UNS N06002 at a Glance
UNS N06002, widely known as nickel-chromium-iron-molybdenum alloy UNS N06002, is a nickel-chromium-iron-molybdenum alloy with a nominal composition of nickel balance, chromium about 21-22%, iron about 18%, molybdenum about 9%, plus cobalt and tungsten in small amounts. It offers excellent high-temperature strength and oxidation resistance up to about 2200 °F (1204 °C), with good forming and welding characteristics, and is a standard material for gas-turbine combustors, afterburners, furnace rollers and heat-treatment fixtures. The plate form, however, behaves as a structural and fabrication material rather than a conduit.
Plate versus Pipe: The Primary Distinction
While N06002 offers consistent high-temperature properties across all product forms, plate stock fundamentally shifts the application from conveying media to load-bearing and heat-containment duty. Plate, typically 3/16 inch (4.8 mm) to several inches thick, is used for burner plates, baffles, heat shields and support structures in industrial heaters, forging furnaces and gas-turbine combustors; for heat-exchanger headers and manifolds that must withstand high-pressure, high-temperature gases; for catalyst support grids, radiant tube sheets and other large internals in steam-methane reformers and ethylene crackers; and as a source for weld wire or strip used to overlay less resistant substrates. The primary engineering considerations differ from pipe: through-thickness properties, thermal-stress gradients across the section, and heavy forming and machining become critical.
Fabrication of N06002 Plate
Machining requires rigid setups and positive-rake, sharp carbide tools, with ceramic or CBN tools for heavy milling or turning, low-to-moderate speeds, consistent moderate feeds, and generous high-pressure coolant; grinding uses aluminum oxide or silicon carbide wheels with light pressures. Plasma arc cutting is the standard profiling method but leaves a recast heat-affected layer of about 0.5-1 mm that must be removed before high-temperature service; waterjet cutting is an excellent alternative because it produces no HAZ. Cold forming is possible for moderate bends with minimum bend radii of about 4-5 times plate thickness for 90-degree bends, with annealing between severe forming steps if needed; hot forming between 1600 °F and 2250 °F (870-1230 °C) suits complex shapes, followed by solution annealing and rapid quenching to restore optimum microstructure and corrosion or oxidation resistance.
Thermal Stability under Cycling
N06002 resists the formation of brittle sigma and Laves phases during prolonged high-temperature exposure, so plates retain ductility and toughness after thousands of hours of service, which is critical for components that are regularly shut down and restarted. The alloy forms a thin, dense and adherent chromium oxide scale with a coefficient of thermal expansion close to that of the base metal, so it resists spalling during thermal cycles. Design mitigations for thermal stress include flexible supports that allow lateral expansion, generous radii instead of sharp corners, and controlled heating and cooling rates for thick sections to minimize through-thickness gradients.
Welding and Certification
For plate over 1/2 inch thick, GTAW is preferred for root passes and thin sections, SMAW with matching electrodes for all positions, GMAW with pulsed transfer for filling large grooves, and SAW for long straight welds with flux designed for nickel-base alloys. Use single or double V-groove or U-groove preparations over 3/8 inch, with preheat not required and interpass temperature strictly controlled below 300 °F (150 °C). The matching filler is ERNiCrMo-2 (AWS A5.14), and post-weld heat treatment is generally not required because the as-welded condition is acceptable for high-temperature service. For ASME-coded or critical applications, plate must be supplied to ASME SB-435 with a certified mill test report covering heat chemistry, mechanical tests and hardness; traceability by heat number must be maintained through fabrication; and supplementary ultrasonic testing per ASTM A578, intergranular corrosion testing such as ASTM G28 Method A, and positive material identification by XRF are commonly specified.
Frequently Asked Questions
What is UNS N06002? UNS N06002 is the designation of nickel-chromium-iron-molybdenum alloy UNS N06002, a nickel-chromium-iron-molybdenum alloy for high-temperature service up to about 1204 °C, covered by ASME SB-435 for plate and related ASTM/ASME product standards.
Why choose plate rather than pipe for N06002? Plate provides thickness and area for load-bearing, heat-containment and large-area fabrication such as combustor liners, headers, tube sheets and catalyst support grids, while pipe is suited to conveying hot gases or media.
What filler metal is used for N06002? The matching filler is ERNiCrMo-2 (AWS A5.14), which maintains high-temperature strength and oxidation resistance similar to the base plate in the weld metal.
Does N06002 need post-weld heat treatment? Generally no. The alloy is stable in the as-welded condition for high-temperature service; stress relief is complex and usually avoided.
Can N06002 be plasma cut? Yes, plasma arc cutting is standard for profiling plate, but the recast layer of about 0.5-1 mm must be machined or ground away before high-temperature service.
Is N06002 suitable for thermal cycling? Yes. Its resistance to embrittling phases and the adherent chromium oxide scale make it well suited to cyclic heating and cooling, provided the design allows for differential expansion.
