Powder Metal Processing

1. Powder Metal Processing Manufacturing Processes By: Dr.BehzadHeidarshenas

2. Outline • Introduction • Powder Manufacturing • Powder Metallurgy Process • Sintering • Other Powder Metal Processes • Powder Metal Products • Powder Metallurgy Design

3. Powder Metallurgy

4. Powder Metallurgy Metal Powder Metal Product

5. Examples of Powder Metal Products Gears Cams Cranks Bearings Roller bearing cages Housings Light bulb filaments Sprinkler mechanisms

6. Powder Metal Materials Elemental A pure metal, most commonly iron, aluminum or copper Prealloyed An alloy of the required composition, most commonly copper alloys, stainless steel or high-speed steel

7. Powder Manufacturing Conversion of molten metal to powder Atomization

8. Powder Manufacturing Other methods of producing powder: • Chemical reduction of particulate compounds • Electrolytic deposition • Pulverization or grinding of brittle materials • Thermal decomposition • Precipitation from solutions • Condensation of metal vapors

9. Particle Shape

10. Particle Size The process of separating particles by size is called classification

11. Particle Size Micrograph of screened powder particles, showing that particles may be longer than the mesh is wide

12. Particle Size Mixing particles of different sizes allows decreased porosity and a higher packing ratio void smaller, more numerous voids voids filled by smaller particles, small voids remain

13. Powder Metallurgy Process

14. Blending and Mixing Blending Combining powders of the same material but possibly different particle sizes Mixing Combining powders of different materials

15. Compaction High pressure is applied to squeeze the powder into the desired shape

16. Example of a Powder Press

17. Other Powder Metal Processes Cold Isostatic Pressing Hot Isostatic Pressing Injection Molding Powder Rolling Powder Extrusion Plasma Spraying

18. Isostatic Pressing Uses pressurized fluid to compress the powder equally in all directions Cold Isostatic Pressing Compaction performed at room temperature Hot Isostatic Pressing Performed at high temperatures and pressures

19. Example of an Isostatic Press

20. Injection Molding The powder is mixed with a binder and molded, and the binder is removed before sintering

21. Powder Rolling Powder is compressed in a rolling mill to form a strip

22. Powder Extrusion The powder can be extruded within a container or after being formed into billets

23. Plasma Spraying Uses a plasma arc to propel molten droplets at a surface at a high velocity, forming a high-density structure

24. Plasma Spraying

25. Sintering Heats the powder below the melting point to allow solid-state diffusion and bond the particles together

26. Sintering Diagram of particles in sintering, showing the possible movements of atoms

27. Sintering

28. Sintering

29. Sintering Production Lines

30. Examples of Sintering Production Lines

31. Sintering Strength of sintered structures as related to density, showing that the strength is higher when the density is higher (less residual porosity)

32. Powder Metal Products • Porous or permeable products • Products of complex shapes • Products made of materials that are difficult to machine or have high melting points • Products which require the combined properties of multiple materials • Products in which powder metallurgy produces superior properties

33. Powder Metallurgy Design • The shape must permit removal from the die • The shape should not have thin walls or sharp corners • The shape should permit the construction of strong tooling • The shape of the part should be within the thickness range for which the powder can be properly compacted • The part should have as few changes in section thickness as possible

34. Powder Metallurgy Design • Parts can be designed to take advantage of the capabilities of the powder metallurgy process • The design should be consistent with available equipment • Consideration should be given for product tolerances • Design should consider the dimensional changes that occur after pressing, such as shrinkage during sintering

35. Powder Metallurgy Design

36. Powder Metallurgy Design

37. Powder Metallurgy Advantages • Elimination/reduction of machining • High production rates • Complex shapes can be produced • Wide composition variations are possible • Wide property variations are possible • Scrap is eliminated or reduced

38. Powder Metallurgy Disadvantages • Inferior strength properties • Relatively high die cost • High material cost

39. Summary Powder metallurgy can create parts that would otherwise be difficult to form, including those with complex shapes or porosity Sintering bonds particles together by allowing atoms to move, forming necks and grain boundaries between the particles