Chapter 16: Powder Metallurgy

MC 16.10 Which of the following design features would be difficult or impossible to achieve by conventional pressing and sintering? (3) a) outside rounded corners b) side holes c) threaded holes d) vertical-stepped holes e) vertical wall thickness of 1/8 in

a, b, c

MC 16.9 Which of the following processes combines pressing and sintering of the metal powders? (3) a) hot isostatic pressing b) hot pressing c) metal injection molding d) pressing and sintering e) spark sintering

a, b, e

MC 16.5 Which of the following statements is correct in the context of metallic powders? (3) a) porosity+packing factor=1 b) packing factor=1/porosity c) packing factor=1-porosity d) packing factor=-porosity e) packing factor=(bulk density)/(true density)

a, c, e

MC 16.22 Which of the following most closely typifies the sintering temperatures in PM? a) 0.5 Tm b) 0.8 Tm c) Tm (Tm=melting temp of material)

b

MC 16.2 For a given weight of metallic powders the total surface area of the powder is increased by which of the following? (2) a) larger particle size b) smaller particle size c) higher shape factor d) smaller shape factor

b and c

MC 16.7 Impregnation refers to which of the following? (2) a) filling the pores of the PM part with a molten metal b) putting polymers into the pores of a PM part c) soaking oil by capillary action into the pores of a PM part d) something that should not happen in a factory

b, c

MC 16.1 The particle size that can pass through a screen is obtained by taking the reciprocal of the mesh count of the screen. a) true b) false

b. The given description neglects consideration of the screen wire thickness

MC 16.4 Which of the following powder shapes would have the lowest inter-particle friction? a) acicular b) cubic c) flaky d) spherical e) rounded

d

Powder Metallurgy- Outline

1. The Characterization of Engineering Powders 2. Production of Metallic Powders 3. Conventional Pressing and Sintering 4. Alternative Pressing and Sintering Techniques 5. Materials and Products for PM 6. Design Considerations in Powder Metallurgy

Powder Metallurgy (PM)

Metal processing technology in which parts are produced from metallic powders Usual PM production sequence: 1. Pressing - powders are compressed into desired shape to produce *green compact ~ Accomplished in press using punch-and-die 2. Sintering - green compacts are heated to bond the particles into a hard, rigid mass ~ Temperatures are below melting point

MC 16.3 As particle size increases, inter-particle friction a) increases b) decreases c) stays the same

a

MC 16.6 Repressing refers to a pressworking operation used to compress a sintered part in a closed die to achieve closer sizing and better surface finish a) true b) false

a

MC 16.8 In cold isostatic pressing the mold is most typically made of which of the following? a) rubber b) sheet metal c) textile d) thermosetting polymer e) tool steel

a