Tungsten Heavy Alloys
Tungsten heavy alloys are 90–97 % tungsten grains liquid-phase sintered in a nickel-iron or nickel-copper binder. The binder gives up a little density — 17.0 g/cm³ at 90 % W, 18.5 g/cm³ at 97 % — and in return turns brittle tungsten into a metal that yields 500–700 MPa, stretches 2–10 % and machines like an alloy steel. ASTM B777 grades them as Class 1 to Class 4 by tungsten content; a modulus near 350 GPa and high damping make them stiff as well as heavy.
Popular tungsten heavy alloy grades
Compare in the explorer| Grade | Yield, MPa | Tensile, MPa | Density, g/cm³ | Machinability | Weldability | Best for |
|---|---|---|---|---|---|---|
| WHA-90 | 620 | 900 | 17 | Poor | Poor | The default counterweight and shielding grade |
| WHA-95 | 610 | 820 | 18.05 | Poor | Poor | More mass per volume; aerospace balance weights |
| Class 1 Tungsten | 590 | 800 | 19.25 | Not recommended | Not recommended | ASTM B777 90 % W; most ductile |
| Class 2 Tungsten | 800 | 1,050 | 19.25 | Not recommended | Not recommended | ASTM B777 92.5 % W middle grade |
| Class 3 Tungsten | 900 | 1,100 | 19 | Not recommended | Not recommended | ASTM B777 95 % W, 18 g/cm³ |
| Class 4 Tungsten | 1,400 | 1,800 | 19.7 | Not recommended | Fair | ASTM B777 97 % W; densest, least ductile |
| 90W-7Ni-3Cu | 550 | 700 | 17 | Fair | Not recommended | Non-magnetic Ni-Cu binder for instruments |
All 8 tungsten heavy alloy grades
Choose tungsten heavy alloy for
Mass in a fixed volume — balance weights in aircraft control surfaces, rotors and racing cars, vibration dampers, boring-bar and tool-holder shanks that must not chatter, gyroscope rotors — and radiation shielding that must be machined to fit: collimators, isotope containers, syringe and vial shields, where it attenuates 1.7 times as much as lead per millimetre without the toxicity.
Look elsewhere when
The volume is not constrained (steel or lead is far cheaper by the kilogram of mass), the part runs above about 1,000 °C where the binder melts (Pure W or Pure Mo), it is a wear or cutting surface (WC-10Co), or the density is only needed to about 11 g/cm³, which lead or a lead-antimony alloy gives at a small fraction of the price.
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Tungsten heavy alloy by application
- Counterweights and balance masses
- WHA-90 for most parts, machined and tapped like steel; WHA-95 or Class 3 Tungsten when the envelope is fixed and the extra 6 % density earns its price.
- Radiation shielding and collimators
- WHA-95 and Class 3 Tungsten for collimators, isotope pigs and syringe shields — thinner than lead, non-toxic, dimensionally precise; 90W-7Ni-3Cu near MRI or sensitive sensors where the part must be non-magnetic.
- Vibration-damping tooling
- WHA-90 and Class 1 Tungsten shanks for long-reach boring bars and tool holders: a modulus near 350 GPa, about 1.7 times steel, plus high internal damping.
Working with tungsten heavy alloy
- Machining
- Behaves like a hard, abrasive alloy steel: carbide tooling, moderate speed, positive rake, steady feed and flood coolant. Turns, mills, drills and taps conventionally and holds ±0.01 mm; keep tools sharp so the nickel binder does not smear. Chips are heavy and abrasive.
- Forming and joining
- Not formed after sintering except by swaging, which raises strength toward 1,200 MPa. Joined by bolting, shrink fits, adhesives or brazing with silver alloys; welding is avoided because the binder melts far below the tungsten.
- Finishing
- Ground or polished as required; electroless or electrolytic nickel plating for corrosion protection and appearance. The bare alloy is stable in air at room temperature and oxidizes only above about 500 °C.
Other tungsten alloy series
Tungsten Heavy Alloys — frequently asked
What is tungsten heavy alloy?
Tungsten heavy alloys are 90–97 % tungsten grains liquid-phase sintered in a nickel-iron or nickel-copper binder. The binder gives up a little density — 17.0 g/cm³ at 90 % W, 18.5 g/cm³ at 97 % — and in return turns brittle tungsten into a metal that yields 500–700 MPa, stretches 2–10 % and machines like an alloy steel. ASTM B777 grades them as Class 1 to Class 4 by tungsten content; a modulus near 350 GPa and high damping make them stiff as well as heavy.
Which grade of tungsten heavy alloy should I use?
WHA-90 (Class 1 Tungsten, 90 % W, 17.0 g/cm³) for most counterweights, shielding and machined parts — the most ductile, the easiest to machine and thread, and the most widely produced. WHA-95 (Class 3 Tungsten, 18.0 g/cm³) when the volume is fixed and every gram counts, as in aerospace balance weights and collimators; Class 2 Tungsten sits between them at 92.5 % W. Class 4 Tungsten and 97W-2.1Ni-0.9Fe reach 18.5 g/cm³ but with about 2 % elongation, for simple shapes that are not shock-loaded. 90W-7Ni-3Cu is the nickel-copper version: non-magnetic and slightly less strong, for gyroscopes, medical imaging and instrument parts near sensors.
Which grade of tungsten heavy alloy is the strongest?
Class 4 Tungsten has the highest yield strength in the series at 1,400 MPa; Class 3 Tungsten follows at 900 MPa. Values are for each grade's default condition.
Which grade of tungsten heavy alloy is easiest to machine?
90W-7Ni-3Cu (machinability fair, 40/100), then 97W-2.1Ni-0.9Fe (40/100).
WHA-90 or WHA-95?
WHA-90 unless the volume is fixed. It is 17.0 g/cm³, the most ductile and machinable grade, and the one most producers keep in the widest range of sizes. WHA-95 adds about 6 % density (18.0 g/cm³) at the cost of ductility and machinability, which matters only when the envelope cannot grow — aerospace trim weights, dental and medical shields, and collimators are the usual cases.
Is tungsten heavy alloy magnetic?
The standard nickel-iron binder grades are slightly ferromagnetic because of the iron; for most counterweights that is irrelevant. Where the part sits near an MRI, a magnetometer or a gyroscope, specify a nickel-copper grade such as 90W-7Ni-3Cu, which is non-magnetic at a small penalty in strength and ductility.