Nickel-based superalloys

The material. With a name like superalloy there has to be something spe­cial here. There is. Superalloy is a name applied to nickel-based, iron-based, and cobalt-based alloys that combine exceptional high-temperature strength with excellent corrosion and oxidation resistance. Without them, jet engines would not be practical: they can carry load continuously at temper­atures up to 1200°C. The nickel-based superalloys are the ultimate metal­lic cocktail: nickel with a good slug of chromium and lesser shots of cobalt, aluminum, titanium, molybdenum, zirconium, and iron. The data in this record spans the range of high-performance, nickel-based superalloys.

Composition

Ni + 10 to 25% Cr + Ti, Al, Co, Mo, Zr, B, and Fe in varying proportions. General properties

Density

7750

– 8650

kg/m3

Price

*28.5

– 31.4

USD/kg

Mechanical properties

Young’s modulus

150

– 245

GPa

Yield strength (elastic limit)

300

– 1.9e3

MPa

Tensile strength

400

– 2.1e3

MPa

Compressive strength

300

– 1.9e3

MPa

Elongation

0.5

– 60

%

Hardness—Vickers

200

– 600

HV

Fatigue strength at 107 cycles

*135

– 900

MPa

Fracture toughness

65

– 110

MPa. m1/2

Thermal properties

Melting point

1280

– 1410

°C

Maximum service temperature

*900

– 1200

°C

Thermal conductor or insulator?

Good conductor

Thermal conductivity

8

– 17

W/m. K

Specific heat capacity

380

– 490

J/kg. K

Thermal expansion coefficient

9

– 16

p, strain/°C

Electrical properties

Electrical conductor or insulator?

Poor conductor

Electrical resistivity

84

– 240

pnhm. cm

Nickel is the principal ingredient of superalloys used for high-temperature turbines and chemical engineering equipment. On the left, a gas turbine (image courtesy of Kawasaki Turbines). On the right, a single superalloy blade.

Reserves

6.3 X 107

– 6.5 X 107

tonne

Embodied energy, primary production

135

– 150

MJ/kg

CO2 footprint, primary production

*7.89

– 9.2

kg/kg

Water usage

*134

– 484

l/kg

Eco-indicator

4900

– 5500

millipoints/kg

Ecoproperties: processing

Casting energy

*3.38

– 4.09

MJ/kg

Casting CO2

*0.20

– 0.24

kg/kg

Forging, rolling energy

*3.26

– 3.95

MJ/kg

Forging, rolling CO2

*0.26

– 0.31

kg/kg

Metal powder forming energy

*11.3

– 13.6

MJ/kg

Metal powder forming CO2

*0.90

– 1.09

kg/kg

Recycling

Embodied energy, recycling

33.8

– 37.5

MJ/kg

CO2 footprint, recycling

*1.97

– 2.3

kg/kg

Recycle fraction in current supply

22

– 26

%

Ecoproperties: material

Annual world production

1.5 X 106 – 1.6 X 106 tonne/yr

Typical uses. Blades, disks, and combustion chambers in turbines and jet engines; rocket engines; general structural aerospace applications; light springs, high-temperature chemical engineering equipment; bioengineering and medical.