Powder Metal Processing Manufacturing Processes

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

Particle Size

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

Sintering

Sintering

Sintering Production Lines

Examples of Sintering Production Lines

Sintering

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

• 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

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

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

Powder Metallurgy Design

Powder Metallurgy Design

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

Powder Metallurgy Disadvantages

• 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