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Precision C • UNS N09902

Precision C is a heat treatable Nickel-Iron Alloy used in critical diaphragm applications, such as, metal diaphragms for aerospace sensors and burst discs. The alloy composition provides a unique constant elastic modulus value over a temperature range of -50ºF to 150ºF.

Precision C can be readily formed from the annealed temper. It has a work hardening rate similar to austenitic stainless steel. The material can be joined by TIG, EB, and resistance welding as well as by brazing and soft solder technique. The heat treatment of Precision C can be adjusted to produce the desired value for the thermoelastic coefficient at or near zero. The elevated strength in the heat treated temper results in low mechanical hysteresis and low drift.

Available Sizes:

Precision C is available from Hamilton Precision Metals as strip product in thickness from 0.0005” to 0.040” (0.0127 mm to 1.016 mm) and widths up to 8.0” (203.2 mm). The material conforms to ASM 5221 and UNS N09902.

Nominal Composition
Nickel 42%
Chromium 5.3%
Titanium 2.4%
Aluminum 0.55%
Silicon 0.50%
Manganese 0.40%
Carbon 0.02%
Iron Balance

Mechanical Properties
TREAT 1250°F
/ 3½ HRS
50% COLD
50% C.R./HEAT
TREAT 1200°F
/ 2½ HRS
Ultimate Tensile Strength 95,000 PSI 170,000 PSI 140,000 PSI 200,000 PSI
Yield Strength (0.2% Offset) 40,000 PSI 110,000 PSI 130,000 PSI 180,000 PSI
Elongation in 2” * 35% 18% 6% 7%
Proportional Limit 15,000 PSI 65,000 PSI 55,000 PSI 110,000 PSI
Rockwell Hardness B75 RC33 RC29 RC42
Tensile Modulus of Elasticity 25 x 106 PSI 26 x 106 PSI 25.5 x 106 PSI 28 x 106 PSI
Poisson’s Ratio 0.33 - - -

The measured elongation will be less as thickness decreases to 0.004” and less.
These values may be adjusted by control of process variables – consult HPM for desired values.

Physical Properties
Density (Heat Treated) 0.294 lbs/
Melting Point (Approx.) 1455° C
Electrical Resistivity 102 Microhm·cm
Thermal Expansion Coefficient (-45°C to 65°C) 8.1 x 10-6/°C
Thermal Conductivity @ R.T. 13.0W/m·K
Curie Temperature (Heat Treated) 193°C Approx.
Magnetic Attraction Yes

Typical values to guide alloy selection but are not a guarantee of minimum or maximum