{"id":1797,"date":"2025-12-10T10:48:12","date_gmt":"2025-12-10T09:48:12","guid":{"rendered":"https:\/\/www.nickelcasting.com\/?p=1797"},"modified":"2026-01-30T03:04:38","modified_gmt":"2026-01-30T02:04:38","slug":"incoloy-800h-vs-incoloy-800ht","status":"publish","type":"post","link":"https:\/\/www.nickelcasting.com\/ru\/incoloy-800h-vs-incoloy-800ht\/","title":{"rendered":"\u0418\u043d\u043a\u043e\u043b\u043e\u0439 800H \u043f\u0440\u043e\u0442\u0438\u0432 \u0418\u043d\u043a\u043e\u043b\u043e\u0439 800HT"},"content":{"rendered":"
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This article gives a focused, engineer-level comparison of Incoloy 800H vs 800HT<\/strong>, explains how to choose<\/strong> between them for high-temperature service, and breaks down 800H vs 800HT creep resistance<\/strong> with actionable guidance for purchasing, design and specification language.<\/p>\n

Incoloy 800H vs 800HT comparison<\/strong><\/h1>\n

What they are (short):<\/strong> Incoloy 800H (UNS N08810) and Incoloy 800HT (UNS N08811) are controlled-chemistry, heat-treated versions of alloy 800 intended for elevated-temperature service. Both are derived from the base Incoloy 800 chemistry but are processed and limited to tighter compositional ranges (notably carbon, aluminium and titanium) and specific heat-treatment\/grain-size requirements to improve long-term strength and creep behavior.<\/p>\n

Key compositional and process differences<\/strong><\/p>\n

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    Carbon control:<\/strong> 800H targets a controlled carbon band (~0.05\u20130.10% C) to increase creep-strength over basic 800; 800HT has similarly restricted C (commonly specified ~0.06\u20130.10%) but paired with stricter Al+Ti limits. These small carbon windows materially affect carbide precipitation and creep life.<\/p>\n<\/li>\n

  • \n

    Aluminum + Titanium (Al+Ti):<\/strong> 800HT typically has a narrower, higher Al+Ti control (often specified as ~0.85\u20131.20% combined) compared with the broader limits allowed for 800H. That tighter control encourages stable microstructures and better high-temperature strength\/oxidation resistance.<\/p>\n<\/li>\n

  • \n

    Heat treatment & grain size:<\/strong> 800H\/800HT are frequently given a high-temperature anneal (e.g., \u22651149\u00b0C \/ ~2100\u00b0F) to produce a coarser, controlled grain size (ASTM 5 or coarser) which improves creep performance vs standard 800. 800HT is often specified to meet the strictest heat-treatment and grain-size controls.<\/p>\n<\/li>\n<\/ul>\n

    Performance summary<\/strong><\/p>\n

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      Creep & rupture strength:<\/strong> Both 800H and 800HT show significantly higher creep and rupture strength than base alloy 800. 800HT generally exhibits the highest long-term creep strength, especially at the upper end of high-temperature service (above ~700\u00b0C), due to its tighter chemistry and heat-treat requirements.<\/p>\n<\/li>\n

    • \n

      Temperature window:<\/strong> Use 800H for reliable service in the 600\u2013700\u00b0C range (and above where appropriate); when the design calls for the maximum possible long-term creep resistance or service above ~700\u00b0C for extended durations, 800HT is often the preferred grade.<\/p>\n<\/li>\n<\/ul>\n

      Typical applications<\/strong><\/p>\n

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        800H:<\/strong> furnace components, petrochemical reformers, heat exchangers and other equipment where creep resistance above 600\u00b0C for many thousands of hours is required.<\/p>\n<\/li>\n

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        800HT:<\/strong> the same applications but where longer life at higher stress\/temperature is required \u2014 tubes, springs, critical pressure parts and petrochemical crackers operating at more severe temperatures or where ASME\/Code case stress-rupture limits require the tighter HT chemistry.<\/p>\n<\/li>\n<\/ul>\n<\/section>\n

        \"\"<\/h1>\n

        Incoloy 800H vs 800HT how to choose<\/strong><\/h1>\n

        Selecting between Incoloy 800H vs 800HT<\/strong> is a matter of matching time-at-temperature<\/strong>, stress<\/strong>, oxide\/carburizing environment<\/strong>, and code\/certification<\/strong> requirements to the alloy\u2019s microstructure and guaranteed properties.<\/p>\n

        Step-by-step selection checklist (practical)<\/strong><\/p>\n

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        1. \n

          Define design temperature and time horizon.<\/strong><\/p>\n

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            If the continuous service temperature is below ~600\u00b0C and life is moderate, base 800 could suffice; for continuous operation at or above ~600\u00b0C for long durations, start with 800H. For extended life above ~700\u00b0C or for very long design lives (tens of thousands to 100k+ hours), prioritize 800HT.<\/p>\n<\/li>\n<\/ul>\n<\/li>\n

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            Estimate applied stress and environment.<\/strong><\/p>\n

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              High applied stress or environments that promote carburization\/oxidation favor 800HT because its restricted Al+Ti and controlled heat-treatment yield better creep and oxidation resistance.<\/p>\n<\/li>\n<\/ul>\n<\/li>\n

            • \n

              Check applicable codes and stress tables.<\/strong><\/p>\n

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                Many codes\/ASME Code Cases publish allowable stresses for 800H and 800HT; when code compliance matters, select the grade listed or call out dual-certified material (800H\/800HT) and reference the supplier\u2019s certified data.<\/p>\n<\/li>\n<\/ul>\n<\/li>\n

              • \n

                Consider manufacturing form and finishing.<\/strong><\/p>\n

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                  If forming\/welding is heavy, confirm post-weld heat treatment and whether the chosen alloy\u2019s grain size\/chemistry will be preserved by fabrication steps. 800HT\u2019s tighter chemistry sometimes requires stricter control in fabrication.<\/p>\n<\/li>\n<\/ul>\n<\/li>\n

                • \n

                  Ask suppliers for creep-rupture curves and long-term data.<\/strong><\/p>\n

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                    For any final choice, request supplier data (1000, 10k, 100k-hour stress-rupture or creep curves). This is the definitive input for design margins. Many mills publish normalized curves for 800H and 800HT.<\/p>\n<\/li>\n<\/ul>\n<\/li>\n<\/ol>\n

                    Specification language to use in purchase orders \/ datasheets (examples)<\/strong><\/p>\n

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                    • \n

                      Acceptable:<\/em> \u201cMaterial: Incoloy 800HT (UNS N08811) to ASTM\/ASME [insert spec], heat-treated to 1149\u00b0C (2100\u00b0F) min.; chemical composition and grain-size to meet manufacturer\u2019s 800HT limits; mill cert required showing Al+Ti and C ranges.\u201d<\/p>\n<\/li>\n

                    • \n

                      Alternative (dual cert):<\/em> \u201cMaterial: Alloy 800H\/800HT dual-certified; supplier to certify to both UNS N08810 and N08811 limits and provide creep-rupture data for intended service temperature.\u201d
                      Using precise wording like this reduces ambiguity for procurement and supports SEO when published on product\/spec pages.<\/p>\n<\/li>\n<\/ul>\n

                      \"\"<\/h1>\n

                      800H vs 800HT creep resistance<\/strong><\/h1>\n

                      Mechanisms that matter<\/strong><\/p>\n

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                      • \n

                        Carbide precipitation and grain size:<\/strong> Controlled carbon content and heat treatment determine the distribution and type of carbides; these features control creep cavitation and grain-boundary weakness. 800HT\u2019s tighter controls produce a microstructure that resists creep deformation longer under the same stress\/temperature.<\/p>\n<\/li>\n

                      • \n

                        Al+Ti control & oxidation:<\/strong> Higher and controlled Al+Ti in the right balance promotes stable oxide scales and strengthens the matrix at high temperature (gamma prime formation is not strong in these alloys, but Al\/Ti do influence precipitates and oxidation resistance), which helps long-term creep life and resistance to embrittlement.<\/p>\n<\/li>\n<\/ul>\n

                        What the data says (how to interpret mill charts)<\/strong><\/p>\n

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                        • \n

                          Supplier graphs show creep rupture strength curves<\/strong> for 800H and 800HT plotted as stress vs log(time) at fixed temperatures. Typical observations: at a given stress and temperature, 800HT reaches a target rupture time at a higher<\/em> stress than 800H \u2014 i.e., 800HT lasts longer or carries more stress for the same life. Ask suppliers for curves at your design temperatures (600\u00b0C, 700\u00b0C, 760\u00b0C etc.).<\/p>\n<\/li>\n<\/ul>\n

                          Design rule of thumb<\/strong><\/p>\n

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                            If your component must survive very long<\/strong> exposures (>10,000\u2013100,000 hours) at \u2265700\u00b0C<\/strong> or you require the highest allowable stress values from ASME tables, choose 800HT<\/strong>. For robust service above ~600\u00b0C where 800H\u2019s creep tables already meet allowable stress and cost sensitivity matters, 800H<\/strong> is often the pragmatic choice. Always validate with supplier creep-rupture data for the actual stress and temperature.<\/p>\n<\/li>\n<\/ul>\n

                            Incoloy 800H vs 800HT Difference Quick Check Table<\/strong><\/h1>\n\n\n\n\n\n\n\n\n\n\n
                            Property \/ Feature<\/th>\nIncoloy 800H (UNS N08810)<\/th>\nIncoloy 800HT (UNS N08811)<\/th>\nPractical note<\/th>\n<\/tr>\n<\/thead>\n
                            Carbon (typical spec)<\/td>\n~0.05 \u2013 0.10%<\/td>\n~0.06 \u2013 0.10% (tighter control)<\/td>\nBoth higher than base 800; HT often slightly tighter.<\/td>\n<\/tr>\n
                            Al + Ti (combined)<\/td>\nWider range (broader limits)<\/td>\nNarrower, more restrictive (e.g. 0.85\u20131.20% combined)<\/td>\nHT\u2019s restricted Al+Ti improves high-T strength\/oxidation.<\/td>\n<\/tr>\n
                            Heat treatment<\/td>\nHigh-temp anneal customary<\/td>\nHigh-temp anneal required; stricter min temp<\/td>\nHT often called out with specific anneal temperature.<\/td>\n<\/tr>\n
                            Grain size control<\/td>\nControlled (coarser than base 800)<\/td>\nControlled; often specified ASTM 5 or coarser<\/td>\nGrain control helps creep life.<\/td>\n<\/tr>\n
                            Creep resistance<\/td>\nHigh (vs 800)<\/td>\nHigher (best of the 3)<\/td>\nChoose HT for max long-term creep life.<\/td>\n<\/tr>\n
                            Typical use temp focus<\/td>\n~600\u2013700\u00b0C service<\/td>\n\u2265700\u00b0C service and longest lives<\/td>\nMatch to time-at-temp and stress.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

                            Related Q&A<\/h1>\n

                            Q1 \u2014 Can I substitute 800H for 800HT to save cost?<\/strong>
                            A:<\/strong> Substitution is possible in some cases but not universally safe. If the application\u2019s allowable stress is derived from 800HT tables or the design life\/temperature demands HT\u2019s tighter chemistry, substitution can reduce life or violate code limits. Always check ASME\/code allowable stresses and supplier creep data before substituting.<\/p>\n

                            Q2 \u2014 What temperatures are considered \u201csafe\u201d for continuous service for 800H and 800HT?<\/strong>
                            A:<\/strong> There\u2019s no single cutoff\u2014designers use creep\/rupture data and code allowable stresses. In practice, 800H is commonly specified for reliable long-term service at and above 600\u00b0C; 800HT is chosen when the design calls for reliable, long life at or above ~700\u00b0C or when the highest allowable stresses are required. Confirm with mill-published stress tables.<\/p>\n

                            Q3 \u2014 Do 800H and 800HT weld similarly, and does welding affect creep life?<\/strong>
                            A:<\/strong> Both weldable with standard Ni-Cr procedures, but welding can locally alter chemistry and microstructure; post-weld heat treatment and fabrication controls should be specified if creep life is critical. HT\u2019s tighter chemistry means fabricator controls (filler metal, heat input, PWHT) should be verified to avoid degraded creep properties in the weld or HAZ.<\/p>\n<\/section>\n","protected":false},"excerpt":{"rendered":"

                            This article gives a focused, engineer-level comparison of Incoloy 800H vs 800HT, explains how to choose between them for high-temperature service, and breaks down 800H vs 800HT creep resistance with actionable guidance for purchasing, design and specification language. Incoloy 800H vs 800HT comparison What they are (short): Incoloy 800H (UNS N08810) and Incoloy 800HT (UNS […]<\/p>\n","protected":false},"author":1,"featured_media":1799,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3],"tags":[],"class_list":["post-1797","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-blog"],"_links":{"self":[{"href":"https:\/\/www.nickelcasting.com\/ru\/wp-json\/wp\/v2\/posts\/1797","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.nickelcasting.com\/ru\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.nickelcasting.com\/ru\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.nickelcasting.com\/ru\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.nickelcasting.com\/ru\/wp-json\/wp\/v2\/comments?post=1797"}],"version-history":[{"count":2,"href":"https:\/\/www.nickelcasting.com\/ru\/wp-json\/wp\/v2\/posts\/1797\/revisions"}],"predecessor-version":[{"id":1801,"href":"https:\/\/www.nickelcasting.com\/ru\/wp-json\/wp\/v2\/posts\/1797\/revisions\/1801"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.nickelcasting.com\/ru\/wp-json\/wp\/v2\/media\/1799"}],"wp:attachment":[{"href":"https:\/\/www.nickelcasting.com\/ru\/wp-json\/wp\/v2\/media?parent=1797"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.nickelcasting.com\/ru\/wp-json\/wp\/v2\/categories?post=1797"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.nickelcasting.com\/ru\/wp-json\/wp\/v2\/tags?post=1797"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}