UNIT IV HEAT TREATMENT

1. Vacuum and Plasma Surface
Hardening
To meet the highest surface quality and mechanical
properties of the components.
Vacuum surface hardening
Plasma surface hardening

2. Vacuum Surface Hardening
Heat treatment process of steel carried out in a vacuum space
Low pressure and high uniform hardening temperature
(above 1000 °C)
Suitability
High wear and High load bearing applications

3. Vacuum Carburising Process
Evacuating and heating
Supplying Hydrocarbon Gas
Diffusion cycle
Quenching

5. Advantages of vacuum carburising
Oxide free surface
Absence of inter-granular oxidation
Better process and cycle flexibility
Excellent finish
Easy integration into manufacturing
Excellent hole penetration
Lower distortion
Shorter process times
Improved reliability and reproducibility

6. Disadvantages of Vacuum Carburising
Higher initial capital equipment cost
Part cleanliness is more critical

7. Plasma Surface Hardening
Plasma - High temperature ionized gas
Two types
Plasma carburising
Plasma nitriding

8. Plasma carburising process
Evacuating and heating
Supplying hydrocarbon gas
Generation of plasma
Diffusion cycle
Quenching

10. Advantages of plasma carburising
Shorter cycle times
No oxidation at grain boundaries
Lower process gas and energy consumption
Automation
Ability to treat hard to carburise materials

11. Disadvantages of plasma carburising
High initial capital equipment cost
Not applicable to bulk loads
Hollow cathode effect