Hastelloy alloy is a widely used superalloy known for its outstanding resistance to high temperatures and corrosion. It comes in various grades, each with a distinct chemical composition.
You might wonder:
1. What common features do all Hastelloy alloys share?
2. How does Hastelloy differ from other superalloys?
3. Why are there so many different grades of Hastelloy?
This article will address all your questions and clarify the distinctions between these alloys.
Hastelloy refers to a range of nickel-chromium-molybdenum or nickel-molybdenum alloys, with nickel and molybdenum being the key elements.
Nickel is essential in all superalloys, stabilizing the crystal structure at high temperatures and providing some corrosion resistance. It is the source of the high-temperature resistance found in superalloys.
Molybdenum, a solid solution strengthening element, significantly enhances corrosion resistance, particularly against reducing environments. It also greatly strengthens the alloy’s base structure.
In summary, Hastelloy is a superalloy known for its excellent resistance to reducing corrosion and superior strength compared to other solid solution alloys.
Hastelloy alloys are commonly categorized into three families: B, C, and G. Additionally, there are some less common variants such as Hastelloy N, S, W, and X.
What Is Hastelloy Made Of?
Nickel, chromium, and molybdenum are crucial elements in superalloys, and their ratios determine the distinct properties of these materials. In Hastelloy alloys, the proportions of these elements vary across different grades.
Nickel primarily influences the high-temperature resistance of Hastelloy alloys. Generally, higher nickel content enhances the alloy’s ability to withstand high temperatures.
Chromium and molybdenum both contribute to the corrosion resistance of the alloy, but in different ways. Chromium serves as an antioxidant, while molybdenum acts as an anti-reduction agent. The ratio of chromium to molybdenum determines whether the alloy is more focused on resisting oxidative or reductive corrosion.
In the Hastelloy family:
- The Hastelloy B series has the highest molybdenum content and the lowest chromium content, making it highly resistant to reductive corrosion.
- The Hastelloy C series has a balanced content of molybdenum and chromium, offering comprehensive corrosion resistance.
- The Hastelloy G series has a higher chromium content than molybdenum, emphasizing oxidation resistance.
Chemical Composition of Hastelloy Alloys
Hastelloy is a family of nickel-based superalloys that incorporate molybdenum. Nickel imparts excellent high-temperature resistance to the alloy, while chromium and molybdenum enhance its overall corrosion resistance. Additional elements contribute unique properties to the alloy, further optimizing its performance in various applications.
| Composition | Content Range | Effect | Typical Alloy |
|---|---|---|---|
| Nickel | 37% ~ 80% | High Temperature Resistance | Hastelloy N |
| Chromium | 4% ~ 35% | Corrosion Resistance | Hastelloy G-35 |
| Molybdenum | 4% ~ 32% | Corrosion Resistance, Strength | Hastelloy B-3 |
| Cobalt | 0% ~ 5% | High Temperature Resistance | Hastelloy X |
| Tungsten | 0% ~ 4.5% | Strength | Hastelloy C-276 |
| Copper | 0% ~ 1.9% | Corrosion Resistance | Hastelloy C-2000 |
Hastelloy Alloys Chemical Compositions Comparison Table:
| Alloy Grade | Cr% | C% | Co% | W% | Mo% | V% | Ai% | Ti% | Nb % | Fe% | Cu% | Ni% | Other % |
| Alloy B | 0.60 | 0.1 | 1.25 | – | 28 | 0.3 | – | – | – | 5.5 | – | balance | Mn 0.80; Si 0.70 |
| Alloy B-2 | 1.00 | 0.02 | 1 | – | 26.0-30.0 | – | – | – | – | 2 | – | balance | Mn 1.0, Si 0.10 |
| Alloy C-276 | 14.0-16.5 | 0.02 | 2.5 | 3.0-4.5 | 15.0-17.0 | 0.35 | – | – | – | 4.0-7.0 | – | balance | Mn 1.0; Si 0.05 |
| Alloy X | 22.00 | 0.1 | 1.5 | 0.6 | 9 | – | – | 18.5 | – | – | – | balance | Mn 0.6; Si 0.60 |
| Alloy C | 16.00 | 0.07 | 1.25 | 40 | 17 | 0.3 | – | – | – | 5.75 | – | balance | Mn 1.0; Si 0.70 |
| Alloy C4 | 14.0-18.0 | 0.015 | 2 | – | 14.0-17.0 | – | – | 0..70 | – | 3 | – | balance | Mn 1.0 ; Si 0.08 |
| Alloy N | 7.00 | 0.06 | 0.25 | 0.2 | 16.5 | – | – | – | – | 3 | 0.1 | balance | Mn 0.40; Si 0.25; B 0.01 |
| Alloy S | 15.50 | 0.02 | 2 | 1 | 14.5 | 0.6 | 0.2 | – | – | 3 | – | balance | Mn 0.50; Si 0.40; B0.0009; La 0.02 |
| Alloy F | 22.00 | 0.02 | 1.25 | 0.5 | 6.5 | – | – | – | 2.1 | 21 | – | balance | Mn 1.50; Si 0.50 |
| Alloy G | 21.0-23.5 | 0.05 | 2.5 | 1 | 5.5-7.5 | – | – | – | 1.7-2.5 | 18.0-21.0 | 1.5-2.5 | balance | Mn 1.0-2.0; P0.04; Si 1.0; |
| Alloy G2 | 23.0-26.0 | 0.03 | – | – | 5.0-7.0 | – | – | 0.70-1.50 | – | balance | 0.70-1.20 | 47.0-52.0 | Mn 1.0; Si 1.0 |
| Alloy W | 5.00 | 0.06 | 1.25 | – | 24.5 | – | – | – | – | 5.5 | – | balance | Mn 0.050; Si 0.50 |
Mechanical Properties of Hastelloy
Superalloys can be categorized into solid solution strengthened alloys and precipitation strengthened alloys based on their crystal phase structure. Precipitation strengthened alloys exhibit higher strength, while solid solution strengthened alloys offer better plasticity.
Unlike Monel, Inconel, and Incoloy alloys, most Hastelloy alloys are solid solution strengthened. While they may not achieve the same strength levels as precipitation strengthened alloys, Hastelloy alloys are relatively strong among solid solution strengthened alloys. This is largely due to the significant presence of molybdenum and tungsten in their composition.
The larger atomic radii of molybdenum and tungsten compared to nickel enhance the interatomic bonding forces, thereby increasing the alloy’s strength. Consequently, the higher the molybdenum and tungsten content, the stronger the Hastelloy alloy. For example, Hastelloy B, with approximately 30% molybdenum, possesses significantly higher hardness and strength than typical solid solution strengthened alloys.
A unique member of the Hastelloy family is Hastelloy C-22HS, the only precipitation strengthened alloy in this group. It can be significantly strengthened through aging treatment.
Physical Properties of Hastelloy
| Grade | Density (g/cm3) | Melting Point (°C) | Tensile Strength (MPa) | Yield Strength (0.2 % Offset) (MPa) | Elongation (%) |
| B2 | 9.2 | 1370 | 760 | 350 | 40 |
| B3 | 9.2 | 1370 | 760 | 350 | 40 |
| C4 | 8.64 | 1350-1400 | 783 | 365 | 55 |
| C22 | 8.69 | 1399 | 690 | 310 | 45 |
| C276 | 8.89 | 1370 | 790 | 355 | 40 |
| X | 8.22 | 1355 | 655 | 240 | 35 |
Grades of Hastelloy Alloys
Along with containing nickel and molybdenum, the different grades of Hastelloy alloys may contain percentages of iron, aluminum, tungsten, carbon, titanium, chromium, and other elements.
The most widely used and versatile Hastelloy alloys are the C-grades.
1.Hastelloy B
Hastelloy B is a nickel-molybdenum based alloy that is highly resistant to corrosion in reducing environments such as hydrochloric acid and performs well under high temperature conditions.
Hastelloy B is one of numerous metal alloys sold by American Elements under the trade name AE Alloys™.
Generally immediately available in most volumes, AE Alloys™ are available as bar, ingot, ribbon, wire, shot, sheet, and foil. Ultra high purity and high purity forms also include metal powder, submicron powder and nanoscale, targets for thin film deposition, and pellets for chemical vapor deposition (CVD) and physical vapor deposition (PVD) applications.
2.Hastelloy B-2
Hastelloy B-2 also referred to as the UNS N10665/W.Nr. 2.4617 alloy.
Hastelloy B-2 is a solid solution strengthened, nickel-molybdenum alloy, with significant resistance to reducing environments like hydrogen chloride gas, and sulfuric, acetic and phosphoric acids.
Molybdenum is the primary alloying element which provides significant corrosion resistance to reducing environments. This nickel steel alloy can be used in the as-welded condition because it resists the formation of grain-boundary carbide precipitates in the weld heat-affected zone.
3.Hastelloy B-3
Hastelloy B-3 also referred to as the UNS N10675/W.Nr. 2.4600 alloy. Hastelloy B-3 alloy exhibits extremely high resistance to pure hydrochloric, hydrobromic, and sulfuric acids.
Furthermore, it has greatly improved structural stability compared with previous B-type alloys, leading to fewer concerns during welding, fabrication, and service.
Like other nickel alloys (in the mill annealed condition), it is ductile, can be formed and welded, and resists stress corrosion cracking in chloride-bearing solutions. Also, it is able to withstand fluoride-bearing media and concentrated sulfuric acid, both of which result in damage to zirconium alloys. It is used in numerous chemical process industry (CPI) applications, especially in the construction of reaction vessels for pure, reducing acid service.
4.Hastelloy C-4
Hastelloy C-4 alloy (UNS N06455) is the most (microstructurally) stable of the widely used nickel-chromium-molybdenum materials, which are well known for their resistance to many aggressive chemicals, in particular hydrochloric acid, sulfuric acid, and chlorides.
This stability means that the alloy can be welded without fear of sensitization, i.e. the nucleation and growth of deleterious, second phase precipitates in the grain boundaries of the weld heat-affected zone (HAZ).
5.Hastelloy C-22
HASTELLOY® C-22® alloy (UNS N06022) is one of the well-known and well-proven nickel-chromium-molybdenum materials, the chief attributes of which are resistance to both oxidizing and non-oxidizing chemicals, and protection from pitting, crevice attack, and stress corrosion cracking.
Its high chromium content provides much higher resistance to oxidizing media than the family standard, C-276 alloy, and imparts exceptional resistance to chloride-induced pitting, an insidious and unpredictable form of attack, to which the stainless steels are prone.
Like other nickel alloys, HASTELLOY® C-22® alloy is very ductile, exhibits excellent weldability, and is easily fabricated into industrial components. It is available in the form of plates, sheets, strips, billets, bars, wires, pipes, tubes, and covered electrodes. Typical chemical process industry (CPI) applications include reactors, heat exchangers, and columns.
6.Hastelloy C-276
Hastelloy C-276 (UNS N10276 / W.Nr. 2.4819) is a very commonly used nickel-chromium-molybdenum alloy. Among superalloys, it is known for its high molybdenum content.
First, as a corrosion-resistant element, molybdenum brings very high resistance to reductive corrosion to the alloy. By combining with nickel and chromium, Hastelloy C-276 has very good overall corrosion resistance. Compared with stainless steel, its excellent resistance to stress corrosion cracking in chloride-containing solutions cannot be replaced.
Secondly, the solid solution strengthening effect of molybdenum and tungsten elements is very obvious, and they bring very high strength to Hastelloy C-276 alloy. Like other nickel alloys, Hastelloy C-276 has good ductility. It is easy to shape and weld.
7.Hastelloy C-2000
Hastelloy C-2000 also referred to as the UNS N06200/W.Nr. 2.4675 alloy. It is unique among the versatile nickel-chromium-molybdenum materials in having a deliberate copper addition.
This provides greatly enhanced resistance to sulfuric acid. It also has a high chromium content, to maximize its resistance to oxidizing chemicals and process streams contaminated with ferric ions and dissolved oxygen.
Like other nickel alloys, it is ductile, easy to form and weld, and possesses exceptional resistance to stress corrosion cracking in chloride-bearing solutions (a form of degradation to which the austenitic stainless steels are prone). It is able to withstand a wide range of oxidizing and non-oxidizing chemicals, and exhibits outstanding resistance to pitting and crevice attack in the presence of chlorides and other halides.
8.Hastelloy G-30
Hastelloy G-30 also referred to as the UNS N06030/W.Nr. 2.4603
alloy. Alloy G-30 is a nickel-chromium-iron material highly resistant to “wet process” phosphoric acid.
P2O5 is one of the most important industrial chemicals, being the primary source of phosphorus for agrichemical fertilizers. G-30 alloy is also moderately resistant to chloride-induced localized attack, which can be a problem beneath deposits in the evaporators used to concentrate P2O5. Furthermore, G-30 alloy is less susceptible to chloride-induced stress corrosion cracking than the stainless steels.
As a result of its high chromium content, G-30 alloy is also very resistant to other oxidizing acids, such as nitric, and mixtures containing nitric acid. It possesses moderate resistance to reducing acids, such as hydrochloric and sulfuric, as a result of its appreciable molybdenum and copper contents.
Hastelloy G-30 alloy is available in the form of plates, sheets, strips, billets, bars, wires, pipes, tubes, and covered electrodes. Applications include P2O5 evaporator tubes and nitric acid-based, metal pickling hardware.
9.Hastelloy X
Hastelloy X also referred to as the UNS N06002/W.Nr. 2.4665 alloy. Hastelloy X is a nickel-chromium-iron-molybdenum alloy that possesses an exceptional combination of oxidation resistance, fabricability and high-temperature strength.
It has also been found to be exceptionally resistant to stress-corrosion cracking in petrochemical applications. X alloy exhibits good ductility after prolonged exposure at temperatures of 1200, 1400, 1600°F (650, 760 and 870°C) for 16,000 hours.
Hastelloy X alloy has excellent forming and welding characteristics. It may be forged or otherwise hot-worked, providing it is held at 2150°F (1177°C) for a time sufficient to bring the entire piece to temperature.
Applications of Hastelloy Alloys
Hastelloy metals and alloys are extensively utilized across various industries due to their superior mechanical properties. Their ability to withstand moderate to severe corrosion makes them ideal for applications in welding, aerospace engineering, and chemical processing.
With excellent resistance to stress corrosion cracking and non-oxidizing acids, Hastelloy alloys are employed in numerous applications, including:
- Stack liners
- Reaction vessels
- Heat exchangers
- Aircraft cabin heaters
- Transition ducts
FAQs
1.What is the price of Hastelloy alloys?
Due to the high molybdenum content, the raw material price of Hastelloy alloy is higher than many nickel-based superalloys. Also, due to their high strength, Hastelloy alloys are more difficult to process, which further increases their price.
2.What is the difference between Hastelloy alloys and other superalloys?
As mentioned in the main text, the defining characteristic of Hastelloy alloys is their significant molybdenum content. This sets them apart from other superalloys. While other superalloys may contain molybdenum, the concentration is typically lower than in Hastelloy. Consequently, Hastelloy alloys demonstrate superior overall corrosion resistance and higher solid solution strength compared to other superalloys.
3.Do Hastelloys cost more than Inconel alloys?
Hastelloy will cost a little extra than Inconel alloy because molybdenum is more costly than chromium.
4.What is the difference between Hastelloys and Monel?
The differences between Hastelloy and Monel primarily lie in their properties and applications.
Hastelloy and Monel are two widely used families of nickel-based alloys, each with distinct properties and applications.
Monel is a nickel-copper alloy, while Hastelloy is a nickel-based alloy containing molybdenum, chromium, and other elements.
Both alloys excel in corrosive environments, but Hastelloy offers superior performance at higher temperatures and possesses greater strength than Monel, with the ability to withstand pressures up to ten times higher.
Additionally, Hastelloy is more suitable for acidic environments, resisting a range of corrosive acids such as sulfuric acid, nitric acid, hydrochloric acid, hydrofluoric acid, and chromic acid. In contrast, Monel is typically used in marine applications.
Conclusion
Hastelloy B was developed to excel in reducing environments.
Hastelloy B-2 aimed for enhanced reduction corrosion resistance but revealed some practical shortcomings.
Hastelloy B-3 improved upon the chemical composition of Hastelloy B-2 and has become the most widely used alloy in the Hastelloy B series today.
HZW is dedicated to providing high-quality Hastelloy alloys. Please contact us for any purchasing inquiries.
HASTELLOY® is a registered trademark of Haynes International, Inc.
Inconel® and Monel® are registered trademarks of Special Metals Corporation.
