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Nimonic 90 (UNS N07090 / W.Nr. 2.4632) and Nimonic 263 (UNS N07263 / W.Nr. 2.4650) are both γ′-precipitation hardened nickel-base superalloys originally developed in the UK (Wiggin / Rolls-Royce heritage) for 650–850°C (1200–1560°F) creep-resistant service. They share a Ni–Cr–Co matrix with γ′ formers (Ti, Al), but differ significantly in:
γ′ volume fraction & Al/Ti ratio → Nimonic 90 has higher Al+Ti (≈ 4.0–4.8% total) vs. Nimonic 263 (≈ 0.45–0.65% mostly Ti, Al kept ≤0.15%)
Weldability / Strain-Age Cracking (SAC) tendency
Optimum product form & application focus (rotating / stressed parts vs. thin-walled welded fabrications)
This article provides a rigorous side-by-side comparison to guide alloy selection for the 650–850°C operating window.
1. Nominal Chemistry Comparison
|
Element |
Nimonic 90 (N07090 / 2.4632) |
Nimonic 263 (N07263 / 2.4650) |
Functional Difference |
|---|---|---|---|
|
Ni |
Bal. (~55–60) |
Bal. (~48–52) |
— |
|
Cr |
18.0–21.0 (typ 19.5) |
19.0–21.0 (typ 20.0) |
Both form Cr₂O₃; 263 slightly higher Mo |
|
Co |
15.0–21.0 (typ 18.0) |
19.0–21.0 (typ 20.0) |
Co raises γ′ solvus in both; 263 Co≈20% |
|
Mo |
— (≤ 0.50 max imp.) |
5.6–6.1 (typ 5.9) |
263 has Mo for solid-solution creep + pitting res. |
|
Ti |
2.2–3.0 (typ 2.6) |
0.30–0.60 (typ 0.40) |
Major γ′ former in both; 90 >> 263 |
|
Al |
1.0–2.0 (typ 1.5) |
≤0.15 typ (spec max 0.30–0.60) |
90 uses Al heavily → more γ′; 263 keeps Al low → SAC resist. |
|
C |
0.04–0.10 |
0.04–0.08 |
Grain-boundary carbide control |
|
Fe |
≤ 3.0 (typ ≤1.0) |
≤ 0.50 (some spec ≤0.30) |
— |
|
B |
≤ 0.008–0.015 |
≤ 0.005 |
Micro grain-boundary strengthener |
|
(Al+Ti) total |
≈ 3.8–4.8 % |
≈ 0.45–0.65 % |
Key: 90 = high γ′ vol.; 263 = low γ′ vol., Mo substituted |
2. Heat Treatment & Aging Practice
|
Item |
Nimonic 90 |
Nimonic 263 |
|---|---|---|
|
Solution Anneal (SA) |
1080–1150°C × soak → AC/WQ (typ 1120–1140°C) |
1120–1150°C × soak → AC/WQ (typ 1140–1150°C for sheet) |
|
Aging (Precipitation) |
Two-stage common: 1080–1150°C SA → 700–750°C × 16 h + 650°C × 16 h (or 700°C×24h) |
Single-stage: 800°C × 8 h / AC (BS HR 10) or 700–760°C × 16 h |
|
γ′ Solvus |
≈ 985–1010°C |
≈ 885–900°C |
|
Over-aging Risk |
η (Ni₃Ti) forms > 1050°C / long hold |
η forms > 950–975°C extended; less γ′ to lose → slightly wider safe window |
→ Nimonic 263's lower γ′ solvus & single-step aging simplify production; Nimonic 90's two-stage aims to optimize γ′ size distribution for max. stress-rupture.
3. Typical Mechanical Properties (Aged Condition)
Room Temperature (Aged):
|
Property |
Nimonic 90 (BS HR 1 / AMS 5829 ref.) |
Nimonic 263 (BS HR 10 / AMS 5872) |
|---|---|---|
|
Rm |
1100–1280 MPa |
950–1080 MPa |
|
Rp0.2 |
750–900 MPa |
620–720 MPa |
|
A₅₀ |
15–25 % |
25–35 % |
|
Hardness |
32–40 HRC |
30–36 HRC |
Elevated-Temperature Tensile (Typical Aged):
|
T(°C) |
Nimonic 90 Rm/Rp0.2 (MPa) |
Nimonic 263 Rm/Rp0.2 (MPa) |
|---|---|---|
|
20 |
1150–1220 / 800–870 |
1000–1060 / 660–710 |
|
650 |
950–1020 / 650–720 |
820–880 / 510–570 |
|
760 |
780–850 / 520–590 |
650–720 / 400–460 |
|
815 |
620–690 / 410–470 |
520–590 / 320–380 |
|
870 |
480–550 / 300–360 |
400–460 / 250–310 |
Creep / Stress-Rupture (Representative for Preliminary Estimate):
|
Condition |
Nimonic 90 |
Nimonic 263 |
|---|---|---|
|
750°C / 200 MPa |
≈ 200–500 h |
≈ 100–200 h |
|
800°C / 140 MPa |
≈ 100–300 h |
≈ 80–150 h |
|
815°C / 105 MPa |
≈ 50–150 h |
≈ 50–100 h |
|
850°C / 70 MPa |
≈ 50–100 h (marginal) |
≈ 30–80 h (marginal) |
→ Nimonic 90 has higher creep-rupture strength & yield, especially > 750°C, due to higher γ′ fraction.
→ Nimonic 263 has better ductility after aging & better SAC resistance.
4. Weldability & Strain-Age Cracking (SAC)
|
Factor |
Nimonic 90 |
Nimonic 263 |
|---|---|---|
|
SAC Susceptibility |
Higher — high Al+Ti → γ′ reforms rapidly on heating HAZ during weld cool → HAZ constraint can crack if thick/restrained; often requires careful PWHT or controlled bead sequencing; some specs restrict thickness/ |
Low / Good — low Al+Ti, Mo substitution → HAZ less prone to spontaneous γ′ re-precip + strain; welded thin-gauge assemblies can be aged directly |
|
Recommended Filler |
Matching N07090 wire or (in some cases) Inconel 82/625 for less critical — check design |
Matching N07263; Inconel 625 filler lowers creep strength → not for primary aged load paths |
|
Post-Weld Heat Treatment |
Stress relieve @ ~1080°C (solution) then re-age (2-stage) — complex for large assys |
Solution-anneal (if required locally) + single-step age — simpler for fabricated cans/liners |
|
Typical Welded Fabrication |
Blade roots, disc rim attachments, thick-section springs — often machined / forged then welded in sub-assemblies |
Combustor liners, transition ducts, exhaust cones (thin sheet 0.5–2.0 mm) — formed, rolled, welded, then whole assy aged |
5. Oxidation / Environmental Resistance
Both form Cr₂O₃ scales; continuous useful limit ≈ 980–1040°C in static air (briefly to 1050°C).
Nimonic 90 historically used in turbine blade / vane outer airfoil zones (coated with aluminide/MCrAlY for > 950°C service life).
Nimonic 263 used uncoated for combustor / duct inner surfaces (≤ 900–950°C gas path T typical).
Mo in 263 slightly improves pitting resistance in cooled zones (if condensate present) vs. 90 (no Mo) — minor advantage in mixed env.
6. Typical Applications by Alloy
|
Nimonic 90 (N07090 / 2.4632) |
Nimonic 263 (N07263 / 2.4650) |
|---|---|
|
Turbine blades & vanes (aero & industrial) ≤ 870°C (with coating > 900°C) |
Combustor liners (annular & can-type) |
|
High-temp springs (valve, governor) |
Transition ducts / crossover ducts (gas turbine) |
|
Fasteners, bolts, studs for hot section (with proper coating) |
Afterburner / augmentor casings & seals |
|
Exhaust cones (thick / forged ring) |
Flame holders (fabricated) |
|
Selection Driver: Highest creep + stress-rupture in 650–850°C; can manage weld/HAZ SAC in restrained parts |
Selection Driver: Weldable thin-wall fab → age post-weld; adequate creep for sheet-metal hot section; good formability |
7. Decision Guide (Selection Tree)
Is the component a THIN-WALLED WELDED FABRICATION (combustor liner / duct / cone)?
├─ YES → ✅ Nimonic 263 (N07263)
│ Reason: SAC-resistant, single-step age, good sheet formability, adequate creep to ~800°C
└─ NO → Is it a FORGED / MACHINED PART (blade, vane, bolt, spring) requiring MAX creep @ 650–850°C?
├─ YES → ✅ Nimonic 90 (N07090)
│ Reason: Higher γ′ vol. → superior stress-rupture & yield; manage SAC in weld repairs only
└─ NO → Re-evaluate: maybe Inconel 718 (if < 650°C peak + fatigue), Inconel 625 (if no creep), Haynes 188 (if cyclic oxidation > 950°C)
8. Summary Comparison Table
|
Feature |
Nimonic 90 (N07090) |
Nimonic 263 (N07263) |
|---|---|---|
|
Al+Ti (γ′ formers) |
≈ 3.8–4.8 % |
≈ 0.45–0.65 % (mostly Ti) |
|
Mo (wt%) |
≤ 0.5 (impurity) |
5.6–6.1 |
|
Aging |
2-stage (700–750°C + 650°C) |
1-stage (800°C×8h or 700–760°C×16h) |
|
RT YS (aged) |
750–900 MPa |
620–720 MPa |
|
Creep 750–800°C |
★★★★☆ (higher) |
★★★★☆ (good, slightly lower) |
|
SAC Sensitivity (weld) |
Higher (care needed > ~3–4 mm / restrained) |
Low (good for thin-weld assy) |
|
Best Product Form |
Forging / Bar / Machined parts |
Sheet / Strip / Welded fabrications |
|
Primary Use |
Turbine blades, vanes, springs, bolts ≤ 870°C |
Combustor liners, transition ducts, exhaust cones |
|
Oxidation Limit (air) |
≈ 980–1040°C (with coat > 900°C) |
≈ 980°C (uncoated) |
9. Conclusion
Choose Nimonic 90 (UNS N07090 / W.Nr. 2.4632) for forged/machined components requiring maximum creep and stress-rupture strength at 650–850°C (turbine blades, vanes, high-temp springs), accepting greater care in welding/HAZ control.
Choose Nimonic 263 (UNS N07263 / W.Nr. 2.4650) for large thin-walled welded sheet-metal assemblies (combustor liners, transition ducts, exhaust cones) that must survive 650–800°C creep, be welded without post-weld strain-age cracking, and then be precipitation-aged in one step.
Neither is a direct substitute for the other in their primary application domain — the difference in Al+Ti level, Mo addition, and SAC behavior dictates the split.
