Inconel 800

Introduction to Inconel 800

Inconel 800 is a solid-solution-strengthened, nickel-iron-chromium alloy engineered for superior performance in high-temperature, corrosive environments. It is especially suited for structural components exposed to prolonged heat, oxidation, carburization, and stress—making it a preferred material in power generation, chemical processing, and petrochemical industries.

Unlike precipitation-hardened superalloys, Inconel 800 maintains dimensional stability and mechanical integrity through solid-solution strengthening. Its stable austenitic structure, high nickel content (~30–35%), and chromium (~19–23%) composition provide exceptional resistance to chloride stress-corrosion cracking and intergranular attack. The alloy performs reliably at temperatures up to 800–900°C in oxidizing and reducing environments.

Chemical, Physical, and Mechanical Properties of Inconel 800

Inconel 800 (UNS N08800 / ASTM B409 / ASME SB409) is typically supplied in annealed or cold-drawn condition and used in fabricated and CNC-machined components in high-temperature service applications.

Chemical Composition (Typical)

Physical Properties

Mechanical Properties (Annealed Condition)

Key Characteristics of Inconel 800

• High-Temperature Strength: Maintains mechanical stability and load-bearing capacity up to 800–900°C in service.

• Excellent Oxidation and Carburization Resistance: Forms stable oxide layers and resists carbon diffusion in furnace and reactor environments.

• Structural Stability: Resists embrittlement during long-term thermal exposure due to its balanced Ni-Fe-Cr matrix.

• CNC Machinability: Easily CNC machined in the annealed condition with precise dimensional control (±0.01–0.02 mm) and excellent finish (Ra ≤ 0.8 µm).

CNC Machining Challenges and Solutions for Inconel 800

Machining Challenges

Moderate Work Hardening

• Inconel 800 has a moderate work hardening rate, requiring proper feeds and sharp cutting edges to avoid surface damage.

Built-Up Edge (BUE) Formation

• Tends to form BUE during low-speed machining, affecting surface integrity and tool life if cutting parameters are not optimized.

Tool Wear

• Extended machining at elevated surface temperatures leads to flank wear without high-performance coatings or proper coolant delivery.

Optimized Machining Strategies

Tool Selection

Cutting Parameters (ISO 3685)

Surface Treatment for Machined Inconel 800 Parts

Hot Isostatic Pressing (HIP)

HIP can enhance the mechanical properties and eliminate internal defects in Inconel 800 cast components prior to CNC finishing.

Heat Treatment

Heat Treatment stabilizes the microstructure and ensures optimal mechanical performance through annealing at 980–1000°C followed by air cooling.

Superalloy Welding

Superalloy Welding is well-suited for Inconel 800 using TIG or MIG processes with controlled filler materials to reduce grain boundary sensitization.

Thermal Barrier Coating (TBC)

TBC Coating extends thermal fatigue life by applying ceramic YSZ layers (up to 250 µm) to resist hot gas exposure.

Electrical Discharge Machining (EDM)

EDM is ideal for forming complex features such as threads, pockets, and blind holes with ±0.01 mm tolerance in hardened or thick-walled parts.

Deep Hole Drilling

Deep Hole Drilling supports accurate internal cooling and gas flow channels with L/D ratios up to 50:1 in pressure-retaining components.

Material Testing and Analysis

Material Testing includes intergranular corrosion testing (ASTM G28), mechanical testing (ASTM E8), and grain structure evaluation.

Industry Applications of Inconel 800 Components

Nuclear Reactors

• Steam generator tubing, core baskets, and support grids.

• Resists chloride stress corrosion and intergranular attack under radiated conditions.

Chemical and Petrochemical Processing

• Heat exchanger shells, reformer outlet manifolds, and transfer piping.

• Withstands carburizing and oxidizing environments at high temperatures.

Industrial Furnaces

• Trays, fixtures, and muffles for heat-treating and carburizing operations.

• Maintains dimensional stability and strength over repeated thermal cycles.

Aerospace

• Exhaust components, thermocouple sheaths, and gas turbine liners.

• Operates reliably under thermal shock and scaling environments up to 900°C.

FAQs

1. What makes Inconel 800 more suitable than stainless steel in high-temperature corrosive environments?

2. What machining strategies prevent work hardening and tool wear when processing Inconel 800?

3. Can Inconel 800 be used in pressure vessels or nuclear steam generators?

4. How does Neway ensure the dimensional and structural integrity of Inconel 800 parts?

5. What heat treatment and post-processing steps optimize Inconel 800’s creep and oxidation resistance?