Hastelloy® X

metal

nickel superalloy — solid-solution strengthened

UNS N06002Alloy XNicrofer 4722Haynes 230 precursor alloyAMS 5754 (wrought ref.)NiCrFeMoW.Nr. 2.4665

Density

8.22 g/cm³

YS (LPBF as-built (XY))

520–660 MPa

UTS (LPBF as-built (XY))

720–860 MPa

Elongation (LPBF as-built (XY))

22.0–40.0 %

Elastic modulus

196–215 GPa

Thermal conductivity

11.3 W/m·K

Max service temp

1200 °C

Composition — UNS N06002 / ASTM B435

Element	Min %	Max %	Notes
Ni	—	—	balance; provides high-temperature oxidation and corrosion resistance
Cr	20.50	23.000	Primary oxidation resistance via Cr₂O₃ film; also SCC and pitting resistance
Fe	17.00	20.000	Keeps cost lower than all-Ni alloys; solid-solution strengthening
Mo	8.00	10.000	Solid-solution strengthening; improves SCC resistance in reducing environments
Co	0.50	2.500	Solid-solution strengthening at high temperature
W	0.20	1.000	Solid-solution strengthening
Mn	—	1.000
Si	—	1.000
C	0.05	0.150	M₂₃C₆ carbide formers at grain boundaries — beneficial for creep resistance
B	—	0.010
P	—	0.040
S	—	0.030

Mechanical & thermal properties — 4 conditions

Property	LPBF as-built (XY)	LPBF as-built (Z)	LPBF solution-annealed (1175°C / 0.5–1h / RC) (XY)	DED as-built (XY)
Elastic modulus	196–215 GPa	—	—	—
Yield strength (0.2%)	520–660 MPa	430–580 MPa	345–420 MPa	370–480 MPa
Ultimate tensile strength	720–860 MPa	620–780 MPa	760–830 MPa	640–780 MPa
Elongation at break	22.0–40.0 %	18.0–38.0 %	32.0–50.0 %	22.0–42.0 %
Hardness (HV)	230–290 HV10	—	—	—
Density	8.22 g/cm³	—	—	—
Thermal conductivity	11.3 W/m·K	—	—	—
CTE	13.5–14.5 µm/m·K	—	—	—
Max service temperature	1200 °C	—	—	—

Values shown as min–max where a spread is reported, otherwise as typical ± unit. Ranges reflect inter-source variation, not single-sample scatter. All values are for AM-processed specimens unless noted.

Engineering considerations

Post-processing selection: for room-temperature structural use, as-built + stress relief (1050°C/0.5h) is acceptable. For forming, repair, or high-temperature fatigue applications, full solution anneal (1175°C/0.5–1h + rapid cool) is recommended — it recrystallises the microstructure and maximises ductility.
Oxidation resistance: Hastelloy X forms a protective Cr₂O₃ scale in air, combustion gases (H₂O, CO₂, SO₂), and halogen-free atmospheres up to 1200°C. Above 1200°C, scale spallation begins. Avoid reducing sulfur-containing environments — Fe and Ni sulfides cause severe hot corrosion.
Creep design: use the Larson-Miller parameter data from Haynes International for wrought SA Hastelloy X as conservative baseline. LPBF Hastelloy X creep data is sparse — do not use for long-duration (>100h) creep applications without specific test data. LPBF builds typically show better short-term creep (100h) but may behave differently long-term due to grain boundary character differences.
Sigma phase: extended service at 650–900°C can cause sigma-phase precipitation on grain boundaries over hundreds to thousands of hours. For long-life furnace applications, specify solution anneal after first 1000h of service. LPBF grain boundaries may have different sigma phase kinetics than wrought — monitor hardness in service.
DED suitability: DED is particularly well-suited to Hastelloy X repair of combustion liner cracks and spallation damage. The lower residual stress of DED and high ductility of the alloy enable effective near-net-shape repair. Verify geometry restoration with CMM before returning to service.
Atmosphere control during LPBF: Hastelloy X requires Ar atmosphere, O₂ < 500 ppm. Mo content makes it sensitive to oxidation — oxygen pickup in powder degrades properties.
Anisotropy in as-built: for combustion liner applications where thermal cycling causes biaxial loading, orient the primary thermal gradient direction (Z in LPBF) perpendicular to the dominant hoop stress direction where possible to exploit higher XY properties.

Advantages

Outstanding oxidation resistance to 1200°C in air and combustion gases — better than IN718 or IN625 at very high temperatures
Solid-solution strengthened — no precipitation hardening required; simpler heat treatment vs. IN718
Good forming and fabricability vs. γ'-strengthened alloys — enables complex shapes by forming before LPBF post-processing
Excellent high-temperature ductility at 1000°C — allows localised yielding without fracture under thermal shock
Good weldability — compatible with TIG, laser, and electron beam welding for repair
LPBF enables complex internal cooling features not achievable in sheet/plate fabrication
Wide LPBF processing window — lower cracking susceptibility than precipitation-hardened Ni superalloys

Limitations

Lower room-temperature and intermediate-temperature strength than precipitation-hardened alloys (IN718, Waspaloy) — structural efficiency limited
High cost — Ni-Cr-Mo alloy powder is 4–7× the cost of SS316L powder
No dedicated AM ASTM/ISO standard — qualification cost is higher than for IN718 (ASTM F3055)
Creep strength at 980°C is modest (~35 MPa for 100h rupture) — not suitable for high-stress creep applications
High residual stress in LPBF builds — stress relief before part removal from build plate is important
Solution anneal required for optimum ductility — adds process step and cost
High Mo content (8–10%) increases powder cost and requires careful atmosphere control to prevent Mo oxidation
Sigma-phase embrittlement can occur after prolonged service at 650–900°C — time-temperature must be managed

Typical applications

Gas turbine combustion liners and transition ducts — primary application, exploits oxidation resistance to 1200°CIndustrial gas turbine afterburner components and flame holdersIndustrial furnace fixtures, muffles, and retorts operating above 1000°CChemical process reactor components in oxidising atmospheresNuclear reactor support structures and shielding componentsPetrochemical reforming and cracking furnace componentsHigh-temperature wind tunnel test specimens and heat shieldsAerospace exhaust nozzle components and heat shields