Powder Metal Processing Manufacturing Processes Outline Introduction Powder

Powder Metal Processing Manufacturing Processes

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

Powder Metallurgy

Powder Metallurgy Metal Powder Metal Product

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

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

Powder Manufacturing Conversion of molten metal to powder Atomization

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

Particle Shape

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

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

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

Powder Metallurgy Process

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

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

Example of a Powder Press

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

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

Sintering

Sintering

Sintering Production Lines

Examples of Sintering Production Lines

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

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

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

Example of an Isostatic Press

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

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

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

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

Plasma Spraying

Powder Metal Products 1. Porous or permeable products 2. Products of complex shapes 3. Products made of materials that are difficult to machine or have high melting points 4. Products which require the combined properties of multiple materials 5. Products in which powder metallurgy produces superior properties

Powder Metallurgy Design 1. The shape must permit removal from the die 2. The shape should not have thin walls or sharp corners 3. The shape should permit the construction of strong tooling 4. The shape of the part should be within the thickness range for which the powder can be properly compacted 5. The part should have as few changes in section thickness as possible

Powder Metallurgy Design 6. Parts can be designed to take advantage of the capabilities of the powder metallurgy process 7. The design should be consistent with available equipment 8. Consideration should be given for product tolerances 9. Design should consider the dimensional changes that occur after pressing, such as shrinkage during sintering

Powder Metallurgy Design

Powder Metallurgy Design

Powder Metallurgy Advantages 1. Elimination/reduction of machining 2. High production rates 3. Complex shapes can be produced 4. Wide composition variations are possible 5. Wide property variations are possible 6. Scrap is eliminated or reduced

Powder Metallurgy Disadvantages 1. 2. 3. Inferior strength properties Relatively high die cost High material cost

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