Suresh seminr ppt final

Investigation and Comparison of BZT-Ti6Al4V and

Alumina-Ti6Al4V Brazing for RF Window Application

under High Vacuum Condition

Presentation by

Suresh Beera

12ETMM11

M.Tech

Materials Engineering

SEST, UoH

1/27/2018

Supervisiors :

Dr. Dibakar Das Dr. G. Madhusudhan Reddy

Associate Professor Scientist “G” ,Group Head--MJG

SEST, UoH DMRL, HYDERABAD

CONTENTS

Introduction

Objective

Literature review

Experimental procedure

Result and discussion

Conclusions

References

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INTRODUCTION

Ceramic materials are inorganic, non-metallic materials made

from compounds of a metal and a non metal.They are formed

by the action of heat and subsequent cooling

Traditional ceramics

Advance ceramics

-Oxides

-Non-oxides

:

Ceramics

Industries are extremely attractive towards engineering ceramics

because of their properties

low density & high hardness,

corrosion and oxidation resistance at elevate temperature

low thermal conductivity, high electrical resistance

low friction, good chemical resistance

exhibit excellent dielectric properties

These materials are brittle and stronger than that of

metals because of their covalent and ionic bonding.

4

Applications of advanced ceramics

Electronic Components

Vacuum tubes

Gas Turbine, Diesel Engines

Nuclear Reactors

Electrical Insulators

Oil drill bit

However, they are relatively

expensive and Ceramics are most

frequently used in conjunction with

other material where joining

becomes a critical issue

tensile force

Ao

Addie

die

Adapted from

Fig. Callister

7e.

The main problems when joining ceramics are miss matches

coefficient of thermal expansion, poor wettability of

ceramics by most metals and alloys. Most of the regular

filler materials do not wet ceramics.

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CERAMIC-METAL JOINING PROCESS

These are chosen on the basis of temperature, ease of implementation, functionality .

Among those joining processes, the most adaptable technique is Brazing.

It is a metal-joining process whereby a filler

metal is brought slightly above its melting (liquidus)

temperature (>450°C), but lower than the melting

temperature of the base metal and distributed between

two or more close-fitting parts by capillary action.

It is protected by a suitable atmosphere, usually a flux.

It is similar to soldering different to welding process.

Merits & demerits of brazing process

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wettability & contact angle in brazing process

wettability is the capability of solids to build interfaces with liquids.

Wetting is measured in terms of the contact angle.

BRAZING

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Indirect Brazing (Metallisation) : The ceramic surface is usually coated with a metal

which is suitable to be wetted by a regular filler metal. The metallic coating acts as a

transition material between metal and ceramic. The most widely used method of

metallisation are metalizing by Moly-Manganese Paste process

Direct Brazing(Active Metal Brazing) : This is a single step processes where an active

filler metal is placed between the ceramics & metals and then heated in vacuum. The

reactive metal that is able to form a reaction layer on the ceramic surface that can be

wetted by the conventional filler metal..

Methods to Increase Wettability

Apply surface treatments to the ceramics so that the brazing alloy will wet,

Deposit reactive metal into the brazing alloy that will induce wetting

Advantages of Active metal brazing over

metalizing Route

single step process.

Processing Time is less

It is an economical process

The main drawback is brazed joint

strength is less

Flux & Filler materials for Vacuum Brazing

The filler metal for a particular application is chosen based on its

ability to:

• Wet the base metals

• Withstand the service conditions required.

• Melt at a lower temperature than the base metals or at a very

specific temperature

Filler materials are generally alloys of silver (Ag), gold (Au), copper

(Cu), cobalt (Co) or nickel (Ni). Brazing of non-metallic materials

ceramics and graphite active brazing alloys containing active metals(

Ti, Vor Hf,)are used

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Brazing operation takes place either in a controlled atmosphere, such as nitrogen

or argon, or a vacuum better than 10-3N.m-2

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In the framework of thermonuclear fusion

reactor, RF power is used to heat the plasma and

accelerate particles in order to drive steady state

currents in the plasma.

Radio frequency windows, used in transmission

lines of the Tokamak reactor, are one of the

critical components limiting the power that can be

coupled with the plasma current into the reactor.

The critical functions of RF window are to act as

temperature barrier, vacuum barrier and to be

transparent to RF power with minimal losses.

The window failures are thought to be due to

multipacting and material imperfection.64 Waveguide RF Window

Schematic view of In-vessel LHCD

system on SST 1 Tokamak

The most common material used for RF windows is high purity

polycrystalline alumina and the frame is made of Ti6Al4V alloy.

RF window in Tokamak fusion reactor

Barium Zinc Tantalate (BZT)ceramics

Large dielectric constant

High quality factor(low dielectric loss) at the microwave frequency.

low temperature coefficient of resonant frequency

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Radio frequency (RF) window sections require high mechanical strength along

with excellent microwave dielectric properties which are exhibits in Perovskite

ceramics Barium Zinc Tantalate (BZT.)

Therefore we can develop a BZT ceramic considered as an alternative dielectric

material for high power RF window application

Applications of BZT ceramics

Dielectric resonator

Microwave telecommunication

In satellite broadcasting

In mobile phone base stations

LITERATURE REVIEW

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P.K. Sharma et al [2], in his paper describes some of the critical UHV compatible

In-Vessel RF devices, their design, fabrication, and testing for LHCD system on

SST-1 Tokamak.

Swathi Manivannan and Dibakar Das et al [1], in their paper they prepared BZT

ceramics pellets by conventional solid state reaction and sintering at temperatures

1550oC and1600oC with 94% and 95% of the theoretical density(TD) . 97% of the TD

was achieved for the samples containing 0.5 wt% B2O3 when sintered at 1500oC.

These samples were unable to withstand the polishing action

Literature Review

K. Walls et al [3], were brazed with Alumina and Titanium6424 Cusil, Incusil 15,

Incusil 10 and ceramic is coated with Mo-Mn metallization process under vacuum for

RF window devices.

K. M. Erskine et al [4], has done Brazing of Perovskite ceramics Lead Magnesium

Niobate (PMN). with silver/copper oxide (Ag/CuO) system .The dielectric constant

decreased slightly between the monolithic and brazed samples.

Literature review on Brazing of ceramics & metal

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Jong-Heon Kim et al [5], Alumina brazed with Ag-Cu-Zr alloy, and the brazing alloy

interface was identified as single ZrO2 layer.. The fracture shear strength was strongly

influence by morphology of the joint, which was related to ductility of the joint.

Yanming He et al [6],in their paper discussed with Ag-Cu-Ti+WC composite filler was

employed for the joining of Si3N4 ceramic and 42CrMo steel, with increasing in the

content of WC particle, was gradually decreasing. the thickness of reaction layer and

increase in the flexural joint strength over the Ag-Cu-Ti brazing alloy

A.H. ElSawy et al [7], has done Brazing of Si3N4 to Cu using Cusil-ABA. The shear

strength of the brazed joints increased substantially as a result of applying a light load

on the joints during brazing and fine surface finish of copper base-metal

Jean S. Piment et al [8] reported on brazing with Zirconia and Titanium metal using

non active eutectic Ag-28Cu filler alloy. Titanium diffusion from the metallic

counterpart to the ceramic surface produced sound brazing joints.

Literature Review

OBJECTIVE OF THE WORK1/2

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The current study is to prepare a BZT ceramic by conventional solid state

method.

To develop a brazing procedure with a suitable filler materials and that

provides a high quality hermetic seal between BZT –Ti6Al4V alloy that

withstand operating temperature up to 250°C, under vacuum with a

differential pressure of 3 bar.

Technical approach

BZT was brazed with Ti6Al4V using active and non active brazing alloy of Ag-Cu

alloys. Ticusil® (4.5%Ti) Cusil-ABA® (1.5%Ti), BAg8 were brazed under high

vacuum.

Optical microscopy, Scanning Electron Microscopy, Dispersive Energy

Spectroscopy (SEM-EDS), and Electron Probe Micro Analyser(EPMA) were

characterised in order to study the interface of brazed joints.

Using universal testing machine, Shear strength of the brazed sample were carried

out.

For comparison study, alumina is also brazed with Bag8

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Experimental Procedure

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Preparation of Barium Zinc Tantalate Ba(Zn0.33Ta0.67)O3 Ceramic Pellet -Solid

State Method

BZT powder

Green pellet

Sintered pellet

1 inch X 1 inch size square pellets (25.4 X25.4 X4 mm) 97-98% of (Theoretical

Density-TD).Density of BZT- 7.92 g/cc

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Chemical compounds Al2O3 SiO2 MgO Na2O Fe2O3 CaO

Wt% 99.7% 0.05 0.08 0.03 0.015 0.03

Moreover to study the effect of ceramic on the brazed joint strength, commercially

available Alumina plates (97-98% of TD) with the same dimension as that of BZT

pellet were used for brazing. The nominal chemical composition of alumina is as

follows

Eleme

nt

Titaniu

m

Aluminiu

m

Vanadiu

m

Carb

on

Iro

n

Oxyg

en

Nitrog

en

Hydrog

en

Wt% 89.707 6 4 0.03 0.1 0.15 0.01 0.003

Chemical Specification of Ti6Al4V alloy

Ti6Al4V alloy is commercially available and its chemical composition as follows

Alumina Plate

Prior to brazing process all polished samples were cleaned by acid pickling

process to remove the surface impurities, tough deposits of scale and oxides.

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Brazing filler

alloy

% copper in

alloy

% silver in

alloy

%titanium in

alloy

Ticusil 26.7 68.3 4.5%

Cusil-ABA 35.25 63 1.75%

BAg8 28 72 nil

Brazing Filler alloy Composition

Thickness of filler material (foil) is around 100-130 μm

Eutectic Cu-Ag alloy used in ceramic brazing

-chemically inert & ductile

-reduces the oxidation behavior at the interface

-minimize residual stress during cooling at the end of the joining

process

Cu-Ag Brazing Filler Material

A normal load was applied to the assembly on

each joint to avoid eventual misalignments.

Brazed joint of ceramics and TI6Al4V alloy

Comparison

Active Brazing

Alloy

Ag-Cu

(BAg8)

TiCuSilCuSil-ABA

Ceramics (BZT) &

Ti alloy (Ti-6Al-4V)Ceramics (Al2O3) &

Ti alloy(Ti-6Al-4V)

BRAZING

Ag-Cu

(BAg8)

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Flowchart of Brazing operation on various filler alloy with Ti6Al4V

alloy

Brazed joint of ceramics

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Brazing Process in Vacuum Brazing Furnace

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S.No Ceramics Base

material

Filler

Material

Brazing

Temperature

Soaking

Time

(min.)

1 BZT Ti-6Al-4V Ticusil 8500 C 30

2 BZT Ti-6Al-4V Cusil-ABA 8500 C 30

3 BZT Ti-6Al-4V BAg8 8300 C 30

4 Al2O3 Ti-6Al-4V BAg8 8300 C 30

During brazing process The assembly is maintained vacuum pressure of

1.5 x10-5 to 3 x10-5 mbar.

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Square Threaded PlungerFixture assembly for shear strength

Shear Test using Universal Testing Machine

UTM-Walter-baiag

Shear strength-τ MPa

Load –F kN

Brazed Area-A mm2

Initial load of 0.05kN is applied with a cross

head speed of 0.1 mm/min.

All dimension are in mm

Brazed lap joint of ceramics -TI6Al4V alloy

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Shear Testing with Brazed Lap Joint

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Characterization Techniques

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Scanning Electron Microscope Equipment

Electron Probe Micro Analyzer Equipment

Inverted Olympus Optical Microscope

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Results and discussion

26

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Figure 1 Optical Micrographs of BZT-Ti6Al4V-TiCuSil Figure 2 Optical Micrographs of BZT-Ti6Al4V-CuSil ABA

Figure 3 optical Micrographs of BZT-Ti6Al4V-BAg8 Figure 4 Optical Micrographs of alumina -Ti6Al4V-BAg8

The joints are free of interfacial

micro defects, and exhibit excellent

physical contact and good

metallurgical bonding with high

diffusivity.

Ceramic FillerReaction

Zone (µm)

Ceramic-

filler (µm)

Filler-base

metal (µm)

BZT Ticusil 90 9 25

BZT Cusil-ABA 80 5 30

BZT BAg8 120 25 48

Al2O3 BAg8 100 24 50

Optical Micrographs of Brazed JointTable Thickness layer of various brazed joints

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EDS % WT of Brazed JointBZT-Ti6Al4V-TiCuSil BZT-Ti6Al4V-CuSil ABA

Element

spot 1 spot 2 spot 3 spot4 spot 5

Element


Weight% Weight% Weight% Weight% Weight% Weight% Weight% Weight% Weight% Weight%Ti K 49.12 34.66 8.1 34.57 32.11 Ti K 4.38 44.59 33.95 43.44 66.59

Cu L 41.92 45.43 14.66 47.13 42.73 Cu L 12.07 44.88 0 45.83 29.48

Ag L 0 19.91 77.23 18.3 21.11 Ag L 83.55 6.05 20.52 10.73 3.94

O K 8.96 0 0 0 4.04 O K 0 4.48 45.53 0 0Totals 100 100 100 100 100 Totals 100 100 100 100 100

BZT-Ti6Al4V-BAg8 ALUMINA-Ti6Al4V-BAg8

Element


Element


Weight% Weight% Weight% Weight% Weight% Weight% Weight% Weight% Weight% Weight%Ti K 28.51 6.69 43.34 46.05 32.26 Ti K 19.65 16.44 28.52 43.77 29.97

Cu L 57.13 11.98 15.64 37.18 63.84 Cu L 54.93 67.32 68.13 46.14 0Ag L 14.35 73.18 28.36 5.8 3.9 Ag L 25.42 16.23 3.35 0 70.03

O K 0 8.15 12.66 10.98 0 O K 0 0 0 10.09 0Totals 100 100 100 100 100 Totals 100 100 100 100 100

Element Composition at the Interface of the Brazed Joint with SEM-EDSFigure Brazed joint with EDS spectrum and SEM-SE Micrograph

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Electron Probe Micro Analyzer

Elemental Mapping & Line Scan analysis between brazed interface

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EPMA- Mapping & Line analysis of BZT-

Ti6Al4V-Ticusil

EPMA-Elemental Mapping of BZT-Ti6Al4V-Ticusil

EPMA-Line scan analysis of BZT-Ti6Al4V-Ticusil

2 1

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EPMA-Elemental Mapping of BZT-Ti6Al4V-Ticusil

1 2

EPMA-Line Scan analysis of BZT-Ti6Al4V-CusilABA


Ti6Al4V-Cusil ABA

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EPMA-Elemental Mapping of BZT-Ti6Al4V-BAg8

EPMA-Line Scan analysis of BZT-Ti6Al4V-BAg8

2


Ti6Al4V-BAg8

1

32

1 2

EPMA- Mapping & Line analysis of

Alumina-Ti6Al4V-BAg8

Figure EPMA-Elemental Mapping of Alumina-Ti6Al4V-BAg8

EPMA-Line Scan analysis of Alumina-Ti6Al4V-BAg8

S.No Brazed Sample Id Length(mm) Breath(mm) Max

Load(kN)

Shear

Strength(MPa)

1(a) BZT-Ti64-TiCuSil(4.5%Ti) 25.10 15 12.12 32

1(b) BZT-Ti64-TiCuSil(4.5%Ti) 24.5 15 12.13 33

1(c) BZT-Ti64-TiCuSil(4.5%Ti) 22.8 13.5 10.41 34

2(a) BZT-Ti64-CuSilABA(1.75%Ti) 24.5 14.3 10.52 30

2(b) BZT-Ti64-CuSilABA(1.75%Ti) 22.85 12.6 8.9 31

2(c) BZT-Ti64-CuSilABA(1.75%Ti) 25 15 11.98 32

3(a) BZT-Ti64-Bag8(72ag) 23.15 15.3 16.20 46

3(b) BZT-Ti64-Bag8(72ag) 22.7 15.5 15.90 45

3(c) BZT-Ti64-Bag8(72ag) 22.8 15.5 15.90 45

4(a) Al203-Ti64-Bag8(72ag) 25.1 14.9 16.74 45

4(b) Al203-Ti64-Bag8(72ag) 25.1 14.6 15.91 43.5

4(c) Al203-Ti64-Bag8(72ag) 25.1 15.6 17.23 44

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Shear Strength calculation of the Brazed Joint

In Ticusil, Cusil-ABA, the excess amount of Titanium (due to base & filler material)

leads to brittle joint, forming an inter-metallic compounds at the brazed interface thereby

strength has decreased

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Brazed sample of Ticusil, BZT & Ti-6Al-4V alloy Brazed sample of CuSil-ABA , BZT & Ti-6Al-4V

alloy

Partial Failure is on ceramic region and remaining is between ceramics & filler material

In a ceramic brazed joint, the base material and ceramic components

experience tensile and compressive residual stresses. The maximum thermal

residual stress appeared in the ceramic region adjacent to the ceramic/filler

interface

Fracture Surface of Active Brazed Joint( Ticusil, Cusil-ABA)

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Fracture Surface of (BAg8) Non Active Brazed Joint

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Brazed sample of BZT & Ti-6Al-4V alloy

complete fracture is on ceramics side only

Brazed Sample Of Alumina & Ti-6al-4v Alloy

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BZT pellets are prepared by solid state reaction with a maximum of 97~

98% Theoretical Density (TD) respectively.

Brazing of BZT and Ti-6Al-4V was carried out with active (Ticusil,

Cusil-ABA) and non active (BAg8) brazing alloy. Alumina-Ti6Al4V is

successfully brazed with BAg8.

Titanium layer is distributed between ceramic and brazing alloy along

the brazed joints. the presence of Titanium enhance more wettability for

getting sound brazed joints.

Non active brazing alloy (BAg8) exhibits more shear strength (~45MPa)

when compared to active brazing alloy, since reaction layer thickness

(∼25μm) is more in BAg8.

Visual observation of fracture surface of shear strength test samples of

brazed joints indicates, complete fracture were observed in ceramic side

in case of BAg8 (non active filler alloy) brazed joints, where as partial

fracture was noticed in ceramic side of Ticusil, Cusil-ABA (active filler

alloy) brazed joints.

CONCLUSION

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1. Swathi Manivannan, Dibakar Das, Effect of flux addition on mechanical and

microwave dielectric properties of Barium Zinc Tantalate ceramics, Transactions of the

Indian Ceramic Society, Vol. 73 (2) .2014.

2. P.K. Sharma et al. / Fusion Engineering and Design 83 (2008) 601–605.

3. R.Walls S Bernabei, Fabrication of phased array microwave, Princeton University,

Plasma Physics Laboratory Ch2820-9/89/1989 IEEE.

4. K. M. Erskine, Brazing perovskite ceramics with silver/copper oxide braze alloys,

Journal of Materials Science 37 (2002) 1705 – 1709.

5. Jong-Heon Kim, Journal of Materials Science Letters 16(1997)1212-1215.

6. Yanming He, Investigation of Si3N4 ceramic/42CrMo steel joints brazed with Ag-

Cu-Ti brazing alloy plus WC particles, ACSE- Volume 2 Issue 4, November 2013.

7. Brazing of Si3N4 ceramic to copper A.H. ElSawy, Journal of Materials Processing

Technology 77 (1998) 266–272.

8. Jean S. Pimenta, Brazing of Zirconia to Titanium using Ag-Cu and Au-Ni filler alloys.

Soldag. Insp. Sao Paulo, Vol. 18, no. 04, p.349-357, Oct / Nov 2013

REFERENCES

9.Humpston & Jacobson, Principles of Soldering and Brazing 1993.

10. Brazing ,joining process of ceramic picture - Wikipedia, the free encyclopedia.

11. An introduction to brazing, Sulzer metco, August-2011.

12.C.Ferro A.Orsini, Multiple brazing of ceramic windows to a single flange491,Fusion

Technology 1992.

13.Review Advances in brazing of ceramics O. M. Akselsen . Journal Of Materials

Science 27 (1992) 1989 2000.

14.Brazing of Si3N+ ceramic to copper A.H. ElSawy, Journal of Materials Processing

Technology 77 (1998) 266–272.

15.Victor A. Green hut, Metal-Ceramic joining, the Minerals, Metals & Materials

Society, 1991, 104-119.

16.Welding Hand Book, 8th Edition Vol. 3, 390-416

17. Markku Ainali, the Cuprobraze brazing Handbook Edition Nr 8, September 2006.

18.The CuproBraze brazing handbook, Edition Nr 8, September 2006

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REFERENCES

27-01-2018

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University of Hyderabad

Dr. Dibakar Das,

Associate Professor , SEST

Prof.Rajender Singh,

Dean, SEST

Prof. M. Sundararaman, former Dean,

and other faculty of SEST

Mr Mallesh, Smt.M. Padma, Mr Venu,

Mr Venkat Ramana and

other staff members of SEST

ACKNOWLEDGEMENTS

DMRL,HYD

Dr. G. Madhusudhan Reddy, Sci- “G

Dr.Amola Gokhale, Outstanding Sci, Director

Mr. Amit Singh Sci-“D”,

Mr. Ramdas

I express my gratitude towards

Mr. Vamsi Krishna R, Mrs. Swathi M,

Paul, Y.Pardhu, K.V.Sreenivasulu,

Vijay , Sunil, Vinitha, my friends,

classmates, students of SEST in UoH

My parents DhanaRaju Beera, Smt. Pusphavathi and

my family members for their financial support, strong

motivation and constant encouragement during the

course of my project work

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Thank you for kind attention

-Suresh Beera