Soubhik De (Autosaved)

Fabrication and characterization of tungsten based alloy

(Product development lab report, 5th semester)

Prof.A.patra

NIT rourkela

Department of Metallurgical & Materials Engineering

1

Declaration

I hereby declare that the project report entitled “Fabrication and characterization of tungsten

based alloy” is a record of the work carried out by me as part of my product development lab

work under the guidance of Prof. A.Patra, Department of Metallurgical and Materials

Engineering, National Institute of Technology, rourkela.

Name- SOUBHIK DE

Roll number : 714MM1131

Course: B.Tech- M.Tech Dual Degree

Department of Metallurgical and Materials engineering

National Institute of Technology, Rourkela

ORISSA-769008

2

Acknowledgement

At the very outset, I take the opportunity to express my deep sense of gratitude and profound

regard to my product development lab supervisor Prof. A.Patra, department of Metallurgical and

Materials Engineering, National Institute of technology, Rourkela, for his able guidance and

moral supports through the wonderful journey, that has culminated in this Project Report.He has

been instrumental in helping with the work. The fruitful discussions have helped me understand

the problems. I am thankful to the National Institute of Technology, Rourkela for providing me

sufficient space and facilities for this work. At last but not the least, I want to express my sincere

gratitude to all of my family members, especially my parents for their constant encouragement

and moral support during my project work.

CONTENTS

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1. ABSTARCT

2. INTRODUCTIN

2.1 Composition:

2.2 Properties and Uses of alloying elements

3. METHODS AND METHODOLOGY

3.1Ball milling

3.2Compaction

3.3Sintering

3.4Density measurement

3.5Mounting

3.6Planar grinding

3.7 Polishing

4. RESULT AND DISCUSSION

4.1 XRD analysis

4.2 Microstructure observation

4.3 Hardness Testing (Vicker’s micro hardness testing)

5. CONCLUSION

6. REFERENCES

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1. ABSTARCT:This invention is directed to the use of tungsten base alloys containing about 80 weight percent

tungsten, about 10 weight percent of nickel and about 10 percent of molybdenum. Tungsten has

lower ductility higher strength so we can’t able to give it a desire shape and also it has higher

DBTT so by addition of Ni and Mo we are trying to increase ductility with proper combination

of strength and decrease the DBTT for high temperature application of that alloy W80Ni10Mo10.

With the help of powder metallurgy using ball mill elements of the alloy has mixed up

properly.After that the powder sample has taken for XRD analysis. Using uniaxial cold isostatic

press powder has compacted. Then the green pallet has sent for sintering 15000C for two hours.

Before and after sintering density measurement of the alloy has taken place. Microstructure of

that sample has observed using optical microscope after proper polishing so that grain

boundaries on that surface properly observe under microscope. With the help of Vicker’s

hardness test hardness of the alloy has calculated .

Tungsten has lower ductility higher strength so we can’t able to give it a desire shape and also it

has higher DBTT so by addition of Ni and Mo we are trying to increase ductility with proper

combination of strength and decrease the DBTT for high temperature application of that alloy

W80Ni10Mo10.

2.INTRODUCTION:2.1 Composition:Table number 1.

Elements Symbol Weight

fraction(%)

Atomic

mass(gm)

Density(gm/cc) Melting

point(0C)

Crystal

structure

Tungsten W 80 183 19.15 3422 BCC

Nickel Ni 10 59 8.41 1455 FCC

Molybdenum Mo 10 42 10.28 2623 BCC

2.2: Properties and Uses of alloying elements:Tungsten: Also known as wolfram, one of the hardest rare earth material is a chemical

element with symbol W and atomic number 74.

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Tungsten and its alloys have numerous applications, including incandescent light

bulb filaments, X-ray tubes (as both the filament and target), electrodes in TIG

welding, superalloys, and radiation shielding. Tungsten's hardness and high density give it

military applications in penetrating projectiles. Tungsten compounds are also often used as

industrial catalysts.

Tungsten is the only metal from the third transition series that is known to occur in biomolecules,

where it is used in a few species of bacteria and archaea. It is the heaviest element known to be

essential to any living organism. Tungsten interferes with molybdenum and copper metabolism

and is somewhat toxic to animal life

Nickel: Nickel oxidizes at room temperature and is considered corrosion-resistant.Presencde of

nickel tensile strength of the specimen increase. Nickel is used in many specific and recognizable

industrial and consumer products, including stainless steel, alnico magnets,

coinage, rechargeable batteries, electric guitar strings, microphone capsules, plating on plumbing

fixtures and special alloys such as permalloy, elinvar, and invar. It is used for plating and as a

green tint in glass.

Molybdenum:

It increases toughness .Molybdenum does not occur naturally as a free metal on Earth it is found

only in various oxidation states in minerals. It does not visibly react with oxygen or water at

room temperature, and the bulk oxidation occurs at temperatures above 600 °C, resulting

in trioxide, the trioxide is volatile and sublimes at high temperatures. This prevents formation of

a continuous protective (passivating) oxide layer, which would stop the bulk oxidation of metal.

The estimated global use is structural steel 35%, stainless steel 25%, chemicals 14%, tool &

high-speed steels 9%, cast iron 6%, molybdenum elemental metal 6%, and superalloys 5% [1 to

3]

3. METHODS AND METHODOLOGY:3.1 Ball milling: A Ball Mill grinds material by rotating a cylinder with steel grinding balls,

causing the balls to fall back into the cylinder and onto the material to be ground. The rotation is

usually between 4 to 20 revolutions per minute, depending upon the diameter of the mill. The

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larger the diameter, the slower the rotation. If the peripheral speed of the mill is too great, it

begins to act like a centrifuge and the balls do not fall back, but stay on the perimeter of the

mill. The point where the mill becomes a centrifuge is called the "Critical Speed", and ball mills

usually operate at 65% to 75% of the critical speed. 

Ball Mills are generally used to grind material 1/4 inch and finer, down to the particle size of 20

to 75 microns. To achieve a reasonable efficiency with ball mills, they must be operated in a

closed system, with oversize material continuously being recirculated back into the mill to be

reduced. Various classifiers, such as screens, spiral classifiers, cyclones and air classifiers are

used for classifying the discharge from ball mills. Here planetary ball mill has used to have finest

particle. On that ball mill duration of rotation fixed up to 60 minutes and 60 minutes of cooling

is set in the mill. This process has been continuing for 10 hours. For cooling purpose the fans are

used near the base.

Affecting parameters are:

1. RPM of the mill

2. Ball to powder ratio(10:1) and Process control agent (PCA) like toluene. 2/3 rd part of the vial

should be filled by toluene for to provide coating to the balls to avoid contact with the powder.

3.100 lls of 10 mm size are used

3.2 Compaction:It is the one of important part of powder metallurgy. Compacting is a mass-conserving shaping

process. Fine metal particles are placed into a flexible mould and then high gas or fluid pressure

is applied to the mould. The resulting product is then sintered in a furnace which increases the

strength of the part by bonding the metal particles.

First of all The lower punch die of the isostatic press has taken and the sample alloy powder has

put into it.Then the upper die of the punch has placed over the lower punch die by applying

powder alloy has compressed in it .This arrangement has placed in the uniaxial cold isostatic

press carefully such that the die is directly below the center part of the press. After that press has

manually made to tight with the die.The load has been increasing slowly in the cold isostatic

press, so that there is a uniform distribution of load. The load increases continuously until we

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have reached up to a certain load of 950 Mpa.Then the dwell time set for 10 minutes. Then the

die has carefully removed and we obtain a green pellet of very low strength has punched from

the die.

3.3 Sintering: It is a heat treatment process applied to a powder compact in order to impart strength

and integrity.Usualy the temperature is used for sintering is below the melting point of the major

constituent of the Powder Metallurgy material. After compaction, neighboring powder particles are held

together by cold welds, which give the compact sufficient “green strength” to be handled. At sintering

temperature, diffusion processes cause necks to form and grow at these contact points.

Objective of sintering:

1. Removal of the pressing lubricants from the surface of the alloy by evaporation and burning of

the vapors.

2. Reduction of surface oxides from the powder particles in compact.

Tungsten-based nickel molybdenum alloy has fabricated from mixed elemental powders using

liquid phase sintering. Alloy has placed in sintering furnace, then heated up to 1500 degree

centigrade. At the starting of sintering process heating rate has fixed 50 C per minute ,after that

40C , and 30 C after some time heating rate has become constant .Due to different thermal shock

absorption coefficients of the alloy composition there is a decrease in heating rate.After the

temperature has reached up to 15000 C which is lower than the melting point of other alloying

elements, the sample has soaked for certain time in which the solvent has allowed to soak all

over the surface has followed by a spinning for solvent draining, it is found to produce

perovskite layers with high uniformity on a centimeter scale and with much improve reliability.

Besides the enhance surface morphology due to the rinsing induce surface precipitation that

constrains the grain growth underneath in the precursor films, this has been performed by post

sintering deformation. After soaking for 2 hours’ time slow furnace cooling has done at the same

rate of heating. All the sintering cycle has done under argon atmosphere because in open

atmosphere there will be formation of oxides which is brittle. The hydrogen gas incorporate and

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do hydrogen sintering it will react with oxygen and get away in the form of moisture so that

embrittlement will not occur. Total duration is 10-12 hours.

3.4 Density measurement:Archimede’s Principle: When a body is fully (or partially) submerged in a fluid, a buoyant force

(Fb) from the surrounding fluid acts on the body. The force is directed upward and has the

magnitude equal to the weight mfg (ρfvg in terms of density) of the fluid that has been displaced

by the body. mfg = (ρfvg) =Fb = where (mf ) is the mass, (ρf )density of the fluid that is displaced.

When a body floats in a fluid, the magnitude of the buoyant force, Fb on the body is equal to the

magnitude of the gravitational force, Fg on the body. Thus, Fb = Fg = mfg = ρfvg

For a solid object of volume V, heavier than water, when completely submerged in water, the

buoyant force is Fb = ρwvg , where ρw is the density of water. The mass of the object,M, when

weighed in air is

M = ρv where ρ is the density of the object, therefore the volume of the object is v = M/ρ .

Apparent weight is the difference between the actual weight of an object and the magnitude of

the buoyant force.

weightapp = weightactual − Fb .

The apparent weight of the object is Mwg , and Mw is the mass of the object when totally

submerged in the water. Thus the density of the object is calculated by [4]

Mwg = Mg − ρwvg

ρw= Mρw/(M-Mw)

Procedure : First of all theoretical density of that alloy has calculated using formula theoretical

density of the alloying element W80Ni10Mo10 has calculated.

1ρ=

Xρ x +

Yρ y +

Zρ z

(ρ= density af the product, X,Y and Z are the mass of the alloying elements and ρx , ρy ,ρz

are corresponding their densities)

Then dry weight of the green pellet has measured. Then the sample immerged into a water for 24

hours to calculate soaked weight. With the help of archmedes principle the suspended weight of

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the sample calculated by immerging into water .After that density, %densification and %

porosity has calculated.Same steps are applied for sintered pellet.

Density =dry weight soak weight - supended weight ×1 gm/cc

% Densification =Practical Density Theoritical Density × 100 %

% Porosity =100 - (% densification)

After that before sintering soaked wet of the compact green pellet sintered pellet has calculated

Wa

Dry weight

(grams

)

WSS

Suspende

d weight

(grams)

WS

Soaked

weight

(grams

)

Actual

Densit

y

(g/cc)

Theoretica

l Density

(g/cc)

%

Densificatio

n

%

Porosit

y

Green

Pellet

7.3300 6.4600 7.2900 8.831 15.9970 55.20 44.80

Sintere

d Pellet

5.4748 5.0600 5.4800 13.035 15.9970 81.48 18.52

Table number 2.

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Before sintering density has found 8.331 g/cc. Due to presence of volatile product and higher

amount of porosity (44.80%) it is much less than theoretical density.

After sintering green pellet become more compact, all volatile product has pulled out and porosity is less than 2.5 times of green pellet. 3.5 Mounting:

The mounting operation accomplishes two important functions

(1) It protects the specimen edge and maintains the integrity of a materials surface features

(2) Improves handling of irregular shaped samples, especially for automated specimen

preparation. The majority of metallographic specimen mounting is done by encapsulating the

specimen into a compression mounting compound (thermo sets - phenolics, epoxies, diallyl

phthalates or thermoplastics - acrylics), casting into ambient cast able mounting resins (acrylic

resins, epoxy resins, and polyester resins), and gluing with a thermoplastic glues. There are

mainly two types of mounting

Compression mounting (For metals, compression mounting is widely used).

Cast able mounting resins (commonly used for electronic and ceramic materials).

, and using above information Cold mounting has used. On sintered specimen bottom part of the

sample which has direct contact with the furnace face so on that part higher amount of

refractories have stacked and as during sintering hominization of alloying element has not

properly done so higher amount of Nickel has found in bottom part and showing yellowish in

nature. Upper part is rougher than lower part. It is difficult to polish bottom surface so keeping

upper part outside the sample has mounted properly.

3.6 Planar grinding: (course grinding) is required to planerize the specimen and to reduce the

damage created by sectioning/cutting. The planar grinding step is accomplished by decreasing

the abrasive grit/ particle size sequentially to obtain surface finishes that are ready for polishing.

Surfaces of that sample has grinded properly to have a flat surface. Here SiC paper is used for

grinding purpose. Another thing required during grinding is applying a proper pressure. Higher

grinding/polishing pressures can also generate additional frictional heat, which may actually be

beneficial for the chemical mechanical polishing but it can burn the surface. During grinding by

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hand, the specimens were rotated at 90 degrees and continually ground until all the scratches

from the previous grinding direction are removed. If necessary the abrasive paper can be replace

with a newer paper to increase cutting rates.

3.7 Polishing:The purpose of the rough polishing is to remove the damage produced during planar grinding.

Proper rough polishing would maintain specimen flatness and retain all inclusions or secondary

phases, by eliminating the previous damage and maintaining the micro structural integrity of the

specimen at this step, a minimal amount of time should be required to remove the cosmetic

damage at the final polishing step. The polishing has done using abrasive sheet papers of Sic, has

used for rough polishing => 1/0,2/0,3/0,4/0. Initially, the lapping has performed with coarser

paper (grit no.1/0,2/0) in order to reduce the thickness and also to get nearly parallel surfaces.

Then after the polishing has done started with grit 3/0 and 4/0 in a increasing way.

The purpose of final polishing is to remove only surface damage create due to rough polishing.

To improve the surface finish, a polishing cloth has taken and diamond paste (particle size of ~ 3

μm) along with few drops of lubrication oil is spread on it. Then the sample has polished on this

cloth for about 10 -15 minutes for improving the surface finish.

Fig.1 polished sintered pellet

4. RESULT AND DISCUSSION:

4.1 XRD analysis:

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X-ray powder diffraction (XRD) is a rapid analytical technique primarily used for phase

identification of a crystalline material and can provide information on unit cell dimensions. The

analyzed material is finely ground, homogenized, and average bulk composition is determined.

X-ray diffractometers consist of three basic elements: an X-ray tube, a sample holder, and an X-

ray detector. X-rays are generated in a catthode ray tube by heating a filament to produce

electrons, then accelerating the electrons toward a target by applying a voltage, and bombarding

the target material with electrons. When electrons have sufficient energy to dislodge inner shell

electrons of the target material, characteristic X-ray spectra are produced.

Fig.2 Bruker's X-ray Diffraction D8-Discover instrument. [5]

sample.Bragg’s law should be satisfied.

Bragg’s law: nλ=2dsin θ

Where λ=Wavelength of X-ray, d=interlamellar spacing, θ=diffraction angle.

The diffracted X-rays are detected,processed and counted.By scanning the sample

through a range of 2θ angles,all possible diffraction direction of the lattice should be

attained due to the random orientation of the powdered material.conversion of diffraction

peaks to d-spacings allows identification of mineral as everyone has unique d-spacing.

The affecting parameters are :

Scan range: Specific 2θ range where the changes are taking place.(200-100)

Step size: Increment of angle in 2θ (0.02 or 0.05)

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Scan rate: Speed (5-20°/min).

Scherrer equation:

Bcosϴ = € sinϴ + 0.94* λ/ d

B= Full width half maxima , € = lattice stra , λ = wave length of anode , d = crsytallite

size

After 0 hour,1hour,5 hour,10 hour milling XRD study has done.Intensity vs 2ϴ graph has

drawn using origin software.

Observation:

1. the tungsten shows highest peak intensity from 0 to 10 hours, also nickel shows

lower peak intensity.

2. No peak of molybdenum observed

3. After 10 hours milling Inclusion formation starts.

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4.2 Microstructure observation:

Metallurgical analysis (metallographic) of the micro structural provides the Material Scientist or

Metallurgist information varying from phase structure, grain size, solidification structure, casting

voids, etc. Analysis of a materials grain size provides valuable information regarding a materials

physical hardness and ductility. Micro structural analysis can also provide very useful

information about the types of phases that occur during cooling.SEM, TEM and Optical

microscope are used in analyzing of microstructure, here we have used Optical microscope for

analyzing phase present in the alloying element and to observe grain boundaries.

After proper polishing the specimen has placed under Optical microscope for observation.

1. Grain boundaries has properly detected.

2. Circular like grains of tungsten are seen with shiny yellowish phase of nickel, molybdenum

phase has not detected properly.

3. Inclusion and pores are found as black dots.

Fig.2 and Fig.3 shows the microstructure of the alloy at 200x And 500x magnification

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Fig.3 200x Fig.4 500x

3.3 Hardness Testing (Vicker’s micro hardness testing):After proper polishing and micro structure observation it has proceed for vicker’s micro hardness

testing. As our sample is a tungsten based alloy so for taking the hardness at different phase with

respect to overall hardness of the alloy Vicker’s micro hardness testing has done.

In Vickers Test, the load is applied smoothly, without impact forcing the indenter into the test

piece. The indenter is placed in a particular place of that sample for 10 or 15 seconds. The

physical quality of the indenter and accuracy of applied load must be controlled to have a perfect

hardness. After the load was removed, the impression diagonals shows in Fig.10.a&b are

measured usually to the nearest 0.1-μm with a filar micrometer and averaged. The Vickers

hardness (HV) is calculated using this formula. [7]

HV =1854.4∗Ld 1∗d 2

Where the L load is in gf unit and average diagonal d is in μm.and d2 = d1 * d2

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Fig.5(shows vicker’s micro hardness method, size of indenter)

Using this formula at different load (100 gf, 500 gf, 50gf) and at constant dwell time 10

seconds ,micro hardness of that sample has measured. Application of different load with at

constant dwell time changing in micro hardness (HV value) has observed using micro harness

testing machine model number LECO LM24880 .Result of micro hardness testing at different

loads with same dwell time have tabulated (table number 3 and 4 ) and graph (a,b,c,d) has plotted

comparing Experimental and Theoretical Hard ness.

From that Hardness data has obtained from Theoretical and Experimental, Hardness value is

higher in Experimental.

Table number 3.(For Experimental hardness)Load (in

gf)

Sl.

No

.

D1 (in

μm)

D2 (in

μm)

Hardness (VHN) Hardness (in

MPa)

50 1 11.07 12.04 694.4 6810

2 12.42 12.66 589.6 5782

3 12.85 12.96 556.7 5460

4 13.2 13.27 529.3 5191

100 1 18.53 16.42 607.3 5956

2 18.82 19.35 509.1 4993

3 19.02 19.7 494.8 4853

4 19.31 18.42 521.1 5110

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500 1 45.94 47.21 427.4 4192

2 46.32 45.86 436.4 4280

3 43.82 46.69 452.7 4440

4 46.45 46.7 427.4 4192

1000 1 74.96 75.21 328.9 3226

2 82.17 83.8 269.3 2641

3 75.67 74.79 327.7 3214

4 75.92 74.71 326.9 3206

Table number 4.(Theoretical)

Load (in

gf)

Sl.

No.

D1 (in

μm)

D2 (in

μm)

Hardness (VHN) Hardness (in MPa)

50 1 12.38 11.59 646.2 6337

2 13.12 13 543.6 5331

3 13.87 14.09 474.5 4653

4 14.22 13.63 478.4 4692

100 1 17.6 18.72 562.9 5520

2 18.72 18.47 536.4 5260

3 20.01 20.44 453.4 4446

4 20.2 18.87 486.5 4771

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500 1 46.12 45.16 445.2 4366

2 45.86 46.3 436.7 4283

3 46.56 42.53 468.3 4593

4 46.56 43.58 457.0 4482

1000 1 76.09 72.94 334.2 3277

2 82.41 82.41 273.1 2678

3 74.68 75.37 329.5 3231

4 82.32 80.29 280.6 2752

Hardness graphs

0 1 2 3 4 54500

5000

5500

6000

6500

7000

Experimental Hardness Theoretical Hardness

Har

dnes

s (in

MP

a)

Indentation Number

For 50 gf

0 1 2 3 4 5

4400

4600

4800

5000

5200

5400

5600

5800

6000

For 100 gf Experimental Hardness Theoretical Hardness

Har

dnes

s (in

MP

a)

Indentation Number

(a) (b)

19

0 1 2 3 4 5

4200

4300

4400

4500

4600

For 500 gf Experimental Hardness Theoretical Hardness

Har

dnes

s (in

MP

a)

Indentation Number

0 1 2 3 4 5

2600

2700

2800

2900

3000

3100

3200

3300

For 1000 gf Experimental Hardness Theoretical Hardness

Har

dnes

s (in

MP

a)

Indentation Number

(c) (d)

Fig.6 and Fig.7 shows indentation for calculating theoretical hardness at 500gf load

Fig.6 Fig.7

5. CONCLUSION:

With help of the powder metallurgy we have fabricated a new alloy W80Ni10Mo10 and observe its

different characteristics. Try to increase ductility with inducing proper hardness in that alloy for

using higher temperature application. We have reduced sintering temperature also.

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6. REFERENCES:

1. Proceeding of the European Materials Research Soceity 2001-Symposium F "Tungsten,

nickel, and molybdenum Schottky diodes with different edge termination", University Erlangen,

Cauerstr. 8, 91058 Erlangen, Germany

2.STATUS AND DEVELOPMENT OF TUNGSTEN-BASED ALLOY RESEARCH

(State Key Laboratory for Powder Metallurgy,Central South University,Changsha

410083,China) 3. Volume 166, Issue 1, 3 March 2003, Pages 84–88 Science Direct “Microstructural characterization and wear behavior of laser cladded nickel-based and tungsten carbide composite coatings”

4..Archimedes’s principle gets updated". R. Mark Wilson, Physics 

5. Xray powder diffraction by Barbara L Dutrow, Louisiana State University ,Christine M.

Clark, Eastern Michigan University

 6. Elements of X-Ray Diffraction. B.D. Cullity & S.R. Stock. Prentice Hall, Upper Saddle ...

7. Effect of indentation load and time on knoop and vickers microhardness tests for enamel and

dentin” Chanya Chuenarrom*; Pojjanut Benjakul; Paitoon Daosodsai Department of Prosthetic

Dentistry, Faculty of Dentistry, Prince of Songkla University, Songkhla, Thailand

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