Powder Metallurgy.pptx
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Powder metallurgy is a process that involves blending fine metal powders, pressing them into a desired shape, and then heating to bond the particles. It has four basic steps - powder manufacture, mixing/blending, compacting, and sintering. During sintering, the pressed compacts are heated to bond the particles without melting. This allows for unusual mixtures with little waste to be used for automotive, appliance, and equipment parts.
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Powder Metallurgy.pptx
- 2. Powder Metallurgy • Process by which fine powdered materials are blended, pressed into a desired shape, and then heated to bond surfaces • Little material waste and unusual mixtures can be utilized • Used for parts in the automotive industry, household appliances, and recreational equipment
- 3. The Basic Process • Four basic steps 1. Powder manufacture 2. Mixing or blending 3. Compacting 4. Sintering Elemental or alloy metal powders Additives (lubricants or binders) Blending Compaction Sintering Optional secondary manufacturing Optional secondary finishing Finished P/M product
- 5. Factors to Consider in P/M Type and size of powder Amount and type of lubricant Pressing pressure Sintering temperature and time Finishing treatments
- 7. Powder Manufacture • Properties of powder metallurgy products are highly dependent on the characteristics of starting powders • Some important properties and characteristics: Chemistry and purity Particle size Size distribution Particle shape Surface texture
- 8. Powder Manufacture • The majority of commercial powder is produced by atomization Atomization is a process where liquid metal is fragmented into small droplets that cool and solidify into particles
- 10. Additional Methods of Powder Manufacture • Methods Chemical reduction of particulate compounds Electrolytic deposition Pulverization or grinding Thermal decomposition of particulate hydrides Precipitation from solution Condensation of metal vapors • Almost any metal or alloy can be converted into powder
- 11. Powder Testing and Evaluation • Apparent density measure of a powder’s ability to fill available space without external pressure • Flow rate measures the ease with which powder can be fed and distributed into a die • Compressibility Measure of the effectiveness of applied pressure • Green strength describe the strength of the pressed powder after compacting
- 12. (2) BLENDING
- 13. Blending • Powder and a combination of other elements and additives are blended together into a fully homogeneous mixture. • Each blend is tailored to meet the exact physical requirements of the finished component.
- 15. Powder Compacting Process of compacting metal powder in a die through the application of high pressures. The compacted component is said to be in the "green" state.
- 16. Powder Compacting • Most compacting is done with mechanical presses and rigid tools • Hydraulic and pneumatic presses are also used
- 17. Compaction Sequence • Two opposing force is created from a combination of resistance by the bottom punch friction between the particles and die surface
- 19. Additional Considerations During Compacting • When the pressure is applied by only one punch, the maximum density occurs right below the punch surface and decreases away from the punch • For complex shapes, multiple punches should be used.
- 20. (4) SINTERING
- 21. Sintering • Process wherein the pressed-powder compacts are heated in a controlled atmosphere to right below the melting point • Three stages of sintering Burn-off (purge) High-temperature Cooling period
- 22. Sintering BURN-OFF (PURGE) HIGH- TEMPERATURE COOLING PERIOD combusts any air and removes lubricants or binders that would interfere with good bonding desired solid-state diffusion and bonding occurs lowers the temperature of the products in a controlled atmosphere
- 23. Hot Isostatic Pressing • Process used to reduce the porosity of metals and influence the density of many materials. • The HIP process subjects a component to both elevated temperature and isostatic gas pressure in a high pressure containment vessel.
- 25. Metal Injection Molding (MIM)
- 26. Metal Injection Molding (MIM)
- 27. Secondary Operations • Enhance precision • Improve properties • Produce special characteristics • Correct/remove distortion
- 28. Secondary Operations • P/M forging – Increases density and adds precision • Infiltration and impregnation – gives the part self lubricating properties and improves strength • Heat treatment – increase strength and also hardness for improved wear resistance • Machining • Surface treatments
- 29. Advantages and Disadvantages of P/M • Advantages – Elimination or reduction of machining – High production rates – Wide variations in compositions – Wide property variations – Scrap is eliminated or reduced • Disadvantages – High tooling costs – High material cost – Size and shape limitations – Dimensional changes during sintering – Density variations
- 30. QUIZ
- 31. The Basic Process • Four basic steps 1. Powder manufacture 2. _____________ 3. _____________ 4. _____________ Elemental or alloy metal powders Additives (lubricants or binders) 1 2 3 Optional secondary manufacturing Optional secondary finishing Finished P/M product
- 32. Question # 4 • Process of producing commercial powder.
- 33. Question # 5 •Describes the strength of the pressed powder after compacting.
- 34. Question # 6 • Process that subjects a component to both elevated temperature and isostatic gas pressure in a high pressure containment vessel.
- 35. Question # 7-9 • Three stages of sintering
- 36. Question # 10
Editor's Notes
- Mechanical properties are dependent on density Products should be designed (and materials selected) so that the final properties will be achieved with the anticipated final porosity
- Two methods for producing metal powders: melt atomization – use high pressure water jets that breaks molten metal stream into very fine droplets atomization from a rotating consumable electrode. Note: Research on these two processes
- Powders should be evaluated for their suitability for further processing
- A controlled amount of powder is fed into a precision die and is compacted. Dimensions and density are closely controlled in this process. The density of the compacted powder is directly proportional to the amount of pressure applied.
- To attain the same compression ratio across a component with more than one level or height, it is necessary to work with multiple lower punches. A cylindrical work piece is made by single-level tooling. A more complex shape can be made by multiple-level tooling.
- Powders do not flow like liquid, they simply compress until an equal and opposing force is created.
- All three stages must be conducted in oxygen-free conditions
- Hot isostatic pressing (HIP) is a manufacturing process used to reduce the porosity of metals and influence the density of many ceramic materials. This improves the material's mechanical properties and workability. The HIP process subjects a component to both elevated temperature and isostatic gas pressure in a high pressure containment vessel. The pressurizing gas most widely used is argon. An inert gas is used, so that the material does not chemically react. The chamber is heated, causing the pressure inside the vessel to increase. Many systems use associated gas pumping to achieve the necessary pressure level. Pressure is applied to the material from all directions (hence the term "isostatic").
- Ultra-fine spherical-shaped metal, ceramic, or carbide powders are combined with a thermoplastic or wax Becomes the feedstock for the injection process The material is heated to a pastelike consistency and injected into a heated mold cavity After cooling and ejection, the binder material is removed Most expensive step in MIM and PIM
- Most powder metallurgy products are ready to use after the sintering process. Distortion may occur during nonuniform cool-down so the product may be repressed, coined, or sized to improve dimensional precision.
- Heat Treatment:- Sintered parts may be heat treated to increase strength and also hardness for improved wear resistance. Oil Impregnation:- The controlled porosity of P/M parts permits their impregnation with oil and resin. This operation is used to give the part self lubricating properties. Infiltration:- An alternative method of improving the strength of inherently porous sintered parts is to fill the surface connected pores with a liquid metal having a lower melting point. Machining :- All normal machining operations can be carried out on sintered components.