Thread Content
1. Powder: Powder generally refers to a collection of discrete particles with sizes ranging from 0.1 um to 1 mm. Slurry: a pourable, viscous dispersion formed by powder in a liquid. The blank feedstock is a plasticized powder used as raw material for injection molding or powder extrusion. Atomized powder: Powder in which molten metal or alloy is dispersed into droplets and then solidified into individual particles. (The dispersion medium is usually a high-speed gas or liquid stream.) Carbyl powder: a powder obtained by the thermal decomposition of metal carbyl compounds. Electrolytic powder: A powder produced by electrodeposition. Reduced powder: A powder produced by reducing metal compounds using chemical reduction methods. Sponge powder: a porous reduced powder obtained by crushing highly porous metal sponges produced by the reduction method. Alloyed powder is a metal powder obtained by partially or fully alloying two or more components. Pre-alloyed powder generally refers to a fully alloyed powder produced by atomizing a melt. Composite powder: A powder in which each particle is composed of two or more different components. Coated powder is a composite powder formed by a layer of a different material coating the surface of the particles. Blended powder is a powder made by mixing powders from different batches that have the same nominal components. A binder is a substance added to the powder in order to increase the strength of the compact or to prevent powder segregation; it can be removed before or during sintering. A dopant is a small amount of substance added to metal powder in order to prevent or control recrystallization or grain growth of the sintered body during the sintering process or in use. (Mainly used in tungsten powder metallurgy) Lubricant: A substance added to the powder to reduce friction between particles as well as between the compact and the surface of the die walls. A plasticizer is a thermoplastic material used in binders to improve the formability of powders. Granulation is a process in which finer particles are aggregated into larger powder pellets in order to improve the flowability of the powder. Mechanical alloying is a process of solid-state alloying achieved using high-energy grinders or ball mills. Apparent density is the mass of powder that fills a unit volume under specified conditions when it is freely packed. Bulk density is the mass of powder per unit volume measured under non-standard conditions. Tap density is the mass per unit volume of powder in a container, as measured after the powder has been compacted under specified conditions. Compressibility refers to the degree to which a powder is compressed under pressure, usually through uniaxial compression in a closed die. Compactibility is the ability of a powder to be compressed into a certain shape and to retain that shape during subsequent processing; it is a function of the powder’s fluidity, compressibility, and green compact strength. Compression ratio: the ratio of the volume of the powder before compression to the volume of the compact after demolding. Fill factor: the ratio of the height of the powder filling the mold to the height of the compact after demolding. Flowability is a qualitative term that describes the ability of a powder to flow through a defined orifice. Hydrogen loss refers to the relative mass loss of metal powders or compacts when heated in pure hydrogen under specified conditions. Specific surface area refers to the total surface area per unit mass of powder. Particle size is the linear dimension of individual powder particles, as determined by sieving or other appropriate methods. Particle size distribution refers to the classification of a powder sample into various size categories, with the percentage of powder in each category indicated (based on mass, quantity, or volume). The powder portion that falls between the two nominal particle size limits after particle size grading. 2 Molding 1. Forming: The process of transforming powder into agglomerates with the desired shape. 2. Pressing: A process in which, within a mold or other container and under external force, powder is compressed into a shape and size as specified. 3. Compact, green compact: A green body made from powder through cold pressing or injection molding. 4. A blank is a compact, pre-sintered or sintered part that has not yet reached its final dimensions and shape. 5. The skeleton is a porous compact or sintered body used for infiltration. 6. Cold pressing: Uniaxial compression of powder at room temperature. 7. Warm pressing is a type of uniaxial powder compression that is typically carried out at a temperature between the ambient temperature and the temperature at which diffusion may occur, with the aim of enhancing densification. 8. Hot pressing: Uniaxial compression of powder or compact at high temperatures to induce diffusion and creep phenomena. 9. Isostatic pressing is a pressing method that applies roughly equal pressure in all directions to the surface of the powder (or compact) or to the surface of the soft die component in which the powder (or compact) is placed. 10. Cold isostatic pressing (CIP) is isostatic pressing at room temperature, with a liquid usually serving as the pressure transmission medium. 11. Hot isostatic pressing (HIP) involves isostatic pressing at high temperatures, thereby enabling diffusion and creep processes to occur. The pressure transmission medium is usually a gas. 12. Metal injection moulding (MIM) is a manufacturing method in which a plasticized mixture of metal powder and its binder is injected into a mold. 13. Powder rolling: A method of introducing powder between a pair of rotating rollers to compress it into a cohesive, continuous strip. 14. Volume filling: A method of measuring the powder filled into the female mold by setting the filling depth. 15. Weight filling: A method of measuring the amount of powder to be filled into the female mold by weighing the powder. 16. (Auxiliary) vibration-assisted filling: A method of filling powder into a vibrating mold or cavity. 17. Dwell time: The time during which the compact is held under a constant pressure during shaping. 18. Molding tool set: A complete set of molds used to produce specific powder products through pressing or re-pressing. 19. A mold part in which powder is compressed or sintered parts are re-pressed to form a cavity. 20. Lower puncher: a component in the upper and lower dies used to seal the female die from below and to apply pressure to the powder or sintered part from bottom to top. 21. Upper punch: In a pressing die, it is the component used to seal the lower die from above and to apply pressure to the powder or sintered part from top to bottom. 22. Core rod: A component of a mold used to shape the contour surface of a compact or sintered body in the pressing direction. 23. Feed shoe: A component in the molding die used by the pressing machine to feed powder into the cavity of the female mold. 24. Segmented punch: A set of punches used to control the amount of powder filled and the pressing height when compressing two- or multi-faced compactes. 25. Green body: a compact that has been pressed or injection-molded but not sintered yet. 26. Lamination refers to the formation of layered structural defects in compacts or sintered bodies, or to the defects themselves. 27. Spring back: the phenomenon of increased dimensions in a compressed part after it is demolded. 3. Sintering 1. Sintering is a heat treatment of powders or compacted materials at temperatures below the melting point of their main components, aimed at enhancing their strength through metallurgical bonding between the particles. 2. Packing material: A material that is inserted into the compact during the pre-sintering or sintering process to serve as a separator and for protection purposes. 3. Presintering is a heating treatment of the compact at a temperature lower than the final sintering temperature. 4. Pressure sintering: A sintering process in which uniaxial pressure is applied during sintering. 5. Loose-powder sintering, gravity sintering: Sintering of powder that is carried out without compression. 6. Liquid-phase sintering: Powder or compact containing at least two components is sintered in a state where a liquid phase is formed. 7. Oversintering: A sintering process in which excessively high sintering temperatures and/or prolonged sintering times result in a deterioration of the final properties of the product. 8. Under-sintering: A sintering process in which the sintering temperature is too low and/or the sintering time is too short, resulting in the product not achieving the desired properties. 9. Infiltration: A process in which a metal or alloy with a lower melting point than that of the product is used, in its molten state, to fill the pores in unsintered or sintered products. 10. Dewaxing: The process of removing organic additives (binders or lubricants) from the compact by heating. 11. A mesh belt furnace is a sintering furnace in which parts are continuously transported within the furnace by a mesh belt protected by a muffle. 12. Walking-beam furnace: A sintering furnace in which the parts placed on the sintering tray are transported within the furnace through a walking-beam system. 13. Pusher furnace: A sintering furnace in which parts are placed in a heating boat, and these parts are moved around within the furnace using a pushing system. 14. Neck formation: During sintering, neck-like connections are formed between the particles. 15. Blistering: The phenomenon of bulges forming on the surface of the sintered part due to the intense release of gas. 16. Sweating: The phenomenon of liquid phase seepage during the heating treatment of compacted materials. 17. Sinter skin: A surface layer that forms on the sintered part during the sintering process, with properties different from those of the interior of the product. 18. Relative density: It is the ratio of the density of a porous material to the density of the same material in its non-porous state, expressed as a percentage. 19. Radial crushing strength: The breaking strength of sintered cylindrical specimens determined by applying radial pressure. 20. Porosity is the ratio of the volume of all pores in a porous material to its total volume. 21. Diffusion porosity: Pores formed as a result of the diffusion of one component into another due to the Köckendorf effect. 22. Pore size distribution: The percentage, in terms of quantity or volume, of pores of various sizes present in a material. 23. Apparent hardness is the hardness of a sintered material measured under specified conditions, and it takes into account the effect of pores. 24. Solid hardness refers to the hardness of a certain phase, particle, or region of a sintered material as measured under specified conditions, with the effects of pores being excluded. 25. Bubble-point pressure: The minimum pressure required to force gas to produce the first bubble in a product soaked in liquid. 26. Fluid permeability is the amount of liquid or gas that passes through a porous material per unit time, as measured under specified conditions. 4. Post-sintering treatment 1. Re-pressing: To improve physical and/or mechanical properties, pressure is usually applied to the sintered products. 2. Finishing sizing: Re-pressing to achieve the desired size. 3. Shaping coining: Repressuring carried out to achieve a specific surface morphology. 4. Powder forging: Unsintered, presintered, or sintered preforms made from powder are thermally densified through forging, accompanied by a change in shape. 5. Impregnation: A method of filling the interconnected pores in sintered parts with non-metallic substances such as oil, paraffin, or resin. 6. Steam treatment: The sintered iron-based products are heated in superheated steam, resulting in the formation of a ferric oxide protective layer on the surface, thereby improving certain properties. Powder metallurgy materials 1. Heavy metals: Sintered materials with a density of not less than 16.5 g/cm3. For example: tungsten alloys containing nickel and copper. 2. Cermet is a sintered material composed of at least one metallic phase and at least one non-metallic phase that typically has ceramic properties. 3. Sintered part: A sintered product formed from powder and strengthened through sintering; such parts typically have precise tolerances and are easy to install. 4. Sintered structural parts are typically used in mechanical manufacturing; they do not include bearings, filters, and friction materials. 5. Oil-retaining bearing: a sintered bearing whose openings are impregnated with lubricating oil. 6. Sintered metal filter: A sintered metal component with permeability, commonly used for solid-liquid or solid-gas separation. 7. Sintered magnetic part: A sintered part that meets the magnetic requirements. 8. Sintered friction material: This type of sintered material is a composite made up of a metal matrix along with metal or non-metallic additives, which are used to modify the material’s friction and wear properties. 9. Sintered electrical contact material: A sintered material with high electrical conductivity and resistance to arc corrosion; examples include tungsten-copper, tungsten-silver, silver-graphite, and silver-cadmium oxide composite materials. 10. Hardmetal: Also known as tungsten carbide or cemented carbide