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When selecting high-performance alloys for critical applications in industries such as aerospace, chemical processing, and marine engineering, Hastelloy and Inconel are two of the most recognized names. Both are known for their exceptional resistance to harsh environments, but they have distinct differences that make them suitable for different conditions. This article will provide a detailed comparison of Hastelloy and Inconel, helping engineers, designers, and purchasing specialists make informed decisions.
Overview of Hastelloy
Hastelloy is a trademarked name for a family of corrosion-resistant metal alloys primarily consisting of nickel, with varying amounts of molybdenum, iron, chromium, cobalt, and other elements. It is particularly renowned for its excellent resistance to oxidizing and reducing agents, making it ideal for chemical processing applications.
Overview of Inconel
Inconel refers to a family of austenitic nickel-chromium-based superalloys. Known for their ability to withstand extreme temperatures and maintain mechanical integrity under severe conditions, Inconel alloys are commonly used in aerospace, marine, and chemical processing industries.
Chemical Composition Comparison
| Element | Hastelloy C-276 (%) | Inconel 625 (%) |
|---|---|---|
| Nickel (Ni) | Min 57 | 58.0 |
| Chromium (Cr) | 14.5 - 16.5 | 20.0 - 23.0 |
| Molybdenum (Mo) | 15.0 - 17.0 | 8.0 - 10.0 |
| Iron (Fe) | 4.0 - 7.0 | Balance |
| Carbon (C) | 0.01 Max | 0.10 Max |
| Other Elements | W, Co | Nb, Ta |
Mechanical Properties
| Property | Hastelloy C-276 | Inconel 625 |
|---|---|---|
| Tensile Strength (MPa) | 760 | 827 |
| Yield Strength (MPa) | 283 | 414 |
| Elongation (%) | 60 | 30 |
| Hardness (HRB) | 100 | 96 |
Corrosion Resistance
Hastelloy C-276 excels in extremely aggressive chemical environments, including strong oxidizers and reducers. It shows superior resistance to localized corrosion, such as pitting and crevice corrosion. Inconel 625, while also corrosion-resistant, is particularly suited for oxidizing environments and seawater applications but may not perform as well in highly reducing conditions compared to Hastelloy.
Temperature Resistance
| Alloy | Maximum Service Temperature |
|---|---|
| Hastelloy C-276 | up to 1038°C (1900°F) |
| Inconel 625 | up to 1093°C (2000°F) |
Applications
| Industry | Hastelloy Applications | Inconel Applications |
|---|---|---|
| Chemical Processing | Heat exchangers, reactors | Distillation columns, reaction vessels |
| Aerospace | Exhaust ducts | Jet engine components |
| Marine | Pumps and valves | Submarine hulls |
| Energy | Pollution control | Nuclear reactor cores |
Weldability
Both Hastelloy and Inconel are weldable, but special techniques must be used to prevent cracking and maintain corrosion resistance. Hastelloy C-276 is known for its exceptional weldability compared to many other high-performance alloys, while Inconel 625 also offers excellent weldability but may require post-weld heat treatment for certain applications.
Cost Comparison
| Material | Relative Cost |
|---|---|
| Hastelloy C-276 | High |
| Inconel 625 | Moderate to High |
Summary Table
| Category | Hastelloy C-276 | Inconel 625 |
|---|---|---|
| Corrosion Resistance | Excellent, even in reducing environments | Excellent, best in oxidizing environments |
| Temperature Resistance | Very High | Extremely High |
| Mechanical Strength | Good | Excellent |
| Weldability | Exceptional | Excellent |
| Cost | Higher | Moderate to Higher |
Frequently Asked Questions
1. Which is better for chemical processing, Hastelloy or Inconel?
For highly aggressive chemical environments, Hastelloy C-276 is generally better due to its superior resistance to reducing agents and localized corrosion.
2. Which alloy can withstand higher temperatures, Hastelloy or Inconel?
Inconel 625 can withstand slightly higher maximum service temperatures, up to 1093°C (2000°F), compared to Hastelloy C-276's limit of about 1038°C (1900°F).
3. Is Hastelloy more expensive than Inconel?
Yes, Hastelloy C-276 is generally more expensive than Inconel 625, largely due to its higher molybdenum content and specialized properties.