RU2779482C2 - Composite worn component - Google Patents

Abstract

FIELD: engineering elements.

SUBSTANCE: invention relates to a composite worn component with a hierarchical structure, produced by casting and exhibiting high resistance to combined wear loads/impact loads, and to a method for production thereof. Composite worn component with a hierarchical structure comprises reinforcement in the most wear-prone part. The reinforcement comprises a three-dimensionally linked network of periodically alternating millimetre metal-ceramic composite granules with millimetre gaps, wherein said metal-ceramic composite granules contain at least 52 vol.% micrometre particles of titanium carbide embedded in a first metal matrix. The three-dimensionally linked network of metal-ceramic composite granules with the millimetre gaps is therein embedded in a second metal matrix, wherein the first metal matrix differs from the second metal matrix containing a cast iron alloy.

EFFECT: best wear resistance and mechanical properties of the part are ensured, as well as safety during production.

10 cl, 12 dwg, 5 tbl, 4 ex

Description

FIELD OF TECHNOLOGY

[0001] The present invention relates to a composite wear component with a hierarchical structure, obtained by casting technology, having improved resistance to combined wear/impact loads. The wear component comprises a three-dimensional network of aggregated mm-gauge cermet-metal composite pellets, where TiC-based micron-sized particles are embedded in the binder, referred to as the first metal matrix, the millimeter-long gaps being filled with cast metal, referred to in the present invention as the second metal matrix.

State of the art and problem to be solved

[0002] The present invention relates to wear components used in grinding and crushing industries such as cement plants, quarries and mines. These components are often subject to significant mechanical stress throughout and significant abrasive wear on the working surfaces. Therefore, it is desirable that such components have high abrasion resistance and some ductility so that they can withstand mechanical loads such as impacts.

[0003] Since it is rather difficult to combine these two properties in the same material, composite components having a relatively ductile alloy core embedded with ceramic inserts with good wear resistance have been previously proposed.

[0004] US 4,119,459 (Sandvik, 1977) discloses a composite wear article consisting of cast iron and crushed granules of sintered cemented carbide. The cemented carbide in the binder metal is of the WC-Co type with possible additions of Ti, Ta, Nb or other metal carbides. The possible volume percentage of TiC in the granules or in the reinforced part of the product is not reported.

[0005] US 4,626,464 (Krupp, 1984) discloses an in-hammer hammer comprising a metal alloy base material and a wear zone containing, in addition to ferroalloy, hard metal particles having a diameter of 0.1 to 20 mm and a percentage of hard metal particles in the wear-resistant zone is from 25 to 95 vol.%; and wherein said hard particles are firmly embedded in said metal alloy base material. The possible average volume concentration of TiC in the reinforced part is not disclosed in this document.

[0006] US 5,066,546 (Kennametal, 1989) discloses a hierarchical wear-resistant article comprising at least one layer of a variety of carbide materials, including titanium carbide, embedded in a cast steel matrix. The carbide material has a particle size of 4.7 to 9.5 mm, said carbide material being in the form of crushed pieces, powder or irregular molded articles. This document does not disclose the average concentration of TiC in the reinforced part of the wear resistant product, nor the composition of the reinforcing structure.

[0007] US 8999518 B2 discloses a composite material with a hierarchical structure containing a titanium carbide reinforced iron alloy having a certain geometric configuration, in which the specified reinforced part contains an alternating macro-microstructure of millimeter-sized areas in which micrometer-sized spherical particles of titanium carbide are concentrated, separated by millimeter regions, essentially free of micrometer spherical particles of titanium carbide, where these regions are filled with an iron alloy. In this patent, the maximum concentration of TiC is 72.2 vol.% when compacting a powder mixture of Ti and C with a maximum relative density of 95%. The porosity of the granules exceeds 5 vol.%, and in the absence of a possible reaction retardant, only one metal matrix is present - cast metal. Composite material with a hierarchical structure is obtained by self-propagating high temperature synthesis (SHS), which usually achieves reaction temperatures above 1500°C or even 2000°C. Very little energy is required to initiate a reaction locally. The reaction then spontaneously propagates to the entire mixture of reactants.

[0008] A composite with a hierarchical structure according to this document is obtained by reaction in a mold of granules containing a mixture of powders of carbon and titanium. After the initiation of the reaction, a reaction front develops, which thus spontaneously propagates (self-propagates), which makes it possible to obtain titanium carbide from titanium and carbon. The titanium carbide produced in this way is called "in situ produced" because it is not obtained from a cast iron alloy. This reaction is initiated by the heat from the iron or steel casting used to cast the entire part, and therefore both the unreinforced and the reinforced part. The SHS reaction Ti+C→TiC is very exothermic and has a theoretical adiabatic temperature of 3290°K.

[0009] Unfortunately, an increase in temperature causes degassing of the reactants, i. e. volatile substances contained in them (H ₂ O in carbon, H ₂ , N ₂ in titanium). All impurities contained in the reagent powders, organic or inorganic components around or inside the powder / compacted granules, evaporate. In order to weaken the intensity of the reaction between carbon and titanium, iron alloy powder is added to it as a moderator to absorb heat and reduce temperature. However, this also reduces the maximum achievable TiC concentration in the finished wear part, and the aforementioned theoretical concentration of 72.2% in this case can no longer be achieved in practice on an industrial scale.

[0010] Document WO 2010/031663A1 relates to a composite impactor for percussion crushers containing a ferroalloy at least partially reinforced with titanium carbide of a certain shape in accordance with the same method as in the previously described document US 8999518 B2. To weaken the intensity of the reaction between carbon and titanium, iron alloy powder is added. In one of the examples in this document, the reinforced areas contain a total of approximately 30 vol.% TiC. For this, a tape with a relative density of 85% is obtained by pressing. After crushing the ribbon, the resulting granules are screened to a size of 1 to 5 mm, preferably 1.5 to 4 mm. Get a bulk density of approximately 2 g/cm ³ (45% space between the granules + 15% porosity in the granules). Thus, the granules in the wear part to be reinforced contain 55 vol.% porous granules. In this case, the concentration of TiC in the reinforced area is only 30%, which is not always sufficient and can adversely affect the wear resistance of the cast product, in particular with grains with high porosity before the SHS reaction.

[0011] US 2018/0369905A1 describes a method for more precise control of the SHS process during retarder casting. The inserts in the cast product are made from a powder mixture containing the reagents for forming TiC and a moderator consisting of cast high manganese steel containing 21% Mn.

Objectives of the invention

[0012] The aim of the present invention is to provide a composite wear component with a hierarchical structure obtained by conventional casting containing a metal matrix of iron or steel, in which a reinforced structure is embedded with a high concentration of micrometer particles of titanium carbide embedded in a metal binder (the first metal matrix ) forming ceramic-metal composite granules with low porosity. The first metal matrix, comprising micrometer-sized titanium carbide particles of the reinforced part, is different from the metal matrix present in the rest of the composite wear component.

[0013] Yet another object of the present invention is to provide a safe, gas-free manufacturing process for reinforced composite wear parts, resulting in an improved composite wear component with good impact and corrosion resistance.

Brief description of the invention

[0014] The first aspect of the present invention relates to a composite wear component with a hierarchical structure, containing reinforcement in the most subject to wear part, where the reinforcement contains a three-dimensionally connected network of periodically alternating mm cermet composite granules with millimeter gaps, where these cermet composite granules contain at least 52 vol.%, preferably at least 61 vol.%, more preferably at least 70 vol.% micrometer particles of titanium carbide embedded in the first metal matrix, where the ceramic-metal composite granules have a density of at least 4.8 g/cm ³ , where a three-dimensionally bonded network of ceramic-metal composite pellets with its millimeter gaps is embedded in a second metal matrix, where the specified reinforcement contains on average at least 23 vol.%, more preferably at least 28 vol.%, most preferably at least 30 vol.% car titanium bid, and the first metal matrix is different from the second metal matrix, where the second metal matrix contains a cast iron alloy.

[0015] According to preferred embodiments of the invention, the composite wear component is further characterized by one of the following features, or a suitable combination thereof:

the ceramic-metal composite pellets have a porosity of less than 5% by volume, preferably less than 3% by volume, more preferably less than 2%;

the embedded cermet composite pellets have an average particle size d50 of 0.5 to 10 mm, preferably 1 to 5 mm;

the embedded titanium carbide particles have an average particle size d50 of 0.1 to 50 µm, preferably 1 to 20 µm;

the first metal matrix is selected from the group consisting of an iron-based alloy, a ferromanganese-based alloy, a ferrochromium-based alloy, and a nickel-based alloy;

- the second metal matrix contains an iron alloy, in particular high chromium white cast iron or steel.

[0016] The present invention further discloses a method for manufacturing cermet composite pellets, comprising the following steps:

- grinding powder compositions containing TiC and the first metal matrix, in the presence of a solvent, preferably to achieve an average particle size d50 from 1 to 20 μm, preferably from 1 to 10 μm;

- mixing with powder composition from 1 to 10%, preferably from 1 to 6% of wax;

- removing the solvent by vacuum drying to obtain an agglomerated powder;

- compaction of the agglomerated powder into strips, sheets or rods;

- crushing strips, sheets or rods into granules, preferably with an average size d50 of 0.5 to 10 mm, preferably 1 to 5 mm;

- sintering at a temperature of 1000-1600 °C in a vacuum or inert atmosphere furnace until a density of at least 4.8 g/cm ³ is reached.

[0017] The present invention further discloses a method for manufacturing a composite wear component according to the present invention, comprising the following steps:

- mixing the ceramic-metal composite granules obtained in accordance with the invention, with approximately 1 to 8 wt.%, preferably from 2 to 6 wt.% adhesive;

- pouring the mixture and compacting it in the first mold;

- drying the mixture at a suitable temperature and duration to remove the solvent from the adhesive or to allow curing;

- extracting the dried mixture from the mold and obtaining a three-dimensionally connected network of periodically alternating millimeter cermet composite granules with millimeter gaps for use as reinforcement in the wear part of the wear component with a hierarchical structure.

[0018] According to preferred embodiments of the invention, the method for manufacturing a wear component is further characterized by the following steps, or a suitable combination thereof:

placing a three-dimensionally bonded network of periodically alternating millimetric cermet composite pellets at millimeter intervals into a portion of the mold volume for a composite cast wear component with a hierarchical structure to be cast;

pouring a second metal matrix into a second mold representing a mold for a cast wear part and simultaneously infiltrating millimetric gaps of a three-dimensionally connected network;

- removing the composite cast wear component with a hierarchical structure from the mold.

[0019] The present invention further discloses a composite cast wear component with a hierarchical structure obtained by the method of the invention.

Brief description of graphic materials

[0020] FIG. 1 shows the impact ring of the grinding machine in which the present invention was tested.

[0021] In FIG. 2 shows a separate fender of the fender of FIG. one.

[0022] FIG. 3 shows a worn separate fender.

[0023] FIG. 4 is a schematic representation of the arrangement of the reinforcement structure in the most wear-prone part of an individual fender.

[0024] FIG. 5 is a general view of a reinforcing structure, defined as a three-dimensionally bonded network of periodically alternating millimeter-sized cermet composite pellets at millimeter-sized intervals.

[0025] FIG. 6 and 7 are enlarged views of the reinforcing structure of FIG. 5.

[0026] FIG. 8 is a cross-sectional view of a cast wear component incorporating millimeter-sized cermet composite pellets with interstices (voids) filled with a second metal matrix (cast metal matrix).

[0027] In FIG. 9 shows microscopic spheroidal TiC particles embedded in a first metal matrix that binds the TiC particles. The image is a high magnification of one cermet composite grain shown in FIG. eight.

[0028] FIG. 10 is a schematic representation of the concept of the present invention based on the scale difference between embedded micrometer TiC particles in a first metal matrix forming millimeter-sized grains of a cermet composite integrated in a three-dimensional network into the reinforced part of the wear component.

[0029] FIG. 11 is a schematic cross-sectional view of a sample containing granules, which is used in the method to obtain the average particle size of sintered granules (as described below).

[0030] FIG. 12 is a schematic representation of a Feret diameter measurement method (with minimum and maximum Feret diameters). These Feret diameters are used in the process to obtain the average particle size of the sintered granules (as described below).

Description of preferred embodiments of the invention

[0031] The present invention relates to a composite wear component with a hierarchical structure obtained using conventional casting. It consists of a metal matrix containing a special reinforcing structure containing dense (with low porosity less than 5%) irregularly shaped ceramic-metal composite granules with an average millimeter size of 0.5 to 10 mm, preferably 0.8 to 6 mm, more preferably from 1 to 4 mm, even more preferably 1 to 3 mm.

[0032] Ceramic-metal composites consist of ceramic particles bound by a metal binder, referred to in the present invention as the first metal matrix. In wear applications, ceramic provides high wear resistance, while metal improves toughness, among other properties. TiC-based ceramic-metal composites contain micrometer-sized spheroidal titanium carbide particles (from 52 to 95 vol.% of granules, preferably from 61 to 90 vol.%, more preferably from 70 to 90 vol.%, with a size of from 0.1 to 50 μm, preferably 0.5 to 20 µm, more preferably 1 to 10 µm) bound by a metal phase (first metal matrix) based on, for example, Fe, Ni or Mo. An iron alloy, preferably chromium iron or steel (second metal matrix), is cast in a mold and infiltrates only the interstices of said reinforcing structure.

[0033] In the present invention, the term "TiC" should be understood not in the strict stoichiometric chemical sense, but as titanium carbide in its crystallographic structure. Titanium carbide has a wide range of compositions with C/Ti stoichiometry from 0.47 to 1, C/Ti stoichiometry above 0.8 is preferred.

[0034] The volume content of ceramic-metal composite granules in the insert forming the reinforced volume of the wear part (excluding hollow parts or recesses, if any) is generally from 45 to 65 vol.%, preferably from 50 to 60 vol.%, which corresponds to average concentrations of TiC in the reinforced volume from 23 to 62 vol.%, preferably from 28 to 60 vol.%, more preferably from 30 to 55 vol.%.

[0035] A reinforced part with a wear component hierarchical structure is produced from an aggregate of millimeter irregularly shaped ceramic-metal composite pellets having an average size of approximately 0.5 to 10 mm, preferably 0.8 to 6 mm, more preferably 1 to 4 mm, still more preferably 1 to 3 mm.

[0036] The ceramic-metal composite beads are preferably aggregated into the desired three-dimensional shape with an adhesive (inorganic, such as well-known inorganic adhesives based on soda (or potassium) silicate glasses, or organic adhesives, such as polyurethane or phenolic resins), or inside a container, or behind a baffle (usually metallic, but said container or baffle may also be of a ceramic, generally inorganic or organic nature). This desired shape forms an open structure formed by a three-dimensionally bonded network of agglomerated/aggregated cermet composite pellets, bonded by a binding agent or maintained in the desired shape by a container or baffle, the pellets being stacked leaving millimeter-long open spaces between them, which can be filled with liquid cast metal. This agglomerate is placed or positioned in a mold prior to pouring the iron alloy to form the reinforced part of the wear component. Liquid metal is then poured into said mold, which fills the open spaces between the pellets. The millimeter gaps are to be understood as gaps of 0.1 to 5 mm, preferably 0.5 to 3 mm, depending on the tightness of the reinforcing structure and the size of the granules.

[0037] Ceramic-metal composite pellets are typically made in a conventional manner, using powder metallurgy, by forming a mixture of ceramic and metal powders of suitable particle size distribution, followed by liquid-phase sintering.

[0038] Typically, the powders have a diameter of 0.1-50 µm and contain TiC as the main component and from 5 to 48% of the metal binder, which can be a powder of one component or already alloyed powders (first metal matrix). The powders are first mixed and/or milled (depending on the original powder size) in a ball mill, either dry or wet milled (eg with alcohol to avoid oxidation of the metal powder). Some organic additives may be added for dispersion or shaping purposes. In the case of wet grinding, a drying step may be required. It can be carried out, for example, by vacuum drying or spray drying. Forming is usually carried out by cold unidirectional isostatic pressing or injection molding, or any other forming methods, to form a strip, rod or sheet.

[0039] Tapes or sheets, for example, can be crushed to grains and optionally screened. It can be an advantage to obtain irregularly shaped pellets without an orientation in which they can be easily torn out (the pellets are very well mechanically held in the cast metal). The pressed, extruded or crushed pellets are then sintered at a suitable temperature under low or high vacuum conditions, in an atmosphere of inert gas, hydrogen, or combinations thereof. During liquid-phase sintering, the particles are rearranged under the action of capillary forces.

[0040] The casting alloy (second metal matrix) in which the cermet composite grains of the wear component are embedded is preferably an iron alloy (white chromium cast iron, steel, manganese steel...) or a nickel or molybdenum alloy. This alloy can be selected to achieve locally optimized properties depending on the final requirements of the wear part (e.g. manganese steel will provide high impact resistance, high chromium white cast iron will provide higher wear resistance, nickel alloy will provide excellent thermal and corrosion resistance, etc.) .

Advantages

[0041] The present invention makes it possible to obtain, in a product obtained by conventional casting, a concentration of TiC particles, which can be very high in cermet composite pellets (from 52 to 95 vol.%), without the risk of defects inside the cast structure (gas holes, cracks, discontinuities…) or uncontrolled and hazardous reactions and releases that occur when TiC is formed in situ by a self-propagating exothermic reaction (SHS, see above).

In the present invention, good average TiC concentrations can be achieved in the reinforced volume of the wear part due to the low porosity of the cermet composite pellets. Values up to about 62 vol.% can be achieved depending on the compaction/stacking of the ceramic-metal composite granules in the reinforced volume.

[0042] The hierarchical wear component of the present invention is substantially free of porosity and cracks, which provides more favorable mechanical properties and wear resistance.

[0043] The particle size of titanium carbide and cermet composite pellets (TiC + binder) according to the present invention during the manufacturing process can be controlled on a large scale (selection of raw materials, grinding process, molding and sintering conditions). The use of sintered millimeter TiC-based cermet composite pellets produced by well-known powder metallurgy, allows control of grain size and porosity, use of various compositions of metal alloys as the first metal matrix, high concentration of TiC, easy molding of inserts without excessive need for human labor and good internal condition of the grains after pouring even under conditions of strong thermal shock.

Production of ceramic-metal composite granules:

[0044] Grinding and/or mixing of inorganic TiC powder (from 52 to 95 vol.%, preferably from 61 to 90 vol.%, more preferably from 70 to 90 vol.%) and metal powders as the first metal matrix (from 5 to 48% by volume, preferably 10 to 39% by volume, more preferably 10 to 30% by volume, as mentioned above, in a ball mill with a liquid which may be water or alcohol, depending on the sensitivity of the metal binder for oxidation. Various additives (antioxidant, dispersant, binder, plasticizer, lubricant, press wax, ...) can also be added for various purposes.

[0045] After reaching the desired average particle size (typically less than 20 microns, preferably less than 10 microns, more preferably less than 5 microns), the suspension is dried (by vacuum drying or spray drying) to obtain powder agglomerates containing organic additives.

[0046] The agglomerated powder is introduced into the granulator through the hopper. This machine includes two pressurized rollers through which the powder is passed and compacted. At the output, a continuous tape (sheet) of pressed material is obtained, which is then crushed to obtain metal-ceramic composite granules. These granules are then screened to the desired grain size. Fractions of granules of undesirable size are returned to the process as desired. The resulting granules usually have a relative density of 40 to 70% (depending on the degree of compaction, powder characteristics and mixture composition).

[0047] It is also possible to adjust the granulometric composition of the granules, as well as their shape, to more or less cubic or flat shape, depending on the crushing method (impact crushing will produce more cubic granules, while crushing will give flatter granules). The resulting granules generally have a size which, after sintering, will provide a granule size of 0.5 to 10 mm, preferably 0.8 to 6 mm, more preferably 1 to 4 mm, even more preferably 1 to 3 mm. Granules can also be obtained by classical unidirectional pressing or granulation of a powder mixture directly in the form of grains or into much larger pieces, which will then be crushed into granules before or after sintering.

[0048] Finally, liquid-phase sintering can be carried out in a furnace at a temperature of 1000-1600 ° C for several minutes or hours, in vacuum, in an atmosphere of N ₂ , Ar, H ₂ or mixtures, depending on the metal phase (type and amount binder) until the desired porosity is achieved, preferably less than 5%, more preferably less than 3%, most preferably less than 2%.

Implementation of a three-dimensional reinforcing structure (core)

[0049] As mentioned above, the ceramic-metal composite pellets are agglomerated, either with an adhesive or by enclosing them in a container, or by any other means. The proportion of adhesive does not exceed 10 wt.% of the total mass of the granules and preferably ranges from 2 to 7 wt.%. This adhesive may be inorganic or organic. A sodium or potassium silicate adhesive or a polyurethane or phenolic resin adhesive may be used.

[0050] The low porosity cermet composite beads are mixed with an adhesive, typically an inorganic silicate adhesive, and placed in a mold (eg silicone) of the desired shape. After the adhesive has set (achieved at 100° C., for example, after the water in the inorganic silicate adhesive has dried; adhesive setting can also be achieved by gassing with CO ₂ or amine-based gas, for example, for polyurethane-based adhesive), the core solidifies and can be taken out of the mold. Depending on the shape of the granules, particle size distribution, vibration during placement of the granules, or rapping of the layer of granules during the manufacture of the core, the core usually contains from 30 to 70 vol.%, preferably from 40 to 60 vol.% dense granules and from 70 to 30 vol. %, preferably from 60 to 40 vol.% voids (millimeter gaps) in a three-dimensionally connected network.

Wear part casting

[0051] The core (three-dimensional reinforcing structure) is placed and fixed with screws or any other available means in the part of the mold for the wear part to be reinforced. A hot liquid iron alloy, preferably chromium white iron or steel, is then poured into the mold.

[0052] In this case, the hot liquid iron alloy fills only millimeter gaps between the pellets of the core. When using an inorganic adhesive, the limited melting of the metal binder (the first metal matrix) on the surface of the pellets results in a very strong bond between the pellets and the second matrix alloy. When using an organic adhesive containing sodium silicate, metal binding is limited, but can still occur on the surfaces of the granules that are not coated with adhesive.

[0053] Contrary to the prior art, no reaction (exothermic reaction or outgassing) or shrinkage (24% volume reduction for the Ti+C→TiC reaction) occurs during pouring, and the cast metal will infiltrate gaps (millimeter gaps between pellets ), but will not infiltrate cermet composite beads as they are not porous.

Measurement methods

[0054] For measurements of porosity, granule or particle size, a sample for metallographic examination is obtained that does not have traces of milling and grinding. Care must be taken to ensure that particles are not torn out, as this may lead to an incorrect assessment of porosity. Guidelines for sample preparation are provided in ISO 4499-1:2020 and ISO 4499-3:2016 paras. 8.1 and 8.2.

Definition of porosity:

[0055] The volume fraction of porosity of free granules can be calculated from the measured density and the theoretical density of the granules.

[0056] The volume fraction of porosity of the pellet embedded in the metal matrix is measured in accordance with ISO 13383-2:2012. Although this standard is specifically for thin ceramics, the method described for measuring porosity volume fraction can also be applied to other materials. Since in this case the specimens are not pure thin ceramics, but solid metal-based composites, preparation of the specimens must be carried out in accordance with ISO 4499-1:2020 and ISO 4499-3:2016 paras. 8.1 and 8.2. Etching is not required to measure porosity, but can still be done as it will not affect the measurement result.

Average particle size of titanium carbide:

[0057] The average size of the embedded particles of titanium carbide is calculated by the secant method in accordance with ISO 4499-3:2016. Five images of the microstructure of five different granules are obtained using an optical or electron microscope at a known magnification so that 10 to 20 titanium carbide particles are in the field of view. Four secants are drawn on each calibrated image so that no particle is crossed by the line more than once.

[0058] At the point where the line intersects the titanium carbide particle, the line length (l _i ) is measured using a calibrated ruler (where i=1,2,3...n for the 1st, 2nd, 3rd, ..., nth grains). Incomplete particles touching the edges of the image should be ignored. At least 200 particles must be counted.

[0059] The average particle size by the secant method is defined as:

Average particle size of cermet granules:

[0060] A photomicrographic panorama of the polished cross-section of the sample is obtained so that there are at least 250 cermet granules in the field of view, using stitching (the process of combining a series of digital images of various parts of an object into a panoramic view of the entire object while maintaining good resolution) using computer program and an optical microscope (for example, a general panorama of the image field obtained using Alicona Infinite Focus). Appropriate binarization allows the grayscale image to be segmented into elements of interest (granules) and background (see FIG. 11). If the binarization is not stable due to poor image quality, a manual step is used, involving hand-drawing the granules, the scale bar if present, and the border of the image on the tracing paper, and then scanning the tracing paper.

[0061] The Feret diameter, which is the distance between two tangents perpendicular to the measurement direction, is measured in all directions for each bead using image analysis software (eg, ImageJ). An example is shown in FIG. 12.

[0062] The minimum and maximum Feret diameter of each granule in the image is determined. The minimum Feret diameter is the shortest Feret diameter of the measured set of Feret diameters. The maximum Feret diameter is the longest Feret diameter of the measured set of Feret diameters. Grains touching the edges of the image should be ignored. The average value of the minimum and maximum Feret diameters of each granule is taken as the equivalent diameter x. The volume distribution of granule size q ₃ (x) is then calculated based on spheres of diameter x.

в соответствии с ISO 9276-2:2014.D ₅₀ granules should be understood as the weighted average size

in accordance with ISO 9276-2:2014.

The average particle size of sintered granules during the production of granules:

[0063] The size of the granules is measured using dynamic image analysis in accordance with ISO 13322-2:2006 using Camsizer from Retsch. The particle diameter used for the size distribution is X _{c min,} which is the shortest chord measured in the set of maximum particle projection chords (for close to sampling/sieving results).

[0064] d ₅₀ granules is the weighted average volumetric distribution size based on X _{c min} .

Powder particle size measurement during grinding:

[0065] The particle size of the powder during the grinding process is measured by laser diffraction according to Mie theory in accordance with the recommendations given in ISO 13320:2020, using a Mastersizer 2000 from Malvern. The refractive index for TiC is set to 3 and the absorbance to 1. The obscuration should be in the range of 10 to 15% and the weighted residual should be less than 1%.

Density measurement of sintered pellets:

[0066] Determination of the density of sintered pellets is carried out with water in accordance with ISO 3369:2006. For granules without open porosity, a gas displacement pycnometer (eg Micromeritics AccuPyc II 1345 pycnometer) can also be used, giving almost the same density value.

Practical use - fender wear part

[0067] In accordance with the present invention, breaker wear parts used in a vertical shaft crusher have been implemented. The reinforced volume of wear parts has various average volume percentages of TiC from about 30 and up to 50% by volume.

They were compared with a wear piece made in accordance with US 8999518 B2, exemplary 4 (with a total volume percentage of TiC of approximately 32 vol.% in the reinforced volume).

[0068] The reason for this comparison is that Example 4 is a typical "in situ" composition (Ti + C and moderator in a self-propagating reaction) that requires careful plant handling and still generates a lot of flames, gases, and hot liquid metal emissions during filling time.

Examples

[0069] Obtaining granules:

The following raw materials have been used for 3 different types of cermet composite pellets:

• TiC powder less than 325 mesh

• Iron powder less than 325 mesh

• Manganese powder less than 325 mesh

• Nickel powder less than 325 mesh

Table 1

Composition (wt%) Example 1 Example 2 Example 3 TiC 45.0 65.0 85.0 Fe 44.8 28.5 12.2 Mn 7.7 4.9 2.1 Ni 2.5 1.6 0.7 Total 100.0 100.0 100.0 Theoretical density after sintering 6.22 5.68 5.22

[0070] The powders according to the formulations in Table 1 were mixed and ball milled with alcohol and metal balls for 24 hours to achieve an average particle size of 3 microns.

[0071] An organic wax binder was added in an amount of 4 wt.% relative to the powder, and mixed with the powder. The alcohol was removed using a rotary blade vacuum dryer (the alcohol was condensed for reuse). The resulting agglomerated powder was then sieved through a 100 µm sieve. Tapes having 60% of the theoretical density of the inorganic/metal powder mixtures were produced by densification between the rotating rolls of a roller press pelletizer. The ribbons were then crushed into irregularly shaped granules by passing them through a sieve with appropriately sized meshes. After crushing, the granules were sieved to a size of 1.4 to 4 mm. These irregularly shaped porous pellets were then sintered at high temperature (1000-1600°C for several minutes or hours) in a vacuum furnace with low argon partial pressure until a minimum porosity (less than 5 vol.%) and a density above 5 g/cm ^{3 were} achieved. .

[0072] Sintered pellets with a low porosity of less than 5 vol.% were then mixed with about 4 wt.% inorganic silicate adhesive and poured into a silicone mold (vibration can be applied to facilitate placement and ensure that all pellets are correctly laid) of the desired size 100 ×30×150 mm. After drying at 100° C. for several hours in an oven to remove water from the silicate adhesive, the cores became hard enough to be removed from the mould.

[0073] These cores, as shown in FIG. 5 contain approximately 55 vol% dense granules (45 vol% voids/millimeter gaps between granules). Each combination of cores/3D reinforcement structures was placed in the molds in the part of the wear parts that needed to be reinforced (as shown in Fig. 4). Then hot liquid high-chromium white cast iron was poured into the molds. This hot liquid high chromium white iron filled approximately 45 vol.% millimeter gaps between the grains of the core. After pouring, 55 vol.% areas with a high concentration of approximately 57 to 90 vol.% titanium carbide particles were obtained in the reinforced part, bound by a metal phase (first metal matrix) different from the rest of the wear part where the cast alloy is present (second metal matrix). The total volume content of TiC in the reinforced macromicrostructure of the wear part varies in Examples 1-3 from about 32% to 50% by volume, but higher values can be achieved.

Comparison with prior art

[0074] Wear parts according to the invention were compared with a wear part obtained analogously to example 4 in US 8999518 B2.

The impact ring of the grinding machine in which these tests were carried out is illustrated in FIG. one.

[0075] In this machine, the inventor alternately placed a fender containing an insert (as shown in Figs. 2 and 3) in accordance with the present invention, surrounded on one side by a reinforced fender in accordance with the prior art source US 8999518 B2, example 4 , to assess wear in exactly the same conditions.

The crushed material hits the working surface of the breaking elements at high speed (a separate breaking element before wear is shown in Fig. 2). Crushing wears out the working surface. The worn out fender is shown in Fig. 3.

[0076] For each fender, the mass loss is measured by weighing each fender before and after use.

mass loss = (final mass - initial mass) / initial mass

The performance index is determined as shown below, where the weight loss of the control is the average weight loss of the fender according to US 8999518 B2, example 4, on each side of the fender being tested.

PI = mass loss of the control / mass loss of the fender under test

[0077] A performance indicator above 1 means that the wear of the tested fender is less than that of the control, below 1 - that the wear of the tested fender is greater than that of the control.

• Performance Index (PI) of the reinforced fender according to Example 1 of the present invention (cermet composite grains containing 57 vol.% (45 wt.%) titanium carbide): 1.05 (higher index of cermet composite grains with a local volume content close to to US 8999518 B2, example 4, can be explained by fewer defects such as cracks and porosity in the part)

• Performance index (PI) of the reinforced fender according to example 2 of the present invention (metal-ceramic composite grains containing 75 vol.% (65 wt.%) titanium carbide): 1.16

• Performance index (PI) of the reinforced fender according to example 3 of the present invention (metal-ceramic composite grains containing 90 vol.% (85 wt.%) titanium carbide): 1.24

table 2

Granules from 1.4 to 4 mm example 1 example 2 example 3 example 4 before pouring Relative density of granules (%) 99.8% 99.6% 99.7% 85.0% Granule porosity (%) 0.2% 0.4% 0.3% 15.0% Quantity (g) 1579 1356 1289 900 Density of granules (g/cm³) 6.19 5.65 5.21 4.25 Reinforced area dimensions (mm) 150×100×30 150×100×30 150×100×30 150×100×30 The volume of the reinforced area (cm ³ ) 450 450 450 450 Filling of the reinforced part of the part (vol.%) 57% 54% 55% 55% Volume of granules (cm ³ ) 255 241 248 249 after pouring Final content of TiC in granules (vol.%) 57% 74% 90% 57% Final content of TiC in the reinforced part (vol.%) 32% 40% fifty % 32% Porosity in the reinforced area (vol.%) <0.5 <0.5 <0.5 3.00 Performance indicator 1.05 1.16 1.24 1.00

Composite density as a function of porosity and density of joints (titanium carbide and alloys)

[0078] Below are two tables with the density of the composite as a function of vol.% TiC and vol.% porosity (for alloys based on iron and Nickel).

Table 3

density (g / cm ³ ) Titanium carbide 4.93 iron alloy 7.87 Nickel alloy 8.91

Table 4

Density of composite with iron alloy (g/cm ³ ) porosity (vol.%) 5 % 3% 2% 0.10% Titanium carbide content (vol.%) 52% 6.02 6.15 6.21 6.33 61% 5.77 5.89 5.96 6.07 70% 5.52 5.64 5.70 5.81 85% 5.10 5.21 5.26 5.37 96% 4.80 4.90 4.95 5.04 99% 4.71 4.81 4.86 4.95

Table 5

Density of Composite with Nickel Alloy (g/cm³) porosity (vol.%) 5 % 3% 2% 0.10% Titanium carbide content (vol.%) 52% 6.50 6.64 6.70 6.83 61% 6.16 6.29 6.35 6.48 70% 5.82 5.94 6.00 6.12 85% 5.25 5.36 5.42 5.52 96% 4.83 4.94 4.99 5.08 99% 4.72 4.82 4.87 4.96

Advantages of the present invention

The present invention has the following advantages over the general state of the art:

• Better wear resistance due to locally higher vol% TiC in the pellets (which is nearly impossible to achieve with prior art SHS technologies)

• Improving the wear resistance or mechanical properties of a wear part by selecting the size and volume content of titanium carbide and using a combination of a binder in the form of a metal phase (first metal matrix), for example, manganese steel with high mechanical properties, in granules of a ceramic-metal composite TiC, with a cast alloy ( a second metal matrix), such as, for example, high chromium white cast iron, for a wear part, the first metal matrix being different from the second metal matrix.

• Better wear resistance or mechanical properties of the wear part due to lower porosity and/or fewer crack type defects because no gas is generated during pouring and the TiC dispersion is homogeneous.

• Greater safety during production, as there will be no dangerous exothermic reaction with the release of combustible gases or emissions of molten liquid metal during pouring.

• Greater production safety due to the handling of less hazardous pellet raw materials (Fe powder is a less explosive powder than Ti, which is a highly explosive powder).

Claims (30)

1. Composite cast wear component with a hierarchical structure, containing reinforcement in the working surface of the wear component, while the reinforcement contains: a three-dimensionally connected network of periodically alternating millimetric cermet composite pellets with millimeter gaps; wherein the ceramic-metal composite granules have a porosity of less than 5 vol.% and contain at least 52 vol.% micrometer particles of titanium carbide embedded in the first metal matrix; wherein the three-dimensionally bonded network of cermet composite beads is interspersed with a second metal matrix, wherein the second metal matrix infiltrates and fills the spaces between the bonded ceramic-metal composite beads of the three-dimensionally bonded network; while the volume content of ceramic-metal composite granules in the specified reinforcement is from 45 to 65 vol.%; and the first metal matrix is different from the second metal matrix, where the second metal matrix contains a cast iron alloy. 2. Composite cast wear component with a hierarchical structure according to claim 1, in which the embedded ceramic-metal composite granules have an average particle size d ₅₀ from 0.5 to 10 mm, and the average particle size is measured by obtaining a photomicrographic panorama of the ground cross section of the sample in such a way, so that there are at least 250 cermet beads in the field of view by stitching using a computer program and an optical microscope, where suitable binarization allows the grayscale image to be segmented into grains and background. 3. Composite cast wear component with a hierarchical structure according to claim 1, in which the embedded particles of titanium carbide have an average particle size d ₅₀ from 0.1 to 50 μm. 4. The hierarchical composite cast wear component of claim 1, wherein the first metal matrix is selected from the group consisting of an iron-based alloy, a ferromanganese-based alloy, a ferrochromium-based alloy, and a nickel-based alloy. 5. The hierarchical composite cast wear component of claim 1, wherein the second metal matrix comprises high chromium white cast iron or steel. 6. A method of manufacturing a composite cast wear component with a hierarchical structure according to any one of paragraphs. 1-5, including the following steps: a) providing or manufacturing cermet composite pellets containing at least 52 vol.% micrometer particles of titanium carbide embedded in the first metal matrix, and cermet composite pellets have a porosity of less than 5 vol.%; b) fabricating a three-dimensionally bonded network of periodically alternating millimetric cermet composite pellets with millimeter gaps from the pellets of step a); c) placing the three-dimensionally connected network obtained in step b) into a part of the mold volume for the composite cast wear component with a hierarchical structure to be cast; d) pouring a second metal matrix containing a cast iron alloy and simultaneously infiltrating millimetric gaps of a three-dimensionally bonded network placed according to step c) with a second metal matrix; e) removing the composite cast wear component with the hierarchical structure from the mould. 7. A method for manufacturing a composite cast wear component with a hierarchical structure according to claim 6, wherein step a) comprises the following steps: - grinding powder compositions containing TiC and the first metal matrix, in the presence of a solvent; - mixing with the powder composition from 1 to 10%, preferably from 1 to 6% wax; - removing the solvent by vacuum drying to obtain an agglomerated powder; - compaction of the agglomerated powder into strips, sheets or rods; - crushing tapes, sheets or rods into granules; - sintering at a temperature of 1000–1600°C in a vacuum furnace or an inert atmosphere furnace until the cermet granules porosity is less than 5 vol.%. 8. The method according to p. 7, in which the stage of grinding powder compositions containing TiC and the first metal matrix, in the presence of a solvent, is carried out until an average particle size d ₅₀ is reached from 1 to 20 μm, preferably from 1 to 10 μm, and the particle size of the powder measured by laser diffraction. 9. The method according to claim 7 or 8, in which the granules obtained by crushing tapes, sheets or rods have an average particle size d ₅₀ from 0.5 to 10 mm, preferably from 1 to 5 mm, while the size of the granules is measured using dynamic image analysis. 10. The method for manufacturing a composite cast wear component with a hierarchical structure according to claim 6, in which step b) includes the following steps: - mixing cermet composite granules with from 1 to 8 wt.%, preferably from 2 to 6 wt.% adhesive; - pouring the mixture and compacting it in the first mold; - drying the mixture at a suitable temperature and duration to remove the solvent from the adhesive or to allow curing; - extracting the dried mixture from the mold and obtaining a three-dimensionally connected network of periodically alternating millimeter cermet composite granules with millimeter gaps for use as reinforcement in the wear part of the wear component with a hierarchical structure.

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