1. What is metallurgy?
a) Technology of designing metals
b) Art and science of extracting metals from their ores
c) Technology of welding metals
d) None of the mentioned
Explanation: The art and science of extracting metals from their ores and altering them for application is known as metallurgy. Metals’ chemical, physical, and atomic properties and structures, as well as the processes by which metals are mixed to produce alloys, are all covered.
2. What is powder metallurgy?
a) Production and working of metals as fine powders
b) Working with metals as fine powders
c) Methods for utilizing metals as fine powders
d) None of the mentioned
Explanation: Powder metallurgy is a metal-forming technique in which compacted metal powders are heated to just below their melting temperatures. Powder metallurgy is a renowned green technology because of these factors, which contribute to sustainability.
3. Which of the following is the application of powder metallurgy?
a) create unique materials with specific qualities that are impossible to accomplish using melting or shaping
b) create unique materials with specific qualities that are possible to accomplish using melting or shaping
c) All of the mentioned
d) None of the mentioned
Explanation: Powder metallurgy is used to create unique materials with specific qualities that are impossible to accomplish using other procedures such as melting or shaping. It allows for the mixing of elements that would otherwise be impossible to combine, as well as the processing of materials with extremely high melting points.
4. Which of the following is a step of powder metallurgy?
a) The production of metal powder
b) The consolidation and fusing of the powder into a solid metal
c) The compaction and shaping of the powder
d) All of the mentioned
Explanation: Powder metallurgy is a fabrication technology that entails three key stages:
(i) The production of metal powder
(ii) The compaction and shaping of the powder
(iii) The consolidation and fusing of the powder into a solid metal component at high temperatures and pressures.
5. What is powder sintering process?
a) Cold treatment used to improve a material’s strength and structural integrity
b) Metal freezed to improve its strength and structural integrity
c) Thermal treatment used to improve a material’s strength and structural integrity
d) None of the mentioned
Explanation: Sintering is a thermal treatment that is widely used to improve a material’s strength and structural integrity. Sintering is used in powder metallurgy techniques to turn metal powders and other unusual materials into finished products.
6. Which of the following transforms compacted mechanical bonds between powder particles into metallurgical bonds?
b) Metal Injection Molding
d) Mechanical alloying
Explanation: Sintering is defined as the heating of loose or compacted aggregate of metal powders below the melting point of base metal to transform it to a denser material by interparticle bonding and thus, sintering transforms compacted mechanical bonds between powder particles into metallurgical bonds.
7. Which of the following is used to prepare SiN?
a) Hot forging
b) Liquid phase sintering
c) Reaction sintering
d) Solid-state sintering
Explanation: Reaction sintering may also involve heating in a gas atmosphere, which reacts with the powder compact resulting in the formation of the desired compound. A typical example is the production of reaction bonded SiN made by sintering green compact of Si powders in N2 atmosphere at 1,523 to 1,673 K for time up-to 70 hours.
8. Which of the following additive is added to improve the tool life of steel parts?
Explanation: The machinability can be improved by incorporating certain additions in powder mix like lead, copper, graphite, sulphur or a metal sulphide. Sulphur is added to improve the tool life and surface finish of P/M steel parts by mixing it in powder compact.
9. Steam treatment is not applicable for which of the following parts?
a) annealed parts
b) normalized parts
c) stress relived parts
d) hardened and tempered parts
Explanation: Seam treatment is not generally applicable to hardened and tempered powder metallurgical parts because the exposure to high temperatures will result in over tempering of the parts.
10. Tin powder is made by _________
b) Cold stream process
Explanation: For the production of porous bearings of tin by powder metallurgical route involves production of tin powder by atomization. It consists of mechanically disintegrating a stream of molten metal into the fine particles by means of jet of compressed air, inert gases or water.
11. Which of the following changes do not occur on during recrystallization?
a) Phase changes
b) Grain shrinkage
d) Pore shrinkage
Explanation: Recrystallization includes changes in the microstructure, phase changes, grain growth, precipitation and pore shrinkage.
12. Which of the following substance is added to iron powder to improve the compressive strength of bearing?
Explanation: Copper (up to 10%) is added to the iron powders for improving the compressive strength of the P/M bearings. Iron is used for low-cost bearings, majorly used in automotive applications, farm equipment, and machine tools.
13. Which of the following material on addition to the powder mix lowers the strength of the bearing?
Explanation: The addition of graphite improves lubrication but also results in growth and lowers the strength of the bearings. Lubricants used in the mix have significant effect on the apparent density and flow rate but very little influence on the dimensional change.
14. Which of the following is not a characteristic of powder produced by precipitation from an aqueous solution method?
a) Low apparent density
b) Difficult to remove the adherent salts
c) High apparent density
d) Porous in nature
Explanation: The precipitated metal powders are generally porous in nature and have low apparent density. A major drawback of the precipitation method lies in the fact that the adherent or entrained salts are more difficult to remove than in electrolytic powder products.
15. Which of the following P/M parts exhibit a short cutting tool life?
b) Very dense
Explanation: The presence of porosity alters the machining characteristics thus porous powder metallurgical part exhibit a low-thermal conductivity and hence the cutting tool life is short due to heat erosion.
16. What should be added to the iron powder mix to improve the speed capability?
Explanation: The addition of lead to iron improves the speed capability and even reduces cost. This material so produced for production of P/M bearing is called leaded iron.
17. Which of the following powder production method is used for the production of non-porous bearing with steel backing?
a) Mechanical alloying
b) Water atomization
d) Gas atomization
Explanation: The pre-alloyed powders for the production of non-porous bearing with steel backing are manufactured by gas atomization. In this process the molten metal stream is disintegrated using high velocity argon, nitrogen or helium gas jets and the atomized powders are collected in a water bath.
18. Which of following is the correct set of material variables in sintering?
a) Green density and particle size
b) Particle structure and sintering atmosphere
c) Green density and sintering time
d) Particle composition, particle shape, green density and sintering temperature
Explanation: The major variables in sintering include process variables and material variables. The process variables include sintering atmosphere, sintering time and sintering temperature whereas the material variables include particle composition, particle shape, particle size, particle structure, and green density.
19. Which of the following are the essential parts of a sintering furnace?
a) Burn-off zone, sintering zone, and cooling zone
b) Sintering zone and cooling zone
c) Burn-on zone, sintering zone, and cooling zone
d) Preheat zone and sintering zone
Explanation: The essential parts of a sintering furnace include:
(1) a burn-off zone or preheat zone for the removal of lubricants,
(2) a controlled high-temperature sintering zone, and
(3) a cooling and discharging zone.
20. Which of the following solution is used to fill the dew cup for carrying out moisture analysis?
b) Carboxylic acid
d) Ethyl alcohol
Explanation: The procedure for moisture content analysis includes- first, the dew cup is filled with acetone and the atmosphere gas is passed against the dew cup. After about 5 minutes, dry ice is added to the cup with stirring. Moisture or dew appears on the surface of the cup and the dew point is read from the thermometer in the dew cup.
21. Which of the following is not a characteristic of infiltrant?
a) Must not alloy or react with the skeleton metal
b) Good or perfect wetting
c) High surface tension
d) Melting point lower than the skeleton metal
Explanation: The essential requirements in choosing a suitable infiltrant are: (1) Its melting point must be lower than the skeleton metal; (2) Low surface tension so as to fill small interstices; (3) There should be ‘good or perfect wetting’ of the skeleton (solid) by the infiltrant (liquid); and (4) It must not alloy or react with the skeleton metal.
22. Which of the following treatment is given to a thin-walled bushing that is oversize on both inside and outside diameter?
a) Negative sizing on both inside and outside
b) Positive sizing on both inside and outside
c) Positive sizing on inside, and negative sizing on outside
d) Positive sizing on outside, and negative sizing on inside
Explanation: A thin-walled bushing which is oversize on both inside and outside diameter after sintering can be subjected to positive sizing on outside, and negative sizing on inside.
23. Which of the following is not a benefit of impregnation?
a) Dimensional tolerance
b) Improved machinability
d) Porosity elimination
Explanation: The benfits of impregnation include-
(1) self lubricating ability,
(2) Increase in mechanical properties,
(3) Pressure-tightness due to sealing off the porosity,
(4) Prevention of the entry of corrosive salts into pores during plating, and
(5) Improvement in machinability.
24. Which of the following are major components of atomization set-up?
a) Melting, atomization chamber, collection tank
b) Melting and superheating facility
c) Melting, atomization chamber, dry collection
d) Melting, atomization chamber
Explanation: The major components of a typical atomization set-up include: (1) Melting and superheating facility, (2) Atomization chamber, and (3) Powder collection tank which is further of two types- dry collection and wet collection.
25. Which of the following are the stages of sintering, according to Sauerwald theory?
a) Adhesion, crystallization
b) Adhesion, recrystallization
c) Adhesion, bonding
Explanation: According to Sauerwald theory, there are two stages in sintering- adhesion which occurs during heating due to atomic attraction, and recrystallization consists of diffusion of atoms between adjacent grains.
26. Which of the following is not a mechanism of by which surface transportation occur during solid-state sintering?
a) Viscous flow
b) Volume diffusion
c) Surface diffusion
d) Plastic flow
Explanation: In solid-state sintering, mass transportation can take place either by surface transportation, grain boundaries or bulk transportation. Surface transportation can occur through diffusion, adhesion or evaporation-condensation or by surface diffusion.
27. Which of the following condition is necessary for obtaining consistent and satisfactory sintered components?
a) Short sintering time
b) Long sintering time
c) High power consumption
d) More labor cost
Explanation: For obtaining consistent and satisfactory sintered components, it is essential to make use of furnaces operating at the lowest temperatures for the shortest times using the cheapest possible sintering atmosphere with lowest maintenance and power consumption as well as the least labor costs.
28. Which of the following are the important temperature controls used in sintering furnace?
a) Radiation pyrometers
c) On-off controllers and proportional controllers
d) On-off controllers
Explanation: The various important temperature controls used in sintering furnace include: on-off controllers, proportional controllers and transformer controls. Thermocouple and radiation pyrometers are instruments used to measure temperature for low-temperature and high-temperature furnaces respectively.
29. Which of the following treatment fives a ferrito-pearlitic structure in P/M steel forgings?
Explanation: The main purpose of annealing heat treatment is to obtain a ferrito-pearlitic structure which gives good machining characteristics. The temperature employed for annealing depends on the carbon content.
30. Which of the following kind of porosity leads to longer tool life?
a) Either very high or very low
b) Very high
d) Very low
Explanation: Longer tool life is achieved when the porosity is either very high or very low because the material hardness and residual porosity also affect the tool life. For very low-density parts, tool life may be improved by infiltrating the pores with a low-melting metal before machining.
31. Which of the following is not a characteristic of the bearings produced from iron?
a) High porosity
b) Good wear resistance
c) Low-oil-volume capacity
d) High-oil-volume capacity
Explanation: Low-oil-volume capacity is not a characteristic of the bearings produced from iron. The iron material used for production of P/M bearings have a relatively low-limiting value of V in the PV factor, but have high-oil-volume capacity due to the high porosity. They have good wear resistance and are used with hardened and ground steel shafts for heavy and shock loads.
32. Which of the following is not a type of bearing?
a) Babbit backed steel
b) Steel backed steel
c) Unbacked bearings
d) Teflon bearing
Explanation: The various type of bearings available are: (1) Steel backed materials with non-porous sintered lining, (2) Steel backed materials with porous sintered lining, (3) Unbacked porous sintered metallic parts impregnated with oil, (4) Unbacked porous sintered metallic parts containing graphite as a dry lubricant, and (5) Teflon bearing.
33. Which of the following conditions are necessary for the development of fluid film in porous bearings?
a) High speed
c) High speed and viscosity
d) Low speed
Explanation: For boundary film lubrication, the performance of a bearing depends upon the ability of fluid film to carry load. Thus, for the development of fluid film, higher speed and viscosity are essential in the porous bearings than that in solid sintered bearings.
Chapterwise Multiple Choice Questions on Powder Metallurgy
- Production of Powders
- Powder Treatment and Handling
- Metal Powder Characteristics
- High Temperature Compaction
- Postsintering Operations
- Powder Metallurgy Products
- Advanced Powder Metallurgy Processing Techniques
- Tool Materials
- Powder Manufacture
- Characteristics and Testings of Metal Powders
1. Powder Metallurgy MCQ on Production of Powders
The section contains Powder Metallurgy multiple choice questions and answers on powder production types, physical methods, chemical methods like reduction, thermal decomposition, hydride, dehydride and precipitation, metal powders applications and ceramics powder production.
2. Powder Metallurgy Multiple Choice Questions on Powder Treatment and Handling
The section contains Powder Metallurgy questions and answers on powder treatment and its methods, metal powders coating and pyrophoricity.
3. MCQ on Metal Powder Characteristics
The section contains Powder Metallurgy MCQs on metal powders sampling, characterization and sedimentation, packing and flow characteristics, powder pressing, pressureless compaction technique, pressure and die compactions, die compaction design and its parts, cold isostatic compaction process, cip types and advantages, powder rolling steps, advantages and disadvantages, techniques like continuous and explosive.
4. Powder Metallurgy Multiple Choice Questions on High Temperature Compaction
The section contains Powder Metallurgy multiple choice questions and answers on uniaxial hot pressing, hot extrusion and isostatic pressing.
5. Powder Metallurgy MCQ on Sintering
The section contains Powder Metallurgy questions and answers on sintering types, sintering theory and mechanism, sintering structure and properties, multicomponent system sintering, sintering types and effects, sintering atmosphere, infiltration, sintering practice and furnace.
6. Powder Metallurgy Multiple Choice Questions on Postsintering Operations
The section contains Powder Metallurgy MCQs on postsintering secondary operations like sizing, coining, repressing, impregnation, infiltration, heat and steam treatment, machining joining and plating.
7. MCQ on Powder Metallurgy Products
The section contains Powder Metallurgy multiple-choice questions and answers on porous bearings and its types, sintered production, non porous bearings, porous bearings production, bearings testing and applications, cermets classification and characterization, dispersion strengthened materials, cermets production and its types, p/mm electrical applications, sintered friction material and constituents production.
8. Multiple Choice Questions on Advanced Powder Metallurgy Processing Techniques
The section contains Powder Metallurgy questions and answers on atomization and its types, self propagating high temperature synthesis and its types, atomization unit advantages, atomized product characteristics, inert and water gas atomization, centrifugal and ultrasonic atomization, mechanical alloying, milling parameters, mim steps, advantagees and requirements, microwave sintering and its advantages, mim applications and defects, shs terminology, processing and advantages, mim comparison with conventional types, shs products and applications.
9. Powder Metallurgy MCQ on Tool Materials
The section contains Powder Metallurgy MCQs on cemented carbides and its production, cemented carbides applications, properties and testing.
10. Multiple Choice Questions on Powder Manufacture
The section contains Powder Metallurgy multiple choice questions and answers on alloy powders, electrochemical and physico-chemical methods of powder production.
11. MCQ on Characteristics and Testings of Metal Powders
The section contains Powder Metallurgy questions and answers on particle size measurement techniques, particle characterisation, particle shape and specific area.
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