The document is a presentation on diffusion welding, detailing its definition as a solid-state welding process, schematic representation, and working principles involving deformation, grain boundary migration, and volume diffusion. It discusses specific applications in titanium and nickel welding, advantages like minimal deformation, and limitations such as costly equipment and preparation. Overall, diffusion welding allows for joining dissimilar materials while maintaining similar properties to base metals.

1. Presentation on
Diffusion welding
PRESENTED BY: LIMON SAHA

2. Contents
 Definition
 Schematic Figure
 Working principles
 Applications
 Titanium Diffusion Welding
 Nickel Diffusion Welding
 Advantages
 Limitations

3. Definition of Diffusion Welding
 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.

4. Schematic Figure
Schematic representation of
diffusion welding using
electrical resistance for heating
A
B
Force Work piece

5. Diffusion Welding Working
Principles
 1st stage
 deformation forming interfacial
boundary.
 2nd stage
 Grain boundary migration and
pore elimination.
 3rd stage
 Volume diffusion and pore
elimination. 2nd stage grain
boundary migration
and pore elimination
3rd stage volume
diffusion pore
elimination
asperities come
into contact.
1st stage deformation
and interfacial boundary
formation

6. 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.
 Space Shuttle designed to have 28 Diffusion Welding
Components
 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.

7. Titanium Diffusion Welding
• Temp As High As Possible Without Damage to Base Metal
75 to 100 F.
• Time varies with other facts below but 1 hour to 4 hour
typical
• Pressure near yield (at temp)
• Smooth Faying Surface (rough surfaces = more time,
pressure)
• Clean Surface (usually acid cleaning)

8. Superplastic Formed &
Diffusion Bonded Titanium
Heat Exchanger

9. Nickel Diffusion Welding
 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)

10. Advantages
 This solid state process avoids pitfalls of fusion welding
 Dissimilar materials welds are possible
 Properties and microstructures remain similar to those of base
metals
 Multiple welds can be made in one setup at the same time
 Produces a product finished to size and causes minimal
deformation
 Presents less shrinkage and stresses compared to other
welding processes
 Highly automated process does not need skillful workforce

11. Limitations
 Costly equipment especially for large weldments
 Costly preparation with smooth surface finish and exceptional
cleanliness
 Protective atmosphere or vacuum required
 Long time to completion
 Not suited to high production rates
 Difference in thermal expansion of members may need
special attention
 Limited nondestructive inspection methods available

12.  How to build a Heat Sink with
Diffusion Welding