Nickel-Alloy Bellows Material Specifications

METAL COMPOSITION

Electrodeposited (electroformed) bellows are available in three types of nickel: regular, low-sulfer, and weldable.  Servometer offers these options to help satisfy customers satisfy performance requirements.

Our standard bellows have a 0.0001″ lamination of copper between equal thicknesses of nickel.  Servometer bellows have about the same chemical analysis as commercial “A” nickel with the exclusion of the copper lamina.  By taking this important step in the manufacturing process, Servometer creates leak-tight assemblies.  The chemistry has greater overall strength and flexibility, whereas other electroforming technologies can become brittle.

Nickel Plus Cobalt: 99.8%

Interstitially deposited impurities: 0.05%

Standard nickel bellows chemistry is bright and has a high yield strength.  The main limitation is its installation method, since its temperature limitation is approximately 350 degrees Fahrenheit.

Low sulfur nickel bellows have a satin finish and better corrosion resistance properties.  This material can be soldered or brazed for installation into customer assemblies.

Weldable nickel bellows are the equivalent to the low sulfur nickel bellows with 0.020 maximum sulfur, but it can be welded or brazed.

Servometer engineers are at your service to help find the right style of material for the application.  Servometer also offers sub-assembly services for its customers.  Our expertise in design and manufacturing miniature components has been a natural fit to offer the assembly capability.

TOLERANCES

Specifications based on standard designs. Contact Servometer with questions on applications that require different specifications.

Inside Diameter:

• ±0.005″ for bellows ID 0.250″ or larger
• ±0.003″ for bellows ID less than 0.250″

Outside Diameter

• Tolerances vary with wall thickness and size.  Contact Factory.
• Diameters up to 9 inches

Length of Convolutions

• ±0.010″

Length of End Trims

• ±0.005″

Spring Rate

• Standard is ±30%.  Contact factory with requirements if different.

MECHANICAL PROPERTIES

Properties encompass all nickel bellows compositions.

• Yield Strength = 110,000 PSI
• Tensile Strength = 125,000 PSI
• Elongation = 1.0%
• Hardness = 270 Vickers
• Young’s Modulus = 23,350,000
• Metal Hysteresis = within stress limits is very low
• Specific weight = 0.321 lb/in3

LEAK TIGHTNESS

Bellows are 100% tested via mass spectrometer to 1×10-9 cc/sec of helium.  This rate is the equivalent of one cubic centimeter of helium in 32 years.  For applications requiring testing tighter tolerances, contact the factory.

MAGNETIC PROPERTIES

Servometer electrodeposited nickel is ferromagnetic.  Electrodeposited copper is non-magnetic and can be utilized for special applications.

CORROSION RESISTANCE

Nickel is more resistant to corrosion than brass or bronze, but not as much as stainless steel.  Electroformed bellows will not oxidize in air or be affected by liquids that are an alkaline.  For applications, requiring a metal bellows assembly with more corrosion resistant properties, contact BellowsTech, LLC for an edge welded bellows design. www.bellowstech.com

SURFACE FINISHES

- Gold Plate – 24 carats – ASTM-B-488 is supplied either to enable soft soldering without flux or to provide a surface for microwave fields.

- Silver Plate – commonly applied to bellows in microwave guides.

- Parylene coating can assist in protection from certain corrosive atmospheres and media.