Waspaloy is a superalloy used in aerospace applications. Melting point: 1,330 °C. Tensile strength: 1,275 MPa.
When a rocket engine fires, some of its spinning parts have to stay strong while glowing orange-hot. Waspaloy is one of the metals engineers trust to do exactly that.
Quick facts
- What it is: A wrought, precipitation-hardenable, nickel-based superalloy. “Superalloy” simply means a metal designed to keep its strength at very high temperatures. “Wrought” means it is shaped by forging or rolling rather than poured as a casting.
- Material code: UNS N07001 (part of the AMS 5706/5707/5708/5709 family). “Waspaloy” is a registered trademark of United Technologies, where it was developed at Pratt & Whitney.
- Main ingredients: Mostly nickel (~53-58%), plus chromium ~19.5%, cobalt ~13.5%, molybdenum ~4.25%, titanium ~3.0%, aluminum ~1.4%, with small amounts of carbon, boron, zirconium, and up to ~2% iron.
- Density: ~8.20 g/cm³ (0.296 lb/in³).
- Melts at: ~1,330-1,360 C (2,425-2,475 F).
- Useful up to: ~980 C (1,800 F); it holds strength well to about 760-870 C and resists oxidation to about 870 C.
- Room-temperature strength: tensile strength ~1,100 MPa (160 ksi), yield ~760 MPa (110 ksi), elongation ~15%, Brinell hardness ~310.
- Origin: Developed by Pratt & Whitney; first produced in 1952; used in the P&W J48 engine.
What it is and how it works
Waspaloy gets its strength from a process called precipitation hardening, also known as age hardening. A carefully controlled heat treatment grows a fine mist of tiny particles, called gamma-prime, throughout the metal. These particles are a compound of nickel with aluminum and titanium, written Ni₃(Al,Ti).
To picture why this helps, imagine trying to slide one playing card across a deck. If the deck is smooth, the card glides. Now scatter grains of sand between the cards: the sliding stops. Inside a metal, strength depends on stopping internal slips called dislocations from moving. The gamma-prime particles act like that sand, blocking the slips so the alloy stays strong and resists creep (slow stretching under load at high heat).
Each ingredient has a job. Chromium forms a protective oxide skin that resists corrosion in hot air. Cobalt and molybdenum add stability and dissolve into the nickel to stiffen it. Trace boron and zirconium strengthen the boundaries between metal grains. Together they let Waspaloy stay strong and steady in extreme heat and even in hydrogen-rich rocket environments, where ordinary metals fail.
Why it matters
Hotter engines produce more power and run more efficiently, but that heat punishes the most heavily stressed rotating parts. Waspaloy lets engineers build turbine disks, rotors, shafts, and fasteners that keep their strength and resist creep, oxidation, and hydrogen embrittlement (cracking caused by hydrogen) up to about 980 C. In rocket turbopumps spinning at tens of thousands of revolutions per minute, often in hydrogen, Waspaloy is a trusted choice for the rotor and disk hardware that carries the blades. It is one of the foundational wrought superalloys that made modern high-performance jet and rocket engines possible.
Where it is used and notable examples
- Space Shuttle Main Engine / RS-25 (Rocketdyne): The high-pressure fuel turbopump’s turbine blade rotor, the disk that carries the blades, is forged from Waspaloy. The blades themselves use a different cast alloy, Mar-M 246. This shows Waspaloy’s role in liquid-hydrogen rocket turbopumps.
- Pratt & Whitney J48 turbojet (early 1950s): One of the first engines to use Waspaloy, originally for turbine blades, marking its entry into military aircraft propulsion.
- Jet engine hot sections in general: Turbine and compressor disks, rotors, shafts, spacers, seals, rings, casings, and high-temperature fasteners across many aircraft engines.
- Rocket and missile propulsion hardware: Turbopump rotating and structural parts and missile engine components that must survive high heat and stress.
- Future materials research: NASA has studied tungsten-fiber-reinforced Waspaloy composites (such as tungsten with 1.5% thoria reinforcement) as advanced, higher-temperature materials for future rocket-engine turbine parts in hydrogen.
Trade-offs to know
Waspaloy is harder to forge and machine than ordinary steel. It work-hardens quickly, so it is often shaped by grinding or wire EDM (a cutting method that uses electrical sparks), which makes it costly to produce. Its strength depends on a tightly controlled solution-treat-and-age heat treatment, and overheating in service can coarsen the gamma-prime particles and weaken it. Because it is a wrought alloy rather than a single-crystal casting, its temperature ceiling of about 980 C sits below that of directionally solidified or single-crystal blade alloys like Mar-M 246. That is exactly why engineers pair them: Waspaloy for the cooler but highly stressed disk and rotor, and a cast alloy for the hottest blades.
Ni 58%, Cr 19%, Co 13.5%, Mo 4.3%, Ti 3%, Al 1.4%
| DENSITY | 8 kg/m³ |
| TENSILE STRENGTH | 1,275 MPa |
| YIELD STRENGTH | 795 MPa |
| STRENGTH-TO-WEIGHT | 155677.7 kN·m/kg |
| MELTING POINT | 1,330 °C |
| MAX SERVICE TEMPERATURE | 870 °C |
| THERMAL CONDUCTIVITY | 11.7 W/m·K |
| THERMAL EXPANSION | 12.4 µm/m·K |
| CATEGORY | Superalloy |
| DESIGNATIONS | UNS N07001, AMS 5706, AMS 5707 |
| MANUFACTURER | Allegheny Technologies (ATI) |
| DENSITY | 8 kg/m³ |
| TENSILE STRENGTH | 1,275 MPa |
| YIELD STRENGTH | 795 MPa |
| MELTING POINT | 1,330 °C |
| MAX SERVICE TEMP | 870 °C |
| THERMAL CONDUCTIVITY | 11.7 W/m·K |
| THERMAL EXPANSION | 12.4 µm/m·K |
| CORROSION RESISTANCE | Excellent |
| WELDABILITY | Fair |
| MACHINABILITY | Poor |
| COST RATING | Very High |
