Hastelloy B, Hastelloy B-2, and Hastelloy B-3 are three high-performance alloys known for their exceptional corrosion resistance.
You might be wondering: How are they related? What are the differences in their performance? Which alloy is the best choice for your project?
This article will address all your questions and clarify the distinctions between these alloys.
Hastelloy Alloy B
In 1921, Haynes International secured the first patent for a series of nickel-molybdenum alloy compositions, marking the beginning of their work on incorporating molybdenum into superalloys. That same year, they developed Hastelloy A, which, though no longer in use, paved the way for the creation of subsequent alloys.
Following extensive research on Hastelloy A, the Hastelloy B alloy was developed. This new alloy featured 60% nickel and nearly 30% molybdenum. At that time, the market had several nickel-chromium and nickel-chromium-iron alloys, which were excellent for high-temperature corrosion resistance but not suitable for all applications. Hastelloy B stood out as one of the few superalloys with a high molybdenum content.
The significant molybdenum content greatly enhanced the alloy’s resistance to reducing environments. This made Hastelloy B an ideal choice for applications involving hydrogen chloride gas, sulfuric acid, acetic acid, and phosphoric acid. The Hastelloy B series has since evolved into a family of alloys that continue to play a vital role in various industries today.
Hastelloy Alloy B-2
The success of Hastelloy B in specific applications inspired developers to optimize the alloy’s composition, leading to the creation of Hastelloy B-2.
Generally, silicon is a detrimental element for superalloys, significantly reducing their durability. The original Hastelloy B alloy required a silicon content of less than 1%, which was not particularly stringent. To maximize the alloy’s durability, Hastelloy B-2 was designed with a silicon content of 0.1% or less.
Additionally, to achieve superior reduction resistance, Hastelloy B-2 has a higher nickel content and lower iron content than Hastelloy B, even though this increases the cost of the alloy.
Hastelloy B-2 excels in all aspects, making it a highly sought-after alloy.
Hastelloy Alloy B-3
After the development of Hastelloy B-2, it was anticipated to be a superior alternative to Hastelloy B in industrial applications. As a completely new generation within the Hastelloy B alloy family, it was termed the modern B-type alloy.
However, the results were disappointing to many. During use, Hastelloy B-2 exhibited poor high-temperature performance. In the temperature range of 500 to 900 degrees Celsius, a significant amount of a harmful phase (Ni4Mo) precipitated in the alloy. This phase negatively impacted the ductility and stress corrosion cracking resistance of the alloy.
It became clear that designing superalloy compositions was far more complex than initially thought. The properties of an alloy are not determined solely by the content of specific elements but also by the ratios between them.
Researchers continued to study and optimize the B-type alloy, leading to the eventual introduction of Hastelloy B-3. This alloy has become the most widely used in the Hastelloy B series today.
Hastelloy B-3 features several key improvements:
1. A reduction in harmful elements such as sulfur and phosphorus.
2. Controlled content of many trace elements, including zirconium, aluminum, titanium, niobium, tantalum, vanadium, tungsten, and copper.
3. Adjusted ratios of nickel and molybdenum, reducing nickel content and increasing molybdenum, optimizing the balance without compromising reduction resistance.
These optimizations have resulted in Hastelloy B-3 performing exceptionally well in practical applications, ensuring its continued use today.
Similarities among Hastelloy Alloy B, B-2 and B-3
Standards
1. ASTM B333 – Plate, Sheet and Strip
2. ASTM B335 – Billet, Rod and Bar
3. ASTM B366 – Fittings
4. ASTM B619 – Welded Pipe
5. ASTM B622 – Seamless Pipe & Tube
6. ASTM B626 – Welded Tube
The three alloys have almost the same standard, they are defined in the standard as UNS N10001 (Hastelloy B), UNS N10665 (Hastelloy B-2) and UNS N10675 (Hastelloy B-3) respectively.
Types
All three alloys are solid solution strengthened. Due to the high molybdenum content, the Hastelloy B-type alloys are better solution strengthened. The strength is higher.
Brands
All three alloys are generally distinguished by the HASTELLOY® brand.
Use Temperature
Hastelloy Alloy B, B-2 and B-3 are widely used for high temperature.
Differences among Hastelloy Alloy B, B-2 and B-3
Chemical Composition
Hastelloy B-2 achieves higher reduction resistance through the extreme pursuit of composition. Hastelloy B-3, on the other hand, optimizes the performance deficiencies of Hastelloy B-2 by controlling more trace elements.
Mechanical Properties
| Hastelloy B | Hastelloy B-2 & B-3 | |
|---|---|---|
| Solution Annealed | Solution Annealed | |
| Tensile Strength, MPa, min | 690 / 795 | 760 |
| Yield Strength, MPa, min | 345 / 310 | 350 |
| Elongation, %, min | 45 / 40 | 40 |
| Hardness, HRB, max | 100 | 100 |
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.
