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Incoloy 330 (UNS N08330) is a nickel-iron-chromium austenitic heat-resistant alloy engineered for demanding high-temperature environments. Its combination of carburization resistance, oxidation resistance, thermal shock resistance, and metallurgical stability makes it a widely used material for carburizing furnace baskets, muffles, retorts, radiant tubes, and heat-treatment fixtures.
Material designation: Incoloy 330 / Alloy 330 / RA330
UNS designation: N08330
Commonly referenced Werkstoff number: 1.4886; alternative references should be verified against the applicable specification and material certificate.
Alloy family: Austenitic nickel-iron-chromium heat-resistant alloy
Density: Approximately 8.0 g/cm³
Melting range: Approximately 1,400–1,450°C
High-temperature oxidation resistance: Commonly rated up to approximately 1,148°C (2,100°F), depending on the atmosphere and operating conditions
Primary applications: Carburizing furnace baskets, muffles, retorts, radiant tubes, and heat-treatment fixtures
Incoloy 330 at a glance: A silicon-containing, nickel-rich heat-resistant alloy designed for high-temperature service where resistance to carburization and repeated thermal cycling is essential.
Industrial heat-treatment furnaces expose components to some of the most demanding conditions in materials engineering. Depending on the process, furnace baskets, muffles, retorts, and radiant tubes may experience carbon-rich atmospheres, high operating temperatures, repeated heating and cooling, and rapid quenching.
Under these conditions, conventional heat-resistant steels may suffer from carbon ingress, embrittlement, surface degradation, oxidation, or thermal fatigue cracking. Selecting an alloy that can withstand the combined effects of carburization and thermal cycling is therefore critical to equipment reliability and service life.
Incoloy 330 was developed to address these requirements through a carefully balanced nickel-chromium-iron composition with a significant silicon addition.
Its performance relies on three principal alloying elements:
● Nickel (Ni): Typically 34–37%, nickel stabilizes the austenitic microstructure and contributes to resistance to carburizing environments and chloride stress corrosion cracking.
● Chromium (Cr): Typically 17–20%, chromium supports the formation of protective chromium-rich oxide scales and improves high-temperature oxidation resistance.
● Silicon (Si): Silicon enhances oxidation resistance and helps improve resistance to carburization under suitable furnace conditions.
Unlike precipitation-hardening superalloys, Incoloy 330 is not designed to develop strength through age hardening. Its properties are primarily derived from its alloy chemistry, austenitic matrix, and stability during prolonged high-temperature exposure.
This makes Incoloy 330 particularly suitable for furnace components that must retain useful ductility and resist damage during repeated thermal cycles.
An important distinction is that Incoloy 330 is a heat-resistant austenitic alloy, not a precipitation-hardened structural superalloy. Its primary value lies in its resistance to furnace-related degradation rather than exceptionally high room-temperature strength.
The chemical composition of Incoloy 330 determines its oxidation resistance, carburization resistance, microstructural stability, and fabrication characteristics.
The following table presents representative composition limits commonly associated with Alloy 330 under established product specifications. Actual limits depend on the applicable standard, product form, and purchase specification.
Element | Representative content (wt.%) | Primary function |
Nickel (Ni) | 34.0–37.0 | Stabilizes austenite and contributes to resistance in high-temperature carburizing environments |
Chromium (Cr) | 17.0–20.0 | Promotes protective oxide formation and improves oxidation resistance |
Iron (Fe) | Balance | Principal matrix constituent and a major contributor to the alloy's cost-performance balance |
Silicon (Si) | Commonly 0.75–1.50 | Enhances oxidation resistance and contributes to carburization resistance |
Carbon (C) | ≤0.08 | Controlled to balance strength, fabrication characteristics, and microstructural behavior |
Manganese (Mn) | ≤2.00 | Supports steelmaking and deoxidation practices |
Phosphorus (P) | Commonly ≤0.030 | Controlled residual element |
Sulfur (S) | Commonly ≤0.030 | Controlled residual element |
Important specification note: Silicon content is frequently specified at 0.75–1.50 wt.% for standard Alloy 330 products. Higher silicon ranges may appear in supplier-specific descriptions or alternative specifications. The 1.0–2.5% range should not be treated as a universal UNS N08330 requirement. Buyers should verify the applicable specification and the actual mill test certificate.
Silicon is a key contributor to the high-temperature performance of Alloy 330. In conjunction with chromium and the alloy's nickel-rich matrix, silicon helps improve resistance to oxidation and carbon-rich furnace environments.
Its benefits are particularly relevant in heat-treatment processes where components are repeatedly exposed to carburizing atmospheres and subsequent cooling or quenching.
The alloy's performance can be understood through the following relationships:
● Oxidizing atmospheres: Chromium-rich protective oxide scales provide the principal oxidation resistance, with silicon contributing to scale performance.
● Carburizing atmospheres: The combined effects of nickel, chromium, and silicon improve resistance to carbon ingress and associated degradation.
● Repeated thermal cycling: The stable austenitic structure and resistance to thermal shock help reduce the risk of premature damage under properly controlled operating conditions.
However, the protective surface scale is not an impermeable barrier under every condition. Its effectiveness depends on temperature, furnace chemistry, exposure duration, scale integrity, and the presence of contaminants.
This is why Incoloy 330 is particularly attractive for carburizing furnace baskets, heat-treatment boxes, muffles, and retorts, where both carburization resistance and thermal-cycle durability are important.
Incoloy 330 differs fundamentally from precipitation-hardened alloys such as A-286 and Alloy 925. Rather than relying on aging treatments to precipitate strengthening phases, Alloy 330 obtains its performance primarily from solid-solution strengthening and metallurgical stability.
Nickel, chromium, and silicon contribute to the alloy's solid-solution characteristics. These elements influence lattice behavior and dislocation movement, helping the alloy maintain useful mechanical strength at elevated temperatures.
Nevertheless, Alloy 330 should not be selected solely on the basis of room-temperature tensile strength. Its principal engineering advantage is the combination of heat resistance, environmental resistance, and thermal-cycle durability.
Incoloy 330 retains an austenitic, face-centered cubic (FCC) matrix over a broad temperature range. Its high nickel content contributes to this stability.
The alloy is recognized for its resistance to embrittlement associated with sigma-phase formation under conditions relevant to many furnace applications. This is an important advantage for components exposed to repeated heating and cooling.
Microstructural stability does not mean that the alloy is immune to every form of degradation. Prolonged exposure, contamination, local chemistry, and mechanical loading can still affect service performance.
At elevated temperatures, chromium and silicon contribute to the formation and performance of protective oxide scales. These scales help limit further oxidation and, under suitable conditions, reduce the rate of carbon ingress.
If the surface scale is damaged or disrupted by thermal cycling, mechanical abrasion, or aggressive furnace contaminants, its protective effect may decrease.
For this reason, furnace cleanliness, atmosphere control, appropriate operating temperatures, and component maintenance are important factors in maximizing service life.
Incoloy 330 cannot be strengthened through conventional precipitation-aging treatments in the manner of A-286 or Alloy 925. Heat treatment may be used for solution annealing, stress relief where appropriate, or restoration of a suitable metallurgical condition, depending on the product and fabrication process.
Its selection should therefore be based on high-temperature environmental resistance and service stability rather than expectations of age-hardening response.
The following values are reference data for preliminary engineering and material selection. They are not a substitute for the governing product specification or certified test results.
Element | Representative content (wt.%) |
Nickel (Ni) | 34.0–37.0 |
Chromium (Cr) | 17.0–20.0 |
Silicon (Si) | Commonly 0.75–1.50 |
Carbon (C) | ≤0.08 |
Manganese (Mn) | ≤2.00 |
Phosphorus (P) | Commonly ≤0.030 |
Sulfur (S) | Commonly ≤0.030 |
Iron (Fe) | Balance |
The composition must be confirmed against the applicable ASTM, ASME, AMS, or other agreed product specification. Minor-element limits and permitted additions may differ between specifications.
Property | Approximate value or description |
Density | Approximately 8.0 g/cm³ |
Melting range | Approximately 1,400–1,450°C |
Crystal structure | Austenitic, face-centered cubic (FCC) |
Magnetic behavior | Generally nonmagnetic in the annealed condition; magnetic response may vary with processing and cold work |
High-temperature oxidation resistance | Commonly reported up to approximately 1,148°C (2,100°F), subject to atmosphere and operating conditions |
Operating-temperature clarification: The upper oxidation-resistance rating is not a universal continuous-use temperature limit. Actual service capability depends on furnace atmosphere, applied stress, component geometry, thermal cycling, and the required service life.
The following figures are indicative reference values for annealed or solution-treated material. They should not be regarded as guaranteed minimum values for every product form.
Property | Indicative reference value |
Ultimate tensile strength, Rm | Approximately 520 MPa or higher in some reference datasets |
0.2% proof strength, Rp0.2 | Approximately 240 MPa or higher in some reference datasets |
Elongation, A5 | Approximately 30% or higher in some reference datasets |
The values above are retained as preliminary reference figures rather than universal specification requirements. For design approval, buyers should obtain mechanical-property requirements applicable to the exact product form, thickness or diameter, heat-treatment condition, and governing standard.
At room temperature, the tensile and proof strengths of annealed Incoloy 330 may appear modest compared with precipitation-hardened alloys. This is consistent with its intended design philosophy.
Its principal advantages emerge under high-temperature furnace conditions, where oxidation resistance, carburization resistance, microstructural stability, and thermal-cycle durability can be more important than maximizing room-temperature strength.
For furnace baskets and fixtures, component geometry, loading, temperature gradients, and the frequency of quenching must also be considered. Material selection should therefore be based on the complete service environment rather than a single mechanical-property value.
Selecting a heat-resistant alloy requires more than comparing nominal chemical compositions. Carburization resistance, oxidation resistance, thermal shock resistance, high-temperature strength, aqueous corrosion resistance, and product form must all be evaluated against the intended application.
The following comparison provides a practical starting point for material selection.
Material | Carburization resistance | Thermal-cycle performance | High-temperature strength | Aqueous corrosion resistance | Typical applications |
Incoloy 330 (UNS N08330) | Excellent in suitable carburizing environments | Excellent for many furnace applications | Good | Environment-dependent; not primarily an aqueous-corrosion alloy | Carburizing furnace baskets, muffles, retorts, radiant tubes |
Incoloy 800 (UNS N08800) | Good in many high-temperature environments; performance depends on furnace chemistry | Good | Good | Generally useful in selected aqueous and high-temperature environments | Furnace components, heat exchangers, process equipment |
310S stainless steel | More limited in severe carburizing environments | Application-dependent | Good for many heat-resistant applications | Good in selected environments; not universally corrosion-resistant | Furnace internals, heat-resistant supports, general high-temperature components |
HK/HP centrifugal-cast heat-resistant alloys | Often excellent in their intended high-temperature process environments | Depends strongly on casting grade, geometry, and thermal cycling | Often well suited to high-temperature creep and stress requirements | Generally not selected primarily for aqueous corrosion resistance | Reforming and pyrolysis furnace tubes, high-temperature pressure-bearing cast components |
Inconel 600 (UNS N06600) | Good in many high-temperature environments, depending on chemistry | Good in many applications | Good | Often selected for corrosion resistance in specific environments | Furnace equipment, heat-treatment components, chemical-processing equipment |
The ratings above are qualitative and application-dependent. They are not a substitute for comparative test data under identical operating conditions.
Incoloy 330 is particularly attractive when a component must withstand both carbon-rich furnace atmospheres and repeated thermal cycling.
Its silicon-containing chemistry, high nickel content, and stable austenitic structure make it well suited to many heat-treatment applications. However, it is not automatically the best choice for every furnace component.
● Choose Incoloy 330 when carburization resistance and thermal-cycle durability are primary requirements.
● Consider Incoloy 800 for general high-temperature components where the atmosphere and service requirements do not specifically favor Alloy 330.
● Consider 310S stainless steel for less demanding heat-resistant applications where its performance is sufficient.
● Consider HK/HP cast alloys for appropriately designed high-temperature process tubes requiring creep strength and pressure-bearing capability.
● Consider Inconel 600 when its combination of high-temperature and environment-specific corrosion properties offers a better fit.
A reliable comparison should account for actual furnace chemistry, service temperature, component loading, thermal gradients, expected life, fabrication costs, and replacement frequency.
Incoloy 330 is widely used in industrial thermal-processing equipment because it combines high-temperature oxidation resistance, carburization resistance, and thermal-cycle durability.
Furnace baskets and heat-treatment boxes repeatedly expose their surfaces to high temperatures and, depending on the process, carbon-rich atmospheres. Conventional materials may experience carbon ingress, embrittlement, deformation, or premature failure.
Incoloy 330 is often selected for these components because it offers a useful combination of carburization resistance and resistance to repeated heating and cooling.
Muffles and retorts contain or isolate materials during heat-treatment and thermal-processing operations. Their service life depends on resistance to oxidation, process-gas chemistry, thermal gradients, and repeated temperature changes.
Incoloy 330 is a suitable candidate for many such applications, particularly where carburization resistance is a major selection criterion.
Fixture racks, support frames, heat-treatment baskets, and quenching equipment may experience frequent temperature changes, mechanical loading, and liquid-quench thermal shock.
Incoloy 330's resistance to thermal shock makes it useful for appropriately designed fixtures operating within suitable temperature and loading limits.
Radiant tubes, furnace internals, conveyor components, and related heat-resistant parts operate under elevated temperatures and may be exposed to oxidizing, reducing, or carburizing atmospheres.
Incoloy 330 can be considered where its oxidation resistance, metallurgical stability, and fabrication characteristics meet the required service conditions. For heavily loaded or pressure-bearing components, creep and stress-rupture data must also be evaluated.
Incoloy 330 may also be used in selected heat exchangers, industrial heating systems, and other elevated-temperature equipment.
Its suitability depends on the actual process medium. The alloy's principal advantage is heat resistance rather than universal resistance to corrosive aqueous solutions.
Sulfur-bearing compounds, lead, other low-melting-point contaminants, and unfavorable process-gas chemistry may accelerate degradation or interfere with protective surface scales.
To improve service life:
● Maintain stable and appropriately controlled furnace atmospheres.
● Minimize contamination from fuels, process gases, residues, and workpieces.
● Evaluate sulfur-bearing environments and other potentially aggressive impurities.
● Control thermal cycling and quenching practices where the process permits.
● Inspect components periodically for oxidation, carburization damage, distortion, cracking, and loss of section thickness.
The correct alloy is only one part of a successful furnace design. Atmosphere management, component geometry, fabrication quality, and operating procedures are equally important.
Not in every application.
Both alloys are nickel-iron-chromium austenitic alloys used in high-temperature environments, but their compositions and performance characteristics differ. Incoloy 330 is particularly well suited to applications requiring resistance to carburization combined with repeated thermal cycling.
Incoloy 800 may be suitable for general high-temperature service where the furnace atmosphere does not require the specific advantages of Alloy 330. Before substituting one alloy for the other, compare the applicable chemical specifications, operating atmosphere, mechanical requirements, and expected service life.
Incoloy 330 is not a precipitation-hardening alloy and cannot be strengthened by conventional solution-and-aging treatments in the same way as A-286 or Alloy 925.
Heat treatment may be used to establish or restore an appropriate metallurgical condition, depending on the product form and fabrication process. It should not be assumed that aging will increase its strength.
Cracking can result from several interacting factors, including:
● Repeated thermal cycling and thermal fatigue.
● Excessive temperature gradients or severe quenching conditions.
● Mechanical overloading, distortion, or stress concentration.
● Aggressive furnace chemistry or contamination that damages protective scales.
● Fabrication defects, weld-related issues, or unsuitable component design.
Sulfur-bearing contaminants and low-melting-point metals may contribute to accelerated degradation, but cracking should not automatically be attributed to contamination alone.
A failure investigation should review furnace operating records, component loading, crack location, metallography, surface deposits, and material certification.
It depends on the process medium, temperature, concentration, and corrosion mechanism.
Incoloy 330 is primarily valued for high-temperature service. It should not automatically be selected as the primary material for aggressive aqueous chemical environments.
For applications involving acids, chlorides, or other corrosive solutions, alternatives such as Alloy 825 or Alloy 926 may be worth evaluating. The final selection must be based on corrosion data for the actual medium and operating conditions.
Incoloy 330 is commonly supplied in annealed or solution-treated conditions appropriate to the product specification and intended application.
Depending on the supplier and applicable standards, available product forms may include:
● Plate and sheet
● Strip and coil
● Round bar and rod
● Wire and wire rod
● Pipe and tube
● Forgings and forging stock
● Selected fittings and fabricated components
Availability varies by size, specification, manufacturing route, and stock level. Buyers should confirm the required product form and delivery condition before placing an order.
Incoloy 330 can be welded and fabricated using suitable procedures for nickel-chromium-iron austenitic alloys. However, welding consumables, heat input, interpass temperature, joint preparation, and post-weld requirements must be selected for the specific application.
The welding procedure should follow the applicable material manufacturer's recommendations and relevant construction code. Matching or specifically qualified filler metals should be used rather than assuming that any filler labeled “330” is suitable.
For forming and machining, fabrication parameters should be selected with consideration for the alloy's work-hardening behavior and the requirements of the finished component.
To obtain an accurate quotation for Incoloy 330, buyers should provide:
● Required product form: plate, sheet, bar, tube, strip, wire, or forging.
● Dimensions, tolerances, and total quantity.
● Required material specification and delivery condition.
● Chemical composition and mechanical-property requirements, where specified.
● Required inspection documents and material traceability.
● Intended application and any special fabrication requirements.
Providing this information helps suppliers confirm material compliance, product availability, lead time, and suitability for the intended service.
Bozhong Metal supplies Incoloy 330 products for industrial heating, heat treatment, and high-temperature processing applications.
Available product forms, subject to current stock and production arrangements:
● Incoloy 330 plate and sheet
● Incoloy 330 round bar and rod
● Incoloy 330 pipe and tube
● Incoloy 330 strip and wire
● Incoloy 330 forgings and other agreed product forms
Supply and quality support:
● Domestic mill supply and imported material sourcing options.
● Shanghai and Wuxi warehouse arrangements, subject to stock availability.
● Standard-size dispatch targets of approximately 24–72 hours for eligible in-stock products.
● Material test certificates and chemical-composition verification, subject to the order and supplied material documentation.
● Spectrometric verification by arrangement.
● Cut-to-size services and small-quantity orders, subject to product availability and processing requirements.
For a quotation, please specify the required dimensions, product form, quantity, material standard, and delivery condition. Our team can help assess available supply options against your technical and procurement requirements.
Incoloy 330 (UNS N08330) is a proven candidate for demanding heat-treatment environments where carburization resistance, oxidation resistance, and thermal-cycle durability must work together.
Its nickel-rich austenitic matrix and silicon-containing chemistry make it particularly valuable for furnace baskets, muffles, retorts, radiant tubes, and related high-temperature components.
For procurement and engineering decisions, the key is to verify the actual chemical composition, product specification, mechanical properties, operating atmosphere, and fabrication requirements rather than relying on the alloy designation alone.
Contact Bozhong Metal for Incoloy 330 material inquiries, technical documentation, and quotation support.
The technical information in this guide is compiled from published Alloy 330 and RA330 technical literature and general material-selection references. Commonly referenced sources include UNS N08330 specifications and manufacturer technical data sheets.
Chemical composition, mechanical properties, physical properties, and service-temperature capability may vary with the applicable standard, product form, processing route, and operating conditions. Final acceptance and design decisions should be based on the governing specification and the material test certificate supplied with the actual product.
