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A INDEPENDENT STUDY SEMINAR REPORT ON Diffusion Welding” INSTITUTE OF TECHNOLOGY AND MANAGEMENT MAHARISHI DAYANAND UNIVERSITY ROHTAK 124001 April 12, 2012 Submitted by:- Submitted to:-

Seminar on diffusion welding

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Page 1: Seminar on diffusion welding

A INDEPENDENT STUDY SEMINAR REPORT

ON

“Diffusion Welding”

INSTITUTE OF TECHNOLOGY AND MANAGEMENT

MAHARISHI DAYANAND UNIVERSITY ROHTAK 124001

April 12, 2012

Submitted by:- Submitted to:- Abhishek thakur Mr. Abhishek Pratap Singh 08ME304

TABLE OF CONTENTS

Page 2: Seminar on diffusion welding

1. Introduction2. TABLE

3. Diffusion Welding Working Procedure4. Free energy as Atom reversibly moves

5. Factors influencing Diffusion Welding

6. Applications of Diffusion welding

7. Titanium Diffusion welding

8. Nickel Diffusion welding

9. Diffusion welding of dissimilar metals10. Refrences.

Page 3: Seminar on diffusion welding

Introduction

 Diffusion welding (DFW) is a solid state welding process by which two metals (which may be dissimilar) can be bonded together. Diffusion involves the migration of atoms across the joint, due to concentration gradients. The two materials are pressed together at an elevated temperature usually between 50 and 70% of the melting point. The pressure is used to relieve the void that may occur due to the different surface topographies. The method was invented by the Soviet scientist N.F. Kazakov in 1953. Specific tooling is made for each welding application to mate the welder to the work pieces.

A solid-state welding process that produces coalescence of the faying surfaces by the application of pressure at elevated temperature.

The process does not involve macroscopic deformation, or relative motion of the workpieces.

A solid filler metal may or may not be inserted between the faying surfaces.

1.

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TABLE

2.Diffusion Welding Working Principles

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• 1st stage

– deformation forming interfacial boundary.

• 2nd stage

– Grain boundary migration and pore elimination.

• 3rd stage

– Volume diffusion and pore elimination.

3.

Free Energy as Atom Reversibly Moves

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Factors Influencing Diffusion Welding(Relation between Temperature and Diffusion Coefficient)

• Temperature

• D = D0 e -Q/KT

– D = Diffusion coefficient

– D0 = Diffusion constant

– Q = Activation energy

– T = Absolute temperature

– K = Boltzman’s constant

• Temperature ( effects diffusion coefficient)

• Time

4.

• X = C (Dt)1/2 = Diffusion Length

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– X = Diffusion length

– C = A constant

– D = Diffusion coefficient (see previous slide)

– t =Time

• Pressure

5.

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6.

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Applications of Diffusion Welding• Application in titanium welding for aero-space vehicles.

• Diffusion welding of nickel alloys include Inconel 600, wrought Udimet 700, and Rene 41.

• Dissimilar metal diffusion welding applications include Cu to Ti, Cu to Al, and Cu to Cb-1%Zr. Brittle intermetallic compound formation must be controlled in these applications.

Titanium Diffusion Welding

• Temp As High As Possible Without Damage to Base Metal

75 to 100 F below Alpha-Beta Transus (eg 1700F)

• Time varies with other facts below but 1 hr to 4 hour typical

• Pressure near yield (at temp)

• Smooth Faying Surface (rough surfaces = more time, pressure)

• Clean Surface (usually acid cleaning)

• Space Shuttle designed to have 28 Diffusion Welding Components

7.

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Nickel Diffusion Welding

(More Difficult to Weld)

• Temp close to MP

• High Pressure (because High hot strength)

• Clean Surfaces - Ambient Atmosphere Control

(Surface Oxides Do Not Dissolve)

• Nickel Filler often used (especially for rough surface)

8.

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Diffusion Welding of Dissimilar Metals

• An intermetallic phase or a brittle intermetallic compound may form at the weld interface. Selection of an appropriate filler metal can usually prevent such problems. Joint designs can help also.

• Low melting phases may form. Sometime this effect is beneficial porosity may form due to unequal rates of metal transfer by diffusion in the region adjacent to the weld (Kirkendall Porosity). Proper welding conditions or the use of and appropriate filler metal or both may prevent this problem

9.

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Some Specific Applications Of Diffusion Welding

10.

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REFERENCES:-

1. http://web.mit.edu/allanmc/www/diffusionwelding.pdf .2. http://www.technologystudent.com/PDF4/dfwld1.pdf .3. http://welding.about.com/od/ergonomicbasics/a/imp_comm.htm .4. http://www.hse.gov.uk/waste/diffuse.pdf .

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