Manufacturing method of sintered product and sintered product

Abstract

A method for additively manufacturing a sintered article from a powder composition comprising granules of a hard metal or cermet is disclosed. The method includes additively manufacturing a bottom portion by depositing a plurality of layers of the powder composition (102) and adding a binder to an entire surface of each layer of the bottom portion. The method further includes additively manufacturing a middle portion by depositing a plurality of layers of the powder composition and adding a binder only to an outer portion of each layer of the middle portion (104). The method further includes additively manufacturing a top portion by depositing a plurality of layers of the powder composition (106) and adding a binder to an entire surface of each layer of the top portion, thereby producing a printed article and sintering the printed article (108), wherein the porosity of the granules in the powder is 0-15% by weight.

Description

[Technical field]

[0001] The present disclosure relates generally to methods for making sintered articles and sintered articles. [Background technology]

[0002]

[0002] Additive manufacturing, also known as 3D additive manufacturing, generally uses specialized systems to additively manufacture powder one layer at a time. In particular, a layer of material can be deposited onto a work surface in a build chamber and then bonded with another layer of the same or different material. Additive manufacturing can be used to produce articles from computer-aided design models using techniques such as powder bed fusion (PBF), direct metal laser sintering (DMLS), or binder jet 3D additive manufacturing.

[0003]

[0003] Additive manufacturing of hardmetal or cermet bodies is preferably performed by 3D additive manufacturing techniques, where a green body is first produced and then the green part is sintered in a separate furnace. Binder jetting is the most common form of such 3D additive manufacturing technique.

[0004] In binder jetting, a layer of powder is deposited on a working surface of a build chamber, and then a liquid binding agent, or binder, is added to the powder to fuse the powder particles together.

[0005]

[0005] It would be beneficial if the material properties of a cemented carbide or cermet article produced using additive manufacturing techniques such as binder jetting were more similar to the material properties of a compressed cement or cemented carbide article produced using conventional manufacturing techniques.

[0006]

[0006] Thus, a need exists for improvements in methods for producing sintered articles using binder jetting. Summary of the Invention

[0007]

[0007] It is an object of the present invention to address at least some of the problems and challenges outlined above. It is an object of embodiments of the present invention to produce articles having desirable material properties, at least in terms of fewer and / or smaller areas of accumulation of metal binder phase than conventional binder jetting methods.

[0008] According to one aspect, there is provided a method for additively manufacturing a sintered article from a powder composition comprising granules of a hard metal or cermet. The method includes: a) additively manufacturing a bottom portion by depositing a plurality of layers of the powder composition and adding a binder to an entire surface of each layer of the bottom portion; b) additively manufacturing a middle portion by depositing a plurality of layers of the powder composition and adding a binder only to an outer portion of each layer of the middle portion; c) additively manufacturing a top portion by depositing a plurality of layers of the powder composition and adding a binder to an entire surface of each layer of the top portion, thereby manufacturing a printed article; and d) sintering the printed article, wherein the porosity of the powder granules is 0-15 wt.%.

[0009] According to another aspect, there is also provided an article manufactured using the methods described herein.

[0010]

[0010] Further possible features and advantages of this solution will become apparent from the detailed description below. [Brief description of the drawings]

[0011]

[0011] The solution will now be explained in more detail by means of an exemplary embodiment with reference to the accompanying drawings, in which: [Figure 1]

[0012] FIG. 2 is a flow diagram of a method according to one embodiment. [Diagram 2]

[0013] 1 shows an article according to a first embodiment. [Diagram 3]

[0014] 1 illustrates a printed layer in a central portion of an article according to one embodiment. [Figure 4]

[0015] 2 shows an article according to a second embodiment. [Figure 5A-5B]

[0016] 1 illustrates a microstructure of an article according to one embodiment. Modes for carrying out the invention

[0012]

[0017] Briefly, the present disclosure provides a method for additively manufacturing sintered articles, for example using binder jetting, in which a shell structure containing both powder and binder surrounds a loose powder composition without the addition of binder. The shell structure is achieved by providing a bottom and top part of the molded article in a procedure similar to that of normal binder jetting, where binder is added to the entirety of each layer, and a middle part where binder is added only to the outer parts of each layer. The parts of the printed article to which binder has been added, i.e., the bottom, top and middle outer parts, form a shell structure around the central loose powder. The printed article is then sintered, and the properties of the resulting article are such that the sintered article contains a more uniform distribution of the metallic binder phase and the hard phase, e.g., WC phase in a cemented carbide alloy, at least in the central part of the sintered article. The porosity of the granules of the powder used is in the range of 0-15% by weight.

[0013]

[0018] The method may be performed in some embodiments such that only selected portions of the article are manufactured using shell structures, hi some embodiments, such selected parts may be mating areas of the finished product.

[0014]

[0019] The method is mainly applicable to binder jetting techniques for producing hardmetal or cermet products.

[0015]

[0020] For purposes of this disclosure, regions or portions of an article that do not have binder added are defined as regions of the sintered or green article to which binder was not added during the additive manufacturing process. Additionally, regions with binder added are defined as regions of the sintered or green article to which binder was added during the additive manufacturing process. Thus, even if binder is not present in the sintered article, for example because it is removed during the sintering process, these regions may still be referred to as regions or portions with no binder added and regions or portions with binder added.

[0016]

[0021] The term "cermet" is intended to refer to a material that includes hard constituents in a purely metallic bonding phase, the hard constituents including carbides or carbonitrides of one or more of Ta, Ti, Nb, Cr, Hf, V, Mo and Zr, such as TiN, TiC and / or TiCN.

[0017]

[0022] The term "hard metal" is intended to refer purely to a material that comprises hard constituents in a metallic binder phase, the hard constituents comprising at least 50% by weight of WC particles. The hard constituents may also comprise carbides or carbonitrides of one or more of Ta, Ti, Nb, Cr, Hf, V, Mo and Zr, such as TiN, TiC and / or TiCN.

[0018]

[0023] The metallic binder phase in the cermet or hard metal is a metal or metal alloy, where the metal can be selected from, for example, Cr, Mo, Fe, Co or Ni, either alone or in any combination. Preferably, the metallic binder phase comprises Co, Ni, a combination of Fe, a combination of Co and Ni, or Co. After sintering, the metallic binder phase also comprises other elements that dissolve in the binder during sintering, for example W, Ta, Ti, Nb, Cr, Hf, V, Mo, Zr, depending on the overall composition of the hard metal or cermet. The average content of the metallic binder phase in the powder is 4-30% by weight, preferably 6-17% by weight or 8-13% by weight.

[0019]

[0024] In conventional manufacturing of hard metal or cermet bodies using grinding, spray drying, pressing and sintering, the powder used for pressing is not sintered. However, for additive manufacturing, such powders are too brittle and have too high a porosity. Therefore, dry powders in the form of granules are sintered to various degrees when used for additive manufacturing, and therefore the powders used include sintered granules.

[0020]

[0025] Referring now to FIG. 1, the steps of a method for producing a sintered article according to one embodiment will be described in more detail.

[0021]

[0026] The method includes additively manufacturing 102 the bottom of the article by depositing multiple layers of a powder composition and adding a binder, in other words, a liquid binder used in additive manufacturing, over the entire surface of each layer of the bottom of the article. In other words, the first step of additively manufacturing 102 the bottom includes using conventional binder jetting techniques.

[0022]

[0027] The method further includes additively manufacturing a middle section of the article by depositing multiple layers of the powder composition and adding a binder only to an outer portion of each layer of the middle section (104). In other words, additively manufacturing the middle section 104 differs from traditional binder jetting techniques in that the binder is not added to the entire layer of the powder composition, and the resulting middle section includes loose powder surrounded by a wall formed from the powder mixed with the binder.

[0023]

[0028] The method further includes additively manufacturing 106 the upper portion using the same process as additively manufacturing 102 the top portion, i.e., depositing multiple layers of the powder composition and adding a binder to the entire surface of each layer of the top of the article.

[0024]

[0029] After additive manufacturing steps 102, 104, 106 have been performed, a printed article, also called a green body, is obtained. The printed article includes an interior portion made up of loose powder and an exterior portion made up of binder fused powder.

[0025]

[0030] The method further includes sintering 108 the article, thereby producing a sintered article.

[0026]

[0031] The present solution can improve upon known additive manufacturing techniques in several ways.

[0027]

[0032] Firstly, the properties of the sintered article obtained using the method described herein are better when using a surrounding shell structure than when using conventional binder jetting techniques. By using the method according to the present disclosure, a sintered article can be obtained whose properties are more similar to those of pressed cemented carbide or cermet products. The microstructure of the sintered article is preferably such that there are no regions with a non-uniform distribution between the cobalt and WC phases, or at least a relatively uniform distribution, especially without regions with high cobalt accumulation. Furthermore, the sintered article produced using the method described herein has a higher hardness than articles produced using conventional additive manufacturing techniques.

[0028]

[0033] Secondly, sinter debinding can be performed faster than traditional binder jetting methods because there is less binder to remove and the binder is located on the outer portion of the product. Additionally, there is less risk of the article breaking during debinding because there is no binder in the center of the article.

[0029]

[0034] Furthermore, by using the methods according to the present disclosure, it may be possible to produce products using powders with a lower content of metallic binder phase than is possible with conventional methods. If a powder with too little metallic binder phase is used, the sintered product may have too much porosity, but the porosity may be reduced if the use of a shell structure around the loose powder, rather than a binder throughout the product, allows the production of products using powders with a lower content of metallic binder phase.

[0030]

[0035] During testing, it was found that the method described herein is particularly suitable for powders having certain compositions, such as cemented carbide powders that include granules with a relatively low porosity of up to 15% by weight. Powders used for the purposes of the present disclosure may contain a relatively low level of a metal binder phase, particularly when the metal binder phase is cobalt.

[0031]

[0036] In some embodiments, the powder composition includes cobalt as a metallic binder phase, and the cobalt content is between 7 and 13 percent. In some embodiments, the cobalt content is between 8 and 12 percent. In some embodiments, the cobalt content is between 9 and 11 percent. In some embodiments, the cobalt content is between 9.5 and 10.5 percent.

[0032]

[0037] In some embodiments, the porosity of the granules in the powders used ranges from 0 to 10 wt%, in some embodiments from 0 to 5 wt%, and in some embodiments from 0 to 3 wt%. Low porosity of the powder granules is generally advantageous for achieving sintered articles with desired material properties, such as low porosity and small size of the metallic bond phase accumulation regions.

[0033]

[0038] For the purposes of the methods and articles according to the present disclosure, any binder suitable for printing hardmetals or cermets may be used.

[0034] In some embodiments, the binder used is a water-soluble thermosetting binder, comprising compound A, which is at least one organic non-aromatic substance containing at least two hydroxyl groups, and compound B, which is at least one organic non-aromatic substance containing at least two carboxyl groups, and compound A and compound B are monomers or oligomers. Such binders can have a relatively strong adhesive effect, and therefore can be advantageously used in the method according to the present disclosure, as the area where the binder is applied can be smaller than that of conventional binders.

[0035]

[0040] In some embodiments, compound A is selected from propylene glycol, glycerol, maltodextrin, erythritol, xylitol, sorbitol, and mannitol. In some embodiments, compound B is selected from citric acid, tartaric acid, succinic acid, fumaric acid, maleic acid, polyacrylic acid oligomers, and carballylic acid.

[0036]

[0041] Additionally, it has been found that the methods described herein are particularly suitable when certain types of sintering are used.

[0037]

[0042] In some embodiments, sintering includes using vacuum sintering. For purposes of this disclosure, vacuum sintering can include sintering in a low vacuum at a pressure of up to 1013 mbar. In some embodiments, vacuum sintering includes sintering at a pressure or partial pressure of up to 500 mbar. In some embodiments, vacuum sintering includes sintering at a pressure or partial pressure of up to 250 mbar.

[0038]

[0043] In some embodiments, sintering includes first using vacuum sintering and then using high pressure sintering at a pressure of at least 35 bar. Additionally, in some embodiments, sintering may include a debinding step.

[0039]

[0044] 2 shows a side view of a printed and / or sintered article 200 according to the present disclosure. The article includes a bottom portion 210 containing powder to which a binder has been added, a top portion 230 containing powder to which a binder has been added, and more specifically, a center portion 215 (encircled by dashed lines, not representing a physical structure) in which binder has been added only to the outer portions, two side portions 220 having a structure similar to the top and bottom portions 210, 230, i.e., powder to which a binder has been added, and a center portion 240 containing only free powder to which no binder has been added.

[0040]

[0045] To connect this to the method steps previously described, step 102 is performed to additively manufacture bottom portion 210, step 104 is performed to additively manufacture central portion 215 including two side portions 220 and central portion 240, and step 106 is performed to additively manufacture top portion 230.

[0041]

[0046] In some embodiments, after the product is sintered, the outer portions 210, 220, 230 can be removed so that the remaining product only includes the center portion 240, i.e., the portion where no binder was added to the powder.

[0042]

[0047] The thickness of the outer portions 210, 220, 230 can vary depending on the article being manufactured, in some embodiments, the thickness of the outer portions 210, 220, 230 is in the range of 0.05 to 0.5 mm.

[0043]

[0048] The thickness also depends on the intended use of the article: in the case of an article intended for fitting during machining, such as an insert for a cutting tool, the central portion 240 of the article is the portion of the article that has the improved material properties desired during machining, while the outer portions 210, 220, 230 may be relatively thin so that they can be more easily removed later.

[0044]

[0049] In some embodiments, the method further includes removing 110 some or all of the outer portions 210, 220, 230 of the article, such that some or all of the intermediate portion 215 of the article forms the outer portion of the article 200. Removal of the outer portions can be performed, for example, by grinding.

[0045]

[0050] Figure 3 is a top view of printed layer 300 of central portion 215 of Figure 2. The printed layer includes outer portions 310 to which binder is added and a central portion 320 to which no binder is added. As described above, printed layer 300 is produced using method step 104, i.e., by depositing a layer of powder composition and adding binder only to outer portion 310 of the layer.

[0046]

[0051] 4 shows a side view of a printed and / or sintered article 400 according to one embodiment, where only a selected portion 410 of the article 400 is produced by using a shell structure that encloses a volume having loose powder 420. The remaining portion 430, which occupies a majority of the total volume of the article 400, referred to as the bulk portion 430, is comprised of a combination of powder and binder.

[0047]

[0052] Selected portion 410 in Figure 4 has the same structure as article 200 in Figure 2, i.e., it includes an interior volume 420 that contains loose powder with no added binder, and a surrounding shell structure. As can be seen from the image, the portions that make up the right-most and bottom portions of selected portion 200 may also appear to be part of bulk 430.

[0048]

[0053] By using a shell structure only on selected portions of the article, it may be possible to achieve an article that has higher green strength and is therefore easier to transport and handle, as required during the additive manufacturing and sintering steps. Another advantage may result from parts that contain both powder and binder shrinking differently than parts that contain only loose powder. Thus, by using a shell structure only around selected, relatively small portions of the entire article, an article may be achieved that exhibits more uniform shrinkage than one in which the entire article is surrounded by a shell structure.

[0049]

[0054] Thus, in some embodiments, the method includes producing only a portion of the article using steps 202, 204, 206, producing the remainder of the article by depositing layers of powder composition, and adding a binder to the entire layer of powder composition.

[0050]

[0055] In some embodiments, the method includes producing a plurality of parts using steps 202, 204, and 206, producing the remaining article by depositing layers of the powder composition, and adding a binder throughout the layers of the powder composition.

[0051]

[0056] 5A and 5B, the microstructural differences that can be achieved by using the method according to the present disclosure will now be described. As mentioned above, it is preferable to have a relatively uniform distribution between the hard phase and the metal binder phase so as to avoid a significant accumulation of the metal binder phase in the finished sintered article.

[0052]

[0057] In finished sintered articles produced using the above methods, the microstructure of the article is generally better in areas where no binder was added to the powder, i.e., in the center of the article. Figure 5A shows the microstructure of the center of an article produced using a conventional method, i.e., where binder was added throughout each printed layer, and Figure 5B shows the microstructure of the center of an article produced using a shell structure. The light areas on the figure represent metallic binder phases such as cobalt, and the dark areas represent hard phases such as WC.

[0053]

[0058] 5A, an article made using a binder throughout each printed layer is shown having several regions 510, 520, 530 of relatively large accumulations of metallic binder phase, sometimes referred to as metallic binder phase accumulation regions. These regions 510, 520, 530 are composed mostly of metallic binder phase and substantially no hard phase, which can adversely affect the microstructure of the article.

[0054]

[0059] Turning now to Figure 5B, an article is shown that was produced using binder only on the outer portions of each printed layer, with a relatively uniform distribution between the metal binder phase and the hard phase. It can be seen that some parts of the image are lighter than others, but the overall structure is relatively uniform, and clearly more uniform than the portion shown in Figure 5A.

[0055]

[0060] 5A and 5B show that the distribution of metal binder and hard phases is better in the areas where no binder was added than in the areas where binder was added, which is one of the key insights underlying this disclosure.

[0056] Tests performed

[0061] A number of tests were carried out using different powder compositions and different sintering methods to compare the articles produced using the method according to the present disclosure. The resulting articles were then analyzed using a method to determine the homogeneity of the microstructure by determining the average size of the metallic bond phase accumulation regions. The various sintering methods used and the analytical methods used will be described first and then referenced in the subsequent examples.

[0057] Sintering method A

[0062] The method begins with a debonding step in a hydrogen atmosphere with a temperature ramp up to 550° C. over 210 minutes.

[0058]

[0063] The temperature was then increased under vacuum to 1380°C where CO and Ar were introduced at a 1:1 flow ratio and a partial pressure of 40 mbar for a holding time of 30 minutes. The temperature was then increased to 1410°C. The temperature and CO / Ar atmosphere were maintained for 60 minutes. A controlled cool down to 1200°C was then applied, after which the furnace was allowed to cool freely to room temperature.

[0059] Sintering method B

[0064] The method begins with a debonding step in a hydrogen atmosphere with a temperature ramp up to 550° C. over 220 minutes.

[0060]

[0065] The temperature was then increased under vacuum to 1380°C where CO and Ar were introduced at a 1:1 flow ratio and a partial pressure of 50 mbar for a holding time of 45 minutes. The temperature was then increased to 1410°C. The temperature and CO / Ar atmosphere were maintained for 90 minutes. Afterwards, an Ar pressure of 50 bar was applied for 30 minutes. The furnace was then subjected to a controlled cooling step to 1150°C after which the furnace was allowed to cool freely to room temperature. After reaching 1150°C, an Ar pressure of 50 bar was maintained for 6 hours.

[0061] Sintering method C

[0066] The temperature was increased under vacuum to 1380°C where CO and Ar were introduced at a 1:1 flow ratio and a partial pressure of 5 mbar for a holding time of 30 minutes. The temperature was then increased to 1410°C and the partial pressure was increased to 40 mbar. The temperature and CO / Ar atmosphere were maintained for 60 minutes, after which 50 bar Ar pressure was applied for 30 minutes. The furnace was then cooled in a controlled manner to 1150°C, after which the furnace was allowed to freely cool to room temperature. After reaching 1150°C, 50 bar Ar pressure was maintained for 6 hours.

[0062] Microstructural analysis method

[0067] Microstructural homogeneity was estimated through image analysis of microstructural cross-sectional images taken from polished samples. Multiple cobalt regions and circles were inscribed in the images. 50,000-60,000 regions were analyzed per sample. A weighted average of the inscribed circle diameters was calculated according to Equation 1, with parameters p=6 and q=3. These results are denoted X[6,3] and are in μm. Generally speaking, for the articles and methods described herein, higher values ​​of X[6,3] results are preferred.

[0063] TIFF2024538793000002.tif31170

[0064] Porosity measurement method The porosity of the sintered granules was measured by image analysis of LOM (light optical microscope) images (magnification × 2000) of the cross-sections of the granules using the software Image J. An average of about 50 granules were analyzed per powder sample.

[0065] Example 1 Sintered carbide particles (Table 1) were used to print cubes of specimens (15 × 15 × 6 mm). The granules were prepared by grinding a slurry containing WC and Co powders and spray drying the slurry to form granules, which were then sintered at 1275 °C for 60 min by vacuum sintering to a porosity of approximately 1-3 vol.%, and the WC powder had an average particle size of 0.8 μm.

[0066] The cubes were produced by binder jet printing. Printing was done using ExOne Innovent+ with a layer thickness of 50 μm during printing. The saturation during printing was set to 80% and the binder used was ExOne AquaFuse.

[0067]

[0068] In Reference 1, the binder was added to the entire cube, as in regular binder jet printing. In Invention 1, the binder was only applied 0.5 mm inward from all sides of the cube. Both versions were printed in the same build job.

[0068]

[0069] The printed cubes were first sintered with sintering method A and then with method B. TIFF2024538793000003.tif16170 TIFF2024538793000004.tif21170

[0069]

[0070] As can be seen from Table 2, the average size of the cobalt accumulation regions in the cubes produced using the present invention is much smaller compared to the reference, less than half the size.

[0070] Example 2

[0071] Sintered carbide particles (Table 3) were used to print sample cubes (15 × 15 × 6 mm). The granules were prepared by grinding a slurry containing WC and Co powders and spray drying the slurry to form granules, which were then sintered at 1275 °C for 60 min by vacuum sintering to a porosity of approximately 1-3 vol.%, and the WC powder had an average particle size of 0.8 μm.

[0071]

[0072] The cubes were produced by binder jet printing. Printing was done using ExOne Innovent+ with a layer thickness of 50 μm during printing. The saturation during printing was set to 80% and the binder used was ExOne AquaFuse.

[0072] In inventions 1, 2 and 3, the binder was only applied 0.5 mm inward from all sides of the cube. Both versions were printed in the same build job.

[0073]

[0074] The printed cube of invention 1 was first sintered with sintering method A and then with method B. The printed cube of invention 2 was first sintered with sintering method A and then with method C. The printed cube of invention 3 was sintered with method B. The powder compositions of inventions 1, 2 and 3 were the same. TIFF2024538793000005.tif16170 TIFF2024538793000006.tif26170

[0074]

[0075] As can be seen from Table 4, the cobalt accumulation regions of the cubes produced using sintering method B had a smaller average size than the cubes produced first using sintering method A and then using method B, which in turn had a smaller average size than the cubes produced using sintering method A and then method B.

[0075] Example 3

[0076] Sintered carbide particles (Table 5) were used to print sample cubes (15 × 15 × 6 mm). The granules were prepared by grinding a slurry containing WC and Co powders and spray drying the slurry to form granules, which were then sintered at 1275 °C for 60 min by vacuum sintering to a porosity of approximately 1-3 vol.%, and the WC powder had an average particle size of 0.8 μm.

[0076]

[0077] The cubes were produced by binder jet printing. Printing was done using ExOne Innovent+ with a layer thickness of 50 μm during printing. The saturation during printing was set to 80% and the binder used was ExOne AquaFuse.

[0077]

[0078] In Reference 2, the binder was added to the entire cube, as in regular binder jet printing. In Invention 4, the binder was only applied 0.5 mm inward from all sides of the cube. Both versions were printed in the same build job. The printed cube was first sintered with sintering method A and then sintered with method C. TIFF2024538793000007.tif16170 TIFF2024538793000008.tif21170

[0078]

[0079] As can be seen from Table 6, the cobalt accumulation regions of the cubes produced using the present invention have a smaller average size than those of the reference. Additionally, the cubes produced using the present invention have a higher hardness than the reference.

[0079] Example 4

[0080] Sintered carbide particles (Table 7) were used to print sample cubes (15 × 15 × 6 mm). The granules were prepared by grinding a slurry containing WC and Co powders and spray drying the slurry to form granules, which were then sintered at 1275 °C for 60 min by vacuum sintering to a porosity of approximately 1-3 vol.%, and the WC powder had an average particle size of 1.5 μm.

[0080]

[0081] The cubes were produced by binder jet printing. Printing was done using ExOne Innovent+ with a layer thickness of 50 μm during printing. The saturation during printing was set to 80% and the binder used was ExOne AquaFuse.

[0081]

[0082] In Reference 3, the binder was added to the entire cube, as in regular binder jet printing. In Invention 5, the binder was only applied 0.5 mm inward from all sides of the cube. Both versions were printed in the same build job. The printed cubes were sintered with Sintering Method B. TIFF2024538793000009.tif15170 TIFF2024538793000010.tif21170

[0082]

[0083] As can be seen from Table 8, the average size of the cobalt accumulation regions in the cubes produced using the present invention is significantly smaller than in the reference.

[0083] Example 5

[0084] This example shows the difference in microstructure (X[6,3]) and hardness (Hv10) between three reference samples and three respective samples using the invention, using the same powder, which contained 10% metallic binder phase in the form of cobalt. TIFF2024538793000011.tif36170

[0084]

[0085] As can be seen, the difference in the area of ​​accumulation of the metallic bond phase between batches 2 and 3 was so large that the reference sample article was unusable. In the case of batch 1, the difference between the method using the present invention and the conventional method was also large, but not as large as in batches 2 and 3.

[0085]

[0086] This shows that it may be possible to produce articles using powders with lower metallic binder phase contents than would be possible using conventional manufacturing techniques, particularly where the metallic binder phase is cobalt, and that the relative advantage of using the present invention increases as the cobalt content of the powder decreases through the range of at least 13% to 10%.

[0086]

[0087] As can be seen from the tests performed, by using the methods according to the present disclosure it is possible to produce articles with finer microstructures than can be achieved using conventional additive manufacturing techniques.

[0087]

[0088] Although the above description contains multiple specificities, these should not be construed as limiting the scope of the described concepts, but merely as providing illustrations of some exemplary embodiments of the described concepts. It will be understood that the scope of the concepts described herein fully encompasses other embodiments that will become apparent to those skilled in the art, and thus the scope of the presently described concepts is not limited. Reference to an element in the singular does not mean "one and only," unless expressly stated otherwise, but rather means "one or more." All structural and functional equivalents to the elements of the above-described embodiments known to those skilled in the art are expressly incorporated by reference and are intended to be included herein. Furthermore, it is not necessary for a method to address all of the problems sought to be solved by the presently described concepts in order to be included herein. In the exemplary diagrams, dashed lines generally indicate that the features within the dashed lines are optional.

Claims

1. 1. A method for additively producing a sintered article from a powder composition comprising granules of a hard metal or cermet, comprising: a) additively manufacturing a base by depositing multiple layers of a powder composition and applying a binder to the entire surface of each layer of the base (102); b) additively fabricating an intermediate portion by depositing multiple layers of the powder composition and adding a binder only to the outer portion of each layer of the intermediate portion (104); c) additively manufacturing the top by depositing multiple layers of the powder composition and adding a binder to the entire surface of each layer of the top to produce a printed article (106); d) sintering the printed article (108); Including, The method wherein the porosity of the granules in the powder is 0-15% by weight.

2. 2. The method of claim 1, wherein the porosity of the granules in the powder is 0 to 3% by weight.

3. The method of claim 1, wherein the powder composition comprises 8 to 14% of a metal binder phase.

4. The method of claim 1, wherein the powder composition comprises 9.5 to 10.5 wt. % of the metal binder phase.

5. The method of claim 1 , wherein the sintering step (108) comprises both vacuum sintering and high pressure sintering at pressures greater than 35 bar.

6. 10. The method of claim 1, wherein the thickness of each portion to which the binder is applied is in the range of 0.05 to 0.5 mm.

7. 10. The method of claim 1, wherein a portion of the article is produced using steps a-d of claim 1, and the remaining article is produced by depositing layers of the powder composition and adding a binder over the layers of the powder composition.

8. 10. The method of claim 1, wherein the article comprises a plurality of portions produced using steps a-d of claim 1, and the remaining article is produced by depositing layers of the powder composition and applying a binder throughout the layers of the powder composition.

9. 2. The method of claim 1, wherein the binder is a water-soluble thermosetting binder comprising compound A, which is at least one organic non-aromatic substance containing at least two hydroxyl groups, and compound B, which is at least one organic non-aromatic substance containing at least two carboxyl groups, and compound A and compound B are monomers or oligomers.

10. 10. The method of claim 9, wherein compound A is selected from propylene glycol, glycerol, maltodextrin, erythritol, xylitol, sorbitol, and mannitol, and compound B is selected from citric acid, tartaric acid, succinic acid, fumaric acid, maleic acid, polyacrylic acid oligomers, and carbalilic acid.

11. The method of claim 1 further comprising the step of removing (110) an outer portion of each bottom, top, and middle section.

12. The method of claim 1 , wherein the article is a part of a cutting or grinding tool for machining.

13. A sintered article (200) produced using any one of claims 1 to 12.

14. 14. The sintered article of claim 13, which is an article for machining.

15. 14. The sintered article of claim 13, which is a part for a cutting or grinding tool.

Images