As a globally certified supplier, ZYTC Alloy not only distributes this critical material but ensures full traceability and compliance, backed by our AS 9120B and ISO 9001 certifications. Alloy X-750 (UNS N07750), governed by the AMS 5598G specification for sheet, strip, and plate, is a precipitation-hardenable nickel-chromium superalloy that has been a cornerstone in aerospace and industrial gas turbine applications for decades. This article provides a rigorous, data-driven overview for technical buyers and engineers, covering its metallurgy, manufacturing process, mechanical capabilities, application boundaries, and supply chain considerations.
Chemical CompositionThe performance of Alloy X-750 is rooted in its tightly controlled chemistry under AMS 5598G. The high nickel content provides an austenitic matrix resistant to embrittlement, while a strategic addition of titanium and aluminum enables age-hardening through the precipitation of the gamma prime (γ') phase, Ni3(Al, Ti). The alloy is produced via vacuum induction melting (VIM) or consumable electrode remelting (VAR) to ensure the extreme cleanliness required for aerospace rotating components. | Element | Weight % (AMS 5598G Range) | Function |
|---|
| Nickel (Ni) | 70.00 min (Balance) | Matrix stability, corrosion resistance | | Chromium (Cr) | 14.00 – 17.00 | Oxidation and corrosion resistance | | Iron (Fe) | 5.00 – 9.00 | Strengthening, cost balance | | Titanium (Ti) | 2.25 – 2.75 | Primary precipitation hardener (γ' phase) | | Aluminum (Al) | 0.40 – 1.00 | Secondary precipitation hardener, deoxidizer | | Niobium (Nb) + Tantalum (Ta) | 0.70 – 1.20 | Carbide former for grain boundary control | | Carbon (C) | 0.08 max | Controlled for carbide formation |
Manufacturing Journey Melting: AMS 5598G mandates VIM or VAR. ZYTC Alloy sources stock exclusively produced through these methods to eliminate segregation and inclusions. Hot Forming: The ingot is broken down at temperatures around 1900°F (1040°C). This high-temperature ductility allows for the production of complex forged shapes, heavy plates up to 4.000 inches (101.6 mm), and thin sheets down to 0.187 inch (4.75 mm). Cold Forming: In the solution-annealed condition, Alloy X-750 can be cold-worked into precision strip and sheet. However, it work-hardens rapidly, necessitating intermediate annealing for severe forming operations. Solution Heat Treatment: Per AMS 5598G, the alloy is supplied in the solution-annealed condition, ready for fabrication and final aging by the end-user, or final age-hardening by the supplier if specified. A typical equilibration heat treatment at 1900°F (1040°C) is often followed by a stabilizing treatment. Precipitation Hardening (Aging): The standard two-step age-hardening cycle quoted in the spec is: 1350°F (730°C) for 8 hours, Furnace Cool to 1150°F (620°C) for 8 hours, Air Cool.
This forms the coherent γ' precipitates responsible for the alloy’s high-temperature strength.
Mechanical PropertiesThe data below represents the typical mechanical properties achieved after the standard 1900°F (1040°C) solution treatment followed by the aging cycle detailed above. These properties define the alloy's working envelope. | Mechanical Property | Typical Value (Aged Condition) |
|---|
| Tensile Strength (UTS), room temp | 180 – 195 ksi (1241 – 1344 MPa) | | Yield Strength (0.2% offset) | 115 – 140 ksi (793 – 965 MPa) | | Elongation in 2 inches | 15 – 25% | | Hardness | 30 – 40 HRC | | Stress-Rupture Life (1500°F / 816°C & 25 ksi / 172 MPa) | > 100 hours typical |
Service Temperature Ceiling: Alloy X-750 retains excellent resistance to oxidizing combustion gases up to approximately 1600°F (870°C) . However, its structural load-bearing capacity is most effective up to 1400°F (760°C) , above which Alloy 718 may offer marginally higher strength, though X-750 provides superior relaxation resistance for springs and fasteners across this range.
Application Mapping: Use Cases & Material Selection BoundarySelecting X-750 over other superalloys like 718 or 625 is a decision based on a specific failure-mode resistance profile. The X-750 Sweet Spot: Gas Turbine Hot Sections: The alloy excels in lean, oxidizing combustion environments. Its primary battlefield is in the hot section of aero and land-based gas turbines where resistance to high-temperature oxidation is non-negotiable. Springs & Fasteners (The Stress-Rupture Champion): Where Alloy 718 is a general workhorse, X-750 is a specialist for high-temperature springs and fasteners, especially in nuclear reactors. It maintains clamping force under continuous stress relaxation conditions better than many alternatives. Industrial Heat-Treat Fixtures: The alloy's structural stability and repeated-quench resistance make it a preferred material for baskets, trays, and fixtures in industrial heat-treating furnaces.
Pricing, Forms & Supply ChainSourcing AMS 5598G material involves navigating a complex commodity and processing cost chain. The price is heavily indexed to the London Metal Exchange (LME) nickel price, plus a conversion premium for the precise titanium/aluminum ratio and VIM/VAR process. Price Drivers: Final cost is a function of mill form (highly thin-gauge strip carries a significant premium over 1-inch plate), laboratory testing per heat lot, and dimensional tolerances. As a benchmark, X-750 plate pricing generally commands a premium over standard grade stainless steels, but reflects the multi-decade performance life in a jet engine. Availability at ZYTC Alloy: We maintain an ex-stock inventory to compress lead times for our B2B partners. Round Bar: Equalized (enhanced grain structure) for forging or machining. Sheet & Plate: Cold-rolled sheet up to 0.187"and hot-rolled plate up to 4.000"thickness. Other Forms: Flat bar, forging stock, hexagon, wire, tube, welding wire, and extruded sections.
Are you evaluating Alloy X-750 for a new turbine component or a nuclear fastener specification? Our technical sales team is ready to provide data sheets, pricing, and lead time for your specific dimensions. 📧 Email: daisy@zytcsteel.com
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