Keeping the Heat in Check: Alloy 230 Bars for High-Temperature Recuperators

Introduction: Reclaiming Heat, Demanding Reliability

In today’s industrial push for energy efficiency, heat recovery systems like recuperators play a vital role. Found in furnaces, gas turbines, chemical reactors, and metallurgical lines, recuperators recycle waste heat from exhaust gases to preheat incoming fluids—slashing fuel consumption and emissions.

But to perform this task continuously at temperatures between 800°C and 1150°C, their internal supports—particularly bars, rods, and braces—must withstand severe thermal and oxidative stress. It’s here that conventional materials often falter, and Haynes® Alloy 230 bars rise to the occasion.

High-Temperature Recuperators and Structural Needs

Modern recuperators use arrays of heat exchanger tubes arranged in compact, high-surface-area structures. These arrays are held together by metallic rods, cross braces, and tube sheets—components that:

• Must maintain dimensional stability at extreme temperatures

• Resist oxidation, carburization, and thermal fatigue

• Allow thermal expansion and contraction without cracking

• Survive 20,000+ operating hours without degradation

The wrong material choice for these bars leads to:

• Core misalignment

• Tube sagging or rupture

• Shutdowns for repair or worse, catastrophic failure

For such roles, Haynes 230 bars offer a near-perfect balance of properties.

Why Haynes 230? Built for the Burn

Haynes 230 (UNS N06230) is a Ni-Cr-W-Mo alloy engineered for strength, stability, and oxidation resistance at high temperatures. Developed for gas turbine combustion liners, it has found new life in process heating and waste heat recovery.

Typical Composition:

• Nickel (Ni): ~57%

• Chromium (Cr): ~22%

• Tungsten (W): ~14%

• Molybdenum (Mo): ~2%

• Trace amounts: Cobalt, Iron, Silicon

Key Properties:

• Superior oxidation resistance up to 1149°C (2100°F)

• High creep strength for long-duration loads

• Excellent thermal fatigue resistance

• Weldability and fabricability suitable for complex bar geometries

The addition of tungsten significantly improves creep rupture strength and reinforces the Cr₂O₃ protective layer, enabling Alloy 230 to resist oxidation longer than Inconel 601 or 800HT.

Case Study: U.S. Chemical Plant Heat Recovery Unit

At a large petrochemical complex in Texas, a recuperator supporting frame used Inconel 601 rods to suspend hot gas coils. These rods:

• Softened over time at 1050°C

• Deformed under thermal cycling

• Required replacement every 18–24 months

Solution: Engineers switched to Alloy 230 bars, custom-machined and aged for stress tolerance.

Results:

• Doubling of rod lifespan (now ≥ 4 years)

• Reduced downtime by 50%

• No warping or scaling observed during inspections

• Fabrication and welding achieved without cracking or post-weld distortion

Plant maintenance supervisor:

“Alloy 230 has become our go-to for anything exposed to over 1000°C. It handles the heat and stays in shape.”

Thermal Oxidation and Creep Performance

Alloy 230 excels in high-temperature environments due to:

• Formation of a dense Cr₂O₃ layer, reinforced by tungsten additions

• Resistance to grain growth under thermal exposure

• Slow oxide growth rate, preventing spallation or mass loss

Oxidation Resistance Data (in air at 1100°C for 1000h):

Material	Weight Gain (mg/cm²)	Surface Spallation
Inconel 601	45–60	Moderate
HR-120	38–50	Some spallation
Alloy X	32–48	Slight
Haynes 230	<30	Minimal

In terms of creep rupture strength, Alloy 230 provides:

• 24 MPa stress tolerance at 982°C for 10,000 hours
• Sustained structural performance in cyclic thermal loads

This makes it ideal for support bars under continuous thermal stress.

Fabrication and Maintenance Advantages

Alloy 230 bars are:

• Weldable using standard GTAW (TIG) and automated methods

• Machinable using carbide tooling and flood coolant

• Resilient against thermal shock and phase instability

It offers excellent compatibility with other nickel alloys and furnace-grade steels, allowing integration into hybrid designs. Its low sensitivity to embrittlement makes it perfect for welded support frames and threaded braces inside hot zones.

Comparison with Other Heat-Resistant Alloys

Property	Haynes 230	Alloy X	Inconel 601	HR-120
Max Use Temp (°C)	1149	1093	1100	1120
Oxidation Resistance	Excellent	Very Good	Good	Good
Creep Strength (1000°C)	Excellent	Good	Moderate	Moderate
Weldability	Excellent	Good	Moderate	Moderate
Cost	High	Moderate	Low	Moderate
Typical Service Life	4–6 years	2–4 years	2 years	3–4 years

Verdict: For long-life high-temperature performance, Haynes 230 outperforms most commercial heat-resistant alloys when structural integrity and oxidation resistance are critical.

Use in Broader High-Temperature Systems

Beyond recuperators, Alloy 230 bars are used in:

• Syngas generator frames

• Biomass burner coil supports

• High-temperature reformers

• Cement kilns and waste incinerators

• Thermal oxidizer grates and frames

Its performance also makes it suitable for next-generation hydrogen furnaces and glass industry reheating chambers.

Conclusion: Structure You Can Trust in the Heat

In extreme industrial settings where temperatures exceed 1000°C, failure is never just inconvenient—it’s dangerous and costly. Haynes Alloy 230 bars deliver unmatched longevity, dimensional stability, and resistance to oxidation, making them ideal for structural components in recuperators and beyond.

When the heat never stops, Haynes 230 keeps the structure intact.