Hastelloy S
Hastelloy S (UNS N06635) is a nickel-chromium-molybdenum alloy (nominal 67% Ni, 15.5% Cr, 14.5% Mo with small additions of Al, La, and Fe) designed for excellent high-temperature oxidation resistance combined with a low and stable coefficient of thermal expansion. This combination makes it particularly valuable for gas turbine combustion zone hardware — particularly flame holders, transition liners, and combustor outer panels — where thermal cycling between ambient and 1800°F+ service temperatures generates severe thermal fatigue stresses that are proportional to the coefficient of thermal expansion.
Hastelloy S also exhibits outstanding resistance to dynamic oxidation (the alternating oxidation-reduction conditions typical of combustion environments) and excellent resistance to nitriding. AMS 5838 governs the production of Hastelloy S sheet and strip for combustion liner fabrication in aerospace and industrial gas turbine applications.
Product Forms & Size Range of Hastelloy S
Hastelloy S sheet and strip per AMS 5838 are available in thicknesses from 0.010 inch to 0.188 inch for formed and welded combustion liner components. Sheet is supplied solution annealed for forming; components are typically TIG or resistance welded in the annealed condition and used in service without post-weld heat treatment. Larger plate and bar forms are also available from specialty suppliers to customer specifications.
HEAT TREATMENT OF HASTELLOY S
Hastelloy S is solution annealed at 2050–2150°F (1121–1177°C) followed by rapid quenching to produce a fully solutioned microstructure. A final aging treatment at 1400°F (760°C) for four hours is specified for some applications to develop an optimum carbide dispersion that improves high-temperature creep and fatigue properties in combustion service. Post-forming stress relief at 1600°F (871°C) may be applied after severe cold-forming operations to restore ductility before service. The low thermal expansion characteristic is an intrinsic property of the alloy composition and is not affected by heat treatment within the normal processing range.
Hastelloy N
Ni-Mo alloy with unique resistance to molten fluoride salts — the alloy of choice for advanced nuclear molten salt reactor systems.
Haynes Alloy 230
Ni-Cr-W-Mo alloy for the hottest zones of aerospace and industrial gas turbines, maintaining strength to 2100°F.
Certified Material for Critical Service
Hastelloy S is supplied to AMS 5838 (sheet, strip, and plate). Material is produced by vacuum induction melting (VIM) for controlled composition and cleanliness. Certified mill test reports document composition, mechanical properties at room and elevated temperatures, and solution anneal condition. Thermal expansion coefficient data per ASTM E228 is available from the producer for thermal stress analysis applications.