Haynes 99 (UNS N07099, W.Nr. 2.4634), commercially known as Nimonic 99 and designated GH4099 in the Chinese GB system, is a nickel-chromium-cobalt precipitation-hardenable wrought superalloy engineered for long-duration service at 900°C, with short-term peak capability reaching 1000°C. The alloy deploys three mutually reinforcing strengthening mechanisms: heavy-atom solid-solution hardening from a combined W+Mo content of approximately 9–11%, gamma-prime Ni3(Al,Ti) precipitation hardening, and grain-boundary cohesion enhancement via micro-alloyed boron and cerium. This triple-reinforcement architecture delivers a material that retains over 375 MPa tensile strength at 900°C while remaining formable and weldable in thin-gauge sheet—a combination historically unattainable in most precipitation-hardened superalloys. The defining process advantage of Haynes 99 over earlier Nimonic grades is its tolerance for welding in the solution-annealed condition without mandatory post-weld aging: large thin-wall fabrications such as combustion chambers can be assembled and placed directly into service, dramatically simplifying the manufacturing flow for aero-engine hot-section components. At FUSHUN METAL, Haynes 99 ingots are produced through VIM for tight partitioning of the Co-W-Mo-Al-Ti window, refined via VAR for oxide and nitride inclusion removal, and optionally upgraded with PESR for ingots exceeding 400 mm diameter where centerline solidification quality is critical. Every heat is accompanied by full chemical, tensile, ultrasonic, and grain-size certification traceable through our ISO 9001 and AS9120B accredited quality management system. We tailor the aging cycle to each application: a standard 900°C/4h single-age schedule for balanced strength and ductility in sheet fabrications, or a two-stage 845°C/24h plus 700°C/16h route producing a bimodal gamma-prime distribution for maximum creep resistance in forged turbine rings and discs.
Equivalent Grades of Haynes 99 (N07099)
| Standard | Designation |
|---|---|
| UNS | N07099 |
| BS Aerospace | HR504 |
| AMS | 5733 / 5734 |
| W.Nr. / DIN | 2.4634 / 17742 |
| GB (China) | GH4099 (GH99) |
| GOST (Russia) | ЭП693 / XH68MBKTYuR |
Chemical Composition of Haynes 99 (N07099)
| Element | Wt % | Metallurgical Role |
|---|---|---|
| Ni | Balance | FCC gamma matrix — toughness reservoir |
| Cr | 17.0–20.0 | Cr2O3 oxidation barrier & hot-corrosion resistance |
| Co | 5.0–8.0 | Raises gamma-prime solvus temperature |
| W | 5.0–7.0 | Heavy-atom solid-solution strengthening |
| Mo | 3.5–4.5 | Solid-solution & TCP-phase suppression |
| Al | 1.7–2.4 | Gamma-prime Ni3Al former |
| Ti | 1.0–1.5 | Gamma-prime Ni3Ti co-former |
| Fe | ≤2.0 | Strict residual limit |
| C | ≤0.08 | MC carbide grain-boundary pinning |
| B | ≤0.005 | Grain-boundary cohesion enhancer |
| Ce | ≤0.020 | Oxide-scale adhesion & desulfurization |
Per GB/T 14992 / GJB 1952A. FUSHUN METAL holds the W+Mo sum at 9–11% and Al+Ti at 2.7–3.9% within each VIM heat to guarantee reproducible gamma-prime volume fraction and long-term microstructural stability against sigma and mu TCP-phase precipitation.
GH4099 Bar & Sheet
Applications of Haynes 99 (N07099)
Aerospace Combustion
Flame tubes, combustion chamber casings, and fuel swirlers operating at 900–1000°C under severe cyclic thermal fatigue from repeated engine start-stop transients.
Afterburner Systems
Afterburner ducts, exhaust gas mixers, flame stabilizers, and thermal radiation shields surviving transient excursions to 1100°C in augmented flight regimes.
Turbine Hot Section
Cooled guide vanes, turbine outer rings, and labyrinth seal rings serving as non-rotating structural elements at 850–950°C gas-path temperatures.
Rocket Propulsion
Thrust chamber bodies, nozzle extensions, and hot-gas ducting subjected to brief exposures above 1100°C in liquid-fuel rocket engine environments.
Auxiliary Power Units
Gas generator casings, bellows expansion joints, and thermal compensators in APUs and emergency power systems for commercial and military aircraft.
Industrial Gas Turbines
Transition ducts, combustor baskets, and hot-gas casings for power-generation turbines operating on low-grade fuels with elevated sulfur and vanadium content.
Nuclear Components
High-temperature reactor internals and instrumentation guide tubes where radiation tolerance must coexist with creep stability over multi-year fuel cycles.
Furnace Hardware
Radiant tubes, retorts, and heat-treatment fixtures designed for continuous operation up to 950°C in oxidizing atmospheres with minimal scaling loss.
Supply Range — Haynes 99 (N07099)
| Product Form | Dimensions | Applicable Standard |
|---|---|---|
| Hot-Rolled Bar | 6–200 mm dia. | GB/T 14993 / BS HR504 |
| Forged Bar | 50–600 mm dia. | GJB 1952A / AMS 5733 |
| Forged Flat / Block | 50–500 mm thick, up to 2000 mm wide | AMS 5734 |
| Ring / Disc Forging | OD up to 1500 mm | US AA-grade per GJB 1953 |
| Cold-Rolled Sheet | 0.5–4.0 mm thick | HB 5332 / GJB 1952A |
| Hot-Rolled Plate | 4.0–50 mm thick | GB/T 14992 / QJ/DT0160018 |
| Welding Wire | 0.8–5.0 mm dia. | HB 5333 / BZ 44-903B-06 |
FUSHUN METAL supplies all forms from VIM–VAR ingots with optional PESR refinement for large-section orders. All products ship with EN 10204 Type 3.1 certificates; Type 3.2 witness-tested certification is available on request. Sheet and plate are supplied in the solution-annealed and pickled condition; forged bar is supplied solution-treated with ground or peeled finish per customer specification.
Mechanical and Physical Properties of Haynes 99 (N07099)
| Condition | UTS (MPa) | YS 0.2% (MPa) | EL (%) | Hardness |
|---|---|---|---|---|
| Solution Annealed (Sheet, 1140–1160°C/AC) | ≤1130 | — | ≥35 | HRC 30–38 |
| Solution + Aged (Bar, 1080–1130°C + 900°C/4h) | ≥1050–1100 | ≥685–700 | ≥12–15 | HB 250–400 |
| 900°C Tensile (Aged) | ≥375–450 | — | ≥15 | — |
| 1000°C / 100 h Creep Rupture | ~50–70 MPa typical rupture strength | |||
| Physical Property | Value |
|---|---|
| Density | 8.47 g/cm³ |
| Melting Range | 1345–1390°C |
| Magnetic Property | Non-magnetic |
| Thermal Conductivity (100–1000°C) | 10.5–27.2 W/(m·K) |
| CTE (20–1000°C) | 12.0–17.4 ×10-6 /°C |
| Electrical Resistivity (20°C) | ~1.37 μΩ·m |
| Oxidation Rate (900°C / Air) | <0.1 g/(m²·h) |
Heat treatment per GJB 1952A / HB 5332. Sheet: solution 1140–1160°C (AC), bar/forging: 1080–1130°C (AC). Standard aging: 900°C ×4h (AC) for uniform gamma-prime precipitation. Alternative dual-ageing (845°C/24h + 700°C/16h) creates a bimodal gamma-prime distribution for enhanced creep resistance in turbine disc and ring forgings. A key process advantage of Haynes 99 is that large welded sheet assemblies may enter service directly from the solution-annealed condition without mandatory post-weld aging, simplifying combustion chamber fabrication. FUSHUN METAL verifies the full stress-rupture curve, grain-size distribution (ASTM 4–7, zero duplex grains), and ultrasonic integrity per heat lot under ISO 9001 and AS9120B accredited protocols.
