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Final Report Submitted by: Muhammad Salman Arif Institution: National University of Science & Technology, Islamabad Work place: PIETMAEM, PCSIR Submission Date: July 16,2015
Transcript
Page 1: internship report PCSIR

Final Report

Submitted by: Muhammad Salman Arif

Institution: National University of Science & Technology, Islamabad

Work place: PIETMAEM, PCSIR

Submission Date: July 16,2015

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July 14, 2015 Pakistan Council of Scientific and Industrial Research

Contents:

1. Metallography Pg# 5-91.1. Introduction1.2. Steps

1.2.1. Sectioning1.2.2. Mounting

1.2.2.1. Cold mounting1.2.2.2. Hot mounting

1.2.3. Grinding1.2.4. Polishing1.2.5. Etching1.2.6. Microscopy

1.3. On site metallography1.4. Macro etching tests

1.4.1. Welding fusion1.4.2. Seamless test1.4.3. Forging test

1.5. Coating thickness2. Mechanical testing Pg#10-18

2.1. Introduction2.2. Tensile test

2.2.1. Process2.3. Bend test

2.3.1. Calculation of span2.3.1.1. Steps2.3.1.2. Formula2.3.1.3. Discarding of sample2.3.1.4. ASTM standard

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2.4. Compression test2.4.1. Experiment

2.5. Impact test2.5.1. Calculations2.5.2. Factors effecting impact test

2.6. ASTM standards2.7. Grips

2.7.1. Round2.7.2. Flat2.7.3. Rope

3. Powder metallurgy & Foundry Pg#19-223.1. Introduction3.2. Steps3.3. Procedure3.4. Properties & Advantages3.5. Foundry Shop

3.5.1. Steps3.5.1.1. Preparation of moulds3.5.1.2. Melting3.5.1.3. Pouring3.5.1.4. Breaking of mould3.5.1.5. Finishing

4. Non-Destructive Lab Pg#23-314.1. Introduction4.2. NDT’s

4.2.1. MT4.2.2. PT4.2.3. RT4.2.4. UT4.2.5. Eddy Current

4.3. Hardness tests Pg#32-354.3.1. Vicker’s test

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4.3.2. Rockwell hardness test4.3.2.1. Rockwell hardness scale4.3.2.2. Application of scales4.3.2.3. Rockwell superficial scale

4.3.3. Brinell’s hardness test4.3.4. Shore hardness test4.3.5. IRHD4.3.6. Portable hardness tester

5. Optical emission spectroscope Pg#32-355.1. Principle5.2. Specification5.3. Analysis5.4. ASTM standards5.5. Calibration

6. Bio-materials Pg#36-396.1. Introduction6.2. CS-Determinator

6.2.1. Particulars6.2.2. How heat is accomplished

6.3. Potentiostat7. Jewelry & Hallmarking Pg#40-46

7.1. Introduction7.2. Apparatus

7.2.1. XRF7.2.1.1. Underling physics7.2.1.2. Characteristics radiation7.2.1.3. Primary radiation7.2.1.4. Detection7.2.1.5. X-ray intensity7.2.1.6. Chemical analysis

7.2.2. Densitometer7.2.2.1. Introduction

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7.2.2.2. Working principle7.2.3. Hall marking

7.2.3.1. Apparatus7.2.3.2. Purity of gold

7.3. ASTM standard8. Physical vapor Deposition Pg#47-51

8.1. Introduction8.2. Sputtering8.3. Advantages8.4. Applications8.5. Apparatus required8.6. Coating types8.7. Coating thickness

9. Scanning Electron Microscope Pg#52-559.1. Introduction9.2. Specification9.3. Advantages

10. References Pg#5611. Acknowledgements Pg#56

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Lab 1Metallography

Instructor: ____________

____________

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Introduction:

The microscopic study of the structure of metals and is called metallography. Metallography is the process of preparing a sample of material by polishing and etching so that the structure can be examined using a microscope. The range of magnification of an optical microscope makes it suitable for grain structure examination and grain size estimation.

Steps:

Following steps are carried out during metallography:

Sectioning Mounting Grinding Polishing Etching Microscopy

Sectioning: This is an optional step in metallography in which the proper size of the sample for the further steps is prepared. We cannot observe the whole object, so we take a representative out of it with the help of cutting. Care must be taken to ensure that it is representative of the features found in the larger sample. Cutting can be done: Electrically by diamond cutter. Mechanically by hacksaw.

We ensure continuous flow of water during cutting to avoid any burn.

Mounting: This is also an optional step for the ease of handling the sample. This provide us easy grip and avoid bulging of the sample. There are two types of mounting: Hot mounting

In hot-mounting the sample is surrounded by an organic polymeric powder which melts under the influence of heat (about 200 oC). Pressure is also

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applied by a piston, ensuring a high quality mould free of porosity and with intimate contact between the sample and the polymer.

Cold mounting Mounting can be done cold using two components which are liquid to start with but which set solid shortly after mixing. Cold mounting techniques offer particular advantages when a specimen may be too delicate to withstand the pressures and heat involved in compression molding. The three most common types of materials are Epi-oxides, Polyesters, and Acrylics

Cold molding hot molding

Grinding: It is done to make sample smooth, scratch less and to remove bulging if any. This can be done automatically using a grinding wheel or manually using emery paper. The grinding wheel consists of a disc covered with silicon carbide paper. Water is applied continuously to wash out the sample. There are a number of grades of paper i.e. 180, 400, 600, 800, 1000, 1500 and 2000 grains of silicon

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carbide per square inch. 180 grades therefore represent the coarsest particles and this is the grade to begin the grinding operation.

Polishing:

Polishing is the final step in production a surface that is flat, scratch free, and mirror like in appearance. This can be done by diamond paste or alumina powder. Diamond paste is used for rougher surface (1-10 micron) while alumina powder is used for smother surface (less than 1 micron). The polishers consist of rotating discs covered with soft cloth made of velvet or nylon impregnated with diamond particles (6 and 1 micron size) and an oily lubricant. Begin with the 6 micron grade and continue polishing until the grinding scratches have been removed. It is of vital importance that the sample is thoroughly cleaned using soapy water, followed by alcohol, and dried before moving onto the final 1 micron stage. Any contamination of the 1 micron polishing disc will make it impossible to achieve a satisfactory polish.

Etching: After polishing the specimen is allowed to dry. This can be speed up by using a hot air drier. Etching is then used to reveal the microstructure of the metal. Basically etching is a chemical attack. The etchant attacks high energy sites such as grain boundaries also etchant preferentially attacks specific crystallographic orientations hence a contrasting pattern is formed on the surface of the specimen between grains. In alloys with different phases etching creates contrast between different regions through differences in topography or the reflectivity of the different phases. All this contrast creates a surface finish which allows the grain boundaries, phases, precipitates and different crystal orientations to be easily distinguished.

The specimen is etched using a reagent. This is applied using a cotton bud wiped over the surface a few of times. The specimen should then immediately be washed in alcohol and dried. Care should be taken to avoid over-etching a sample. During etching some localized chemical attack results in formation of pits which usually don’t really obscure the real features of microstructure but in case of over etching these pits can grow and hide the real features of the microstructure.

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Usually for steel family we use Nital solution (2%nitric acid + 98% Alcohol) Cu related alloys uses HF solution as etchant. While electrolyzing etching can also be used as a speedy phenomenon having electrolyte of 10% Oxalic acid

The surface to be examined should be flat and level otherwise if viewing area is moved across the surface it will go out of focus also whole of the field of view will not be in focus i.e. only the center will be in focus the sides won’t be. To rectify this, a simple process can be used. The mounted specimen is placed on plasticene on a microscope slide and the specimen leveling press presses the mounted specimen into the plasticene making it level. A small paper or cloth is placed over the specimen to avoid scratching.

On site metallography:

The type of metallography used for heavy industrial object or the instruments under operation carried out on the site is called on site metallography. This is also known as replica testing. It has same procedure to that of the laboratory metallography while at the end the image is copied on the rubber like material and studied later on the microscope.

Macro Etching tests: Following tests can be done on macro level:

Welding fusion we check voids, corrosion in this process. Sample is grinded from both ends and is swabbed in the aqua regia welding defects appears.

Seamless test this test is carried in the above similar way.

Forging test in this test the sample is boiled in 50% HCl solution with water. If the sample is forged than lamellar lines appear at macro level.

Coating Thickness:

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For this we need a cross-sectional analysis of the specimen. The specimen is then mounted and put under an optical microscope. The thin layer of coating is adjacent to the base metal. The left eye piece has a scale consisting of two perpendicular bisecting lines divided into equal intervals. The number of intervals is counted and divided by the magnification to give the coating thickness in millimeters.

Lab 2Mechanical testing

Instructor: ____________

____________

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Introduction: This lab is a set of destructive tests. This allows us to test the strength of the materials by different tests. Following tests were done:

Tensile test Compression test Bend test Impact test

Tensile test:

The specimen gauge length is marked according to ASTM standards. The specimen is placed in the machine between the grips and an extensometer if required can automatically record the change in gauge length during the test. If an extensometer is not fitted, the machine itself can record the displacement between its cross heads on which the specimen is held. However, this method not only records the change in length of the specimen but also all other extending elastic

components of the testing machine and its drive systems including any slipping of

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the specimen in the grips. Tensile test is used to measure yield point, maximum load and % elongation.

ProcessThe test process involves placing the test specimen in the testing machine and applying tension to it until it fractures. During the application of tension, the elongation of the gauge section is recorded against the applied force. The data is manipulated so that it is not specific to the geometry of the test sample. The elongation measurement is used to calculate the engineering strain, ε, using the following equation:

Where ΔL is the change in gauge length, L0 is the initial gauge length, and L is the final length. The force measurement is used to calculate the engineering stress, σ, using the following equation:

Where F is the force and A is the cross-section of the gauge section. The machine does these calculations as the force increases, so that the data points can be graphed into a stress-strain curve. But the machine here plots data into force-time curve.

Table 1 Data used for calculations in Tensile Testing

Sample ID Weight (g) Length (mm)

Weight/Length (g/mm)

Area (mm2)

Diameter (mm)

1 468 450 1.04 132.48 13.002 460 450 1.02 130.21 12.87

After the calculation of diameter, a gage length of 200 mm was marked on it and then it was fitted in the grips of UTM such that the gage length lies in between the grips. After the completion of test the result were as follows

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UTS = (90.58 KN/130.21 mm2) = 7 x 108 N/m2 = 700 MPa Upper yield point = 71.65 KN = 550 MPa Lower yield point = 70.94 KN =544 MPa

% ageelongation=222−200200

×100 = 11%

BEND TESTBending tests are carried out to ensure that a metal has sufficient ductility to stand bending without fracturing. A standard specimen is bent through a specified arc and in the case of strip, the direction of grain flow is noted and whether the bend is with or across the grain. In engineering mechanics, bending (also known as flexure) characterizes the behavior of a slender structural element subjected to an external load applied perpendicular to an axis of the element. When the length is considerably larger than the width and the thickness, the element is called a beam.

Calculation of span (distance between the rollers)Steps

1-The thickness of sample should be measured. 2-The thickness of the sample is taken twice of its actual thickness. 3-Then Pin diameter in mm should be calculated. 4-A factor of 15 is also used in the calculation well known as a safety factor. 5-The doubled thickness of the sample with the diameter of the pin and a

safety factor are added to get the approximate distance between the two rollers or span.

Formula

Span length=2T+Pin Dia+15

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T=thickness of sample

Discarding of a sample:-The sample would be discarded if there are cracks when it is bent. Moreover even if there appears a crack of even 3mm, then the sample would be discarded.

ASTM Standards used for the bend test A370 ASTM ASTM E290 ISO 7438

Compression Test:

Compressive strength is the capacity of a material or structure to withstand axially directed pushing forces. When the limit of compressive strength is reached, materials are crushed. Concrete can be made to have high compressive strength, e.g. many concrete structures have compressive strengths in excess of 50 MPa, whereas a material such as soft sandstone may have a compressive strength as low as 5 or 10 MPa.

Compressive strength is often measured on a universal testing machine; these range from very small table top systems to ones with over 53 MN capacity. Measurements of compressive strength are affected by the specific test method and conditions of measurement. Compressive strengths are usually reported in relationship to a specific technical standard.

.

Experiment:1. First fix the assembly, the equipment’s and parts of the machine in UTM.2. Then for safety purpose check all the things working correctly or not.3. Now place the sample in the UTM.4. Start the test from the computer and wait for the fracture.5. When the Fracture occurs note down the readings.

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IMPACT TESTThe Charpy impact test, also known as the Charpy v-notch test, is a standardized high strain-rate test which determines the amount of energy absorbed by a material during fracture. This absorbed energy is a measure of a given material's toughness and acts as a tool to study temperature-dependent ductile-brittle transition. It is widely applied in industry, since it is easy to prepare and conduct and results can be obtained quickly and cheaply. A major disadvantage is that all results are only comparative.

The standard Charpy-V specimen (illustrated in Fig.1) is 55mm long, 10mm square and has a 2mm deep notch with a tip radius of 0.25mm machined on one face.

Fig.1. Standard Charpy-V notch specimen

To carry out the test the standard specimen is supported at its two ends on an anvil and struck on the opposite face to the notch by a pendulum. The specimen is fractured and the pendulum swings through, the height of the swing being a measure of the amount of energy absorbed in fracturing the specimen. Conventionally three specimens are tested at any one temperature; and the results averaged.

Calculations:

Length of the Hammer = R = 0.75m

Weight of the Hammer = W = mg = 26 Kg × 9.8 m/s2 = 235.2 N

Angle of fall = α = 1450

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Temperature of the specimen ℃

Angle of rise

Energy absorbed by specimen (Nm)

Energy absorbed by the specimen in (ft-lb)

Case 1 -5 114.5  71.34 515.7

Case 2 -10 132  26.46 191.21

Case 3 -20 140  9.37 67.74

As temperature is decreased fracture tends to be brittle and less energy is absorbed in it.

Factors Affecting Charpy Impact Energy Factors that affect the Charpy impact energy of a specimen will include:

Yield strength and ductility Notches Temperature and strain rate Fracture mechanism

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Standards: Following ASTM standards are followed in this lab:

A-370

It is a more generalized standard which covers a wide area of experiments It is used for steel and cast iron products For tensile test For bend test Charpy impact test Hardness test and many others

E-8/8M:Used for tensile test of round bars of steel product like deform bar, tor bar and simple bar.

E-23: It gives details of test methods and conditions under which the test is carried out for charpy impact test

D-638: Test methods for plastics are different than those from the steel. This standard is for tensile test for plastic products

D-412: Tensile test for rubber products

C-39: For compression test of concrete cylinders

C-140: This standard is specifically for compression test of concrete cubes

C-67: For compression test of bricks

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A-615: It gives specialization for test e.g. diameter, length, gage length, etc

Ultimate testing Grips: A universal testing machine is used to test the tensile stress and compressive strength of materials and also bend type test is performed. The sample is gripped by following methods in this machine:

Round grips: Round grips used for bars.

12-35 mm 35-60 mm

Flat grips: Flat grips used for rectangular sheets.

0-30 mm 30-55 mm

Rope grip: Rope grips used for rope & wires.

8-10mm 16-22 mm

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Lab 3Powder metallurgy and Foundry

Instructor: ____________

____________

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the process of blending fine powdered materials, pressing them into a desired shape or form (compacting), and then heating the compressed material in a controlled atmosphere to bond the material (sintering)

Steps: Powder manufacturing Powder blending Compacting Sintering

Procedure The metal is taken in powder from. Particle size must be uniform. Binder is added to the powder in a fixed ration and the mixture is mixed

properly. The mixture is transferred into the die of the required shape. Pressure is applied on the die with the help of hydraulic press. Pressure

varies with the metal. Usually it is kept around 2000-10000 psi. This creates mechanical bonds among the particles so it retains it shape.

The compacted metal is then placed in furnace for sintering. Sintering temperature is the three fourth of the melting point of the metal. Sintering provide additional strength to the product. In this way the technique is quite better than other techniques.

Properties and advantages High surface finish High density product High dimensional strength and accuracy Intricate and small shapes could be produced Cheap and time saving

Foundry shop:

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Foundry is a workshop containing various machines and facilities of metal fabrication including casting and fabrication tools. The basic process includes the casting of metal starting from preparation of mold to the final machining

Steps:Following steps are being carried:

Preparation of mold

Mold is prepared by molding sand which contains some kind of binder. Usually silica sand and molasses (binder) are used due to being cheap and easily available

Melting

Metal to be casted is placed in the crucible. Crucible is then placed in a furnace. To decrease the melting point of the metal and for efficient slugging, flux is added to the metal during the process which is called Fluxing. After the metal melts, crucible is taken out of the furnace and slag is skimmed off.

Pouring

After melting the melt is poured into the mold and left for solidification. Grain size is directly related to the rate of solidification. Higher the cooling rate, smaller will be the grain size.

Breaking the mold

The mold is then broken down to extract the casted piece. The metal casted in foundry was aluminum.

Finishing

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Prepared Mold

Crucible placed in furnace

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Finally the product is finished through cutting, hammering, grinding, polishing and machining.

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Lab 4Non Destructive testing

Instructor: ____________

____________

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Non destructive tests along with hardness tests were performed in this lab. The brief explanation of these experiments is given below.

NDT’s:

MT - Magnetic Particle TestingMagnetic particle testing is accomplished by inducing a magnetic field in a ferromagnetic material and then dusting the surface with iron particles. The surface will produce magnetic poles and distort the magnetic field in such a way that the iron particles are attracted and concentrated making defects on the surface of the material visible.

PT - Dye Penetrant TestingThe dye penetrant testing can be used to locate discontinuities on material surfaces. A highly penetrating dye on the surface will enter discontinuities after a sufficient penetration time, and after removing the excess dye with a developing agent, the defects on the surface will be visible.

RT - Radiographic TestingRadiographic testing can be used to detect internal defects in castings, welds or forgings by exposure the construction to x-ray or gamma ray radiation. Defects are detected by differences in radiation absorption in the material as seen on a shadow graph displayed on photographic film or a fluorescent screen.

UT - Ultrasonic TestingUltrasonic testing uses high frequency sound energy to conduct examinations and make measurements. Ultrasonic inspection can be used for flaw detection/evaluation, dimensional measurements, material characterization, and more.

Eddy Current TestingEddy-current testing uses electromagnetic induction to detect flaws in conductive materials. There are several limitations, among them: only conductive materials can be tested, the surface of the material must be

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accessible, the finish of the material may cause bad readings, the depth of penetration into the material is limited by the materials' conductivity, and flaws that lie parallel to the probe may be undetectable.

In a standard eddy current testing a circular coil carrying current is placed in proximity to the test specimen (which must be electrically conductive).The alternating current in the coil generates changing magnetic field which interacts with test specimen and generates eddy current. Variations in the phase and magnitude of these eddy currents can be monitored using a second 'receiver' coil, or by measuring changes to the current flowing in the primary 'excitation' coil. Variations in the electrical conductivity or magnetic permeability of the test object, or the presence of any flaws, will cause a change in eddy current and a corresponding change in the phase and amplitude of the measured current. This is the basis of standard (flat coil) eddy current inspection, the most widely used eddy current technique.

Hardness tests:

Vickers hardness

A diamond indenter, in the form of a right pyramid with a square base and an angle of 136 degrees between opposite faces is used to put an indent on the sample by subjecting it to a load of 1 to 100 kgf. The full load is normally applied for 10 to 15 seconds. Then the diagonals of the indentation left in the surface of the sample after removal of the load are measured using a microscope and their average calculated.

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F= Load in kgfd = Arithmetic mean of the two diagonals, d1 and d2 in mmHV = Vickers hardnessThe Vickers hardness is calculated by the following formula

HV= F/D2 × Vickers constant (1.854).

A more convenient way is to use conversion tables. The Vickers hardness is given as 700 HV/20, which means a Vickers hardness of 700, was obtained using a 20 kgf force. The advantages of the Vickers hardness test are that extremely accurate readings can be taken, and just one type of indenter is used for all types of metals and surface treatments.

Micro Vickers hardness is sometimes used when hardness is to be measured on a micro level such as hardness of various phases of a material. Load here varies from 10g to 1kg.

Rockwell Hardness Test:

The test method is based on indenting the test material with a diamond cone or hardened steel ball indenter. The indenter is forced into the test material under a preliminary minor load usually 10 kgf. As minor load is applied, a device responsible for keeping track of the movement of indenter notes this penetration by minor load and sets it to zero as reference line (datum position). Then in addition to minor load, major load is applied for a period of time ‘dwell time’. After this time major load is removed while minor load is still maintained. The removal of the major load

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allows a partial recovery, so reducing the depth of penetration. The permanent increase in depth of penetration, resulting from the application and removal of the additional major load is used to calculate the Rockwell hardness number.

Based upon the type of indenter steel ball/ diamond cone and the amount of major load various Rockwell hardness scales are present. As the steel ball indenter comes in different diameters, a number of Rockwell hardness scales are formed each used for different types of materials.

Rockwell hardness scales

Scale IndenterMinor Load

F0kgf

Major LoadF1kgf

Total LoadF

kgf

Value ofE

A Diamond cone 10 50 60 100

B 1/16" steel ball 10 90 100 130

C Diamond cone 10 140 150 100

D Diamond cone 10 90 100 100

E 1/8" steel ball 10 90 100 130

F 1/16" steel ball 10 50 60 130

G 1/16" steel ball 10 140 150 130

H 1/8" steel ball 10 50 60 130

K 1/8" steel ball 10 140 150 130

L 1/4" steel ball 10 50 60 130

M 1/4" steel ball 10 90 100 130

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P 1/4" steel ball 10 140 150 130

R 1/2" steel ball 10 50 60 130

S 1/2" steel ball 10 90 100 130

V 1/2" steel ball 10 140 150 130

Application of Rockwell Hardness Scales

HRA . . . . Cemented carbides, thin steel and shallow case hardened steelHRB . . . . Copper alloys, soft steels, aluminum alloys, malleable irons, etc.HRC . . . . Steel, hard cast irons, case hardened steel and other materials harder than 100 HRBHRD . . . . Thin steel and medium case hardened steel and pearlitic malleable ironHRE . . . . Cast iron, aluminum and magnesium alloys, bearing metalsHRF . . . . Annealed copper alloys, thin soft sheet metalsHRG . . . . Phosphor bronze, beryllium copper, malleable irons HRH . . . . Aluminum, zinc, lead

Rockwell superficial hardness test methods works on the same aforementioned principles however the total load applied is typically 15, 30 or 45 kgf.

Rockwell Superficial Hardness Scales

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Scale Indenter TypeMinor Load

F0kgf

Major LoadF1kgf

Total LoadF

kgf

Value ofE

HR 15 N N Diamond cone 3 12 15 100

HR 30 N N Diamond cone 3 27 30 100

HR 45 N N Diamond cone 3 42 45 100

HR 15 T 1/16" steel ball 3 12 15 100

HR 30 T 1/16" steel ball 3 27 30 100

HR 45 T 1/16" steel ball 3 42 45 100

HR 15 W 1/8" steel ball 3 12 15 100

HR 30 W 1/8" steel ball 3 27 30 100

HR 45 W 1/8" steel ball 3 42 45 100

HR 15 X 1/4" steel ball 3 12 15 100

HR 30 X 1/4" steel ball 3 27 30 100

HR 45 X 1/4" steel ball 3 42 45 100

HR 15 Y 1/2" steel ball 3 12 15 100

HR 30 Y 1/2" steel ball 3 27 30 100

HR 45 Y 1/2" steel ball 3 42 45 100

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The Brinell hardness Test

The Brinell hardness test method consists of indenting the test material with a 10 mm diameter hardened steel or carbide ball subjected to a load of 3000 kg. For softer materials the load can be reduced to 1500 kg or 500 kg. The full load is normally applied for 10 to 15 seconds in the case of iron and steel and for at least 30 seconds in the case of other metals. The diameter of the indentation left in the test material is measured with a microscope. The Brinell harness number is calculated by dividing the load applied by the surface area of the indentation.

The diameter of the impression ‘d1’ is the average of two readings at right angles and the use of a Brinell hardness number table can simplify the determination of the Brinell hardness. A properly written Brinell hardness number reveals the test conditions, and looks like this, "80 HB 10/3000/15" which means that a Brinell Hardness of 80 was obtained using a 10mm diameter hardened steel with a 3000 kilogram load applied for a period of 15 seconds. On tests of extremely hard metals a tungsten carbide ball is used in place of the steel ball. Brinell hardness test results in the deepest and widest of indentations and the hardness is averaged over a wider region of the specimen compared to other test methods which are more localized hence, it will account for multiple grain structures and irregularities of the specimen. Basically, Brinell gives macro-hardness of a material.

Shore/Durometer hardness method

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 This is mostly used in the plastic and rubber industries. A test force is worked out and is applied upon a spherical or a conical-shaped indenter. This force is applied to the specimen for a predetermined period of time. The resulting indentation is converted into a hardness value by means of a dial gauge. Test loads range from 822 gf (A scale) to 4550 gf (D scale). Non-standard “micro” scales are also available. These micro scales allow testing on thin or very narrow specimens. 

The International Rubber Hardness Degrees (IRHD)

This method as the name implies is reserved for hardness testing of rubbers of various sizes and shapes especially used on rubber rings. An initial test load is applied onto the specimen and the position is noted as reference point or zero. This is followed by the total test force which increases the indentation. The distance between the two points is determined and the IRHD hardness value is calculated. Preliminary test forces are 8.46 gf for micro scales and 295.7 gf for regular scales. Total test forces are 15.7 gf for micro and 597 gf for regular scales. 

Portable Hardness Tester:It gives value of hardness at any angle and in any value by the principle of bounce back.

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Lab 5Optical Emission Spectroscopy

Instructor: ____________

____________

Principle:

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Optical emission spectrometry involves applying electrical energy in the form of spark generated between an electrode and a metal sample, whereby the vaporized atoms are brought to a high energy state within a so-called “discharge plasma”. This gives us qualitative and quantitative composition of the material.

Specifications of apparatus:

Following describes the brief specifications of the apparatus: This particular machine is a 5 based system i.e. it can detect alloys with 5

base metals Iron based alloys, Copper based alloys, Aluminum based alloys, Nickel based alloys, and Zinc based alloys

It has 41 channels to detect 37 different elements The time provided for the application of spark is different for different

metals. For iron based alloys it is 30 sec, for aluminum based alloys it is 25 sec and for zinc based alloys it is 20 sec. least count of this machine is 0.001.

It is a destructive operation in a sense that there remains a spot of spark on the sample. The excitation source is high voltage spark approximately 906 volts.

Temperature of table must be 35 degrees Celsius Vacuum 40-50 mT must be created Gas pressure must be 9-10 Temperature of the room must be below 30o Sample must have thickness of 2mm.

Analysis

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The Intensity of an emission line (colour) is proportional to concentration – allows measurement of ‘how much’ of each element is present.

A number of standards are run first to set up a calibration curve, these take into account any matrix matching difficulties (i.e. overlap of elements in some materials).

Once calibration is completed numerous samples can be analysed. The sample is simply clamped into place, ‘sparked’ and a spectrum

collected. The spectrometer collects the intensity of light at all wavelengths and

compares this to the values for the calibration standard. This gives an accurate value of the elements present in the sample.

Multiple sparks are collected until concordant results are obtained within an acceptable standard deviation.

Further samples of the same alloy type can then be analysed. Different alloys require re-calibration before analysis can occur.

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Maintenance The main thing in its maintenance is its time to time calibration. After a certain period of time, test on the standard sample of known composition provided by the manufacturer is performed and standard results are calibrated

ASTM standards:

ATM standard 346 is followed in this lab.

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Lab 6Bio materials

Instructor: ____________

____________

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Introduction:

This lab is named so because it was designed to make hydroxy appetite. Further in this lab we have two more machines:

C-S determinator Potentiostat

C-S determinator

This particular machine CS-200 gives value up to 3 decimal places. It is used to find the accurate %age of carbon and sulphur in sample. The principle of machine is combustion of carbon and sulphur. A precisely weighed sample is combusted in a small crucible with oxygen and a small amount of tungsten trioxide. Carbon in the sample is oxidized to carbon dioxide or carbon monoxide. The sulfur is oxidized to sulfur dioxide. These combustion gases are carried by oxygen into an infrared (IR) cell where sulfur is detected as sulfur dioxide. Following sulfur analysis, all of the carbon is converted to carbon dioxide. The sulfur is converted to sulfur trioxide and removed by filtration. The carbon dioxide is then measured in a separate IR cell.

Particulars The determination of carbon and sulfur is done by non-dispersive (fixed)

infrared energy at precise wavelengths as the gases pass through their respective IR absorption cells. The changes in energy are then observed at the detectors and the concentration is determined.

The average analysis time is 60 to 120 seconds. Heating is done by induction furnace.

The combustion gasses (CO2, H2O, SO2) coming from the furnace pass through a dust filter.

Temperature of combustion tube is approximately 1400oNitrogen and oxygen gases are used in this machine. Nitrogen is to move stage while oxygen is for combustion. We have absorbers magnesium per chlorate for

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carbon dioxide and sodium hydroxide with silicon is used for absorption of sulphur dioxide.

As the process might be slow so to increase the speed of process we use cadmium as catalyst.

Also cellulose filter is used for the purification of air. Maximum weight of sample can be 1gm.

For analysis of ferrous and non-ferrous sample there is difference of accelerator. As ferrous have high melting point we cannot burn it at this temperature in lab so we add accelerator to lower its melting point. Accelerator in this case is a mixture of tin and tungsten. While non-ferrous have very low melting point to avoid there melting or any such problem we have to increase their melting point. We add iron chips to increase the melting point.

How heating is AccomplishedInduction heating is done in these furnaces. In these furnaces heating of electrically conducting object is done by electromagnetic induction, where eddy currents are generated within the metal and resistance leads to Joule heating of the metal. An induction heater consists of an electromagnet, through which a high-frequency alternating current (AC) is passed.

H=I2RT

Where ‘I’ is current, R is resistance and T is time.

How do Carbon effect SteelCarbon is generally considered to be the most important alloying element in steel and can be present up to 2% (although most welded steels have less than 0.5%). Increased amounts of carbon increase hardness and tensile strength, as well as response to heat treatment (harden ability). Increased amounts of carbon will reduce weld ability.

How do Sulphur effect SteelSulphur is usually an undesirable impurity in steel rather than an alloying element. In amounts exceeding 0.05% it tends to cause brittleness and reduce weld ability. Alloying additions of sulfur in amounts from 0.10% to 0.30% will tend to improve the machinability of steel. School of Chemical & Material Engineering, NUST, Islamabad 38

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Potentiostat:Potentiostat is a polarization technique that allows for the controlled polarization of metal surfaces in electrolytes, in order to directly observe cathodic and anodic behaviors. Corrosion reactions can be monitored or driven at the surface of a desired metal sample. A variety of characteristics related to the metal/environment pairing can be determined through this technique.

A Potentiostat is an electronic instrument that controls the voltage difference between working and reference electrodes, both of which are contained in an electrochemical cell. The Potentiostat implements this control by injecting current into the cell through an auxiliary or counter electrode.

3 electrodes are involved in working of machine:

Working electrode Standard electrode Reference electrode

The potentiostatic technique is used to directly observe anodic and cathodic behaviors of a metal surface in electrolytes. Polarization experiments are performed with a computer controlled Potentiostat. A constant or a varying DC potential (potentiostatic or potential dynamic, respectively), or a constant DC current (galvanostatic) is applied to the metal of interest while it is immersed in the electrolyte.

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Lab 7Jewelry & Hall marking

Instructor: ____________

____________

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Introduction: This lab was related with the work of purity of the jewelry or precious metal like gold and there stamping at state of the art level. We also study to calculate the density of the unknown object.

Apparatus:The brief explanation of the apparatus used is given below:

X-ray fluorescence:It is the emission of characteristic "secondary" (or fluorescent) X-rays from a material that has been excited by bombarding with high-energy X-rays or gamma rays. The phenomenon is widely used for elemental analysis and chemical analysis, particularly in the investigation of metals, glass, ceramics and building materials, and for research in geochemistry, forensic science and archaeology.

Underlying physics: When materials are exposed to short-wavelength X-rays or to gamma rays, ionization of their component atoms may take place. Ionization consists of the ejection of one or more electrons from the atom, and may occur if the atom is exposed to radiation with energy greater than its ionization potential. X-rays and gamma rays can be energetic enough to expel tightly held electrons from the inner orbitals of the atom. The removal of an electron in this way makes the electronic structure of the atom unstable, and electrons in higher orbitals "fall" into the lower orbital to fill the hole left behind. In falling, energy is released in the form of a photon, the energy of which is equal to the energy difference of the two orbitals involved. Thus, the material emits radiation, which has energy characteristic of the atoms present. The term fluorescence is applied to phenomena in which the absorption of radiation of a specific energy results in the re- emission of radiation of a different energy (generally lower).

Characteristic radiation: Each element has electronic orbitals of characteristic energy. Following removal of an inner electron by an energetic photon provided by a primary

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radiation source, an electron from an outer shell drops into its place. There are a limited number of ways in which this can happen, as shown in Figure 1. The main transitions are given names: an L→K transition is traditionally called Kα, an M→K transition is called Kβ, and an M→L transition is called Lα, and so on. Each of these transitions yields a fluorescent photon with a characteristic energy equal to the difference in energy of the initial and final orbital. The wavelength of this fluorescent radiation can be calculated from Planck's Law: The fluorescent radiation can be analyzed either by sorting the energies of the photons (energy-dispersive analysis) or by separating the wavelengths of the radiation (wavelength-dispersive analysis). Once sorted, the intensity of each characteristic radiation is directly related to the amount of each element in the material. This is the basis of a powerful technique in analytical chemistry. Figure 2 shows the typical form of the sharp fluorescent spectral lines obtained in the wavelength-dispersive method (see Moseley's law).

Primary radiation: In order to excite the atoms, a source of radiation is required, with sufficient energy to expel tightly held inner electrons. Conventional X-ray generators are most commonly used, because their output can readily be "tuned" for the application, and because higher power can be deployed relative to other techniques. However, gamma ray sources can be used without the need for an elaborate power supply, allowing an easier use in small portable instruments. When the energy source is a synchrotron or the X- rays are focused by an optic like a polycapillary, the X-ray beam can be very small and very intense. As a result, atomic information on the sub-micrometer scale can be obtained. X-ray generators in the range 20–60 kV are used, which allow excitation of a broad range of atoms. The continuous spectrum consists of "bremsstrahlung" radiation: radiation produced when high-energy electrons passing through the tube are progressively decelerated by the material of the tube anode (the "target"). Dispersion: In energy dispersive analysis, the fluorescent X-rays emitted by the material sample are directed into a solid-state detector which produces a "continuous" distribution of pulses, the voltages of which are proportional to the incoming photon energies. This signal is processed by a multichannel analyzer (MCA) which produces an accumulating digital spectrum that can be processed to obtain analytical data. In wavelength

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dispersive analysis, the fluorescent X-rays emitted by the material sample are directed into a diffraction grating monochromatic. The diffraction grating used is usually a single crystal. By varying the angle of incidence and take-off on the crystal, a single X-ray wavelength can be selected. The wavelength obtained is given by the Bragg Equation: where d is the spacing of atomic layers parallel to the crystal surface.

Detection: In energy dispersive analysis, dispersion and detection are a single operation, as already mentioned above. Proportional counters or various types of solid-state detectors (PIN diode, Si (Li), Ge (Li), Silicon Drift DetectorSDD) are used. They all share the same detection principle: An incoming X-ray photon ionizes a large number of detector atoms with the amount of charge produced being proportional to the energy of the incoming photon. The charge is then collected and the process repeats itself for the next photon. Detector speed is obviously critical; as all charge carriers measured have to come from the same photon to measure the photon energy correctly (peak length discrimination is used to eliminate events that seem to have been produced by two X-ray photons arriving almost simultaneously). The spectrum is then built up by dividing the energy spectrum into discrete bins and counting the number of pulses registered within each energy bin. EDXRF detector types vary in resolution, speed and the means of cooling (a low number of free charge carriers is critical in the solid state detectors): proportional counters with resolutions of several hundred eV cover the low end of the performance spectrum, followed by PIN diode detectors, while the Si (Li), Ge (Li) and Silicon Drift Detectors (SDD) occupy the high end of the performance scale. In wavelength dispersive analysis, the single-wavelength radiation produced by the monochromator is passed into a photomultiplier, a detector similar to a Geiger counter, which counts individual photons as they pass through. The counter is a chamber containing a gas that is ionized by X-ray photons. A central electrode is charged at (typically) +1700 V with respect to the conducting chamber walls, and each photon triggers a pulse-like cascade of current across this field. The signal is amplified and transformed into an accumulating digital count. These counts are then processed to obtain analytical data.

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X-ray intensity: The fluorescence process is inefficient, and the secondary radiation is much weaker than the primary beam. Furthermore, the secondary radiation from lighter elements is of relatively low energy (long wavelength) and has low penetrating power, and is severely attenuated if the beam passes through air for any distance. Because of this, for high- performance analysis, the path from tube to sample to detector is maintained under vacuum (around 10 Pa residual pressures). This means in practice that most of the working parts of the instrument have to be located in a large vacuum chamber. For less demanding applications, or when the sample is damaged by a vacuum (e.g. a volatile sample), a helium-swept X-ray chamber can be substituted, with some loss of low-Z (Z = atomic number) intensities.

Chemical analysisThe use of a primary X-ray beam to excite fluorescent radiation from the sample was first proposed by Glockerand Schreiber in 1928. [1] Today, the method is used as a non- destructive analytical technique, and as a process control tool in many extractive and processing industries. In principle, the lightest element that can be analyzed is beryllium (Z = 4), but due to instrumental limitations and low X-ray yields for the light elements, it is often difficult to quantify elements lighter than sodium (Z = 11), unless background corrections and very comprehensive inter-element corrections are made.

DensitometerIntroduction:

The properties of materials are directly related with their microstructure and hence density. For highly technical applications such as telecommunication devices, densities above 95% of the relevant theoretical densities are required. To measure density of solid and liquid samples, MRL is equipped with Electronic Densitometer MD-300S which provides a highly accurate calculation of specific gravity of almost any object of any shape. The density of rubber, plastic, metals, glass, ceramic, food samples, wood and pharmaceuticals can be measured with this instrument. The density resolution of the installed machine

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is 0.001g/cm³ and specific gravity less than one can be measured. The machine is able to compensate water temperature and specific gravity of solution on front switches, specific gravity is automatically calculated.

Working PrincipleCommonly two methods are used for the determination of density of materials. One is the direct measurement method. This method involves measurement of the mass (in grams) of the body by weighing it and its volume (in centimeter cube) by measuring its length (l), width (w) and height (h); as V= l x w x h. Dividing the mass by volume gives the density in g/cm3.The second and more reliable method is based on Archimedes' Principle which states that an object immersed in a fluid is buoyed up by a force equal to the weight of the displaced fluid. It is known that 1 ml of water has a mass almost exactly equal to 1g. If an object is immersed in water, the difference between the two masses (in grams) will equal (almost exactly) the volume (in ml) of the object weighed. Knowing the mass and the volume of the object allows us to calculate its density.

Densitometer

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Hall marking:Hall marking is the process of marking precious metals about their purity usually. This process was named after its history of marking of gold in Europe in a big hall thus named after it. The apparatus used was laser engraving machine.

Apparatus requirement:

Safety glasses must be worn. This apparatus uses 4 level lasers for engraving. Usually used for stamping. It is better than manual engraving as it has controlled material loss and symmetrical writings.

Purity units of gold:

In Asia Carrot is used as an impurity unit which is marked out of 24, while in Europe finesse is used marked out of 1000. Copper metal is added as an impurity to give strength to gold.

ASTM standards:

ATM standard 346 is followed in this lab.

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Lab 8Physical Vapor Deposition

Instructor: ____________

____________

Introduction:

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Physical vapor deposition (PVD) describes a variety of vacuum deposition methods used to deposit thin films by the condensation of a vaporized form of the desired film material onto various work piece surfaces (e.g., onto semi conductor wafers).

Sputtering:

Sputtering is the thin film deposition manufacturing process at the core of today’s semiconductors, disk drives, CDs, and optical devices industries. On an atomic level, sputtering is the process whereby atoms are ejected from a target or source material that is to be deposited on a substrate - such as a silicon wafer, solar panel or optical device - as a result of the bombardment of the target by high energy particles.

The sputtering process begins when a substrate to be coated is placed in a vacuum chamber containing an inert gas - usually Argon - and a negative charge is applied to a target source material that will be deposited onto the substrate causing the plasma to glow.

Free electrons flow from the negatively charged target source material in the plasma environment, colliding with the outer electronic shell of the Argon gas atoms driving these electrons off due to their like charge. The inert gas atoms become positively charged ions attracted to the negatively charged target material at a very high velocity that “Sputters off” atomic size particles from the target source material due to the momentum of the collisions. These particles cross the vacuum chamber and are deposited as a thin film of material on the surface of the substrate to be coated.

Sputtering only takes place when the kinetic energy of the bombarding particles is extremely high, much higher than normal thermal energies in the “Fourth state of nature” plasma environment. This can allow a much more pure and precise thin film deposition on the atomic level than can be achieved by melting a source material with conventional thermal energies.

The number of atoms ejected or “Sputtered off” from the target or source material is called the sputter yield. The sputter yield varies and can be controlled by the

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energy and incident of angle of the bombarding ions, the relative masses of the ions and target atoms, and the surface binding energy of the target atoms. Several different methods of sputtering are widely used, including ion beam and ion-assisted sputtering, reactive sputtering in an Oxygen gas environment, gas flow and magnetron sputtering.

This technique is used in PCD coating process.

Advantages:

PVD coatings are sometimes harder and more corrosion resistant than

coatings applied by the electroplating process

Most coatings have high temperature and good impact strength, excellent

abrasion resistance.

They are so durable that protective topcoats are almost never necessary.

Ability to utilize virtually any type of inorganic and some organic coating

materials on an equally diverse group of substrates and surfaces using a wide

variety of finishes.

More environmentally friendly than traditional coating processes such as

electroplating and painting.

Low coating thickness (0.5-7 micron)

Chemical resistivity

Uniformity by rotation.

Increase in hardness

Self lubricated

Electroplating defects are overcome by CVD- chemical vapor deposition

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Applications:

As mentioned previously, PVD coatings are generally used to improve hardness,

wear resistance and oxidation resistance. Thus, such coatings use in a wide range

of applications such as:

Aerospace

Automotives

Surgical/Medical

Dies and moulds for all manner of material processing

Cutting tools

Firearms

Optics

Thin films (window tint, food packaging, etc.)

Metals (Aluminum, Copper, Bronze, etc)

Apparatus Requirement:Following requirements are fulfilled during experimentation:

Vacuumed up to 10^-6 milli torr Etching for rough surfaces Biasing Gas center (inert argon)

Coating types:

There are three types of coating in PVD:

Composite: nitrites of aluminum, zirconium, tin Nano composite: done at micro level with titanium nitride & silica nitride DLC-Diamond Like Coatings: chromium Aluminium nitride + silica Nitride gives hardness

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Coating thickness:

Coating thickness is given by:

a2−b2

4× D× 1000microns

Where; a=outer circle diameter obtained by indent

b=inner circle diameter

D=diameter of ball used for indenting/ scratching

-PVD Apparatus overview

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Lab 9Scanning Electron Microscope

Instructor: ____________

____________

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A scanning electron microscope (SEM) is a type of electron microscope that produces images of a sample by scanning it with a focused beam of electrons.

Principle:Accelerated electrons in an SEM carry significant amounts of kinetic energy, and this energy is dissipated as a variety of signals produced by electron-sample interactions when the incident electrons are decelerated in the solid sample. These signals include secondary electrons (that produce SEM images), backscattered electrons (BSE), diffracted backscattered electrons (EBSD that are used to determine crystal structures and orientations of minerals), photons (characteristic X-rays that are used for elemental analysis and continuum X-rays), visible light and heat. Secondary electrons and backscattered electrons are commonly used for imaging samples: secondary electrons are most valuable for showing morphology and topography on samples and backscattered electrons are most valuable for illustrating contrasts in composition in multiphase samples (i.e. for rapid phase discrimination). . Thus, characteristic X-rays are produced for each element in a mineral that is "excited" by the electron beam. SEM analysis is considered to be "non-destructive"; that is, x-rays generated by electron interactions do not lead to volume loss of the sample, so it is possible to analyze the same materials repeatedly.

Specifications:Essential components of all SEMs include the following:

Electron Source ("Gun")

Electron Lenses

Sample Stage

Detectors for all signals of interest

Display / Data output devices

Infrastructure Requirements:

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o Power Supply

o Vacuum System

o Cooling system

o Vibration-free floor

o Room free of ambient magnetic and electric fields

Advantages:

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Following are the advantages of the SEM:It can give us magnification up to 300000 timesIt can resolve the phases within the alloysIt uses electron gun thus is very efficient

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References:

Following references were used during report:

cs-instruments.comhttp://www.microscopemaster.com/scanning-electron-microscope.html http://www.semteclaboratories.com/ www.semicore.com en.wikipedia.org

Acknowledgements:All the instructors help us a lot in learning to operate various apparatus. We had a wonderful experience working with such a competitive staff.

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