TaC was re-sintered in sand containing 1.0% BN. A fine feathered microstructure appeared.

The use of other carbide forming elements such as elements of the IVB.VB. and VIB groups would also be possible. For example: titanium, zirconium, hafnium, vanadin, niobium, tantalum, chromium, molybdenum, and tungsten, and combinations thereof. As the binder metal, manganese, iron, cobalt, nickel, copper, aluminum, silicon, ruthenium, osmium may be used alone or in combination with each other, and the above-mentioned IVB, VB and VIB group carbide forming elements Could be used in combination with any of the above.

Example 11: The table below shows the effect of the amount of boron nitride added to the alumina sand on the corrosion resistance of the sintered body, in particular. Samples in this table, all prepared from the intermediate grain powder 91% WC / 9% Co, all identical with AI ₂ O ₃ sintered sand varying amounts of free boron material of (BN) was added in a graphite boat It was sintered under the conditions (decomposed ammonia atmosphere, sintering temperature 1410 ° C, about 1 hour). The only difference between the samples in processing is the AI
The weight percent of free boron material was added to ₂ o ₃ sand.

As a test for corrosion resistance, each sample was weighed, left in HCI at room temperature for 24 hours, weighed again, and the weight loss due to corrosion was measured. The corrosion amount was minimized at 0.9% BN addition.

“BN / sintering agent” ratio (%) Weight loss (%) 0 0.057 0.1 0.113 0.5 0.056 0.9 0.012 2.0 0.0215 25.0 0.0357 50.0 0.0494 75.0 0.0580 100.0 0.0781 To obtain feathered microstructure, how much Or additional tests were performed to determine if a small amount of BN was needed. As a result, in the present invention, boron can be introduced into the chemical composition of the WC / Co carbonized body even when the BN content is as small as 0.006% in the sintered sand, and even when the entire amount of the sintered sand is replaced with BN. I understood. The practical application range for the WC / Co carbonized body of the present invention is considered to be in the range of 0.1 to 5.5% of boron nitride material in sintered sand. Optimum corrosion resistance is 0.9% BN in alumina sand
Was obtained by the addition of From the other test results shown below, it appears that other optimal properties also appear at about the same BN loading.

Example 12: Various samples made according to the present invention were subjected to a fracture toughness test and an Eddy Current test.
The first group of samples were made of Vermont American 2M12 grade with a coarse 89.5% WC / 10.5% Co composition, with varying amounts of boron nitride mixed into the alumina. The second group of samples consisted of Vermon with a fine-grained composition of 94% WC / 6% Co
Made from American OM2 grade, various amounts of boron nitride were mixed with alumina sand. Sintering is
Operate a continuous stalking furnace in a decomposed ammonia atmosphere,
The sintering was performed at a sintering temperature of 1410 ° C. for about 70 minutes.

 The analysis results are shown in the table below.

In order to measure fracture toughness, the sample was 0.5 inch in diameter,
Formed into a short cylinder with a height of 0.750 inches, this cylinder was cut out according to the method described in the following document: Internati
onal Journal of Fracture, Vol.15, No.6, December 1979, 5
15-536. This document is included as a reference.

FIG. 6 is a plot of the relationship between apparent fracture toughness (Ka) and the weight percent of boron nitride in alumina sand. The apparent fracture toughness is seen to be significantly improved with the addition of BN in the sand. 0.5-2 in sand
It seems that wt.% BN gives optimal fracture toughness. This amount is 0.2 to 0.9 wt.% In terms of the amount of boron in sand.

7 and 8 show eddy current measurement results for the same sample. For OM2 grade, both fracture toughness and eddy current peak at 1.5% BN in sand, and for 2M12 grade both peaks at 1.0% BN. These values seem to be the optimal BN additions.

Analysis of these samples showed that the boron concentration was higher toward the outer surface and gradually decreased toward the center. Post treatment at high temperature such as 1410 ° C
It has been shown that a more uniform distribution of the corrosion pattern can be obtained in a large sample having a change in boron concentration from the surface toward the center after 70 minutes. When such treatment is performed, the form of the third phase is changed from feathers to a round aggregate, so that it is possible that boron is distributed throughout the sintered body and no feather-like corrosive phase appears. .

Further analysis of the boron distribution in these samples confirmed that boron was distributed in the form of leaves of ferns, the shape of which appeared when the treated metal was corroded with acid or Murakami's reagent. Is substantially the same as Since the distribution of boron exhibits the same appearance as that observed when the above-mentioned treated metal was acid-corroded, it is concluded that boron is present in the shape of a fern leaf and its shape appears due to corrosion.

Example 13: Test on a commercial sawing saw blade, using standard WC / C
Fine-grained 94% WC / has the same shape as a saw plate with a blade made of o
It was compared with the one with a cutting edge made of 6% Co. Here, the latter blade is already sintered in the standard process,
It is made by putting 1 wt.% BN into alumina sand mixed with 1 wt.% And resintering in a continuous stalking furnace. The standard saw board could be used for 40 hours. On the other hand, the saw blade having the blade re-sintered according to the present invention endured 462 hours of use, and the cutting state was still good even when removed for evaluation.

Example 14: A circular saw blade with carbide cutting edges was tested, with a standard 94% WC / 6% Co fine grain cutting edge and a similar cutting edge resintered in alumina sand mixed with 1% BN. Were compared. Both were used to cut copper tubing, with 5.408 standard saw blades and 22.743 treated saw blades. The treated saw blade was able to cut another 16.000 pieces by repolishing.

Example 15: This test was performed to compare treated and untreated carbide cutting edges in glass fiber cutting. The test piece was 95.5% WC / 4.5% Co fine grain and compared with that re-sintered in alumina sand with 1% BN. The blade was attached to a hole saw. 16 standard raw blade hole saws
1818 glass fiber panels were cut, and 24 of the treated blades were cut.

Example 16: A test was performed to see what happens when an unsintered carbonized body is sintered in pure boron powder. The saw blade tip was placed in a tray and placed in a vacuum furnace. Argon was present over the entire sintering temperature, and cracked ammonia was present at intermediate temperatures. The green body was surrounded by boron powder and sintered. As a result, a deformed sample having a surface layer was obtained. Therefore, the object of the present invention cannot be achieved by sintering in 100% boron powder.

However, in the same furnace during this test, some of the other carbonized objects that were not surrounded by the boron powder and were located at a remote location showed a feather-like microstructure. It indicates that boron has entered the body. This fact indicates that boron has infiltrated the carbonized body in the gaseous form and provides the desired uniform boron dispersion within the carbonized body by passing the boron-containing gas in the form present in the furnace during sintering. This suggests the possibility of It is believed that the supply of boron can be achieved by inorganic or organic compounds containing boron, which have a vaporization temperature suitable for sending their vapors or gaseous decomposition products containing boron to the treatment zone. .

Example 17: A test was conducted to examine the effect of the atmosphere in the sintering furnace on the amount of boron transferred into the sample. In this test, the samples were OM1 grade containing 91% WC and 9% Co. Samples were placed in sand containing 1% BN in a continuous stalking furnace.
Sintered at 00 ° C for 1 hour. After sintering, the composition was analyzed to determine the amount of boron in the sample. As a result, it was found that much more boron was given to the sample structure in the ammonia atmosphere than in the nitrogen atmosphere, and more boron was given to the microstructure in the pure hydrogen atmosphere. In the case of N ₂ or a dry N ₂ atmosphere, the sample contained boron of approximately 30 ppm. NH ₃
Samples of 430 ppm in the atmosphere and 365 ppm in the dry NH ₃ atmosphere were obtained. Pure hydrogen was 1376 ppm boron.

Obviously, those skilled in the art can modify the above description without departing from the purpose of the present invention.

[Brief description of the drawings]

Fig. 1 is a 200x microscope showing the structure of the polished cross section of the untreated (reference) ultrafine 94.5% WC / 5.5% Co carbonized body sintered in a decomposed ammonia atmosphere. This is a photograph (the polished surface was treated with a standard acid corrosive). FIG. 2 shows ultrafine 94.5% WC / 5.5 produced according to the present invention.
2 is a photomicrograph at × 100 magnification showing the particle structure of a Co-carbonized material (the carbonized material is 2.5 wt.% In a decomposed ammonia atmosphere).
Sintered with sand containing boron nitride (BN), and the polished surface was treated with an acid corrosive). FIG. 3 is a 200 × photomicrograph showing the grain structure of an untreated, intermediate 87% WC / 5.5% Co sample sintered in a decomposed ammonia atmosphere (the polished surface of the above sample was acid-corrosive). Processed). FIG. 4 shows the grain structure of the intermediate grain 87% WC / 13% Co sample.
This is a micrograph of × 00 (the sample was sintered in a decomposed ammonia atmosphere surrounded by sintered sand containing 2.5 wt.% Boron nitride, and the polished surface was treated with an acid corrosive). FIG. 5 shows the grain structure of the intermediate grain 87% WC / 13% Co sample.
It is a microscope photograph of 250 times (the above sample was sintered in sintered sand containing 0.5 wt.% Boron nitride in a decomposed ammonia atmosphere, and the polished surface was treated with an acid corrosive). FIG. 6 is a plot of the relationship between net power (watts) and linear cut length (feet) when a 0.75 inch thick medium density particle board is cut at 5 ft / min using a saw blade. (An untreated saw plate, a saw plate with a borofused edge, and a saw with an edge treated according to the invention were used). Figure 7 shows the apparent fracture toughness (K
It is the figure which plotted the relationship between a) and% BN in sintered sand. FIG. 8 is a plot of the relationship between the eddy current signal and the% BN in the sintered sand for a Vermont American 2M12 grade sample. FIG. 9 is a diagram plotting the relationship between the eddy current signal and the% BN in the sintered sand for the om2 grade sample of Vermont American. Fig. 10 shows the grain structure of the intermediate grain 91% WC / 9% Co sample.
It is a microscope photograph of 040 times (the above sample was sintered in sintered sand containing 1 wt.% BN, and the polished surface was treated with an acid corrosive). FIG. 11 is a 2.040 × microscope photograph showing the grain structure of the polished cross section of the sample of FIG. 10 before corrosion.

Claims (29)

(57) [Claims] 1. A sintered carbonized body comprising the following phases: a tungsten carbide phase; a cobalt binder phase; and a third phase comprising cobalt, tungsten, boron, and carbon. 2. The sintered carbonized body according to claim 1, wherein the weight ratio of tungsten to cobalt in the third phase exceeds 1.0. 3. The sintered carbonized body of claim 2, wherein the weight ratio of boron to carbon in the third phase is greater than 1.0. 4. The weight ratio of boron to carbon in the third phase is 1.0-1.
4. The sintered carbonized body according to claim 3, which is 2.0. 5. The sintered carbonized body of claim 1, wherein the tungsten carbide particles are generally angularly massive in shape, rounded and small in the third phase. 6. The sintered carbonized body of claim 1, wherein the average size of the third phase is greater than the average size of the cobalt binder phase. 7. A method for producing a sintered carbonized body, comprising: a) preparing a shaped body comprising a carbonized body and a binder; and b) in the presence of a boron-containing material, a substantial amount of boron. It migrates from the boron-containing material into the compact and is dispersed throughout the entire microstructure of the compact to a depth of at least 3.18 mm (0.125 in) or, if the compact is thinner than 3.18 mm, the entire compact Sintering the compact so as to disperse it. 8. The sintered carbonized body according to claim 7, wherein after the molded body is sintered, a feather-like corrosive phase appears throughout the carbonized body in a microstructure when corroded with a standard acid corrosive agent. Production method. 9. The method according to claim 7, wherein the sintering is performed in a decomposed ammonia atmosphere. 10. The method according to claim 7, wherein the sintering is performed in a hydrogen atmosphere. 11. A method for producing a sintered carbonized object, comprising:
The compact is made of boron powder, boron nitride, boron oxide, boron carbide, AlB ₂ , AlB, CrB, CrB ₂ , Cr ₃ B, MoB, NbB ₆ , NbB ₂ , B ₃ Si, B ₄
The sintering is performed in the presence of a boron-containing material of one of Si, B ₆ Si, TaB, TaB ₂ , TiB ₂ , WB, W ₂ B, W ₂ B, VB ₂ , and ZrB _2. 7. The method according to 7. 12. A method for producing a sintered carbonized object, comprising:
The method according to claim 7, wherein the compact is immersed in a sintering process in a sintered sand containing an additional mixture as a boron-containing material of one of boron nitride, boron oxide, and boron carbide. 13. A method for producing a sintered carbonized body, comprising:
During the sintering process, the boron content in the sand mixture is 0.00
The method according to claim 7, wherein the method is immersed in a sintered sand containing 3 to 50% by weight of an additive mixture as a boron-containing material. 14. A method for producing a sintered carbonized body, comprising:
The molded body is in the form of one type of boron-containing material selected from the group consisting of BN, boron, boron oxide, and boron carbide, and the sintering agent contains an additional mixed material containing 0.003 to 50% by weight of boron. The method of claim 7, wherein the method is immersed. 15. A method for producing a sintered carbonized object, comprising:
9. The method according to claim 7, wherein the shaped body is immersed in a sintering process in sintered sand containing an additive mixture in which boron nitride is 0.05 to 2% by weight. 16. The method according to claim 7, wherein the previously sintered compact is resintered. 17. A method for producing a sintered carbonized body, comprising:
The method according to claim 7, wherein a boron-containing paint is applied to the molded body prior to sintering. 18. A method for producing a sintered carbonized body, comprising:
The method of claim 7, wherein the compact is placed in contact with a surface coated with boron material prior to sintering. 19. A method for producing a sintered carbonized object, comprising: adjusting a molded body containing a carbide material and a binder; and firing the molded body having an additional mixed material in which the amount of the boron-containing material is adjusted. Immersion in sand; control to have a certain concentration gradient of boron throughout the molded body, ie, to increase the amount of boron on the outer surface and gradually decrease the concentration toward the center. Under the specified conditions, the compact is sintered in the sintered sand; and the microstructure of the manufactured sintered body shows a feather-like corrosive structure when corroded by an acid corrosive. 20. A sintered carbonized body comprising: a) a carbide phase containing a carbide-forming element and carbon: b) a binder phase mainly formed of a binder element: c) the microstructure of the carbide phase is Murakami To show a corrosive phase across the carbonized body when corroded with the reagent
The boron-containing material is dispersed throughout the carbonized object. 21. The sintered carbide body of claim 20, comprising: a) the carbide-forming element is one of the following groups: titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium. , Molybdenum, and tungsten; b) the binder phase is selected from the group consisting of: manganese, iron, cobalt, nickel, copper, aluminum, silicon, ruthenium, and osmium: and c) a compact The boron content in it is 25-3000 ppm, 22. The sintered carbonized body of claim 20, wherein the carbide phase is WC and the binder phase is cobalt. 23. The molded product has a boron content of 25 to 3000 ppm.
21. The sintered carbonized object according to claim 1 or 20, wherein 24. The distribution of the amount of boron in the compact, wherein a specific concentration gradient, that is, the boron concentration of the corrosive phase on the surface is higher, and the concentration decreases toward the center of the compact. 23. The sintered carbonized object according to 20 or 22. 25. The sintered carbonized body of claim 20, wherein the corrosive phase also includes a greater weight percent of a carbide forming element than in the binder phase. 26. A sintered carbonized body comprising: a) a carbide phase; b) a binder phase containing less than 30% by weight of a carbide-forming element:
And c) a third phase comprising a binder and boron; 27. The sintered carbonized body of claim 26, wherein the third phase also comprises at least 40% by weight of a carbide forming element. 28. The carbide forming element is tungsten,
The third phase comprises about 60% by weight tungsten.
27. The sintered carbonized object according to 26. 29. The corrosive phase, before corrosion, contains a certain amount of each of a carbide-forming element, a binding element, carbon, and boron, and the weight ratio of the carbide-forming element to the binding element in the corrosive phase exceeds 1.0. 20. The sintered carbonized object according to item 20.