Novel processing techniques

Question 1

Describe friction stir welding

Answer 1

The joining of materials without the need for filler materials

Question 2

List advantages and disadvantages of friction stir welding

Answer 2

A:

• excellent mechanical properties
• no porosity or distortion
• non consumable tool
• can perform on the spot repair work
• can work at high temperatures

D:

• costly equipment
• same materials are hard to FSW

Question 3

What is the advantage of powder metallurgy processes over casting

Answer 3

PMP have a very low scrap rate compared to casting processes

Question 4

List advantages of additive layer manufacturing

Answer 4

1. Design friendly
2. Low lead times
3. Reduces buy-to-fly ratio
4. Near-net shape products

Question 5

Powder metallurgy processes - laser system

Answer 5

applies heat only the part slice, therefore don’t get uniform heating. This leads to residual stresses.
Impossible to do thin walls.

Question 6

Powder metallurgy processes - Electron beam

Answer 6

Most promising technology. Uses Ti-6Al-4V and CoCr.
Preheats every layer so properties are very good.
Have to build supports, but these are recyclable.
Must be very careful with parameters.
Need skilled workers

Question 7

Disadvantages to additive layer manufacturing

Answer 7

• its expensive
• certain powders are expensive
• cannot have every material in powder form
• highly skilled workers needed

Question 8

Describe metal injection moulding

Answer 8

1. Start with powder
2. Add Binder and heat
3. form granules and inject into mould
4. remove Binder
5. Sinter

Question 9

Why is sintering needed in metal injection moulding

Answer 9

After debinding, the material is very brittle and only 70% dense.
Sintering compacts product and makes it 100%

Question 10

General equation for mechanical effects of porosity

Answer 10

X = Xo * e^(βρ)

Question 11

Describe hot isostatic pressing (HIP)

Answer 11

Simply: put powder in chamber and squeeze creating 100% dense product and eliminating porosity