Chapter 15 - Powder Metallurgy

The particle size that can pass through a screen is obtained by taking the reciprocal of the mesh count of the screen

• true

• false

For a given weight of metallic powders, the total surface area of the powders is increased by which of the following (two best answers)

• larger particle size

• smaller particle size

• higher shape factor

• smaller shape factor

As particle size increases, interparticle friction

• decreases

• increases

• remains the same

Which of the following powder shapes would tend to have the lowest interparticle friction

• acicular

• cubic

• flakey

• spherical

• rounded

Which of the following statements is correct in the context of metallic powders (three correct answers)

• porosity + packing factor = 1.0

• packing factor = 1/porosity

• packing factor = 1.0 - porosity

• packing factor = -porosity

• packing factor = bulk density/true density

Repressing refers to a pressworking operation used to compress a sintered part in a closed die to achieve closer sizing and better surface finish

• true

• false

Impregnation refers to which of the following (two best answers)

• Jack

• filling the pores of the PM part with a molten metal

• putting polymers into the pores of a PM part

• soaking oil by capillary action into the pores of a PM part

• something that should not happen in a factory

In cold isostatic pressing, the mold is most typically made of which one of the following

• rubber

• sheetmetal

• textile

• thermosetting polymer

• tool steel

Which of the following processes combines pressing and sintering of the metal powders (three best answers)

• hot isostatic pressing

• hot pressing

• metal injection molding

• pressing and sintering

• spark sintering

Which of the following design features would be difficult or impossible to achieve by conventional pressing and sintering (three best answers)

• outside rounded corners

• side holes

• threaded holes

• vertical stepped holes

• vertical wall thickness of 1/8 inch (3 mm)