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Powder Metallurgygy

By  S K Mondal

Atomization using a gas stream

Compacting

IES – 2007 ConventionalMetal powders are compacted by many methods, but

sintering is required to achieve which property? What

i h t i t ti i ?is hot iso‐static pressing?

[ 2 Marks]

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IES – 2011 ConventionalWhat is isostatic pressing of metal powders ?What are its advantage ?

[ 2 Marks]

Oil‐impregnated Porous Bronze Bearings

IES 2010Consider the following parts:1. Grinding wheel2. Brake lining3 Self‐lubricating bearings3. Self lubricating bearingsWhich of these parts are made by powdermetallurgy technique?(a) 1, 2 and 3 (b) 2 only(c) 2 and 3 only (d) 1 and 2 only

Ans. (c)

IES 2010Metallic powders can be produced by(a) Atomization(b) Pulverization(c) Electro‐deposition process(c) Electro deposition process(d) All of the aboveAns. (d)

IES – 2002The rate of production of a powder metallurgy partdepends on(a) Flow rate of powder(b) Green strength of compact(c) Apparent density of compact(d) Compressibility of powder

Ans. (c)

IES – 2001Match List‐I (Components) with List‐II(Manufacturing Processes) and select the correctanswer using the codes given below the lists:

List I List IIA C b d ( t l) M hi i A (d)A. Car body (metal) 1. Machining Ans. (d)B. Clutch lining 2. CastingC. Gears 3. Sheet metal pressingD. Engine block 4. Powder metallurgy

Codes:A B C D A B C D(a) 3 4 2 1 (b) 4 3 1 2(c) 4 3 2 1 (d) 3 4 1 2

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GATE 2011The operation in which oil is permeated into thepores of a powder metallurgy product is known as(a) mixing(b) sintering(c) impregnation(d) Infiltration

Ans. (c)

IES – 1998In powder metallurgy, the operation carried out toimprove the bearing property of a bush is called(a) infiltration (b) impregnation(c) plating (d) heat treatment

Ans. (b)

IES – 1997Which of the following components can bemanufactured by powdermetallurgymethods?1. Carbide tool tips 2. Bearings3. Filters 4. Brake liningsSelect the correct answer using the codes given below:(a) 1, 3 and 4 (b) 2 and 3(c) 1, 2 and 4 (d) 1, 2, 3 and 4

Ans. (d)

IES – 1999The correct sequence of the given processes inmanufacturing by powdermetallurgy is(a) Blending, compacting, sintering and sizing(b) Blending, compacting, sizing and sintering(c) Compacting, sizing, blending and sintering(d) Compacting, blending, sizing and sintering

Ans. (a)

IES – 2001Carbide‐tipped cutting tools are manufactured bypowder‐ metal technology process and have acomposition of(a) Zirconium‐Tungsten (35% ‐65%)(b) T t bid C b lt ( % %)(b) Tungsten carbide‐Cobalt (90% ‐ 10%)(c) Aluminium oxide‐ Silica (70% ‐ 30%)(d) Nickel‐Chromium‐ Tungsten (30% ‐ 15% ‐ 55%)

Ans. (b)

IES – 1999Assertion (A): In atomization process of manufacture ofmetal powder, the molten metal is forced through asmall orifice and broken up by a stream of compressedair.Reason (R): The metallic powder obtained by( ) p yatomization process is quite resistant to oxidation.(a) Both A and R are individually true and R is the correctexplanation of A(b) Both A and R are individually true but R is not thecorrect explanation of A(c) A is true but R is false(d) A is false but R is true Ans. (c)

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IES – 2007What are the advantages of powdermetallurgy?1. Extreme purity product2. Low labour cost3. Low equipment cost.Select the correct answer using the code given below(a) 1, 2 and 3 (b) 1 and 2 only(c) 2 and 3 only (d) 1 and 3 only

Ans. (b)

IES – 2006Which of the following are the limitations ofpowdermetallurgy?1. High tooling and equipment costs.2. Wastage of material.3. It cannot be automated.4. Expensive metallic powders.Select the correct answer using the codes given below:(a) Only 1 and 2 (b) Only 3 and 4(c) Only 1 and 4 (d) Only 1, 2 and 4

Ans. (c)

IES – 2004Consider the following factors:1. Size and shape that can be produced economically2. Porosity of the parts produced3. Available press capacity4. High densityWhich of the above are limitations of powdermetallurgy?(a) 1, 3 and 4 (b) 2 and 3(c) 1, 2 and 3 (d) 1 and 2

Ans. (a)

IES – 2009Which of the following cutting tool bits aremade bypowdermetallurgy process?(a) Carbon steel tool bits (b) Stellite tool bits(c) Ceramic tool bits (d) HSS tool bits

Ans. (c)

IAS – 2003Which of the following are produced by powdermetallurgy process?

1. Cemented carbide dies2. Porous bearings3 Small magnets3. Small magnets4. Parts with intricate shapesSelect the correct answer using the codes given below:Codes:(a) 1, 2 and 3 (b) 1, 2 and 4(c) 2, 3 and 4 (d) 1, 3 and 4

Ans. (a)

IAS – 2003In parts produced by powder metallurgy process,pre‐sintering is done to(a) Increase the toughness of the component(b) Increase the density of the component(c) Facilitate bonding of non‐metallic particles(d) Facilitate machining of the part

Ans. (d)

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IAS – 2000Consider the following processes:1. Mechanical pulverization2. Atomization3. Chemical reduction4. SinteringWhich of these processes are used for powderpreparation in powder metallurgy?(a) 2, 3 and 4 (b) 1, 2 and 3(c) 1, 3 and 4 (d) 1, 2 and 4

Ans. (b)

IAS – 1997Assertion (A): Close dimensional tolerances are NOTpossible with isostatic pressing of metal powder inpowdermetallurgy technique.Reason (R): In the process of isostatic pressing, thepressure is equal in all directions which permitsuniformdensity of themetal powderuniformdensity of themetal powder.(a) Both A and R are individually true and R is the correctexplanation of A(b) Both A and R are individually true but R is not thecorrect explanation of A(c) A is true but R is false(d) A is false but R is true

Ans. (d)

IAS – 1998Throwaway tungsten carbide tip tools aremanufactured by(a) Forging (b) Brazing(c) Powder metallurgy (d) Extrusion

Ans. (c)

IAS – 1996Which one of the following processes is performedin powder metallurgy to promote self‐lubricatingproperties in sintered parts?(a) Infiltration (b) Impregnation( ) Pl ti (d) G hiti ti(c) Plating (d) Graphitization

Ans. (b)

IAS – 2007Assertion (A): Mechanical disintegration of amolten metal stream into fine particles by means ofa jet of compressed air is known as atomization.Reason (R): In atomization process inert‐gas orwater cannot be used as a substitute for compressedair.(a) Both A and R are individually true and R is thecorrect explanation of A(b) Both A and R are individually true but R is not thecorrect explanation of A(c) A is true but R is false(d) A is false but R is true Ans. (c)

IAS – 2004The following are the constituent steps in theprocess of powdermetallurgy:1. Powder conditioning2. Sintering3. Production of metallic powder4. Pressing or compacting into the desired shapeIndentify the correct order in which they have to beperformed and select the correct answer using the codesgiven below:(a) 1‐2‐3‐4 (b) 3‐1‐4‐2(c) 2‐4‐1‐3 (d) 4‐3‐2‐1 Ans. (b)

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IAS – 2003Assertion (A): Atomization method for production ofmetal powders consists of mechanical disintegration ofmolten stream into fine particles.Reason (R): Atomization method is an excellent meansof making powders from high temperaturemetals.g p g p(a) Both A and R are individually true and R is the correctexplanation of A(b) Both A and R are individually true but R is not thecorrect explanation of A(c) A is true but R is false(d) A is false but R is true Ans. (c)

IAS – 2007Consider the following basic steps involved in theproduction of porous bearings:1. Sintering2. Mixing3. Repressing4. Impregnation5. Cold‐die‐compactionWhich one of the following is the correct sequence of theabove steps? Ans. (b)

Conventional Questions1. Explain why metal powders are blended. Describe what

happens during sintering. [IES‐2010, 2 Marks]

Conventional Questions1. Discuss the terms fineness and particle size

distribution in powder metallurgy. [IES‐2010, 2 Marks]Ans.

Fineness: Is the diameter of spherical shaped particleand mean diameter of non‐spherical shaped particle.p p p

Particle size distribution: Geometric standarddeviation (a measure for the bredth or width of adistribution), is the ratio of particle size diameterstaken at 84.1 and 50% of the cumulative undersizedweight plot, respectively and mean mass diameterdefine the particle size distribution.

Conventional QuestionsEnumerate the steps involved in “powder metallurgy”process. Discuss these steps. Name the materials usedin “powder metallurgy”. What are the limitations ofpowder metallurgy? [IES‐2005, 10 Marks]