Question & Answer

A solid cube of aluminum with each side = 1.0 m is converted into metallic powders of spherical shape by gas atomization. How much total surface area is added by the process if the diameter of each particle is 100 microns (assume that all particles are the same size)?

A solid cube of copper with each side = 1.0 ft is converted into metallic powders of spherical shape by gas atomization. What is the percentage increase in total surface area if the diameter of each particle is 0.004 in (assume that all particles are the same size)?

Suppose in Problem 16.5 that the average particle diameter = 0.002 in; however, the sizes vary, forming a statistical distribution as follows: 25% of the particles by weight are 0.001 in, 50% are 0.002 in, and 25% are 0.003 in. Given this distribution, what is the total surface area of all the particles in the pile?

Solve Problem 16.5, except that the diameter of the particles is 0.004 in. Assume the same packing factor.

A pile of iron powder weighs 2 lb. The particles are spherical in shape and all have the same diameter of 0.002 in. (a) Determine the total surface area of all the particles in the pile. (b) If the packing factor = 0.6, determine the volume taken by the pile. Note: the density of iron = 0.284 lb/in³ .

Determine the shape factor for metallic particles of the following ideal shapes: (a) sphere, (b) cubic, (c) cylindrical with length-to-diameter ratio of 1:1, (d) cylindrical with length-to-diameter ratio of 2:1, and (e) a disk-shaped flake whose thickness-to-diameter ratio is 1:10.

What is the aspect ratio of a cubic particle shape?

A screen with 10 mesh count has wires with a diameter of 0.0213 in. Determine (a) the maximum particle size that will pass through the wire mesh and (b) the proportion of open space in the screen.

A screen with 325 mesh count has wires with a diameter of 0.001377 in. Determine (a) the maximum particle size that will pass through the wire mesh and (b) the proportion of open space in the screen.

There are 19 correct answers in the following multiple choice questions (some questions have multiple answers that are correct). To attain a perfect score on the quiz, all correct answers must be given. Each correct answer is worth 1 point. Each omitted answer or wrong answer reduces the score by 1 point, and each additional answer beyond the correct number of answers reduces the score by 1 point. Percentage score on the quiz is based on the total number of correct answers.

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 or (b) false?

16.2 For a given weight of metallic powders, the total surface area of the powders is increased by which of the following (two best answers): (a) larger particle size, (b) smaller particle size, (c) higher shape factor, and (d) smaller shape factor?

16.3 As particle size increases, interparticle friction (a) decreases, (b) increases, or (c) remains the same?

16.4 Which of the following powder shapes would tend to have the lowest interparticle friction: (a) acicular, (b) cubic, (c) flakey, (d) spherical, and (e) rounded?

16.5 Which of the following statements is correct in the context of metallic powders (three correct answers): (a) porosity + packing factor = 1.0, (b) packing factor = 1/porosity, (c) packing factor = 1.0 - porosity, (d) packing factor = - porosity, (e) packing factor = bulk density/true density?

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 or (b) false?

16.7 Impregnation refers to which of the following (two best answers): (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, and (d) something that should not happen in a factory?

16.8 In cold isostatic pressing, the mold is most typically made of which one of the following: (a) rubber, (b) sheetmetal, (c) textile, (d) thermosetting polymer, or (e) tool steel?

16.9 Which of the following processes combines pressing and sintering of the metal powders (three best answers): (a) hot isostatic pressing, (b) hot pressing, (c) metal injection molding, (d) pressing and sintering, and (e) spark sintering?

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

List the types of environments that can be present during the sintering process according to the powder metallurgy video.

List the most common methods for forming the pressed parts in powder metallurgy according to the powder metallurgy video.

Why is PM technology so well suited to the production of gears and bearings?

What are the two basic classes of metal powders as far as chemistry is concerned?

Describe liquid phase sintering

How is isostatic pressing distinguished from conventional pressing and sintering in PM?

What is the difference between powder injection molding and metal injection molding?

What are the advantages of infiltration in PM?

What are some of the reasons why a controlled atmosphere furnace is desirable in sintering?

What are the three steps in the sintering cycle in PM?

Describe what happens to the individual particles during compaction.

What is meant by the term green compact?

What are some of the ingredients usually added to the metallic powders during blending and/or mixing?

What is the technical difference between mixing and blending in powder metallurgy?

What are the three basic steps in the conventional powder metallurgy shaping process?