Incoloy 800/800H/800HT: Differences for Heat Exchangers and Furnaces

Introduction

For heat exchangers, furnaces, radiant tubes and high-temperature process equipment, Incoloy 800/800H/800HT are selected according to service temperature, creep strength, oxidation resistance, carburization resistance and fabrication requirements. Incoloy 800 is generally used for corrosion-resistant and heat-resistant service at moderate high temperatures, Incoloy 800H is preferred when improved creep and rupture strength are required above approximately 600°C, and Incoloy 800HT is recommended for more demanding high-temperature furnace and petrochemical applications where controlled carbon, aluminum and titanium levels provide enhanced long-term strength.

These nickel-iron-chromium alloys are widely used in industrial heaters, heat exchanger tubes, furnace components, ethylene pyrolysis equipment, reformer pigtails, thermowells, heat treatment baskets, retorts and high-temperature piping systems. Although the three grades are closely related, buyers should not treat them as fully interchangeable. A correct material selection must consider the design temperature, pressure, atmosphere, corrosion medium, product form, applicable standard, certificate type and inspection requirements.

SASA ALLOY supplies Incoloy 800, Incoloy 800H and Incoloy 800HT in bars, pipes, tubes, plates, sheets, forgings, flanges, fittings and customized alloy products. This guide explains the differences, application scenarios, material benefits, limitations, standards, testing requirements and purchasing points for engineers and industrial buyers.

What Are Incoloy 800, 800H and 800HT?

Incoloy 800, 800H and 800HT are nickel-iron-chromium alloys designed for oxidation resistance, carburization resistance and strength retention in high-temperature environments. Their high nickel content helps maintain an austenitic structure, while chromium improves resistance to oxidation and many corrosive atmospheres. Iron provides a cost-effective balance compared with higher nickel alloys.

The main difference between these grades is not only chemical composition, but also carbon control, grain size control and high-temperature strength requirements. Incoloy 800 is the base alloy. Incoloy 800H has a higher controlled carbon range and is usually solution annealed to develop improved creep properties. Incoloy 800HT further controls aluminum and titanium additions to improve long-term high-temperature performance.

Quick Grade Selection Summary

Grade	UNS	Best Application Scenario	Buyer Recommendation
Incoloy 800	UNS N08800	Heat exchangers, chemical processing, moderate high-temperature equipment.	Choose when corrosion resistance and oxidation resistance are required but creep strength is not the main design factor.
Incoloy 800H	UNS N08810	High-temperature piping, furnace parts, reformer components and heaters.	Choose for improved creep and rupture strength at elevated temperature.
Incoloy 800HT	UNS N08811	Furnace tubes, ethylene cracking, radiant tubes and long-term thermal service.	Choose for demanding high-temperature service where controlled Al + Ti and creep performance are important.

Chemical Composition of Incoloy 800/800H/800HT

Chemical composition is the first point buyers should check when selecting Incoloy 800/800H/800HT. The three grades share a similar nickel-iron-chromium base, but 800H and 800HT are designed with controlled carbon and high-temperature strength requirements. Incoloy 800HT also has tighter control of aluminum and titanium additions, which helps improve creep and rupture performance in long-term service.

For heat exchangers and furnaces, the MTC should clearly show the UNS grade, heat number, chemical composition and applicable standard. For Incoloy 800HT, buyers should pay special attention to carbon, aluminum, titanium and grain size requirements, because these are directly related to high-temperature performance.

Chemical Composition Table

Grade	UNS	Ni	Cr	Fe	C	Al + Ti	Main Composition Point
Incoloy 800	N08800	30.0 – 35.0	19.0 – 23.0	39.5 min	0.10 max	0.15 – 1.20	Balanced corrosion and oxidation resistance for general heat-resistant service.
Incoloy 800H	N08810	30.0 – 35.0	19.0 – 23.0	39.5 min	0.05 – 0.10	0.15 – 1.20	Controlled carbon supports higher creep and rupture strength.
Incoloy 800HT	N08811	30.0 – 35.0	19.0 – 23.0	39.5 min	0.06 – 0.10	0.85 – 1.20	Controlled carbon and Al + Ti improve long-term high-temperature properties.

Mechanical Properties and High-Temperature Performance

Mechanical properties for Incoloy 800/800H/800HT depend on product form, standard, size, heat treatment and testing temperature. At room temperature, the three grades may show similar tensile properties. Their main difference becomes more important at elevated temperatures, where creep strength, rupture life and structural stability are critical.

For heat exchanger tubes, furnace tubes and high-temperature piping systems, buyers should review not only tensile strength and elongation but also design code requirements, solution annealing condition, grain size and creep-related data. In high-temperature service, selecting 800 when 800H or 800HT is required may lead to insufficient long-term strength.

Mechanical Properties Table

Grade	Tensile Strength	Yield Strength	Elongation	High-Temperature Performance Note
Incoloy 800	Typically 520 MPa min, depending on standard and form	Typically 205 MPa min, depending on standard and form	Typically 30% min	Good oxidation and corrosion resistance; not the first choice for long-term creep-critical service.
Incoloy 800H	Typically 450 – 600 MPa, depending on specification	Typically 170 MPa min or according to standard	Typically 30% min	Improved creep and rupture strength for elevated-temperature equipment.
Incoloy 800HT	Typically 450 – 600 MPa, depending on specification	Typically 170 MPa min or according to standard	Typically 30% min	Best long-term high-temperature strength among the three grades.

Applicable Standards and Equivalent Grades

Incoloy 800/800H/800HT can be supplied under different ASTM, ASME, EN, DIN and project standards depending on product form. Heat exchanger tubes may follow ASTM B163, ASTM B407 or ASME SB-407. Plates and sheets may follow ASTM B409. Bars and rods may follow ASTM B408. Forgings and flanges may follow ASTM B564 or ASME SB-564.

For pressure equipment and high-temperature service, buyers should confirm whether ASTM or ASME material standards are required, whether the project needs EN 10204 3.1 MTC, whether third-party inspection is necessary and whether additional testing such as PMI, UT, hydrostatic test, flattening test or intergranular corrosion test is specified.

Standards / Equivalent Grades Table

Commercial Grade	UNS	EN / Werkstoff	Common ASTM / ASME Standards	Common Product Forms	Related Product Link
Incoloy 800	N08800	1.4876	ASTM B163, B407, B408, B409, B564 / ASME SB series	Tube, pipe, bar, plate, sheet, forging, flange	Incoloy 800 Products
Incoloy 800H	N08810	1.4958 / 1.4876 reference depending on specification	ASTM B407, B408, B409, B564 / ASME SB-407, SB-408, SB-409	High-temperature pipe, tube, bar, plate and forged components	Incoloy 800H Products
Incoloy 800HT	N08811	1.4959 reference depending on specification	ASTM B407, B408, B409, B564 / ASME SB series	Furnace tubes, radiant tubes, plates, bars, forgings and fittings	Incoloy 800HT Products

Comparison With Similar High-Temperature Alloys

Incoloy 800/800H/800HT are often compared with stainless steel 310S, Inconel 600, Inconel 601, Inconel 625 and other nickel alloys. For buyers, the right material depends on temperature, corrosion atmosphere, mechanical load, oxidation risk, carburization risk and budget. Incoloy 800 series alloys are widely used where stainless steels may not provide enough high-temperature stability, but where a higher nickel alloy may not be economically necessary.

For heat exchangers and furnace components, Incoloy 800H and 800HT often provide a strong balance between cost and performance. However, in very aggressive oxidation, severe corrosion or highly specific chemical environments, other nickel alloys may be more suitable. Final selection should be based on project design conditions and engineering review.

Material Comparison Table

Material	Main Strength	Compared With Incoloy 800 Series	Typical Selection Advice
310S Stainless Steel	Good oxidation resistance and lower cost.	Lower nickel content and generally lower high-temperature strength stability.	Use for less severe heat-resistant applications when budget is critical.
Incoloy 800H	Improved creep strength and high-temperature performance.	Better for high-temperature load-bearing service than base 800.	Recommended for high-temperature piping, heaters and furnace components.
Incoloy 800HT	Enhanced long-term creep and rupture properties.	More controlled chemistry than 800H for demanding thermal service.	Recommended for radiant tubes, furnace internals and petrochemical high-temperature equipment.
Inconel 600	Higher nickel content and strong resistance in many corrosive atmospheres.	Usually more expensive; may be selected for more severe corrosion environments.	Use when higher nickel performance is required by process conditions.
Inconel 601	Excellent oxidation resistance due to aluminum addition.	May offer better oxidation resistance in specific high-temperature atmospheres.	Consider for severe oxidation service and thermal processing equipment.

Industrial Applications for Heat Exchangers and Furnaces

Incoloy 800/800H/800HT are widely used in equipment exposed to heat, oxidation, carburization and thermal cycling. Heat exchanger tubes require good corrosion resistance, dimensional stability and weldability. Furnace components require high-temperature strength, oxidation resistance and resistance to scale formation. Petrochemical process equipment may require both corrosion resistance and creep strength under continuous operation.

For application scenario selection, Incoloy 800 is commonly used in chemical processing equipment and heat exchangers operating under moderate high-temperature conditions. Incoloy 800H is better suited for high-temperature service where creep strength is part of the design. Incoloy 800HT is often selected for severe furnace, ethylene cracking and radiant tube applications where long-term thermal stability is critical.

Industrial Applications Table

Application	Recommended Grade	Common Product Form	Reason for Selection
Heat Exchanger Tubes	Incoloy 800 / 800H	Seamless tube, welded tube, U-tube	Good corrosion resistance, oxidation resistance and thermal stability.
Furnace Radiant Tubes	Incoloy 800HT	Seamless pipe, welded pipe, centrifugal casting alternative depending on design	Improved long-term creep strength and resistance to high-temperature oxidation.
Ethylene Pyrolysis Equipment	Incoloy 800H / 800HT	Tube, pipe, fitting, forging	Good resistance to carburization and thermal stress in petrochemical service.
Industrial Heaters	Incoloy 800H	Pipe, tube, plate, sheet	Useful for elevated-temperature structural and pressure-containing components.
Heat Treatment Baskets and Fixtures	Incoloy 800 / 800H	Bar, wire, plate, fabricated parts	Resistance to oxidation and thermal cycling in furnace operation.
High-Temperature Piping	Incoloy 800H / 800HT	Pipe, flange, fitting, forged component	High-temperature strength and stable performance under continuous operation.

Material Benefits and Limitations

The main benefits of Incoloy 800/800H/800HT include good resistance to oxidation, carburization and many high-temperature corrosive atmospheres. The alloys also offer good fabrication performance, weldability and stability in many thermal processing environments. For heat exchangers and furnaces, this combination makes them practical materials for long-term industrial service.

However, these alloys also have limitations. They may not be the best solution for all severe corrosion conditions, strongly reducing sulfur-containing atmospheres, certain molten salt environments or applications requiring the highest nickel alloy corrosion performance. In addition, using Incoloy 800 instead of 800H or 800HT in creep-critical service can create design risk. Buyers should confirm operating temperature, atmosphere, pressure and design code before ordering.

Benefits and Limitations Table

Item	Material Benefit	Limitation / Buyer Warning
Oxidation Resistance	Chromium supports protective oxide scale formation at high temperature.	Atmosphere composition and thermal cycling must still be evaluated.
Creep Strength	800H and 800HT provide better high-temperature strength than base 800.	Do not substitute 800 for 800H/800HT without engineering approval.
Fabrication	Good weldability and formability when proper procedures are used.	Welding procedure, filler metal and post-weld requirements should be confirmed.
Cost Performance	Often more economical than higher nickel alloys in suitable environments.	Not always suitable for the most aggressive corrosion conditions.
Availability	Available in tube, pipe, bar, plate, sheet, flange, fitting and forging forms.	Special sizes and 800HT items may require production lead time.

Quality Testing and Material Traceability

For nickel alloy procurement, material traceability is critical. Each Incoloy 800/800H/800HT order should be traceable by heat number from raw material melting to finished product delivery. The heat number on the EN 10204 3.1 MTC should match product marking, labels, packing documents and inspection records.

For heat exchanger and furnace projects, buyers often request PMI testing to verify nickel, chromium and iron content. UT testing may be required for bars, plates, forgings or thick-wall pipes to detect internal defects. Tubes may require hydrostatic testing, eddy current testing, flattening testing, flaring testing or dimensional inspection depending on the standard and application.

Inspection and Certificate Checklist

Quality Item	What to Check	Why It Matters
EN 10204 3.1 MTC	Grade, UNS number, heat number, chemical composition, mechanical properties and standard.	Confirms material identity and compliance before shipment.
Heat Number Control	Match MTC, product marking, package label and packing list.	Maintains traceability for project acceptance and anti-fake material control.
PMI Testing	Ni, Cr, Fe and alloying elements.	Verifies alloy grade and prevents material mix-up.
UT Testing	Internal defects in bars, plates, forgings or thick-wall products.	Important for pressure parts and critical high-temperature components.
Third-party Inspection	SGS, BV, TÜV, DNV, Lloyd’s or customer-designated agency inspection.	Provides independent verification for critical export and engineering orders.
Export Packaging	Wooden cases, pallets, waterproof protection, end caps and bundle marking.	Protects surface, dimensions and traceability during international transportation.

Purchasing Notes for Heat Exchanger and Furnace Projects

Before purchasing Incoloy 800/800H/800HT, buyers should clearly define grade, standard, product form, size, tolerance, heat treatment, surface finish, testing requirements and documentation. For heat exchanger tubes, tube outside diameter, wall thickness, length, straightness, end finish and testing method should be confirmed. For furnace parts, operating temperature, atmosphere, load condition and expected service life should be reviewed with engineers.

Common surface conditions include annealed and pickled, bright annealed, polished, turned, peeled, ground and machined surfaces, depending on product form. For bars and forgings, surface condition may affect machining allowance. For tubes and pipes, internal and external surface requirements are important for heat transfer, cleanliness and welding.

Buyer Specification Checklist

Specification Item	Recommended Details to Confirm
Grade	Incoloy 800, 800H or 800HT; confirm UNS N08800, N08810 or N08811.
Product Form	Pipe, tube, bar, plate, sheet, forged flange, fitting, ring or customized component.
Standard	ASTM B407, B408, B409, B564, ASME SB series or customer project specification.
Inspection	MTC, PMI, UT, hydrostatic test, dimensional inspection, surface inspection and third-party inspection if required.
Application Conditions	Temperature, pressure, medium, furnace atmosphere, corrosion risk, thermal cycling and design life.

Why Choose SASA ALLOY for Incoloy 800/800H/800HT?

SASA ALLOY supplies nickel alloys, corrosion-resistant alloys, heat-resistant alloys, stainless steels and special metal products for petrochemical, heat exchanger, furnace, energy, chemical processing, marine and industrial equipment manufacturers. For Incoloy 800/800H/800HT, we help customers confirm the correct grade and product form according to working temperature, pressure, corrosion atmosphere and fabrication method.

Available supply forms may include Incoloy 800 pipe, Incoloy 800H tube, Incoloy 800HT plate, nickel alloy round bar, forged flange, fitting, sheet, strip and customized machined components. We can support customized sizes, surface treatment, cutting, machining, export packaging and documentation according to order requirements.

SASA ALLOY Supply Advantages

Capability	Buyer Value
Grade Selection Support	Help buyers compare Incoloy 800, 800H and 800HT for heat exchangers, furnaces and petrochemical equipment.
Multiple Product Forms	Pipe, tube, bar, plate, sheet, strip, forged flange, ring, fitting and customized alloy parts.
Quality Documentation	EN 10204 3.1 MTC, PMI report, UT report, inspection photos and third-party inspection support as required.
Customization	Customized size, surface finish, cutting, machining, drawing-based production and special packaging.
Export Delivery Capability	Seaworthy packaging, heat number marking, document preparation and international shipment coordination.

FAQ: Incoloy 800/800H/800HT

What is the main difference between Incoloy 800, 800H and 800HT?

Incoloy 800 is the base nickel-iron-chromium alloy. Incoloy 800H has controlled carbon and heat treatment requirements for improved high-temperature creep strength. Incoloy 800HT has controlled carbon plus tighter aluminum and titanium control for enhanced long-term high-temperature performance.

Which grade is best for furnace tubes?

For furnace tubes, radiant tubes and long-term high-temperature service, Incoloy 800HT is usually the preferred grade. Incoloy 800H can also be suitable for many high-temperature furnace applications, depending on design temperature, atmosphere and mechanical load.

Can Incoloy 800 be used for heat exchangers?

Yes. Incoloy 800 is commonly used for heat exchanger tubes and chemical processing equipment where good corrosion resistance and oxidation resistance are required. If the heat exchanger operates at higher temperatures where creep strength is important, Incoloy 800H or 800HT may be more suitable.

Is Incoloy 800HT always better than Incoloy 800H?

Not always. Incoloy 800HT offers enhanced high-temperature performance, but it may not be necessary for all applications. If the operating temperature and design load are moderate, Incoloy 800H may provide sufficient performance. The final choice should be based on project design conditions and applicable standards.

What certificate should buyers request?

For industrial and export orders, buyers should request EN 10204 3.1 MTC or equivalent material certification. For critical heat exchanger or furnace projects, PMI testing, UT testing, hydrostatic testing, third-party inspection and heat number traceability may also be required.

What related products can SASA ALLOY supply?

SASA ALLOY can supply Incoloy 800 pipe, Incoloy 800H tube, Incoloy 800HT plate, nickel alloy bar, forged flange, fittings, sheets, strips and customized components. Related nickel alloy products may include Inconel 600, Inconel 601, Inconel 625, Hastelloy alloys, Monel alloys and other heat-resistant or corrosion-resistant alloys.

Conclusion

Incoloy 800/800H/800HT are important nickel-iron-chromium alloys for heat exchangers, furnaces, high-temperature piping and petrochemical equipment. Incoloy 800 is suitable for many corrosion-resistant and oxidation-resistant applications, Incoloy 800H provides improved high-temperature strength, and Incoloy 800HT is recommended for demanding long-term thermal service where creep strength and controlled chemistry are critical.

For successful procurement, buyers should confirm grade, UNS number, product standard, size, surface condition, inspection requirement, MTC, PMI testing, UT testing, third-party inspection and export packaging before placing an order. Correct material selection helps reduce maintenance risk, improve equipment reliability and support long-term industrial operation.