Surface treatments

Question 1

What are the 2 main approaches for surface treatments?

Answer 1

Introducing interstitial elements (carburizing and nitriding) and modifying structure (induction hardening).

Question 2

What is carburizing?

Answer 2

Enhances C concentration to increase hardness. It is a slow process carried out at high temperatures (950 degrees).
It causes grain growth which can be reduced by normalization.
It creates a hard outer shell but keeps a ductile core.
Achieved by using C and N.
It reduces residual stresses.

Question 3

What is induction hardening?

Answer 3

Heating the outside of the material into the austenite region and then quenching it so ti forms martensite and hardens.
It reduces residual stresses.

Question 4

What is nitriding?

Answer 4

Very similar to carburizing but carried out at lower temperatures 500-650 degrees and using the following nitrides Mo, Cr, V, Al.
It reduces residual stresses.

Question 5

What is shot peening?

Answer 5

Hardening the surface and inducing compressive stresses in the material to compensate for the residual ones.
It is achieved by shooting tiny particles at the machined part.