RU2354731C2 - Manufacturing method of polycrystalline elements - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: it is prepared mixture of abrasive dust of coarse grain and, at least, of one fine grain, mixture of powders is compacted and impregnated by metals or alloys. In the capacity of powders, at least, of one fine grain there are used powders, surface of which fulfil wettability conditions by impregnating metals or alloys.

EFFECT: method provides increasing of working layer height of elements, and also receiving in the element defined content of abrasive grains for optimal external environment.

12 cl, 1 dwg, 5 ex

Description

The invention relates to the field of engineering and, in particular, to the manufacture of polycrystalline elements, mainly from powders of diamond and / or cubic boron nitride, intended for the manufacture of cutting tools, such as cutters, drills, cutters, drilling and straightening tools, tools for stone processing and etc., as well as for use as structural elements, for example, as wear-resistant linings in friction pairs, centers of precision machines, etc.

A known method of manufacturing a diamond-metal composite cutting tool, in which a mixture of coated metal diamond powders (powders of cubic boron nitride) of various granularities and a binder material wetting the coating metal and having a melting point below 1300 ° C, is placed in a mold and subjected to hot pressing to obtain single mass (US patent No. 5096465, CL 51-295, 1989). The disadvantage of this method is that a metal layer deposited on all diamond powders significantly reduces their volume content in the finished polycrystalline element. The decrease in the volumetric content of abrasive powders leads to a decrease in the physicomechanical properties of the element (wear resistance, elastic modulus, etc.), not allowing the use of tools with such elements for working in difficult conditions (in a drilling, straightening tool, etc.).

The closest is a method of manufacturing polycrystalline elements, in which a mixture of abrasive powders of different grain sizes (a mixture of large and small abrasive powders) is placed in a mold having a bottom and walls, compacted and impregnated with metals or alloys, while the mold walls are made of a material wetted by impregnation metals or alloys, and the distance between the opposite walls of the mold is chosen from the condition h = (1 ÷ 4) A, where h is the distance between the opposite walls of the mold, A is the grain size of the coarsened fraction of grains abrasive (diamond) powder. In the known method, a variant is provided in which the abrasive powders are metallized before being placed into the mold (RF patent No. 1330888, B24D 18/00, 1985). The materials used for the metallization of abrasive powders and the purpose of metallization are not mentioned in the known solution.

The known method has the disadvantage that polycrystalline elements can be manufactured by the method, the height of the working layer of which is limited by the ratio (1-4) of the grain size of the coarsened fraction of the abrasive powder, i.e. with the maximum granularity of the abrasive powder actually used for cutting elements 500/400, elements with a working layer up to 2 mm high can be obtained. When using abrasive powders, for example, with a grain size of 40/28, the height of the working layer of the cutting element can be up to 0.2 mm. The small height of the working layer of the elements significantly reduces the scope of their application, as well as their service life. Metallization of abrasive powders can improve the impregnation of the molded briquette, provided that the coating metal is wetted by the impregnating metal or alloy, and thereby increase the size of the manufactured element. However, as mentioned above, a metal layer deposited on abrasive powders reduces their volumetric content. The decrease in the volumetric content of abrasive powders leads to a decrease in the physicomechanical properties of the element, not allowing the use of a tool with such elements for working in difficult conditions (in a drilling, straightening tool, etc.), i.e. limits the scope of their application.

The technical problem of the proposed solution is to increase the size (height) of the working layer of the polycrystalline element, as well as the ability to achieve a given volumetric content of abrasive grains in the finished element for optimal operating conditions.

The technical result is achieved by the fact that in the method of manufacturing polycrystalline elements, in which a mixture is prepared from coarse-grained powders, for which abrasive powders are taken, and at least powders of one fine-grained grains, the mixture is placed in a mold, compacted and impregnated with metals or alloys, as powders of at least one fine grain take powders whose surface satisfies the wettability condition by impregnating metals or alloys.

As fine-grain powders, powders are selected from the group of abrasive powders and / or powders made from a material whose surface satisfies the wettability condition by impregnating metals or alloys.

To satisfy the condition of impregnation of abrasive powders of fine granularities, a layer of metal or alloy is applied to their surface, which satisfies the wettability condition of impregnating metals or alloys. As powders made from a material satisfying the wettability condition by impregnating metals or alloys, metal powders made from such a material are taken, or metal powders of another metal or alloy can be taken, for example, with properties satisfying the requirement for a binder cutting element, but with a coating of a metal or alloy wetted by impregnating metals or alloys. Such powders can be obtained by any known method, for example, crushing, spraying the corresponding metal or alloy of metals.

To obtain the highest possible volumetric content (concentration) of abrasive powders in a polycrystalline element, the mixture should contain coarse-grained abrasive powders and two fine-grained abrasive powders that differ in size, while the powders should be in a ratio of about 1: 4: 8. For example, when the grain size of large abrasive powders is 60 μm, the fine abrasive powders should have sizes of ~ 15 μm and ~ 7 μm, respectively. To obtain, for example, polycrystalline elements with a lower specified concentration of abrasive powders in the element, the mixture may contain large abrasive powders, to which small abrasive powders of only one size are added. To improve the impregnation condition, powders made from a material satisfying the wettability condition by impregnating metals or alloys can be introduced into the mixture. For a lower specified concentration of abrasive powders in an element, the mixture may contain only large abrasive powders, and to improve the impregnation as fine-grain powders, metal powders whose surface satisfies the wettability condition by impregnating metals or alloys.

The following mixes are available, consisting of coarse-grained abrasive powders and of:

- abrasive powders of one fine granularity, the surface of which is coated with a material wetted by impregnating metals or alloys;

- abrasive powders of two fine grit, wherein the surface of the powders of any one of the fine grit is coated with a material wetted by an impregnating metal or alloy, or the powders of both grit are coated with a material wetted by an impregnated metal or alloy;

- powders of one fine granularity made of a metal material wetted by impregnating metals or alloys;

- powders of two fine granularities, of which uncoated abrasive powders are taken as powders of one fine granularity, and metal powders wetted by impregnating metals or alloys are taken as second fine granular powders;

- powders of two fine grit, of which abrasive powders are taken as powders of one fine grit, the surface of which is coated with a material wetted by impregnating metals or alloys, and metal powders wetted by impregnated metals or alloys are taken as powders of the second fine grit.

For the manufacture of polycrystalline elements, a mold is taken in which at least two opposite side walls are made of a material wetted by impregnating metals or alloys.

As abrasive powders, diamond, cubic boron nitride powders or a mixture thereof can be used, for example, diamond powders can be used as coarse-grained powders, and cubic boron nitride powders as fine-grained abrasive powders.

The invention consists in the following. To obtain the maximum concentration of abrasive powder in an element, the volume content of large and, for example, two fine grains of abrasive powders is in the following ratio: 62.5% - 17.5% - 10%, i.e. large abrasive powders to a greater extent determine the total concentration of abrasive grains in the finished element. Therefore, the use of abrasive powders of large granularity without coating, to a greater extent determining the concentration of the product, contributes to their high volume content due to the fact that powders without coating occupy a smaller volume and, accordingly, more can be placed in their shape. Large powders form the frame of the element, and fine grain powders are located in the free spaces between large abrasive powders, so coating on fine grain powders introduced into the mixture will not significantly reduce the overall concentration. At the same time, coating on fine powders significantly improves the condition for the preform to be impregnated with impregnating metals or alloys, contributing to the movement of the front of the liquid impregnating metal or alloy inward and in the transverse direction of the impregnated preform due to the spreading of the liquid binder not only along the walls of the mold, but also along the coating on fine grain abrasive powders. However, the execution of the walls of the mold from a material wetted by impregnating metals or alloys is not a prerequisite, because when using coated abrasive powders of fine granularity or when using metallic powders as fine granularities, the impregnation of the entire formed element will be satisfactory.

The implementation of at least two opposite side walls of a material wetted by impregnating metals or alloys, allows not only to successfully impregnate the entire area of the element, but also to obtain elements with surfaces adjacent to the walls of the form (working surfaces of the elements), with a fairly smooth the surface on which diamonds are located at the same level, and the free space between them is completely filled with impregnating metals or alloys. The mechanical processing of such elements is subsequently greatly facilitated.

Metals or alloys, as well as nonmetallic materials that are wettable by impregnating metals or alloys, can be used as a coating material for fine grain abrasive powders, and also as a material for metal powders.

The method is illustrated by drawings.

Figure 1 shows a vertical section of a mold filled with a mixture of powders of different grain sizes;

figure 2 shows the abrasive grain of the first fine grain with a metal coating;

figure 3 shows the abrasive grain of the second fine grain coated;

figure 4 schematically shows a form filled with a mixture of abrasive powders of coarse grain and coated abrasive powders of one fine grain, free spaces between which are filled with an impregnating metal or alloy;

figure 5 schematically shows a form filled with a mixture of abrasive powders of coarse grain, abrasive powders of the first fine grain coated and abrasive powders of the second fine grain uncoated, the free spaces between which are filled with an impregnating metal or alloy;

6 schematically shows a mold filled with a mixture of coarse-grained abrasive powders and coated first and second fine grained abrasive powders, the free spaces between which are filled with an impregnating metal or alloy;

Fig. 7 schematically shows a mold filled with a mixture of coarse-grained abrasive powders and uncoated first fine-grained abrasive powders and coated second fine-grained abrasive powders, the free spaces between which are filled with an impregnating metal or alloy;

Fig. 8 schematically shows a mold filled with a mixture of coarse-grained abrasive powders, uncoated first fine-grained abrasive powders and metallic powders as second fine-grained powders, the free spaces between which are filled with an impregnating metal or alloy;

Fig. 9 schematically shows a mold filled with a mixture of coarse-grained abrasive powders, coated first-fine abrasive powders and metallic powders as second fine-grained powders, the free spaces between which are filled with an impregnating metal or alloy;

10 schematically shows a mold filled with a mixture of coarse-grained abrasive powders and metal powders, the free spaces between which are filled with an impregnating metal or alloy;

figure 11 shows the finished polycrystalline element after removing all the walls of the form.

The method is as follows.

In a mold 1 containing, for example, two opposite side walls 2 and 3 made of a material wetted by an impregnating metal or alloy, a mixture of powders of different granularities is placed 4. The mixture of powders contains, for example, abrasive powders of coarse grain 5 and abrasive powders of the first fine grain 6 provided with a coating 7 (FIG. 4). After the mixture of abrasive powders is poured into the mold, the powders are compacted by any known method, for example by compression. To obtain a dense packing of abrasive grains, slip casting, vibrofield, etc. can also be used. After compaction, the abrasive grains making up the powder are arranged so that small abrasive grains fill the free space between the large abrasive grains. Then, impregnating metal or alloy 8 is placed on top of the compacted powders, the mold is heated to a temperature that ensures the fluidity of the impregnating metal or alloy, which is mainly 50 ÷ 100 ° C above their melting temperature. The molten metal or alloy flows along the walls of the mold, along the coating on fine-grained abrasive powders, at the same time filling the pores in the bulk of the compacted powder, linking all the abrasive grains to each other and forming a bond. The spreading of the metal or alloy occurs both in the transverse direction by the specified distance h between the opposite walls (the future height of the polycrystalline element) and deep into the value of H, which determines the dimensions of the polycrystalline element in the direction perpendicular to its height, namely the area of the working layer of the manufactured element.

It is possible to impregnate at low pressure, for example, up to 500 kg / cm ² .

For the manufacture of elements with different concentrations of abrasive grains and with different physical and mechanical properties, in addition to the above mixture, the following mixtures can be prepared. The mixture may contain coarse-grained abrasive powders 5, first fine-grained abrasive powders 6 with a coating of 7 and second uncoated abrasive powders of a second fine-grained 9 (Fig. 5) or abrasive powders of a second fine-grained 10 with a coated 11 (Fig. 6). To the abrasive powders of coarse grain 5 as powders of the first fine grain can be introduced abrasive powders 12 without coating and abrasive powders of the second fine grain 10 with coating 11 (Fig.7). The mixture may also contain coarse abrasive powders 5, abrasive powders of the first fine grain 12 without coating and powders of the second fine grain - metal powders 13 (Fig. 8); coarse-grained powders 5, powders of the first fine-grained 6 coated 7 and powders of the second fine-grained metal powders 13 (Fig. 9). A variant is possible in which the mixture is composed of large abrasive grains 5 and metal powders 13 (Fig. 10).

At the end of the impregnation process, depending on the purpose of the element, all or part of the walls of the mold are removed by any known method: etching, grinding, turning, milling, etc. For example, Fig. 11 shows a cutting element 14 with a working surface 15 obtained after removing all the walls of the mold . Such a cutting element can be fixed in the holder for use, for example, as a cutting element - a cutter. To use a polycrystalline element as, for example, a wear-resistant lining to the machine bed, you can leave the mold wall on one surface of the element, which will serve as a layer for attaching this element to the bed.

Only one of the opposite walls of the material wetted by the impregnating metal or alloy can be made in the mold. The most preferred option is the implementation of two opposite walls, for example 2 and 3 (figure 1) of a material wetted by an impregnating metal or alloy. In the latter case, elements of greater thickness can be obtained. Opposite walls of the mold can be completely made of a material wetted by an impregnating metal or alloy, or the walls can be made composite, i.e. the walls can be made of a material not wettable by the impregnating metal, but provided with inserts made of a material wetted by the impregnating metal or alloy. Instead of installing the inserts, the wettable material can be applied to the walls of the mold in any known manner, for example by spraying, galvanizing, etc.

Example 1. A two-layer plate was made with a working layer height h = 3 mm, with an area H × H = 210 × 210 mm. For a given concentration of cutting grains 82 vol%, a mixture of diamond powders AC35 was taken: coarse-grained powders 400/315 and powders of one fine-grained 40/28. AFM diamond powders with a grain size of 40/28 were applied with a molybdenum coating 5 μm thick. One of these mold walls was made of VK15 hard alloy, the second of steel 45. The diamond grains were compacted with the application of vibrations with a frequency of 50 Hz. Impregnation was carried out with the LNMts 50-2-2 alloy. The wetting angle of the LNMts 50-2-2 alloy of the hard alloy is θ = 30 °, steel θ = 10 °, and the coating metal of the diamond powder θ = 20 °. Impregnation temperature Тпр = 900 ° С, impregnation time - 5 min. After impregnation, all the walls of the mold were removed, except for one made of hard alloy. The result was a two-layer plate with a carbide substrate and a working layer, in which the volumetric content of diamond powders was 82%. The height of the polycrystalline working layer was 3 mm. The filling of pores in the entire volume of the working layer is complete. When coating on large AC 35 diamond powders with a grain size of 400/315, the volume content of diamond grains was 72%.

Example 2. A cutting element was made with a working layer height h = 5 mm, N × N = 210 × 210 mm. To obtain a given concentration of cutting grains of 89 vol%, a mixture of diamond powders AC 35 was taken: coarse grain 400/315 and the first fine grain ACM 40/28. To the mixture, CBN powders of the second fine grain size 5/3 were added. CBN powders with a 5/3 grit were coated with chromium 3 microns thick. The walls of the mold were made from st. 45. The manufacture of the cutting element was carried out as in example 1. After impregnation, all the walls of the mold were ground. The result was a cutting element with a volume content of 89% in the polycrystalline working layer of diamond and CBN grains. The filling of pores in the entire volume of the working layer is complete.

Example 3. A cutting element was made, as in example 2. A metal coating was applied to large diamond powders with a grain size of 400/315. There was no coating on fine powders. As a result, the workpiece was completely saturated, however, the volumetric content of abrasive grains in the element was 77% (instead of 89 vol.%).

Example 4. A two-layer plate was made, as in example 1, only instead of diamond powders of the first fine grain AC 40/28 with a coating, metal powders of the same grain size made from the coating material were taken. The result was a two-layer plate with a carbide substrate and a working layer, in which the volumetric content of diamond powders was 62.5%. The height of the polycrystalline working layer was 3 mm. The filling of pores in the entire volume of the working layer is complete. When coating on diamond powders AC 35 400/315, the concentration of diamond grains decreased to 50 vol.%.

Example 5. A polycrystalline element was made for use as a support center on precision machines: a cylinder with a diameter of 12 mm, a height of 12 mm with a cone of 60 ° at one of the ends of the cylinder. Natural isometric diamond powders with a grain size of 250/200 and natural micropowders with a grain size of 63/50 were taken. Fine powders were coated with chromium about 4 microns thick. The powders were placed in a glass made of steel 45, which was installed in graphite form. Diamond grains were compacted with the application of vibrations with a frequency of 50 Hz. The impregnation was performed with L63 brass alloyed with 4% titanium at a temperature of 980 ° C in vacuum for 5 minutes. An element was obtained with a volumetric content of diamond powders of 82%. Pore filling in the entire volume of the diamond layer is complete. The element was fastened with PSR40KD silver solder to the center shank.

Example 6. A cutting element was made with a working layer height h = 5 mm, N × N = 210 × 210 mm for turning alloy cast iron over the crust. Powders of cubic boron nitride with a grit of 400/315 and diamond powders with a grit of 100/80 with a nickel coating about 3 microns thick chemically deposited were taken. The powders were placed in a ceramic form of zirconium oxide, the walls of which were lubricated with hexagonal boron nitride. After compaction of the powders, they were impregnated with silicon at a temperature of 1550 ° C for 3 min. The volume content of abrasive grains was 84%. The element had full pore filling.

Thus, the coating, wetted by impregnating metals or alloys, on abrasive powders of only fine grain size allows to increase the height of the working layer of the element and the volumetric content of abrasive powders in the finished product.

Claims (12)

1. A method of manufacturing polycrystalline elements, comprising preparing a mixture of coarse-grained abrasive powders and from powders of one or two fine grains, placing the mixture in a mold, compacting and impregnating it with metals or alloys, characterized in that as powders of at least one fine grain powders are taken whose surface satisfies the wettability condition by impregnating metals or alloys. 2. The method according to claim 1, characterized in that the powders of at least one fine grain take abrasive powders, the surface of which is coated with a material wetted by impregnating metals or alloys. 3. The method according to claim 1, characterized in that as powders of at least one fine grain take powders made of a material wetted by impregnating metals or alloys. 4. The method according to claim 3, characterized in that as powders made from a material wetted by an impregnating metal or alloy, take metallic powders. 5. The method according to claim 1, characterized in that the mixture is prepared from abrasive powders of coarse grain and from abrasive powders of one fine grain, the surface of which is coated with a material wetted by impregnating metals or alloys. 6. The method according to claim 1, characterized in that the mixture is prepared from abrasive powders of coarse granularity and from abrasive powders of two fine granularities, while the surface of the powders of one of the fine granularities is provided with a coating of a material wetted by impregnating metals or alloys. 7. The method according to claim 1, characterized in that the mixture is prepared from abrasive powders of coarse granularity and from abrasive powders of two fine granularities, the surface of which is coated with a material wetted by impregnating metals or alloys. 8. The method according to claim 1, characterized in that the mixture is prepared from abrasive powders of coarse grain and powders of one fine grain, which are powders made of a material wetted by impregnating metals or alloys. 9. The method according to claim 1, characterized in that the mixture is prepared from coarse-grained abrasive powders and from two fine-grained powders, while uncoated abrasive powders are used as fine-grained powders, and powders are taken as second fine-grained powders, made of a material wetted by impregnating metals or alloys. 10. The method according to claim 1, characterized in that the mixture is prepared from coarse-grained abrasive powders and from two fine-grained powders, while abrasive powders, the surface of which is coated with a material wetted by impregnating metals or alloys, are taken as fine-grained powders and as powders of the second fine grain take powders made of a material wetted by impregnating metals or alloys. 11. The method according to claim 1, characterized in that the mixture of powders is placed in a mold having at least one pair of opposite side walls made of a material wetted by impregnating metals or alloys. 12. The method according to claim 1, characterized in that as abrasive powders of at least one fine grain take powders from the group: diamond and cubic boron nitride.

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