Forming, Characterization and Evaluation of Hardness of NanoCarbon Cast Iron

By SAI SIRISHA K

M.TECH CAD/CAMGuide:

Dr. K.Padmanabhan (SMBS)VIT University, Vellore

Outline of the presentation

Abstract

Introduction

Experimental procedure

Principles of each step

Results and Discussion

Conclusion

References

• Carbon nanotubes (CNTs) are allotropes of carbon with a cylindrical

nanostructure.

• Nanotubes have been constructed with length-to-diameter ratio of up to

132,000,000:1,significantly longer than any other material.

• These cylindrical carbon nano tubes have unusual properties, which are

valuable for structural, electronics, optics and other fields of material

science and technology.

Properties of carbon nano tubes:

o The strongest and most flexible molecular material because

of C-C covalent bonding.

o Carbon nanotubes are the strongest and stiffest materials yet discovered in terms

of tensile strength and elastic modulus respectively

o High Hardness

o Less dislocations

o Tensile strength – 63gpa-200gpa

o Youngs modulus – 1tpa

o Low density of a solid

Classification of CNT:

Single walled carbon nano tubes(SWCNT)

Multi walled carbon nano tubes(MWCNT)

SWCNT MWCNT

Cast iron reinforced with nano-sized carbon(mwcnt) particles are an

interesting group of advanced materials.

The composites possesses improved physical and mechanical

properties such as

superior strength to weight ratio,

good ductility ,

high strength and high modulus

low thermal expansion coefficient,

excellent wear resistance,

excellent corrosion resistance

high temperature creep resistance and

better fatigue strength.

EXPERIMENTAL PROCEDURE:

•Characterization of MWCNT

•Forming and Characterization of Nano Carbon Cast Iron.

•Heat Treatment and Machining

•Hardness Testing Procedure

I. Characterization of MWCNT

SPECIFICATIONS:

Make : BRUKER, Germany

Model : D8 Advance

Source : 2.2KW Cu anode,

ceramic x-ray tube

Detector : lynx Eye detector(silicon

strip detector technology)

Beta Filter : Ni Filter

Sample Holder : Zero background and

PMMA sample holder

sample

liq N2

detec torX-ray source

Geometry of XDS 2000

Observations made in XRD;

Graph between Intensity and 2-Theta scale for MWCNT

Surface topography of the MWCNT:

Principle of AFM

Between the nano-scale tip and the atoms of the surface is picked up by changes in the laser beamreflection and converted by a computer

into a picture.

Deflection of the cantilever due to varying

forces

Observations are made in AFM:

a) Copper Coating and stir casting:

Why Copper coating?

It prevents clustering of carbon nanotubes (agglomeration)

Cu is good for corrosion resistance and it prevents reactivity between carbon and iron which improves the strength, stiffness of castiron.

Cu forms an oxide thereby reducing reactivity between iron and carbon

Why stir casting?

Distribution of MWCNT will be good in castiron

II Forming and Characterization of Nano Carbon Cast Iron:

Elements for stir casting:

FurnaceBlower Charcoal Coke

Crucible MWCNT Cast iron Copper

Working of stir casting:

Patterns for test specimens:

Mould preparation for test specimens:

After pouring the molten metal into moulds:

Raw castings thus formed are then withdrawn from the moulds

III Heat Treatment and Machining

Dimension for tensile test specimen

Tensile test specimen being machined on lathe

A machined test specimen of NCCI

IV Hardness Testing Procedure:

• Rockwell hardness C test ( HRC) is used to calculate the hardness number of a ferrous material.

•It consists of indenting the test material with a diamond cone or hardened steel ball indenter

•All the six specimens, heat treated and as cast, were hardness tested and the hardness values were recorded.

Results and Discussions

o XRD:

Diffraction peaks will perform in the deflection pattern at 2 ѳ values when

Constructive interference is at a maximum that is braggs law is satisfied .

The number of observed peaks is connected to the symmetry of the unit cell.

The d-spacings of the observed peaks are related to the restating distances

among planes of atoms in the structure. Here in this XRD graph peaks are

observed at (d=3.47092,A=25.6450) and (d=2.08297,A=43.4080)

X Ray diffraction pattern of as cast X Ray diffraction pattern of heat treated andNCCI showing undissolved impurities annealed NCCI Samples

o AFM:

With using AFM the image of the multi walled carbon nano tubes is noticed with

different orientations clearly and the dimensions like length, depth, area roughness

i.e area are observed and shown in table 1 and table 2

o Very hard and strong castirons are obtained

o Microstructure of NCCI:

The optical microstructure of grey cast Micrograph of as cast NCCI showing fair

iron before the addition of MWCNT. distribution of the MWCNT cluster.

Micrograph of a region in a heat treated Another region of the heat treated

and annealed NCCI and annealed NCCI

Observations of Hardness in the NCCI:

S No Hardness Number

1 25

2 21

3 22

S No Hardness Number

1 17

2 19

3 17

HRC of as cast NCCI HRC of Annealed NCCI

Conclusions:

Forming of MWCNT nano carbon reinforced cast iron with the stir casting method was carried out.

The x-ray diffraction, microscopic characterization and measurement of Rockwell C scalehardness before and after heat treatment (of the Nano Carbon Cast Iron or NCCI ) were also conducted.

X- Ray and Atom Force Microscope (AFM) characterization were carried out for the multi walled carbon nano tube reinforcements as well as the nano carbon cast iron formed by adding the nano carbon with the grey cast iron.

As the nano carbon reinforcements tend to agglomerate in the cast iron eutectic melt, prior sonication and coating with copper were done to prevent agglomeration, dissolution and oxidation of nano carbon .

The as cast samples were either cooled naturally or heat treated at 550 ºC and annealed,machined down to size and the Rockwell C scale hardness measured.

The annealed samples show reduced hardness values compared to as cast samples due to the formation of α-ferrite. They also exhibited less porosity and a low tendencyfor graphitization.

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