Inconel vs Hastelloy: Nickel Alloy Selection for Extreme Environments
When engineering components for extreme temperatures, corrosive environments, or high-stress applications, two nickel superalloy families dominate the selection: Inconel and Hastelloy. While both offer exceptional performance beyond the capability of stainless steels, they excel in different conditions. This guide compares these critical materials to help you make the right selection for your application.
Understanding the fundamental differences between Inconel and Hastelloy alloys can mean the difference between decades of reliable service and premature failure in demanding applications like aerospace, chemical processing, and power generation.
What Are Inconel and Hastelloy?
Inconel is a registered trademark of Special Metals Corporation, covering a family of austenitic nickel-chromium-based superalloys designed primarily for high-temperature applications with excellent oxidation resistance.
Hastelloy is a registered trademark of Haynes International, covering a family of nickel-molybdenum or nickel-molybdenum-chromium alloys designed primarily for exceptional corrosion resistance in aggressive chemical environments.
Key Alloy Comparisons
| Property | Inconel 625 | Inconel 718 | Hastelloy C-276 | Hastelloy B-3 |
|---|---|---|---|---|
| Nickel (Ni) | 58% min | 50-55% | 57% min | 65% min |
| Chromium (Cr) | 20-23% | 17-21% | 14.5-16.5% | 1.0-3.0% |
| Molybdenum (Mo) | 8-10% | 2.8-3.3% | 15-17% | 27-30% |
| Max Temp (°C) | 980 | 700 | 540 | 400 |
| Tensile Strength | 830 MPa | 1300 MPa | 790 MPa | 760 MPa |
| Primary Strength | Oxidation resistance | High strength | Corrosion resistance | HCl resistance |
Temperature Performance
Inconel alloys generally outperform Hastelloy in high-temperature applications:
- Inconel 625: Maintains strength up to 980°C (1800°F), excellent oxidation resistance
- Inconel 718: Highest strength of common nickel alloys up to 700°C, age-hardenable
- Inconel 600: Excellent carburization resistance up to 1100°C
Hastelloy alloys are primarily designed for corrosion resistance and typically operate below 540°C (1000°F).
Corrosion Resistance Comparison
| Corrosive Environment | Inconel 625 | Hastelloy C-276 | Hastelloy B-3 |
|---|---|---|---|
| Hydrochloric Acid (HCl) | Fair | Good | Excellent |
| Sulfuric Acid (H₂SO₄) | Fair | Excellent | Good |
| Phosphoric Acid | Good | Excellent | Good |
| Chloride Pitting | Excellent | Excellent | Good |
| Oxidizing Acids | Excellent | Good | Poor |
| Stress Corrosion Cracking | Excellent | Excellent | Good |
| Seawater | Excellent | Excellent | Fair |
Application Selection Guide
Choose Inconel when:
- Operating temperatures exceed 540°C (1000°F)
- Oxidation resistance is the primary requirement
- High mechanical strength at temperature is critical
- Applications: Jet engine components, gas turbines, rocket engines, furnace components, heat treating equipment
Choose Hastelloy when:
- Severe corrosion in chemical processing environments
- Reducing acid conditions (HCl, H₂SO₄)
- Mixed oxidizing and reducing conditions
- Applications: Chemical reactor vessels, pollution control equipment, pulp & digesters, FGD systems
Weldability and Fabrication
Both alloy families are weldable, but with important differences:
- Inconel: Generally easier to machine, but work-hardens rapidly. GTAW (TIG) recommended for welding.
- Hastelloy: C-276 is susceptible to grain boundary precipitation in the heat-affected zone. Post-weld solution annealing may be required.
- Cost consideration: Both are premium materials, typically 5-10x the cost of stainless steel
Availability and Supply
Common forms available for both alloy families:
- Seamless pipe and tube
- Plate, sheet, and strip
- Round bar and flat bar
- Welding wire and electrodes
- Fittings and flanges
Conclusion
The choice between Inconel and Hastelloy depends primarily on whether your application demands high-temperature strength (Inconel) or superior corrosion resistance (Hastelloy). In many chemical processing applications, Hastelloy C-276 is the go-to alloy for its versatility across oxidizing and reducing conditions. For aerospace and high-temperature power generation, Inconel 625 or 718 typically prevails.
Need nickel alloy products? CoreMetal Steel supplies Inconel and Hastelloy in pipe, plate, bar, and fittings. Contact Tracy at tracy@coremetalsteel.com or +86 18291910632 for material recommendations and competitive pricing.