Comparison of Powder Processing Methods

Effective application of powder processing methods requires a general comparison of the major design features, focusing on the similarities, differences, advantages, and disadvantages of each method. Table 4 provides a qualitative comparison, while Table 5 offers more specific design information. Characteristics for each processing method are summarized below.

Conventional die compaction:

• Widest range of most frequently used engineering materials, including iron, steel, stainless steel, brass, bronze, copper, and aluminum

• Most applicable to medium-to-high production volumes; small- to medium-size parts such as gears, sprockets, pulleys, cams, levers, and pressure plates (automotive, appliances, power tools, sporting equipment, office machines, and garden tractors are typical markets)

• Greatest density range, including high-porosity filters, self-lubricating bearings, and high-performance structural parts

• Limited physical and mechanical properties caused by residual porosity

• Most cost-competitive of the powder processes

• Wide range of applications from low- to high-stress applications

Powder forging:

• Potentially applicable to all engineering materials now hot forged, but actual applications currently limited to low-alloy steels

• Product applications limited to high-volume products such as automotive connecting rods and transmission components as well as power tool parts

• Mechanical properties equivalent to wrought steel

• Most cost-competitive of the full-density processes for medium-to-large parts

Metal injection molding:

• Limited range of materials, though most standard engineering alloys available as well as several specialty alloys

• Limited to relatively small, highly complex shaped products for medium-to-high production volumes

• Greatest range in shape complexity including high aspect ratios

• More costly than conventional die-compaction processes

• Superior physical and mechanical properties as compared to conventional process, due to higher density Hot isostatic pressing:

• Materials limited only by the inherent cost of the process, therefore typically applied only to expensive materials

• Most suited for low-to-medium production volumes

• Competitive against large casting or forging products where substantial machining is needed to obtain the final product

• Much shape detail is machined after HIP processing; not normally a "net-shape" manufacturing process

• Physical and mechanical properties meet or exceed those of cast or wrought materials

Table 4 Comparison of powder processing methods

Characteristic

Conventional

MIM

HIP

P/F

Size

Good

Fair

Excellent

Good

Shape complexity

Good

Excellent

Very good

Good

Density

Fair

Very good

Excellent

Excellent

Dimensional tolerance

Excellent

Good

Poor

Very good

Production rate

Excellent

Good

Poor

Excellent

Cost

Excellent

Good

Poor

Very good

Table 5 Application of powder processing methods

Conventional die compaction

MIM

HIP

P/F

Material

Steel, stainless steel, brass, copper

Steel, stainless steel

Superalloys, titanium, stainless steel, tool steel

Steel

Production quantity

>5000

>5000

1-1000

>10,000

Size, lb

<5

<\

5-5000

<5

Dimensional

±0.001 in./in.

±0.003 in./in.

±0.020 in./in.

±0.0015 in./in.

tolerance

Mechanical

80-90% wrought

90-95%

Greater than wrought

Equal to

properties

wrought

wrought

Price per pound

$0.50-5.00

$1-10

>$100

$1-5

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