Hastelloy and Inconel are two prominent families of nickel-based superalloys known for their exceptional corrosion resistance, high-temperature strength, and versatility in various demanding applications across industries. Engineers and material specialists often face the decision of choosing between these alloys based on specific performance requirements. This article explores the differences and similarities between Hastelloy and Inconel, focusing on their properties, chemical compositions, applications, and suitability for different environments.
Chemical Composition
The chemical compositions of Hastelloy and Inconel alloys are tailored to achieve specific mechanical, thermal, and corrosion-resistant properties. Below are the compositions for three grades from each family arranged for comparison:
Hastelloy Alloys
| Grade | Chemical Composition |
|---|---|
| Hastelloy C-276 | Ni: Bal., Cr: 14.5-16.5%, Mo: 15-17%, Fe: 4-7%, W: 3-4.5%, Co: 2.5%, Mn: 1.0%, V: 0.35% |
| Hastelloy C-22 | Ni: Bal., Cr: 20-22.5%, Mo: 12.5-14.5%, Fe: 2-6%, W: 2.5-3.5%, C: 0.015%, Co: 2.5% |
| Hastelloy X | Ni: Bal., Cr: 20.5-23%, Mo: 8-10%, Fe: 17-20%, Co: 0.5-2.5%, W: 0.2-1.0%, C: 0.05-0.15% |
Inconel Alloys
| Grade | Chemical Composition |
|---|---|
| Inconel 600 | Ni: 72%, Cr: 14-17%, Fe: 6-10%, Cu: 0.5%, Mn: 1%, Si: 0.5% |
| Inconel 625 | Ni: 58%, Cr: 20-23%, Mo: 8-10%, Nb+Ta: 3.15-4.15%, Fe: 5%, Al: 0.4%, Ti: 0.4%, C: 0.1% |
| Inconel 718 | Ni: 52.5%, Cr: 19%, Mo: 3%, Nb+Ta: 5.1%, Ti: 0.9%, Al: 5.5%, C: 0.08% |
Properties Comparison
The properties of Hastelloy and Inconel alloys determine their performance in various environments, including high temperatures, corrosive atmospheres, and mechanical stress. Here’s a comparison of their key properties:
| Property | Hastelloy C-276 | Hastelloy C-22 | Hastelloy X |
|---|---|---|---|
| Temperature Resistance | Up to 1093°C (2000°F) | Up to 1093°C (2000°F) | Up to 1204°C (2200°F) |
| Corrosion Resistance | Excellent | Excellent | Good |
| Mechanical Strength | High | High | High |
| Weldability | Good | Good | Good |
| Fabricability | Good | Good | Good |
| Magnetic Properties | Non-magnetic | Non-magnetic | Non-magnetic |
| Applications | Chemical processing, aerospace | Chemical processing, aerospace | Gas turbine engines, industrial heating |
| Property | Inconel 600 | Inconel 625 | Inconel 718 |
|---|---|---|---|
| Temperature Resistance | Up to 1177°C (2150°F) | Up to 980°C (1800°F) | Up to 704°C (1300°F) |
| Corrosion Resistance | Excellent | Excellent | Excellent |
| Mechanical Strength | Good | High | High |
| Weldability | Excellent | Good | Good |
| Fabricability | Good | Good | Good |
| Magnetic Properties | Non-magnetic | Non-magnetic | Non-magnetic |
| Applications | Chemical and food processing | Aerospace, marine | Aerospace, gas turbines |
Detailed Analysis
Hastelloy Alloys
Hastelloy C-276:
- Chemical Composition: Primarily nickel with significant chromium, molybdenum, and tungsten.
- Properties: Exceptional resistance to oxidizing and reducing environments, ideal for aggressive chemical processing.
- Applications: Widely used in chemical reactors, pollution control equipment, and sour gas wells.
Hastelloy C-22:
- Chemical Composition: Higher chromium and molybdenum content than C-276, with enhanced resistance to pitting and crevice corrosion.
- Properties: Superior resistance to both oxidizing and reducing acids, suitable for pharmaceutical and chemical processing applications.
- Applications: Used in pharmaceutical manufacturing, chlorination systems, and pulp and paper production.
Hastelloy X:
- Chemical Composition: High nickel content with significant additions of chromium, molybdenum, iron, cobalt, and tungsten.
- Properties: Excellent oxidation resistance at elevated temperatures, suitable for gas turbine applications and industrial furnace components.
- Applications: Aerospace components, industrial furnace liners, and gas turbine engine seals.
Inconel Alloys
Inconel 600:
- Chemical Composition: Predominantly nickel with substantial chromium and iron content.
- Properties: Excellent resistance to oxidation, corrosion, and stress-corrosion cracking at high temperatures.
- Applications: Used in furnace components, chemical plant equipment, and heat treating fixtures.
Inconel 625:
- Chemical Composition: Significant nickel content with additions of chromium, molybdenum, niobium, and tantalum.
- Properties: Superior fatigue strength, excellent weldability, and resistance to a wide range of corrosive environments.
- Applications: Aerospace applications, marine environments, and chemical processing industries.
Inconel 718:
- Chemical Composition: High nickel and chromium content with additions of molybdenum, niobium, titanium, and aluminum.
- Properties: Exceptional strength and toughness at high temperatures, excellent creep-rupture strength.
- Applications: Gas turbine engines, aerospace components, and cryogenic storage tanks.
Conclusion
Hastelloy and Inconel alloys represent two leading families of nickel-based superalloys designed to withstand extreme environments and demanding applications. The choice between Hastelloy and Inconel depends on specific requirements such as temperature resistance, corrosion resistance, mechanical strength, and weldability. Hastelloy alloys, including C-276, C-22, and X, excel in corrosive chemical environments and high-temperature applications. Inconel alloys, such as 600, 625, and 718, are preferred for their strength, oxidation resistance, and reliability in aerospace and marine applications.
By understanding the distinct properties and applications of each alloy, engineers and materials specialists can make informed decisions to optimize performance, durability, and cost-effectiveness in various industrial sectors.
This comprehensive comparison highlights the strengths and applications of Hastelloy and Inconel alloys, providing valuable insights for selecting the most suitable alloy based on specific engineering requirements and environmental conditions.