Nickel & special alloys

About the material

Nickel and special alloys are used wherever conventional stainless steels reach their limits – for example, at extreme temperatures, in highly aggressive chemical media or for components with the highest requirements in terms of mechanical strength and dimensional stability.

Their special properties result from the targeted combination of nickel with other elements such as chromium, molybdenum, niobium, iron or cobalt. As a result, corrosion and oxidation resistance, thermal expansion, mechanical strength and deformability can be widely adjusted.

Studer-Biennaform processes these high-performance grades into cold-rolled precision flat wire with the tightest tolerances – for applications in medical technology, watchmaking and precision engineering, aerospace, energy and process engineering.

Nickel-iron alloys

Nickel-iron alloys such as Alloy 42 (material no. 1.3917, approx. 42% Ni) and Alloy 36 (1.3912, approx. 36% Ni) are characterised by an extremely low coefficient of thermal expansion. They are used wherever maximum dimensional stability is required in the event of temperature fluctuations.

Mechanically, these nickel-iron alloys are in the medium strength range – typically with a tensile strength of 500–700 MPa. They are easily malleable, but can barely be hardened by heat treatment. As a rule, they are supplied in the ductile-annealed state. A disadvantage compared to stainless steels is the lack of chromium passivation, which limits their corrosion resistance. Tarnishing or rust can occur in humid environments.

Typical areas of application are:

• Watchmaking industry: Alloy 36 and Alloy 42 are used for pendulum springs, balance springs and temperature-independent control parts to ensure accuracy.
• Precision measurement technology: Alloy 36 rods or strips prevent unwanted length changes and ensure maximum measuring accuracy in interferometers, gauges or laboratory scales.
• Electronics: Alloy 42 is used in glass-metal feedthroughs (e.g. hermetic housings for transistors or sensors) as its expansion behaviour is optimally adapted to glass – this allows for tight and reliable seals.
• Optical systems and aerospace technology: Alloy 36 is used in frames, brackets or carrier systems for optical devices (e.g. laser resonators, telescopes, satellite antennas) to minimise thermally induced deformations.
• Geodesy: In yardsticks with an Alloy 36 measuring tape, the extremely low expansion prevents length errors during temperature changes – ideal for precision levelling.

Nickel-iron alloys are therefore the first choice wherever components under moderate mechanical stress but with high levels of geometric stability are required.

Nickel-based alloys

Nickel-based alloys – known under brand names such as Hastelloy or Inconel – offer an outstanding combination of corrosion resistance and high-temperature resistance. They contain at least 50% nickel and, depending on the type of alloy, are combined with other elements such as chromium, molybdenum, iron, niobium, tungsten, aluminium, titanium or cobalt.

A popular example is Hastelloy C-276 (material no. 2.4819), a Ni-Cr-Mo-W alloy. It is considered a reference material for highly corrosive environments, especially in the presence of chloride ions. The high nickel and molybdenum concentration effectively prevents pitting and crevice corrosion – even in mixed acids.
Inconel 625 (2.4856) is a Ni-Cr-Mo alloy with excellent oxidation resistance and high mechanical strength up to approximately 980 °C. A durable chromium oxide layer protects the surface even under thermal stress.

Inconel 718 (2.4668) also contains niobium as well as aluminium and titanium. Thanks to precipitation hardening, it achieves extremely high strength values – up to around 1400 MPa – combined with good heat strength and toughness.

Nickel-based alloys are not only strong and tough under heat, but also extremely resistant to chemical attack by acids, alkalis, chlorides or H₂S. 

Typical areas of application:

• Chemical and process engineering: reactors, valves, pumps in hot, aggressive media
• Pharmaceutical/biotech industry: e.g. Hastelloy C-276 in chloride and acid environments
• Exhaust gas purification: systems for the desulphurisation of industrial exhaust gases
• Aerospace: Inconel 625 for aircraft exhaust systems; Inconel 718 for turbine blades, impellers, engine housings
• Offshore and energy plants: valves, drill heads (sour gas), gas turbines, power plant boilers
• High-temperature technology: springs, screws, seals, sensor sleeves
• Nuclear technology: reactor components with corrosion resistance under the influence of radiation

Nickel-based grades enable reliable operation in extreme conditions – in applications where conventional materials are no longer sufficient.

Heat-resistant nickel alloys

Special nickel-chromium alloys have been developed for applications at extremely high temperatures of around 1000 °C and above. These include classic heating conductor alloys such as NiCr 60/15 (material no. 2.4867) and NiCr 80/20 (2.4869) with a nickel content of around 60–80%, as well as the highly heat-resistant grade Alloy 80A / NiCr20TiAl, which also contains titanium and aluminium.

These alloys combine high oxidation resistance with excellent thermal microstructure stability. They retain their shape and structure even under prolonged annealing loads. In addition, they are good electrical conductors when heated – to be more precise, they have a stable specific resistance, which is crucial for heating operation. They also exhibit excellent resistance to rapid temperature changes (thermal shock) and remain dimensionally stable even under cyclic loads.

Typical areas of application are:

• Furnace and heating construction: heating wires and strips for industrial furnaces, toasters, hair dryers, ceramic radiators
• Thermoelectric applications: thermistor resistors, glow plugs, temperature sensors
• High-temperature screws and small parts where oxidation resistance and thermal stability are required

Nickel-chromium alloys are therefore the first choice for metallic components that are electrically loaded or must remain mechanically stable at high temperatures.

Cobalt-based special alloy

Phynox is a cobalt-chromium-nickel-based alloy with unique properties. It combines biocompatibility, non-magnetisability, high corrosion resistance and excellent mechanical performance – especially under cyclic loads.

In the cured state, Phynox achieves tensile strengths of over 1500 MPa – comparable to high-quality spring steels – while still remaining sufficiently ductile. The hardness can also be increased through targeted ageing treatments, which makes the material particularly suitable for highly stressed springs, clips and implant parts. The alloy also boasts exceptionally high fatigue strength: Phynox springs withstand very many bending cycles without fatigue cracks occurring.

The corrosion resistance is also excellent. Phynox offers similar resistance to bodily fluids, seawater and numerous chemicals as stainless steel. It is non-magnetic, can be sterilised, is non-flammable and shows no outgassing – ideal for sensitive environments. Material performance remains stable over a wide temperature range. The alloy can be easily machined, welded and soldered when not cured.

Originally developed for medical technology, Phynox is now used in a wide range of applications:

• Medical technology: surgical instruments, stents, cardiac clamps, implants, dental tools
• Watchmaking and precision engineering: coil springs (e.g. balance springs in mechanical watches) thanks to its non-magnetisability and resistance to ageing
• Measurement and sensor technology: vibration and clip springs, membranes in devices with high fatigue requirements
• Aerospace: spring and closure parts where corrosion resistance and freedom from magnets are essential
• Electrical engineering: contact springs, e.g. in MRI applications where no magnetic materials are permitted

This makes Phynox one of the most powerful spring materials of all – a grade that meets the highest requirements in safety- and function-critical applications.