Nov 15 2012
Topics Covered
Introduction
Chemical Composition
Physical Properties
Mechanical Properties
Thermal Properties
Fabrication and Heat Treatment
Machinability
Forming
Welding
Heat Treatment
Cold Working
Annealing
Hardening
Applications
Introduction
Super alloys or high performance alloys are used in very high temperature environments above 540ºC (1000ºF) where deformation resistance and high surface stability are chiefly required. They have good oxidation and creep resistance. Cobalt-base, nickel-base and iron-base alloys are the three major types of super alloys. The iron-base super alloys are generally wrought alloys provided with stainless steel technology. Nickel-base and cobalt-base super alloys may be cast or wrought based on its composition or application. Super alloys can be generally forged, rolled to sheet or produced in different shapes. Highly alloyed compositions are formed as castings. They can be strengthened using hardening techniques like work hardening, solid-solution hardening and precipitation hardening.
The following section will discuss in detail about super alloy nickel 220.
Chemical Composition
The following table shows the chemical composition of super alloy nickel 220.
|
Element |
Content (%) |
|
Manganese, Mn |
0.2 max |
|
Carbon, C |
0.15 max |
|
Copper,Cu |
0.1 max |
|
Iron, Fe |
0.1 max |
|
Magnesium, Mg |
0.08-0.01 |
|
Silicon, Si |
0.01-0.05 |
|
Titanium, Ti |
0.01-0.05 |
|
Sulfur, S |
0.008 max |
|
Nickel, Ni |
Balance |
Physical Properties
The physical properties of super alloy nickel 220 are given in the following table.
|
Properties |
Metric |
Imperial |
|
Density |
8.91 g/cm³ |
0.322 lb/in³ |
|
Melting point |
1450ºC |
2642ºF |
Mechanical Properties
The mechanical properties of super alloy nickel 220 are given in the following table.
|
Properties |
Metric |
Imperial |
|
Tensile strength at break (annealed) |
345 MPa |
50000 psi |
Thermal Properties
The thermal properties of super alloy nickel 220 are given in the following table.
|
Properties |
Metric |
Imperial |
|
Thermal expansion co-efficient (@20ºC/68ºF) |
15 µm/m°C |
8.33 µin/in°F |
|
Thermal conductivity |
59 W/mK |
409 BTU in/hr.ft².°F |
Fabrication and Heat Treatment
Machinability
Super alloy nickel 220 can be easily machined using conventional techniques.
Forming
Forming of super alloy nickel 220 can be performed through any conventional methods.
Welding
Super alloy nickel 220 can be welded using all conventional means.
Heat Treatment
Super alloy nickel 220 is heat treated at 1066ºC (1950ºF) and then air cooled.
Cold Working
Super alloy nickel 220 can be readily cold worked through conventional techniques.
Annealing
Annealing of super alloy nickel 220 can be performed at 871ºC (1600ºF) and then air cooled.
Hardening
Super alloy nickel 220 can be hardened only by cold working.
Applications
Super alloy nickel 220 finds its application in the manufacture of cathode plates used in electronic tubes.