AUSTENITIC (NiCr) ALLOYS

Catégories: Matériaux chauffants , Matériaux de résistance

Nickel-chrome (NiCr) alloys possess high mechanical strength that is maintained even at elevated temperatures, making them ideal for use as heat-resistant materials in various industrial processes. Kanthal’s range of NiCr alloy products, branded as Nikrothal®, are also widely used as resistive heating elements in applications such as electric grills, tumble dryers, and blow-dryers.

Content:
Types of Nikrothal® alloys
Advantages of Nikrothal® alloys
Physical and mechanical properties
Summary
Product varieties

Types of Nikrothal® alloys

Nikrothal® 80: Up to 1,200°C (2,190°F)

It is a premium-quality alloy known for its high nickel content, which provides excellent workability and high-temperature strength.

Nikrothal® 80 is widely used in demanding applications within the electric appliance industry, particularly for tubular element applications.

Nikrothal® 60: Up to 1,150°C (2,100°F)

It is suitable for a range of domestic and furnace applications and offers good corrosion resistance, excellent oxidation properties, and superior form stability, making it reliable for high-temperature use.

However, its corrosion resistance may be reduced in sulfur-containing atmospheres.

Typical applications for Nikrothal® 60 include use as suspended coils, where it is most commonly utilized, and less frequently in tubular heating elements.

Nikrothal® 40: Up to1,100°C (2,010°F)

The primary advantage of this alloy is its lower cost due to its reduced nickel content.

It is suitable for use in a variety of domestic appliances and general heating equipment where moderate temperatures are required.

Nikrothal® 70: Up to 1,250°C (2,280°F)

Typical applications for Nikrothal® 70 include use as electrical heating elements in industrial furnaces.

This alloy is particularly well-suited for use in reducing atmospheres, as it is resistant to “green rot,” a type of corrosion that affects some alloys in such environments.

 

Advantages of Nikrothal® alloys

Higher hot and creep strength

Nikrothal® alloys exhibit higher hot and creep strength compared to Kanthal® alloys. Although Kanthal® APM and Kanthal® AF have good form stability and are superior to other Kanthal® grades, they do not match the hot and creep strength of Nikrothal® alloys.

Better ductility after use

Nikrothal® alloys maintain their ductility even after prolonged use, ensuring flexibility and durability over time.

Higher emissivity

Fully oxidized Nikrothal® alloys have a higher emissivity than Kanthal® alloys. This means that at the same surface load, Nikrothal® alloys operate at a somewhat lower element temperature, enhancing efficiency in certain applications.

Non-magnetic properties

Nikrothal® alloys are generally non-magnetic, making them advantageous for low-temperature applications where non-magnetic materials are required. The exception to this is Nikrothal® 60, which is magnetic at low temperatures. In contrast, Kanthal® alloys become non-magnetic only when heated above 600°C (1,100°F).

Better wet corrosion resistance

Nikrothal® alloys generally offer better corrosion resistance at room temperature than non-oxidized Kanthal® alloys, except in environments containing sulfur or certain controlled atmospheres.

 

Physical and mechanical properties

    Nikrothal® 80 Nikrothal® Te Nikrothal® 70 Nikrothal® 60 Nikrothal® 40

Max continuous operating temp.
(element temperature in air)

°C
(°F)

1,200
(2,190)

1,200
(2,190)

1,250
(2,280)

1,150
(2,100)

1,100
(2,010)

Nominal composition (See Note), %

Cr
Al
Fe
Ni

20


80
22

9
balance
30


70
16

balance
60
20

balance
35
Density ρ

g/cm3
Ib/in3

8.30
(0.300)
8.10
(0.293)
8.10
(0.293)
8.20
(0.296)
7.90
(0.285)
Resistivity at 20°C
at 68°F
Ω mm2/m
Ω/cmf
1.09
(655)
1.19
(716)
1.18
(709)
1.11
(668)
1.04
(626)
Temperature factor of the resistivity, Ct
250°C (480°F)
500°C (930°F)
800°C (1,470°F)
1,000°C (1,830°F)
1,200°C (2,190°F)
 
1.02
1.05
1.04
1.05
1.07

1.04
1.06
1.06
1.07
1.07

1.02
1.05
1.04
1.05
1.06

1.04
1.08
1.10
1.11

1.08
1.15
1.21
1.23
Linear thermal expansion coefficient α, × 10-6/K
20 – 100°C (68 – 210°F)
20 – 250°C (68 – 480°F)
20 – 500°C (68 – 930°F)
20 – 750°C (68 – 1,380°F)
20 – 1,000°C (68 – 1,840°F)
 

15
16
17
18


14
15
16
17


14
15
16
17


16
17
18
18


16
17
18
19
Thermal conductivity λ at 50°C
at 122°F
W/m K
(Btu in/ft2 h °F)
15
(104)
14
(97)
14
(97)
14
(97)
13
(90)
Specific heat capacity at 20°C
at 68°F
kJ/kg K
(Btu/lb °F)
0.46
(0.110)
0.46
(0.110)
0.46
(0.110)
0.46
(0.110)
0.50
(0.119)
Melting point (approx.) °C
(°F)
1,400
(2,550)
1,380
(2,515)
1,380
(2,515)
1,390
(2,535)
1,390
(2,535)

Mechanical properties* (approx.)

           
Tensile strength N/mm2
(psi)
810
(117,500)
800
(116,000)
820
(118,900)
730
(105,900)
675
(97,900)
Yield point N/mm2
(psi)
420
(60,900)
390
(56,600)
430
(62,400)
370
(53,700)
340
(49,300)
Hardness Hv 180 190 185 180 180
Elongation at rupture % 30 30 30 35 35
Tensile strength at 900°C N/mm2
(psi)
100
(14,500)

120
(17,400)
100
(14,500)
120
(17,400)

Creep strength***
at 800°C
at 1,470°F
at 1,000°C
at 1,830°F
at 1,100°C
at 2,010°F
at 1,200°C
at 2,190°F

N/mm2
(psi)
N/mm2
(psi)
N/mm2
(psi)
N/mm2
(psi)
15
(2,160)
4
(560)



15
(2,160)
4
(560)










15
(2,160)
4
(560)



20
(2,900)
4
(560)



Magnetic properties   2) 2) 2) 3) 2)
Emissivity, fully oxidized condition 0.88 0.88 0.88 0.88 0.88 0.88

Note: Composition listed is nominal. Actual composition may vary to meet standard electrical resistance and dimensional tolerances.
* The values given apply for sizes of approx. 1.0 mm diameter (0.039 in)
** 4.0 mm (0.157 in) Thinner gauges have higher strength and hardness values while the corresponding values are lower for thicker gauge
*** Calculated from observed elongation in a Kanthal standard furnace test. 1% elongation after 1,000 hours
1) Magnetic (Curie point approx. 600°C (1,100°F)) 2) Non-magnetic 3) Slightly magnetic

 

Summary

Nikrothal® alloys are designed for high temperatures: for creep strength and ductility.

Maximum operating temperature per alloy

Resistivity vs.temperature

Product varieties

Kanthal® and Nikrothal® alloys are available in specialized forms such as wire, strips (0.10–3.5 mm thick, 4–195 mm wide), rods, and straightened wire. These versatile forms ensure adaptability for high-temperature and resistance needs.

  Rod Wire Strip

Straightned

wire

Nikrothal® 80  
Nikrothal® 70  
Nikrothal® 60  
Nikrothal® 40