Hangbo Alloy Group
Shanghai · Est. 2012
UNS N13017 / W.Nr. 2.4602 — High gamma-prime nickel superalloy with exceptional creep-rupture strength at 700–850°C, designed for high-pressure turbine discs, shafts, and aerospace hot-section components.
Astroloy (UNS N13017 / W.Nr. 2.4602) is a precipitation-hardenable nickel-chromium-cobalt superalloy developed in the 1960s as a higher-strength evolution of Waspaloy for the most demanding hot-section components of jet engines. With approximately 4.5% combined aluminum + titanium content, Astroloy achieves a gamma-prime (Ni3(Al,Ti)) volume fraction of approximately 45% — substantially higher than Waspaloy's 25% — which directly translates into exceptional creep-rupture strength at temperatures up to 850°C (1560°F). For over five decades, Astroloy has been the material of choice for high-pressure turbine (HPT) discs, hubs, and shafts in military and commercial jet engines, and remains a benchmark alloy for advanced gas turbine applications.
The development of Astroloy represented a deliberate trade-off in nickel superalloy design. By increasing the Al+Ti content above Waspaloy's level, the alloy achieves superior high-temperature strength at the cost of reduced weldability and increased difficulty in thermomechanical processing. This trade-off is acceptable for forged disc applications where the alloy is hot-worked into near-net shape rather than welded, but it requires careful control of forging temperatures, strain rates, and heat treatment to achieve the desired fine-grain microstructure. Modern powder metallurgy (P/M) processing of Astroloy has further expanded its applications by enabling finer, more uniform microstructures than conventional cast-and-forged material.
Astroloy is melted by vacuum induction melting (VIM) followed by vacuum arc remelting (VAR) for conventional forms, and by vacuum induction melting plus plasma rotating electrode process (PREP) for the powder metallurgy route. The alloy is supplied in the solution-treated and aged condition per AMS 6525, and Hangbo Alloy Group stocks a range of bar, billet, and forging stock for both aerospace and industrial gas turbine customers. Our P/M Astroloy capabilities include HIP'd near-net-shape components for next-generation turbine designs.
Astroloy's composition is engineered to maximize gamma-prime (Ni3(Al,Ti)) volume fraction while maintaining adequate hot-workability. The combined Al+Ti content of approximately 7% (Al 3.4–4.0%, Ti 3.0–3.7%) is significantly higher than Waspaloy's 3% total, producing approximately 45% gamma-prime in the fully aged condition. Cobalt at 15–17% raises the gamma-prime solvus temperature, improving high-temperature strength retention. Boron and zirconium are intentionally added as grain-boundary strengtheners to enhance creep-rupture ductility. Carbon is controlled at a low level (0.01–0.05%) to minimize carbide formation that would deplete the gamma-prime forming elements.
| Element | Min % | Max % |
|---|---|---|
| Nickel (Ni) | 54.5 | 60.0 |
| Chromium (Cr) | 14.0 | 16.0 |
| Cobalt (Co) | 15.0 | 17.0 |
| Molybdenum (Mo) | 4.0 | 5.25 |
| Titanium (Ti) | 3.0 | 3.7 |
| Aluminum (Al) | 3.4 | 4.0 |
| Iron (Fe) | — | 0.5 |
| Carbon (C) | 0.01 | 0.05 |
| Manganese (Mn) | — | 0.20 |
| Silicon (Si) | — | 0.20 |
| Phosphorus (P) | — | 0.015 |
| Sulfur (S) | — | 0.015 |
| Boron (B) | 0.01 | 0.05 |
| Zirconium (Zr) | 0.01 | 0.06 |
| Copper (Cu) | — | 0.10 |
Astroloy has an FCC austenitic matrix in the solution-annealed condition, with gamma-prime precipitates forming on aging. The alloy is non-magnetic. Its density of 8.05 g/cm³ is similar to Waspaloy (8.20 g/cm³) and Udimet 720 (8.08 g/cm³). The relatively low thermal expansion coefficient and moderate thermal conductivity contribute to good thermal fatigue resistance in components subject to repeated temperature cycling, while its high melting point of 1280–1340°C allows for aggressive high-temperature service where other alloys would be metallurgically unstable.
| Property | Value | Unit |
|---|---|---|
| Density | 8.05 | g/cm3 |
| Melting Range | 1280 - 1340 | °C |
| Specific Heat (21°C) | 460 | J/kg·K |
| Thermal Conductivity (21°C) | 11.7 | W/m·K |
| Electrical Resistivity (21°C) | 1.25 | μΩ·m |
| Modulus of Elasticity (21°C) | 200 | GPa |
| Mean CTE (21-93°C) | 12.5 | μm/m·°C |
| Gamma-Prime Solvus | 1140 | °C |
In the fully heat-treated (solution + aged) condition, Astroloy develops tensile strength of approximately 1380 MPa and yield strength of 1050 MPa at room temperature, with adequate ductility (15–25% elongation) for structural reliability. The combination of solid-solution strengthening (from Cr, Co, Mo) and precipitation hardening (from ~45 vol% gamma-prime) gives the alloy outstanding strength-to-weight ratio. Values below are typical for forged bar and billet per AMS 6525.
| Property | Value |
|---|---|
| Tensile Strength | 1380 MPa (200 ksi) |
| Yield Strength (0.2% offset) | 1050 MPa (152 ksi) |
| Elongation in 4D | 15 - 25% |
| Reduction of Area | 18 - 30% |
| Hardness | 38 - 45 HRC |
| Charpy V-notch Impact | 20 - 40 J |
| Fatigue Strength (10^7 cycles, R=-1) | 520 - 600 MPa |
Astroloy is normally supplied in the solution-treated and aged condition. The standard heat treatment cycle is designed to achieve an optimal balance of grain size, gamma-prime distribution, and carbide morphology:
For powder metallurgy components, hot isostatic pressing (HIP) at 1160–1200°C under 100–200 MPa pressure for 3–4 hours consolidates the powder to near-full density, followed by the same solution + two-step aging cycle. For investment castings, the as-cast solution treatment is followed by a single aging step at 1080°C / 4h + 845°C / 16h. Hangbo Alloy Group provides full heat treatment certification with each order, including recorded time-temperature profiles and mechanical test results.
Astroloy's primary advantage is its retention of strength at temperatures in the 700–850°C range, where the high volume fraction of stable gamma-prime continues to impede dislocation motion. The alloy maintains approximately 80% of its room-temperature yield strength at 700°C and 60% at 800°C. Creep-rupture life at 760°C / 690 MPa exceeds 100 hours, making Astroloy one of the strongest production nickel superalloys in this temperature range.
| Temperature (°C) | Tensile Strength (MPa) | Yield Strength (MPa) | Elongation (%) |
|---|---|---|---|
| 21 (Room) | 1380 | 1050 | 18 |
| 538 | 1310 | 1000 | 18 |
| 649 | 1240 | 965 | 18 |
| 704 | 1170 | 900 | 19 |
| 760 | 1030 | 830 | 20 |
| 816 | 830 | 700 | 22 |
| 871 | 620 | 520 | 25 |
| 927 | 410 | 340 | 30 |
Astroloy is not primarily designed for corrosion resistance — that role is filled by alloys like Hastelloy C-276 and Inconel 625. However, its 14–16% chromium content provides adequate resistance to high-temperature oxidation and sulfidation for the combustion environments encountered in jet engines and industrial gas turbines. The alloy forms a protective chromium and aluminum oxide scale that resists spallation up to approximately 950°C in cyclic conditions.
Astroloy is the premium workhorse alloy for the hottest, most highly stressed sections of advanced turbine engines. Its combination of high gamma-prime volume fraction, excellent creep-rupture strength, and proven field service has made it the material of choice for the following applications:
Hangbo Alloy Group supplies Astroloy in a comprehensive range of mill forms, supporting both conventional cast-and-forged applications and modern powder metallurgy components:
| Standard | Description |
|---|---|
| AMS 6525 | Bar, Billet, and Forging Stock, Solution and Precipitation Heat Treated |
| AMS 6524 | Plate, Sheet, and Strip |
| AMS 6436 | Investment Castings |
| UNS N13017 | Unified Numbering System Designation |
| Werkstoff 2.4602 | DIN/EN Designation |
| OEM Specifications | GE C50TF7, Pratt & Whitney, Rolls-Royce, Safran |
Astroloy has a density of 8.05 g/cm³ (0.291 lb/in³) at room temperature, similar to other nickel-cobalt-chromium superalloys like Waspaloy and Udimet 720. The high cobalt and nickel content contributes to the alloy's elevated density.
The melting range of Astroloy is approximately 1280–1340°C (2340–2440°F), comparable to Waspaloy and slightly lower than pure nickel. The alloy's high gamma-prime forming content (Al + Ti = 4.5%) requires careful temperature control during processing.
Astroloy (UNS N13017) nominal composition: Ni 54.5–60%, Cr 14.0–16.0%, Co 15.0–17.0%, Mo 4.0–5.25%, Ti 3.0–3.7%, Al 3.4–4.0%, Fe ≤0.5%, C 0.01–0.05%, Mn ≤0.20%, Si ≤0.20%, B 0.01–0.05%, Zr 0.01–0.06%, S ≤0.015%, P ≤0.015%, Cu ≤0.10%.
Key standards for Astroloy include AMS 6525 (bar, billet, and forging stock, solution and precipitation heat treated), AMS 6524 (plate), AMS 6436 (investment castings), and customer-specific aerospace specifications (GE, Pratt & Whitney, Rolls-Royce). The alloy is also covered by various OEM specifications for military and commercial jet engine components.
Astroloy is typically supplied in the solution treated + aged condition. The standard heat treatment is: solution anneal at 1175–1200°C for 1–4 hours, air cool or oil quench; age at 1080°C for 4 hours, air cool; then age at 845°C for 16 hours, air cool. For powder metallurgy parts, hot isostatic pressing (HIP) at 1160–1200°C under 100–200 MPa pressure is used to close porosity, followed by the same aging cycle.
Astroloy occupies a middle position between Waspaloy and Udimet 720 in terms of temperature capability. Compared to Waspaloy: Astroloy has higher Al+Ti (4.5% vs 3.0%), higher gamma-prime volume fraction (~45% vs 25%), and superior creep-rupture strength above 700°C. Compared to Udimet 720: Astroloy has lower Co (15% vs 25%) and slightly lower creep strength above 750°C, but is more weldable and easier to process. Astroloy is a proven workhorse for jet engine turbine discs in the 700–850°C range.
Astroloy is a premium nickel superalloy with significant cobalt and titanium content. Rough price range: $45–75/kg for round bar and billet, depending on size, specification, and heat treatment condition. Powder metallurgy HIP'd billet for critical turbine disc applications is at the high end. Investment castings are priced per part complexity. Contact Hangbo Alloy Group for current pricing.
Astroloy is available as round bars and billets (50–500 mm dia), forged discs and rings (custom shapes up to 1000 mm), plate and sheet (0.5–50 mm), and powder metallurgy HIP'd near-net shapes for critical turbine disc applications. Investment castings are produced for complex blade and vane geometries. Hangbo Alloy Group supplies Astroloy per AMS 6524, AMS 6525, and customer-specific OEM specifications.
Astroloy is more difficult to weld than solid-solution-strengthened nickel alloys due to its high gamma-prime content. GTAW and GMAW are possible in the annealed condition using matching filler (ERNiCrCoMo-1) or nickel-based fillers like Inconel 718 filler, but post-weld heat treatment is required to restore strength. For most turbine disc applications, Astroloy is forged or HIP'd rather than welded. Repair welding of castings is performed using laser or electron beam processes with very precise thermal control.
Astroloy is designed for long-term service at temperatures up to 850°C (1560°F) with peak capability to 950°C (1740°F) for short durations. The alloy maintains useful creep-rupture strength at 700–800°C and is the material of choice for high-pressure turbine discs in this temperature range. Above 870°C, gamma-prime coarsening and oxidation limit long-term service.
Astroloy is used in the most demanding hot-section components of jet engines and industrial gas turbines: (1) High-pressure turbine (HPT) discs and hubs for military and commercial jet engines. (2) Turbine shafts and drive shafts. (3) Combustion liner and transition duct components. (4) Hot-section structural castings. (5) Rocket engine turbopump housings. (6) Power generation turbine rotors. Its high strength-to-weight ratio and proven track record make it a primary choice for next-generation high-temperature turbine applications.
Yes, Astroloy is one of the most widely used nickel superalloys in powder metallurgy (P/M) form for critical rotating components. Plasma-atomized Astroloy powder is consolidated by hot isostatic pressing (HIP) at 1160–1200°C under 100–200 MPa pressure to produce near-net-shape turbine discs with uniform fine-grain microstructure. The P/M form eliminates macro-segregation typical of large cast/forged billets and enables finer gamma-prime distributions, resulting in superior fatigue and creep-rupture properties compared to conventionally forged Astroloy.
Hangbo Alloy Group supplies Astroloy in bar, billet, forging, plate, and powder metallurgy HIP'd forms per AMS 6525 and customer-specific OEM specifications. We support conventional VIM-VAR melting for large forged components and powder metallurgy processing for near-net-shape turbine disc applications. Full material certification, ultrasonic testing, and metallurgical support are standard.
For quotations, material certifications, or technical consultation, contact our sales team or call +86-136-1165-6360. We typically respond within 10 minutes.
Request a quotation for Astroloy round bars, billets, forgings, plates, or powder metallurgy HIP'd components. We supply conventional and P/M grades per AMS 6525 with full certification.