A method for manufacturing a graded composite cast wear part

Abstract

A graded composite wear part comprising a reinforcement in the most exposed to wear part, the reinforcement comprising a three-dimensional interconnecting network of periodically alternating millimeter-sized ceramic-metal composite granules and millimeter-sized interstitials, the ceramic-metal composite granules comprising at least 52 vol%, preferably at least 61 vol%, more preferably at least 70 vol% of micrometer-sized titanium carbide particles embedded in a first metal matrix, the ceramic-metal composite granules having a density of at least 4.8 g / cm 3 3, the three-dimensional interconnecting network of ceramic-metal composite granules and their millimeter-sized interstitials being embedded in a second metal matrix, the reinforcement comprising on average at least 23 vol%, more preferably at least 28 vol%, most preferably at least 30 vol% of titanium carbide, the first metal matrix being different from the second metal matrix, the second metal matrix comprising a cast ferrous alloy.

Description

[0001] This application is a divisional application of the application that entered the Chinese national phase on October 14, 2021, with application number 202180002908.4. Technical Field

[0002] This invention relates to a method for manufacturing graded composite wear parts with improved resistance to combined wear / impact stresses using casting technology. The wear part comprises a three-dimensional network of aggregated millimeter-scale ceramic-metal composite particles with millimeter-scale gaps, wherein micron-scale TiC-based particles are embedded in a binder referred to as a first metal matrix, and the millimeter-scale gaps are filled by a cast metal referred to in this invention as a second metal matrix. Background Technology

[0003] This invention relates to a method for manufacturing wear parts for use in grinding and crushing industries (such as cement plants, quarries, and mines). These parts are often subjected to high mechanical stress in their main body and high frictional wear on their working surfaces. Therefore, it is desirable for these parts to exhibit high wear resistance and a certain degree of ductility in order to withstand mechanical stresses such as impacts.

[0004] Considering that these two properties are difficult to satisfy with the same material composition, composite material components have been proposed in the past, which have a core made of a relatively ductile alloy and embedded ceramic inserts with good wear resistance in the core.

[0005] Document US 4,119,459 (Sandvik, 1977) discloses a composite wear body composed of cast iron and sintered cemented carbide granules. The cemented carbide in the binder metal is of the WC-Co type and may contain carbides of Ti, Ta, Nb, or other metals. No indication is given regarding the possible volume percentage of TiC in the granules or in the reinforcing portions of the wear body.

[0006] Document US 4,626,464 (Krupp, 1984) discloses a hammerhead to be mounted in a hammer, which, in addition to comprising an iron alloy, includes a metal alloy base material and a wear-resistant zone containing hard metal particles having a diameter from 0.1 to 20 mm, and wherein the percentage of hard metal particles in the wear-resistant zone is between 25 and 95% by volume; and wherein said hard particles are firmly embedded within the metal alloy base material. The average volume concentration of TiC, possibly in the reinforcing portion, is not disclosed in this document.

[0007] US 5,066,546 (Kennametal, 1989) discloses a graded wear body comprising at least one layer of a series of carbide materials, wherein titanium carbide is embedded in a cast steel matrix. The carbide materials have a particle size between 4.7 and 9.5 mm, and are in the form of pulverized parts, powders, or compressed bodies with irregular shapes. This document does not disclose the average concentration of TiC in the reinforcing portion of the wear body, nor the composition of the reinforcing structure.

[0008] Document US 8,999,518 B2 discloses a hierarchical composite material comprising an iron alloy reinforced with titanium carbide according to a defined geometry, wherein the reinforcing portion comprises an alternating macro-microstructure consisting of millimeter-sized regions containing micron-sized titanium carbide spherical particles spaced apart by millimeter-sized regions (which are essentially free of micron-sized titanium carbide spherical particles and filled with the iron alloy). In this patent, the maximum TiC concentration is 72.2 vol% when the powder blend of Ti and C is compressed at 95% of its maximum relative density. The porosity of the particles is greater than 5 vol%, and only one metallic matrix (cast metal) is present in the absence of any possible reaction moderators. This hierarchical composite material is obtained by self-propagating high-temperature synthesis (SHS), where reaction temperatures are typically reached above 1,500 °C, or even 2,000 °C. Only a small amount of energy is required to locally initiate the reaction. The reaction then spontaneously propagates throughout the reagent mixture.

[0009] The graded composite material in this document is obtained by reacting a granular mixture containing carbon and titanium powder in a mold. Following the initiation of the reaction, a reaction front is formed, which thus spontaneously propagates (self-propagating) and allows for the acquisition of titanium carbide from both titanium and carbon. The resulting titanium carbide is said to be "obtained in situ" because it is not derived from cast iron alloys. This reaction is initiated by the heat of casting in cast iron or steel used for casting the entire part and therefore for casting both the unreinforced and reinforced portions. The Ti + C → TiC SHS reaction is highly exothermic, with a theoretical adiabatic temperature of 3290 K.

[0010] Unfortunately, the increased temperature caused the reactants (i.e., the volatiles they contained (H₂O from carbon, H₂ from titanium, N₂)) to degas. All impurities contained in the reactant powder, and organic or inorganic components around or inside the powder / compacted particles, volatilized. To weaken the reaction between carbon and titanium, iron alloy powder was added as a moderator to absorb heat and lower the temperature. However, this also reduced the maximum achievable TiC concentration in the eventually worn parts, and in practice, it was no longer possible to achieve the aforementioned theoretical concentration of 72.2% on a production scale.

[0011] Document WO 2010 / 031663 A1 relates to a composite impactor for an impact crusher, the impactor comprising an iron alloy, which is at least partially reinforced with titanium carbide in a defined shape according to the same method as described in the aforementioned document US 8,999,518 B2. Iron alloy powder is added to reduce the intensity of the reaction between carbon and titanium. In the example of this document, the reinforced region contains approximately 30% TiC by volume. For this purpose, strips with a relative density of 85% are obtained by compaction. After crushing the strips, the resulting granules are sieved to achieve a size between 1 and 5 mm, preferably between 1.5 and 4 mm. A particle size of 2 g / cm³ is obtained. 3 The bulk density is within the range (45% space between particles + 15% porosity in the particles). Therefore, the particles in the wear part to be reinforced contain 55 vol% porous particles. In this case, the concentration of TiC in the reinforcing region is only 30%, which is not always sufficient and may have a negative impact on the wear performance of the casting, especially in the case of particles with high porosity before the SHS reaction.

[0012] Document US 2018 / 0369905 A1 discloses a method for providing more precise control over the SHS process during casting by using a moderator. The casting insert is made from a powder mixture containing reactants that form TiC and a moderator consisting of casting high-manganese steel containing 21% Mn.

[0013] Purpose of the invention

[0014] This invention aims to provide a graded composite wear component produced by conventional casting, comprising a cast iron or steel metal matrix combined with a reinforcing structure having a high concentration of micron-sized titanium carbide particles embedded in a metal binder (first metal matrix) (forming low-porosity ceramic-metal composite granules). The first metal matrix containing micron-sized titanium carbide particles in the reinforcing portion is different from the metal matrix present in the rest of the composite wear component.

[0015] Another object of the present invention is to provide a safe manufacturing method for enhanced composite wear parts that avoids the release of gases and provides improved composite wear parts with good resistance to impact and corrosion. Summary of the Invention

[0016] A first aspect of the invention relates to a graded composite wear component comprising a reinforcement in the portion most exposed to wear, the reinforcement comprising a three-dimensional interconnected network of periodically alternating millimeter-sized ceramic-metal composite particles with millimeter-sized gaps, the ceramic-metal composite particles comprising at least 52 vol%, preferably at least 61 vol%, more preferably at least 70 vol%, micron-sized titanium carbide particles embedded in a first metal matrix, these ceramic-metal composite particles having a density of at least 4.8 g / cm³. 3 The density of the ceramic-metal composite material particles and their three-dimensional interconnected network with millimeter-level gaps are embedded in a second metal matrix, the reinforcement comprising at least 23 vol%, more preferably at least 28 vol%, and most preferably at least 30 vol% titanium carbide on average, the first metal matrix being different from the second metal matrix, the second metal matrix comprising a cast iron alloy.

[0017] According to a preferred embodiment of the invention, the composite material wear component is further characterized by one or a suitable combination of the following features:

[0018] - The ceramic-metal composite material granules have a porosity of less than 5% vol, preferably less than 3% vol, and more preferably less than 2%;

[0019] - These embedded ceramic-metal composite particles have an average particle size d50 between 0.5 and 10 mm, preferably between 1 and 5 mm;

[0020] - These embedded titanium carbide particles have an average particle size d50 between 0.1 and 50 μm, preferably between 1 and 20 μm;

[0021] - The first metal matrix is ​​selected from the group consisting of iron-based alloys, iron-manganese-based alloys, iron-chromium-based alloys, and nickel-based alloys;

[0022] - The second metal matrix contains iron alloys, especially high-chromium white cast iron or steel.

[0023] This invention further discloses a method for manufacturing ceramic-metal composite granules, the method comprising the following steps:

[0024] - The powder composition containing TiC and a first metal matrix is ​​milled in the presence of a solvent to preferably achieve an average particle size d50 between 1 and 20 μm, and more preferably between 1 and 10 μm;

[0025] - Mix 1% to 10%, preferably 1% to 6%, of wax into the powder composition;

[0026] - The solvent is removed by vacuum drying to obtain an agglomerated powder;

[0027] - Compact the agglomerated powder into strips, sheets or rods;

[0028] - Crush strips, sheets or rods into granules with a preferred average particle size d50 between 0.5 and 10 mm, preferably between 1 and 5 mm;

[0029] - Sinter in a vacuum or inert atmosphere furnace at a temperature between 1000°C and 1600°C until a minimum of 4.8 g / cm³ is achieved. 3 The density.

[0030] This invention further discloses a method for manufacturing the composite material wear component of this invention, the method comprising the following steps:

[0031] - The ceramic-metal composite material granules obtained according to the present invention are mixed with about 1 to 8 wt%, preferably 2 to 6 wt%, of adhesive;

[0032] Pour the mixture into the first mold and compact it;

[0033] - Dry the mixture at an appropriate temperature and time to remove the solvent from the adhesive or to allow it to harden;

[0034] - The dried mixture is demolded to obtain a three-dimensional interconnected network of periodically alternating millimeter-scale ceramic-metal composite particles with millimeter-scale gaps, which can be used as reinforcement in the worn portions of graded wear parts.

[0035] According to a preferred embodiment of the present invention, the method for manufacturing wear parts is further characterized by the following steps or a suitable combination thereof:

[0036] - Position the three-dimensional interconnected network of periodically alternating millimeter-scale ceramic-metal composite particles with millimeter-scale gaps within a portion of the volume of the mold for casting the graded composite material wear parts to be cast;

[0037] - Pour the second metal matrix into the second mold—the mold for casting the worn parts—and simultaneously penetrate the millimeter-level gaps of the three-dimensional interconnect network;

[0038] - Demold the wear parts cast from the graded composite material.

[0039] The present invention further discloses a graded composite material casting wear component obtained by the method of the present invention. Attached Figure Description

[0040] Figure 1 The anvil ring of a milling machine is shown, in which the invention is tested.

[0041] Figure 2 express Figure 1 A single anvil of the anvil ring.

[0042] Figure 3 A single anvil indicating wear.

[0043] Figure 4 This is a schematic diagram of positioning the reinforcement structure in the most wear-exposed part of a single anvil.

[0044] Figure 5 This is an overall view of an enhanced structure defined as a three-dimensional interconnected network of periodically alternating millimeter-scale ceramic-metal composite particles with millimeter-scale gaps.

[0045] Figure 6 and Figure 7 express Figure 5 An enlarged view of the enhanced structure.

[0046] Figure 8 A cross-sectional view of a cast wear component having millimeter-scale ceramic-metal composite granular inclusions and gaps (voids) filled by a second metal matrix (cast metal matrix).

[0047] Figure 9 This image shows tiny spherical TiC particles embedded in a first metal matrix (the binder for the TiC particles). Figure 8 The image shows a high-magnification magnification of a single ceramic-metal composite particle.

[0048] Figure 10 This is a schematic diagram of the concept of the present invention, which is based on the scale difference between micron-sized TiC particles embedded in a first metal matrix of millimeter-sized granules of a ceramic-metal composite material that is incorporated in the reinforcing portion of a wear component in the form of a three-dimensional network.

[0049] Figure 11 This is a cross-sectional view of a sample containing granules. This cross-section is used in methods for obtaining the average particle size of ceramic-metal granules (explained below).

[0050] Figure 12 This is a schematic diagram of a method for measuring Feret diameters (minimum and maximum Feret diameters). These Feret diameters are used in methods for obtaining the average particle size of ceramic-metal granules (explained below). Detailed Implementation

[0051] This invention relates to a method for manufacturing graded composite wear parts produced by conventional casting. The graded composite wear parts consist of a metal matrix comprising a specific reinforcing structure comprising dense (<5% low porosity) irregular ceramic-metal composite particles having an average particle size in the millimeter range of 0.5 to 10 mm, preferably 0.8 to 6 mm, more preferably 1 to 4 mm, and even more preferably 1 to 3 mm.

[0052] The ceramic-metal composite material comprises ceramic particles bonded together by a metallic binder referred to in this invention as a first metallic matrix. For wear applications, the ceramic provides high wear resistance, while the metal improves toughness (among other properties). The TiC ceramic-metal composite material comprises micron-sized spherical titanium carbide particles (52 to 95 vol%, preferably 61 to 90 vol%, more preferably 70 to 90 vol%, with a particle size of 0.1 to 50 μm, preferably 0.5 to 20 μm, more preferably 1 to 10 μm) bonded together by a metallic phase (first metallic matrix), which may be based on, for example, Fe, Ni, or Mo. A ferroalloy, preferably chromium cast iron, or steel (second metallic matrix) is cast in a mold and diffused only into the gaps of the reinforcing structure.

[0053] In this invention, the expression TiC should not be understood as having a strict stoichiometric chemical meaning, but rather as titanium carbide exhibiting its crystallographic structure. Titanium carbide has a wide compositional range, wherein the C / Ti stoichiometry varies from 0.47 to 1, preferably above 0.8.

[0054] In the inserts that form the reinforcing volume of the wear parts, the volume content of ceramic-metal composite particles (excluding hollow portions or recesses, if present) typically accounts for between 45 and 65 vol%, preferably between 50 and 60 vol%, resulting in an average TiC concentration in the reinforcing volume of between 23 and 62 vol%, preferably between 28 and 60 vol%, and more preferably between 30 and 55 vol%.

[0055] The graded reinforcement portion of the wear component is generated by aggregates of irregular millimeter-sized ceramic-metal composite particles having an average particle size of approximately 0.5 to 10 mm, preferably 0.8 to 6 mm, more preferably 1 to 4 mm, and even more preferably 1 to 3 mm.

[0056] The ceramic-metal composite granules are preferably aggregated into a desired three-dimensional shape using an adhesive (such as an inorganic material like well-known sodium (or potassium) silicate glass glue or an organic material like polyurethane or phenolic resin) or within a container or behind a barrier (usually metallic, but the container or barrier can also be ceramic, generally inorganic or organic). This desired shape forms an open structure from a three-dimensional interconnected network of agglomerated / aggregated ceramic-metal composite granules, which are held together by an adhesive or maintained in shape by a container or barrier, wherein the filling of the granules leaves millimeter-sized open gaps between the granules, which can be filled by liquid casting metal. This agglomerate is placed or located in a mold before the ferroalloy is poured to form the reinforcing portion of the wear part. Liquid metal is then poured into the mold and fills the open gaps between the granules. The millimeter-sized gaps should be understood as 0.1 to 5 mm, preferably 0.5 to 3 mm, depending on the compaction of the reinforcing structure and the particle size of the granules.

[0057] Ceramic-metal composite granules are typically manufactured in a conventional manner by powder metallurgy, which involves shaping a blend of ceramic and metal powders with appropriate particle size distribution, followed by liquid-phase sintering.

[0058] Typically, the powder has a diameter of 0.1-50 μm and contains TiC as the main component and 5-48 percent of a metal binder, which can be a separate constituent powder or an alloyed powder (first metal matrix). The powder is first mixed and / or ground (depending on the initial powder particle size) in a ball mill, either dry or wet (with alcohol to avoid, for example, oxidation of the metal powder). Organic additives may be added to aid dispersion or forming purposes. A drying step may be required in the case of wet grinding. This can be accomplished, for example, by vacuum drying or spray drying. Forming is typically carried out by uniaxial cold isostatic pressing, injection molding, or any other forming method to form strips, rods, or sheets.

[0059] For example, strips or sheets can be crushed into granules and possibly sieved. Irregular granular shapes without easily pull-out orientation can advantageously be achieved (the granules are mechanically well retained in the cast metal). The pressed, extruded, or crushed granules are then sintered at a suitable temperature under low or high vacuum, inert gas, hydrogen, or combinations thereof. During liquid-phase sintering, particle rearrangement occurs driven by capillary forces.

[0060] The casting alloy (second metal matrix) of the embedded ceramic-metal composite granules in the wear parts is preferably an iron alloy (chromium white cast iron, steel, manganese steel, etc.), a nickel alloy, or a molybdenum alloy. This alloy can be selected to achieve locally optimized properties according to the final requirements of the wear parts (e.g., manganese steel will provide high impact resistance, high-chromium white cast iron will provide high wear resistance, and nickel alloys will provide excellent heat resistance and corrosion resistance, etc.).

[0061] advantage

[0062] This invention allows for the attainment of very high (52 to 95% by volume) TiC particle concentrations in ceramic-metal composite pellets within conventional castings, without defects (porosity, cracks, inhomogeneity, etc.) or uncontrolled and dangerous reactions within the cast structure, and without the risk of splashing that can lead to the in-situ formation of TiC in a self-propagating exothermic reaction (SHS, see above).

[0063] In this invention, a favorable average concentration of TiC can be achieved in the reinforced volume of the wear part via the low porosity of the ceramic-metal composite particles. The compaction / packing density of the ceramic-metal composite particles in the reinforced volume can reach a value of up to approximately 62 vol%.

[0064] The graded wear component of the present invention is essentially free of porosity and cracks, resulting in better mechanical and wear properties.

[0065] The particle size of the titanium carbide particles and ceramic-metal composite granules (TiC + binder) of the present invention can be extensively controlled during the manufacturing process (selection of raw materials, grinding, forming process, and sintering conditions). The use of sintered millimeter-sized TiC-based ceramic-metal composite granules prepared by well-known powder metallurgy allows for control of particle size and porosity, the use of metal alloys of various compositions as the first metal matrix, high TiC concentration, easy forming of inserts without extensive manual labor, and good internal condition of the particles even after dumping and under high thermal shock conditions.

[0066] Manufacturing of ceramic-metal composite granules:

[0067] As described above, in a ball mill, inorganic TiC powder (52 to 95 vol%, preferably 61 to 90 vol%, more preferably 70 to 90 vol%) and metal powder as the first metal matrix (5 to 48 vol%, preferably 10 to 39 vol%, more preferably 10 to 30 vol%) are ground and / or mixed with a liquid (which, depending on the sensitivity of the metal binder to oxidation). Various additives (antioxidants, dispersants, binders, plasticizers, lubricants, waxes for pressing, etc.) may also be added for various purposes.

[0068] Once the desired average particle size is reached (typically less than 20 μm, preferably less than 10 μm, more preferably less than 5 μm), the slurry is dried (by vacuum drying or spray drying) to obtain a powder agglomerate containing organic additives.

[0069] The agglomerated powder is introduced into a granulation unit via a hopper. This machine includes two rollers under pressure, through which the powder passes and is compacted. At the outlet, a continuous strip (sheet) of compressed material is obtained, which is then pulverized to obtain ceramic-metal composite granules. These granules are then screened to the desired particle size. Fractions of undesirable particle sizes are arbitrarily recycled. The resulting granules typically have a relative density of 40% to 70% (depending on the powder compaction level and blend composition).

[0070] The particle size distribution and shape of the granules can also be adjusted to a near-cubic or flattened shape depending on the pulverization method (impact pulverization will provide more cubic granules while compression pulverization will provide more flattened granules). The resulting granules generally have a particle size that, after sintering, will provide granules between 0.5 and 10 mm, preferably 0.8 to 6 mm, more preferably from 1 to 4 mm, and even more preferably from 1 to 3 mm. Granules can also be obtained by conventionally uniaxially pressing or granulating the powder blend directly before or after sintering into particles or larger parts (which will be further pulverized into granules).

[0071] Finally, liquid phase sintering can be carried out in a furnace at a temperature of 1000°C-1600°C under vacuum, N2, Ar, H2 or a mixture (depending on the metal phase (type and amount of binder)) for several minutes or hours until the desired porosity (preferably less than 5%, more preferably less than 3%, and most preferably less than 2%) is achieved.

[0072] Realization of a three-dimensional reinforced structure (core)

[0073] As described above, ceramic-metal composite granules are agglomerated by means of a binder, by confining them in a container, or by any other means. The binder accounts for no more than 10 wt% of the total weight of the granules, and is preferably between 2 and 7 wt%. This binder can be inorganic or organic. Binders based on sodium silicate or potassium silicate, or on polyurethane or phenolic resins, can be used.

[0074] A ceramic-metal composite granule with low porosity is mixed with a binder (typically an inorganic silicate adhesive) and placed in a mold (e.g., silicone) of the desired shape. After the adhesive solidifies (e.g., after water drying of the inorganic silicate adhesive at 100°C; for example, for polyurethane-based adhesives, solidification can also be achieved by purging with CO2 or an amine-based gas), the core hardens and can be demolded. Depending on the granule shape, particle size distribution, vibration during granule positioning, or tapping of the granule bed during core preparation, the core in a three-dimensional interconnected network typically comprises 30 to 70 vol%, preferably 40 to 60 vol%, of dense granules and 70 to 30 vol%, preferably 60 to 40 vol%, of voids (millimeter-scale gaps).

[0075] Casting of wear parts

[0076] The core (three-dimensional reinforcement structure) is positioned and secured to the mold portion of the wear part to be reinforced using screws or any other available means. Then, hot liquid iron alloy, preferably chromium white cast iron or steel, is poured into the mold.

[0077] Therefore, the hydrothermal iron alloy only fills the millimeter-scale gaps between the granules in the core. If an inorganic adhesive is used, the limited melting of the metallic binder (first metal matrix) on the granule surface causes extremely strong adhesion between the granules and the second alloy matrix. When an organic adhesive containing sodium silicate is used, metallic adhesion is limited but can still occur on the granule surface not covered by the adhesive.

[0078] In contrast to existing technologies, there is no reaction (exothermic reaction or gas release) or shrinkage (24% volume reduction for the Ti+C→TiC reaction) during pouring, and the cast metal will penetrate into the gaps (millimeters of space between the particles) but not into the ceramic-metal composite particles (because they are not porous).

[0079] Measurement methods

[0080] For porosity, granular, or particle size measurements, samples prepared for metallographic examination should be free of grinding and polishing marks. Care must be taken to avoid tearing out particles (which could lead to misleading assessments of porosity). Guidelines for sample preparation can be found in ISO 4499-1:2020 and ISO 4499-3:2016, 8.1 and 8.2.

[0081] Porosity determination:

[0082] The volume fraction of porosity of free aggregate can be calculated from the measured density and theoretical density of the aggregate.

[0083] The volume fraction of porosity in the particles embedded in the metal matrix was measured according to ISO 13383-2:2012. While this standard is particularly suitable for fine ceramics, the method for measuring the volume fraction of porosity described herein can also be applied to other materials. Since this sample is not a pure fine ceramic but a hard metal composite, sample preparation should be performed according to ISO 4499-1:2020 and ISO 4499-3:2016, 8.1 and 8.2. Etching is unnecessary for porosity measurement, but it can still be performed since it does not alter the measurement results.

[0084] Average particle size of titanium carbide:

[0085] The average particle size of the embedded titanium carbide particles was calculated using the truncation method according to ISO 4499-3:2016. Five images of the microstructure of five different particles were taken using an optical or electron microscope at a known magnification (ensuring 10 to 20 titanium carbide particles are present in the entire field of view). Four truncation normals were drawn in each calibrated image, such that each particle is crossed by a line no more than once.

[0086] When a line is used to cut off a particle of titanium carbide, the length of the line is measured using a calibrated ruler (l). i (where i = 1, 2, 3...n for the 1st, 2nd, 3rd, ..., nth particles). Incomplete particles that touch the edges of the image must be ignored. At least 200 particles must be counted.

[0087] The average intercept granularity is defined as follows:

[0088]

[0089] Average particle size of ceramic-metal granules:

[0090] A panoramic photomicrograph of a polished section of a sample is produced using a computer program and optical microscope (e.g., a panoramic view of the entire field of view obtained via Alicona Infinite Focus) through stitching (the process of merging a series of digital images of different parts of an object into a well-defined panoramic view of the entire object), ensuring that at least 250 ceramic-metal particles are present throughout the field of view. An appropriate threshold allows the grayscale image to be segmented into relevant features (particles) and background (see [link to relevant image]). Figure 11 If the thresholds are inconsistent due to poor image quality, the manual stage, which includes manually drawing the granules, scale (if available), and image boundaries on tracing paper, is then scanned using that tracing paper.

[0091] The Ferrette diameter of each pellet is measured in all directions using image analysis software (such as ImageJ), and is the distance between two tangents placed perpendicular to the measurement direction. An example is provided. Figure 12 The information is provided in the text.

[0092] The minimum and maximum Ferete diameters for each particle in the image were determined. The minimum Ferete diameter is the shortest Ferete diameter in the set of measured Ferete diameters. The maximum Ferete diameter is the longest Ferete diameter in the set of measured Ferete diameters. Particles touching the edges of the image must be ignored. The average of the minimum and maximum Ferete diameters for each particle is considered as the equivalent diameter x. The volumetric particle size distribution q3(x) of the particles is then calculated based on the sphere diameter x.

[0093] D of granules 50 Interpreted as volume-weighted average particle size according to ISO 9276-2:2014

[0094] Average particle size of ceramic-metal granules during pellet manufacturing:

[0095] The particle size was measured according to ISO 13322-2:2006 using a Camsizer from Retsch via dynamic image analysis. The particle diameter used for particle size distribution is X. c min, It is the shortest chord measured in the set of maximum chords of particle projection (for results close to screening / sieving).

[0096] Granular material d 50 Based on X c min The volume-weighted average granularity of the volume distribution.

[0097] Particle size measurement of the powder during grinding:

[0098] During grinding, the particle size of the powder was measured using laser diffraction employing MIE theory, following the guidelines given in ISO 13320:2020, with the aid of a Mastersizer 2000 from Malvern Instruments. The refractive index of TiC was set to 3, and the absorption was set to 1. The dimness had to be in the range of 10% to 15%, and the weighted residual had to be less than 1%.

[0099] Density measurement of sintered granules:

[0100] The density of the sintered pellets was determined using water according to ISO 3369:2006. For pellets without any open porosity, a gas-displacement hydrometer (e.g., the AccuPyc II 1345 hydrometer from Micromeritics) can also be used to give essentially the same density value.

[0101] Implementation - Anvil Wear Parts

[0102] According to the present invention, an anvil wear part for a vertical shaft impactor has been realized. The reinforcing volume of the wear part contains TiC with varying average volume percentages ranging from about 30 to 50 vol%.

[0103] They were compared with wear parts made according to US 8,999,518 B2 (Inventor's Example 4) (about 32 vol% of TiC in the reinforced volume, total volume percentage).

[0104] 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 can be carefully controlled in a factory, although it still produces a large amount of flame, gas and hot liquid metal splashes during pouring.

[0105] Example

[0106] Granule preparation:

[0107] The following raw materials are used in three different types of ceramic-metal composite pellets:

[0108] TiC powder less than 325 mesh

[0109] Iron powder smaller than 325 mesh

[0110] Manganese powder less than 325 mesh

[0111] Nickel powder smaller than 325 mesh

[0112] 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 sintering density 6.22 5.68 5.22

[0113] Table 1

[0114] The powders according to the composition in Table 1 were mixed and ground with alcohol and metal balls in a ball mill for 24 hours to achieve an average particle size of 3 μm.

[0115] An organic wax binder comprising 4 wt% of the powder was added and mixed with the powder. The alcohol was removed by passing it through a vacuum dryer equipped with rotating blades (the alcohol was condensed for reuse). The resulting agglomerated powder was then sieved through a 100 μm sieve. Strips of 60% of the theoretical density of the inorganic / metallic powder mixture were prepared by compaction between rotating rollers of a roller compactor granulator. The strips were then pulverized into irregular granules by forcing them through a sieve with an appropriate mesh size. After pulverization, the granules were sieved to obtain a size between 1.4 mm and 4 mm. These irregular porous granules were then sintered at high temperature (1000℃–1600℃ for several minutes or hours) in a vacuum furnace with low partial pressure argon until a minimum porosity (<5 vol%) and greater than 5 g / cm³ were achieved. 3 The density.

[0116] The sintered granules with a low porosity of <5 vol% are then mixed with approximately 4 wt% inorganic silicate adhesive and poured into a silicone mold with the desired shape of 100 x 30 x 150 mm (vibration can be applied to ensure filling and that all granules are properly filled). After drying in an oven at 100°C for several hours to remove water from the silicate adhesive, the core is hard enough to be demolded.

[0117] These cores, such as Figure 5 As shown, it contains approximately 55 vol% dense granules (45 vol% voids / millimeter-level gaps between granules). Each core / 3D reinforcement structure is positioned in a mold within the portion of the worn part to be reinforced (e.g., Figure 4 (As shown in the diagram). The hot-liquid high-chromium white cast iron is then poured into a mold. Thus, the gaps between the particles of the hot-liquid high-chromium white cast iron filler core are approximately 45 vol% in the millimeter range. After pouring, a region of approximately 57 vol% to 90 vol% of titanium carbide particles, bonded together with a different metallic phase (first metallic matrix) from the rest of the wear part (where the casting alloy (second metallic matrix) is present), is obtained in the reinforced portion. The total volume content of TiC in the reinforced macro-microstructure of the wear part varies from approximately 32 to 50 vol% in Examples 1 to 3, but can reach even higher values.

[0118] Comparison with existing technologies

[0119] The wear part according to the present invention is compared with the wear part obtained in Example 4, similar to US 8,999,518 B2.

[0120] The anvil of the milling machine (in which these tests are performed) is shown. Figure 1 middle.

[0121] In this machine, the inventors alternately place an anvil (such as an inlay) according to the invention. Figure 2 and Figure 3 As shown in the figure, it is surrounded on both sides by a reinforcing anvil according to embodiment 4 of prior art US 8,999,518 B2 to evaluate wear under exactly the same conditions.

[0122] The material to be pulverized is projected at high speed onto the working surface of the anvil (a single anvil before wear is shown). Figure 2 (Middle). During crushing, the working surface is worn down. The worn anvil is shown. Figure 3 middle.

[0123] For each anvil, the weight loss rate is measured by weighing each anvil before and after use.

[0124] Weight loss rate = (final weight - initial weight) / initial weight

[0125] The performance index is defined as follows: the reference weight loss rate is the average weight loss rate of the anvil of Example 4 of US 8,999,518 B2 on each side of the test anvil.

[0126] PI = Reference weight loss rate / Test anvil weight loss rate

[0127] A performance index higher than 1 means that the test anvil has less wear than the reference anvil, while a value lower than 1 means that the test anvil has more wear than the reference anvil.

[0128] According to the present invention Example 1 The performance index (PI) of the reinforcing anvil (ceramic-metal composite particles containing 57 vol% (45 wt%) of titanium carbide) is 1.05 (the higher performance of the ceramic-metal composite particles with a local volume content close to that of Example 4 of US 8,999,518 B2 can be explained by the lower defects such as cracks and porosity in this part).

[0129] According to the present invention Example 2 The performance index (PI) of the reinforcing anvil (containing 75 vol% (65 wt%) of titanium carbide ceramic-metal composite particles) is 1.16.

[0130] The performance index (PI) of the reinforcing anvil (ceramic-metal composite particles containing 90 vol% (85 wt%) of titanium carbide) according to Example 3 of the present invention is 1.24.

[0131]

[0132] Table 2

[0133] Composite density varies with the porosity and density of the blend (titanium carbide and alloys).

[0134] The following are two tables showing the density of composite materials as a function of TiC %vol and porosity %vol (for iron and nickel-based alloys).

[0135]

[0136] Table 3

[0137]

[0138]

[0139] Table 4

[0140]

[0141] Table 5

[0142] Advantages of the present invention

[0143] Compared with the prior art, the present invention has the following advantages in general:

[0144] • Better wear performance due to the locally higher vol% TiC content in the granules (which is impossible to achieve in practice using existing SHS technology).

[0145] • By customizing the size and volume content of titanium carbide and combining a metallic phase binder (first metallic matrix) such as high mechanical property manganese steel in TiC ceramic-metal composite granules with a casting alloy (second metallic matrix) such as high chromium white cast iron for wear parts, the wear performance or mechanical properties of the wear parts are better.

[0146] • Because no gas is generated during pouring and TiC is uniformly dispersed, resulting in lower porosity and / or fewer crack defects, the wear performance or mechanical properties of the worn parts are better.

[0147] Because there is no dangerous exothermic reaction during pouring that involves the release of flammable gases or splashing of molten metal, it is safer during manufacturing.

[0148] • Because the granules are prepared from raw materials with lower handling risks (Fe powder is less explosive than highly explosive Ti powder), the manufacturing process is safer.

Claims

1. A method for manufacturing a graded composite cast wear part comprising a cast iron alloy reinforced in the most wear-exposed portion by a reinforcement comprising a three-dimensional interconnected network of periodically alternating sintered ceramic-metal composite particles with millimeter-scale gaps, the ceramic-metal composite particles having a porosity of less than 5 vol% and comprising at least 52 vol% of micron-sized titanium carbide particles embedded in a binder metal matrix, the reinforcement comprising a ceramic-metal composite particle volume fraction between 45 and 65 vol%, the method comprising the following steps: a) Providing or preparing ceramic-metal composite pellets comprising at least 52 vol% of micron-sized titanium carbide particles embedded in a binder metal matrix, the ceramic-metal composite pellets having an average particle size d50 between 0.5 and 10 mm and a porosity of less than 5 vol%. b) Prepare a three-dimensional interconnected network of periodically alternating ceramic-metal composite particles with millimeter-scale gaps using the particles from step a). c) Locate the three-dimensional interconnect network obtained in step b) in the part of the mold that is most exposed to wear and needs to be reinforced; d) Pour off the cast wear part and simultaneously infiltrate the gaps in the three-dimensional interconnect network positioned according to step c) with cast iron alloy; e) Demold the wear parts cast from the graded composite material.

2. The method for manufacturing graded composite material cast wear parts according to claim 1, wherein, The ceramic-metal composite granules have a porosity of less than 3 vol% and contain at least 52 vol% of micron-sized titanium carbide particles embedded in a binder metal matrix.

3. The method for manufacturing graded composite material cast wear parts according to claim 1, wherein, These ceramic-metal composite particles have an average particle size d50 between 1 and 5 mm and a porosity of less than 3 vol%.

4. The method for manufacturing graded composite material cast wear parts according to claim 1, wherein, The preparation of step a) includes the following steps: - Grinding a powder composition containing titanium carbide and the binder metal matrix in the presence of a solvent; - The solvent is removed by drying to obtain an agglomerated powder; - Mix 1% to 10% of the wax into the powder composition; - Compact the agglomerated powder into strips, sheets or rods; - Crush these strips, sheets or rods into granules; - The granules are sintered in a vacuum or inert atmosphere furnace at a temperature between 1000°C and 1600°C until the desired ceramic-metal granules are obtained, the desired granules having a porosity of less than 5 vol% and a density of at least 4.8 g / cm³, the density of the ceramic-metal composite granules being determined with water according to ISO 3369:2006.

5. The method for manufacturing graded composite material cast wear parts according to claim 4, wherein, 1% to 6% of wax is mixed into the powder composition.

6. The method for manufacturing graded composite material cast wear parts according to claim 4, wherein, The desired granules have a porosity of less than 3 vol%.

7. The method of claim 4, wherein the step of milling the powder composition comprising titanium carbide and the binder metal matrix in the presence of a solvent is performed until an average particle size d50 between 0.1 and 50 µm is obtained, the particle size of which is measured by laser diffraction using MIE theory according to the guidelines given in ISO 13320:2020, wherein the refractive index of TiC is set to 3, the absorption is set to 1, the luminosity is in the range of 10% to 15%, and the weighted residual is less than 1%.

8. The method of claim 7, wherein the step of milling the powder composition comprising titanium carbide and the binder metal matrix in the presence of a solvent is performed until an average particle size d50 between 1 and 20 µm is obtained.

9. The method of claim 7, wherein the step of milling the powder composition comprising titanium carbide and the binder metal matrix in the presence of a solvent is performed until an average particle size d50 between 1 and 10 µm is obtained.

10. The method of claim 1, wherein the adhesive metal matrix is ​​selected from the group consisting of iron-based alloys, iron-manganese-based alloys, iron-chromium-based alloys, and nickel-based alloys.

11. The method of claim 4, wherein step b) comprises the following steps: - The obtained ceramic-metal composite pellets are mixed with 1 to 8 wt% of adhesive; Pour the mixture into the first mold and compact it; - Dry the mixture at an appropriate temperature and time to remove the solvent from the adhesive or to cure the adhesive; - The dried mixture is demolded to obtain a three-dimensional interconnected network of periodically alternating millimeter-scale ceramic-metal composite particles and gaps to be used as a reinforcement in the most wear-exposed parts of graded wear components.

12. The method according to claim 11, wherein, The obtained ceramic-metal composite granules were mixed with 2 to 6 wt% of adhesive.

13. The method of claim 1, wherein the cast iron alloy comprises high-chromium white cast iron or steel.

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