Here are 1000 Powder Metallurgy MCQ (Chapterwise).
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
View Answer
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
View Answer
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
View Answer
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
View Answer
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
View Answer
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. ________ transforms compacted mechanical bonds between powder particles into metallurgical bonds.
a) SHP
b) Metal Injection Molding
c) Sintering
d) Mechanical alloying
View Answer
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. SiN is prepared by _______
a) Hot forging
b) Liquid phase sintering
c) Reaction sintering
d) Solid-state sintering
View Answer
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. For bronze bearings, the amount of shrinkage _______ as the particle size of powder mix decreases.
a) increases
b) constant
c) moderate
d) decreases
View Answer
Explanation: In the production of bearings by P/M route, powder characteristics like particle size and distribution, and particle shape play an important role. In the bronze bearings, decrease in the particle size of elemental tin or copper powder increases the amount of shrinkage.
9. Which of the following additive is added to improve the tool life of steel parts?
a) Lead
b) Copper
c) Sulphur
d) Bismuth
View Answer
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.
10. Steam treatment is not applicable for ________
a) annealed parts
b) normalized parts
c) stress relived parts
d) hardened and tempered parts
View Answer
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.
11. Tin powder is made by _________
a) Electrolysis
b) Cold stream process
c) Atomization
d) Reduction
View Answer
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.
12. Which of the following changes do not occur on during recrystallization?
a) Phase changes
b) Grain shrinkage
c) Precipitation
d) Pore shrinkage
View Answer
Explanation: Recrystallization includes changes in the microstructure, phase changes, grain growth, precipitation and pore shrinkage.
13. Which of the following substance is added to iron powder to improve the compressive strength of bearing?
a) Lead
b) Copper
c) Sulphur
d) Bismuth
View Answer
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.
14. _____ measures the resistance to fluid flow through a compacted powder bed to calculate the specific surface of the powder.
a) Elutriation Method
b) Sedimentation method
c) Gas adsorption method
d) Permeametry
View Answer
Explanation: Permeametry or permeability method measures the resistance to fluid flow through a compacted powder bed to calculate the specific surface of the powder. The principle involves measuring the pressure drop across the bed of packed powder particles contained in a chamber in relation to the fluid flow. This information is used to determine related properties of the powder such as specific surface area and average particle size.
15. Which of the following material on addition to the powder mix lowers the strength of the bearing?
a) Graphite
b) Oil
c) Sulphur
d) Bismuth
View Answer
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.
16. 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
View Answer
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.
17. ______ is obtained in water atomization compared to gas atomization.
a) Spherical powder
b) Ultra coarse powder
c) Fine powder
d) Coarse powder
View Answer
Explanation: Particle shape of powders produced by atomization is influenced by the factor that determine the cooling rate. Thus, the cooling rates are higher in magnitude in the case of water atomization than in gas atomization which results in finer powder in case of water atomization.
18. The alloy F-0000-10 refers to pure fluorine powder with anultimate breaking strength of 10 ksi.
a) False
b) True
View Answer
Explanation: The alloy F-0000-10 refers to pure iron powder with a yield strength or nominal strength of 10 ksi. This designation is given by the MPIF (Metal Powder Industries Federation, Princeton, New Jersey, USA) has provided a metal powder designation system, according to which, metal and alloy powders are given a prefix and a four-digit code.
19. Mixing of elemental powder is essential prior to compaction.
a) False
b) True
View Answer
Explanation: Mixing of elemental powder is essential prior to compaction. For making bronze bearings, copper powder is mixed with tin and graphite powders and thus it is important to ensure through mixing to avoid segregation of tin particles during sintering resulting in non-uniform sintering.
20. Time and current are the two important variables which affect the amount of powder deposited on the electrode during electrodeposition of copper.
a) False
b) True
View Answer
Explanation: Time and current are the two important variables which affect the amount of powder deposited on the electrode during electrodeposition of copper. As time increases the amount of copper powder deposited on the cathode increases. Similarly, as the current increases, bath conductivity increase and thus the amount of powder deposited also increases.
21. Which of the following P/M part exhibit a short cutting tool life?
a) Dense
b) Very dense
c) Sintered
d) Porous
View Answer
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.
22. What should be added to the iron powder mix to improve the speed capability?
a) Lead
b) Molybdenum
c) Bismuth
d) Vanadium
View Answer
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.
23. _______ are bearings containing bronze or iron powder mixed with graphite.
a) Metal impregnated
b) Plastic impregnated
c) Hydrocarbon impregnated
d) Oil impregnated
View Answer
Explanation: The production of porous bearings involves its infiltration with either oil or plastic. Oil impregnated bearings are typically bearings containing bronze or iron powder mixed with graphite.
24. In which stage of solid-state sintering the pores are interconnected and pore shape is irregular?
a) 2nd
b) 4th
c) 3rd
d) 1st
View Answer
Explanation: During the first stage of solid-state sintering, rapid neck formation and neck growth take place in the powder compact. This effect a greater extent of bonding within the sintered mass and thus during this stage the pores are interconnected and the pore shape is irregular.
25. The equilibrium pore pressure is given by Pp= ________
a) Patm+2γsv/x
b) Patm+2γss/r
c) Patm+2γsv/r
d) Patm-2γsv/r
View Answer
Explanation: The equilibrium pore pressure is given by Pp for an isolated spherical pore is given by Patm+2γsv/r where, Patm is the atmospheric pressure, r is the pore radius, and γsv is the surface energy of solid-vapor interface. Thus, on increasing Patm (as in hot isostatic pressing) will decrease the pore radius.
26. 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
c) Electrolysis
d) Gas atomization
View Answer
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.
27. Coble developed rate equations for three stage sintering assuming the compact to be made of packed spheres and in the final stage form interlocking ___________
a) Tetracontagons
b) Tetrakaioctahedrons
c) Tetrakaitetrahedrons
d) Tetrakaidecahedrons
View Answer
Explanation: Coble developed rate equations for three stage sintering assuming the compact to be made of packed spheres and in the final stage form interlocking tetrakaidecahedrons. According to Coble, the necks form in the initial stage of sintering but the distance between the particle centers remain constant. During the intermediate stage, necks grow, shrinkage may occur and grain growth may occur. During the third stage, the pores become isolated, the pores being considered as spheres at the grain boundaries.
28. Liquid phase sintering is advantageous over solid phase sintering due to ______
a) Microstructure
b) Kinetics
c) Economy
d) Temperature
View Answer
Explanation: Liquid phase sintering promotes enhanced kinetics because of the presence of the liquid phase. The capillary attraction due to wetting allows rapid densification, reduction in interparticle friction leads to a faster rearrangement of particles, and presence of liquid phase aids in material flow and better packing.
29. 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
View Answer
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.
30. _______ has provided a metal powder designation system, according to which, metal and alloy powders are given a prefix and a four-digit code.
a) BIS
b) ASME
c) ASTM
d) MPIF
View Answer
Explanation: MPIF (Metal Powder Industries Federation, Princeton, New Jersey, USA) has provided a metal powder designation system, according to which, metal and alloy powders are given a prefix and a four-digit code. The prefix will refer to the metals present while the four-digit code will give the % of the alloying elements present. The minimum yield strength is referred to by another two-digit code at the end.
31. The modern production of hard metal is attributed to ________
a) Schroter
b) Osram Studiegesellschaft
c) Kieffer
d) Schwarzkopf
View Answer
Explanation: The modern production of hard metal is attributed to Schroter. The technique involves the blending of WC powder with up-to 20% by weight of a metal of the iron group, particularly Co as a binder metal, compaction of the powder mixture and sintering at a temperature close to the melting point of the binder metal.
32. Heterogenous nature of powders improve sintering kinetics.
a) False
b) True
View Answer
Explanation: Heterogenous nature of powders (e.g. alloy powders or powder mix) promotes enhanced diffusion and improves sintering kinetics. Dispersed phases within the matrix may promote sintering by inhibiting grain boundary motion.
33. 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
View Answer
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.
34. Which solution is used to fill the dew cup for carrying out moisture analysis?
a) Acetone
b) Carboxylic acid
c) Propane
d) Ethyl alcohol
View Answer
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.
35. 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
View Answer
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.
36. Why infiltrated pump cylinder blocks are popular in use?
a) Pressure-tightness
b) Light-weight
c) Mechanical strength
d) Resistance to thermal stress
View Answer
Explanation: The infiltrated parts become impermeable due to the absence of interconnected porosity and hence they can be used where pressure tightness is desired. One such example is the infiltrated pump cylinder blocks.
37. Which of the following treatment is given to a thin-walled bushing which 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
View Answer
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.
38. Which of the following is not a benefit of impregnation?
a) Dimensional tolerance
b) Improved machinability
c) Pressure-tightness
d) Porosity elimination
View Answer
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.
39. 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
View Answer
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.
40. In ________ the collection of powder is done in a water tank.
a) Dry collection
b) Water collection
c) Wet collection
d) Hydrated collection
View Answer
Explanation: In wet collection, the powder is collected in a water tank provided at the bottom of the atomization unit. The tank may be cooled externally when large quantities of powders are produced. The powders are then dried to remove the moisture.
41. Milled powder mixtures are unsuitable for automatic pressing in comparison to agglomerated carbide-cobalt powder mixtures.
a) False
b) True
View Answer
Explanation: Milled powder mixtures are unsuitable for automatic pressing due to their very poor flow properties, while the agglomerated carbide-cobalt mixture is required for compaction due to their high apparent density and good flow properties in automatic press. Hence, the powders containing about 2% lubricant are frequently agglomerated by compacting them (e.g. pressure= 3.5 tsi).
42. Which of the following are the stages of sintering, according to Sauerwald theory?
a) Adhesion, crystallization
b) Adhesion, recrystallization
c) Adhesion, bonding
d) Adhesion
View Answer
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.
43. 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
View Answer
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.
44. 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
View Answer
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.
45. Which of the following are the important temperature controls used in sintering furnace?
a) Radiation pyrometers
b) Thermocouple
c) On-off controllers and proportional controllers
d) On-off controllers
View Answer
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.
46. Which of the following treatment fives a ferrito-pearlitic structure in P/M steel forgings?
a) Hardening
b) Nitrocarburizing
c) Tempering
d) Annealing
View Answer
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.
47. Which kind of porosity leads to longer tool life?
a) Either very high or very low
b) Very high
c) Moderate
d) Very low
View Answer
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.
48. 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
View Answer
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.
49. Which of the following is not a type of bearing?
a) Babbit backed steel
b) Steel backed steel
c) Unbacked bearings
d) Teflon bearing
View Answer
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.
50. Which of the following conditions are necessary for the development of fluid film in porous bearings?
a) High speed
b) Viscosity
c) High speed and viscosity
d) Low speed
View Answer
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
- Sintering
- 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 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.
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2. Powder Metallurgy Multiple Choice Questions on Powder Treatment and Handling
The section contains questions and answers on powder treatment and its methods, metal powders coating and pyrophoricity.
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3. MCQ on Metal Powder Characteristics
The section contains 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.
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4. Powder Metallurgy Multiple Choice Questions on High Temperature Compaction
The section contains multiple choice questions and answers on uniaxial hot pressing, hot extrusion and isostatic pressing.
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5. Powder Metallurgy MCQ on Sintering
The section contains 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 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 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.
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8. Multiple Choice Questions on Advanced Powder Metallurgy Processing Techniques
The section contains 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.
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9. Powder Metallurgy MCQ on Tool Materials
The section contains MCQs on cemented carbides and its production, cemented carbides applications, properties and testing.
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10. Multiple Choice Questions on Powder Manufacture
The section contains multiple choice questions and answers on alloy powders, electrochemical and physico-chemical methods of powder production.
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11. MCQ on Characteristics and Testings of Metal Powders
The section contains questions and answers on particle size measurement techniques, particle characterisation, particle shape and specific area.
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