Incoloy 800H / 800HT (UNS N08810/N08811) Forgings — Controlled-Carbon, Coarse-Grain Nickel-Iron-Chromium Alloy for High-Temperature Creep Strength
Shivam Forge manufactures forgings in Incoloy 800H (UNS N08810) and 800HT (UNS N08811) — nickel-iron-chromium alloys with controlled carbon content and larger grain size specifically optimized for creep and stress-rupture strength at temperatures up to roughly 1100°C — for ethylene cracking furnace, hydrogen reformer, and high-temperature process piping components. Rajkot, India. Call +91-9265772827.
Incoloy 800H shares its fundamental nickel-iron-chromium base with Incoloy 825, but the two alloys are engineered to resist entirely different failure mechanisms, and confusing them is a genuine and consequential material selection mistake. Incoloy 825 is optimized for aqueous corrosion resistance at low-to-moderate temperature — its copper and molybdenum additions specifically target reducing acid and chloride pitting attack, the kind of degradation that happens in wet, chemically aggressive process environments. Incoloy 800H addresses a completely different problem: sustained mechanical loading at genuinely high temperature (up to roughly 1100°C in furnace and reformer service), where the dominant failure mechanism isn't corrosion at all but creep — the slow, time-dependent plastic deformation and eventual stress-rupture that metals undergo when stressed continuously at a high enough fraction of their melting point, regardless of whether any corrosive medium is present. 800H achieves its creep and stress-rupture strength through two specific metallurgical levers that standard Incoloy 800 and Incoloy 825 don't share: a controlled, elevated carbon content (0.05–0.10%, versus a much lower and less tightly controlled range in standard 800) that promotes beneficial carbide precipitation strengthening the grain boundaries against creep cavitation, and a specified coarser grain size (ASTM grain size 5 or coarser) that directly improves creep-rupture life, since creep damage accumulates preferentially at grain boundaries and fewer, larger grains simply present less total grain boundary area for that damage to initiate along. 800HT takes this further with additional aluminium and titanium content for even better elevated-temperature strength. Critically, 800H is not the corrosion-resistance specialist that 825 is — it carries no copper addition and comparatively little molybdenum, so it should never be substituted for 825 in aqueous acid or chloride service, just as 825 should never be substituted for 800H in sustained high-temperature furnace duty, where 825's lower carbon and finer grain would leave it with materially inferior creep-rupture life.
Forged 800H components for ethylene cracking furnace tube supports, hangers, and fittings operating at sustained high temperature, where creep-rupture life directly determines furnace run-length between maintenance outages.
Forged 800H/800HT components for steam methane reformer furnace hardware, an application combining high sustained temperature with cyclic thermal loading during startup and shutdown.
Forged 800H flange and fitting components for high-temperature process piping in petrochemical and refining service, where standard stainless steel's creep strength is inadequate for the sustained operating temperature.
Forged 800H components for heat treatment furnace fixtures, baskets, and trays subjected to repeated thermal cycling and sustained high-temperature exposure over extended service life.
Standard supply in the solution-annealed condition with grain size verified to meet the ASTM grain size 5 or coarser requirement that distinguishes 800H from standard Incoloy 800 and directly supports its creep-rupture performance.
Chemical composition verification confirming carbon content falls within the specified 0.05–0.10% range, the controlled carbide-forming carbon addition that gives 800H its elevated-temperature strength advantage over standard 800.
800HT (UNS N08811) available where additional aluminium and titanium content is specified for further improved high-temperature strength beyond standard 800H capability.
Full chemical composition and mechanical property certification per EN 10204 3.1, with 3.2 third-party witnessed certification available for petrochemical furnace and high-temperature process equipment project documentation requirements.
It's a common and understandable mistake to assume that alloys sharing a name family and a similar base composition are broadly interchangeable, differing mainly in degree rather than in kind — and Incoloy 800H versus Incoloy 825 is exactly the pairing where that assumption leads to real material selection errors. Both alloys start from a comparable nickel-iron-chromium foundation, but from there their design intent diverges completely: 825 was engineered to resist aqueous corrosion, specifically the combination of reducing acid attack and oxidizing chloride environments that trip up standard stainless steel, through deliberate copper and molybdenum additions. 800H was engineered to resist an entirely different kind of failure — creep, the slow, cumulative plastic deformation that occurs when metal is held under sustained stress at genuinely high temperature for extended periods, a mechanism that has nothing to do with corrosive chemistry and everything to do with how atoms migrate along grain boundaries when a material is held close to a meaningful fraction of its melting point for months or years at a stretch.
The metallurgical levers that give 800H its creep resistance are specific and deliberate, not incidental. Carbon content, controlled to a 0.05–0.10% range considerably higher and more tightly specified than in standard Incoloy 800, promotes beneficial carbide precipitation along grain boundaries that resists the cavitation and grain boundary sliding through which creep damage typically accumulates — a case where elevated carbon content, often viewed as undesirable in corrosion-focused alloys because of its sensitization risk during welding, becomes a genuine strengthening feature in a high-temperature creep application. Equally important is grain size: 800H specifies a minimum grain size of ASTM 5 or coarser, because creep damage nucleates preferentially at grain boundaries, and a microstructure with fewer, larger grains simply presents less total grain boundary surface area for that damage to initiate along, directly translating into longer stress-rupture life at a given temperature and stress level.
This is precisely why 800H, not 825, is the specification that appears on ethylene cracking furnace tube support drawings, hydrogen reformer furnace hardware, and other high-temperature process equipment where components spend years continuously exposed to furnace temperatures well beyond where aqueous corrosion is even a relevant consideration — the failure mode these components need to resist is fundamentally mechanical and time-temperature-dependent, not chemical. Selecting 825 for this duty, on the strength of its shared alloy family name with 800H, would deliver a component with materially inferior creep-rupture life, since 825's lower, less tightly controlled carbon content and finer grain structure simply were never engineered to resist the specific degradation mechanism high-temperature furnace service imposes.
For petrochemical furnace, ethylene plant, and hydrogen reformer equipment manufacturers sourcing forged Incoloy 800H or 800HT components, Shivam Forge manufactures with verified carbon content and specified grain size supporting the alloy's designed creep-rupture performance. Contact our engineering team at +91-9265772827 or sales@shivamforge.com with your drawing and operating temperature specification for a manufacturability review and quotation.
Both share a nickel-iron-chromium base, but they are optimized for completely different failure modes. 825 is engineered for aqueous corrosion resistance via copper and molybdenum additions, suited to wet acid and chloride environments at low-to-moderate temperature. 800H is engineered for creep and stress-rupture strength at sustained high temperature (up to roughly 1100°C) via controlled carbon content and coarser grain size, with no copper addition and comparatively little molybdenum — it should never be substituted for 825 in corrosive aqueous service, and 825 should never be substituted for 800H in high-temperature furnace duty.
Creep is slow, time-dependent plastic deformation that occurs when a metal is stressed continuously at a high fraction of its melting temperature, eventually leading to stress-rupture failure. Creep damage accumulates preferentially at grain boundaries, so a coarser grain structure — fewer, larger grains — presents less total grain boundary area for that damage to initiate along, directly improving creep-rupture life. This is why 800H specifies a minimum grain size (ASTM 5 or coarser) that standard Incoloy 800 does not control as tightly.
800H (UNS N08810) achieves its creep strength primarily through controlled carbon content and specified grain size. 800HT (UNS N08811) adds further aluminium and titanium content on top of the 800H composition for additional elevated-temperature strength, making it the choice for the most demanding high-temperature creep applications within the 800 family.
800H delivers useful creep and stress-rupture strength up to approximately 1100°C, making it suitable for ethylene cracking furnace, hydrogen reformer, and other sustained high-temperature furnace and process piping applications where standard stainless steel's creep strength is inadequate.
In corrosion-resistant service, higher carbon content is often undesirable because it can promote chromium carbide precipitation at grain boundaries during welding, depleting chromium and increasing sensitization risk. In high-temperature creep service, however, that same carbide precipitation — carefully controlled within the 0.05–0.10% carbon range — strengthens grain boundaries against creep cavitation, which is why 800H's elevated carbon content is a deliberate design feature rather than a compromise.
Why Choose Shivam Forge
Shivam Forge delivers precision hot-forged components from our integrated Shapar, Rajkot facility — covering forging, CNC machining, heat treatment, and quality inspection under one roof.
