Hastelloy B, Hastelloy B-2 and Hastelloy B-3 are three alloys with very high corrosion resistance.

You may have questions. What is the relationship between them? What is the difference in their performance? Which alloy should I choose for use in my project?

In this article, we will solve your doubts once and for all.

In 1921, Haynes International obtained the first patent for a range of nickel-molybdenum alloy compositions. Since then, they have been working on the addition of molybdenum to superalloys. That year, they developed the Hastelloy A alloy. Although this alloy was no longer used in subsequent history. But it set the stage for the creation of a later family of alloys.

Later, after further research on the Hastelloy A alloy, the Hastelloy B alloy was developed. In this alloy, the nickel content is 60% and the molybdenum content is nearly 30%. During the same period, many nickel-chromium alloys and nickel-chromium-iron alloys were available on the market. Although these alloys were already excellent in terms of high temperature corrosion resistance, they were not always suitable for all applications. Hastelloy B was one of the very few superalloys that used large amounts of molybdenum for alloying.

The large amount of molybdenum significantly increased the alloy's resistance to reduction. Since then, there has been a better choice for applications in some reducing environments such as hydrogen chloride gas, sulfuric acid, acetic acid and phosphoric acid. The Hastelloy B series has become a family of alloys that continues to play its unique role today.

The success of Hastelloy B in a specific field gave the developers the idea to optimize the composition of the alloy. Thus a second version of Hastelloy B was born: Hastelloy B-2.

Generally speaking, silicon is a harmful element for superalloys. It significantly reduces the durability of the alloy. The Hastelloy B alloy requires a silicon range of less than 1%. This is not a very strict range. In order to improve the durability of the alloy as much as possible, the silicon content of Hastelloy B-2 is specified to be 0.1% or less.

In addition, in pursuit of the ultimate in reduction resistance, Hastelloy B-2 trades less iron for more nickel than Hastelloy B although this further increases the cost of the alloy.

Hastelloy B-2 is the ultimate in all aspects, which makes it a highly desirable alloy.

After Hastelloy B-2 was developed, it was expected to be a better alternative to Hastelloy B in industry. As a completely new generation of the Hastelloy B alloy family, it was called the modern B-type alloy.

However, the results were a disappointment to many. During use, the high temperature performance of Hastelloy B-2 was found to be defective. In the temperature range of 500 to 900 degrees Celsius, a large amount of a harmful phase (Ni4Mo) precipitated in the alloy. This phase affected the ductility of the alloy and reduced the resistance of the alloy to stress corrosion cracking.

It was finally realized that the composition design of superalloys is much less simple than one might think. Nor are the properties of an alloy determined only by the content of certain elements. The ratio between elemental contents was also an important consideration.

After that, the researchers continued to invest time in studying the optimization of the B-type alloy. Eventually, Hastelloy B-3 was introduced. It became the most widely used Hastelloy B series alloy today.

First, the Hastelloy B-3 alloy has an overall reduction in the amount of harmful elements (sulfur and phosphorus).

Second, the B-3 alloy controls the content of many trace elements (zirconium, aluminum, titanium, niobium, tantalum, vanadium, tungsten and copper).

Finally, Hastelloy B-3 reduces the content of nickel and increases the content of molybdenum. This optimizes the ratio of nickel to molybdenum without affecting the alloy's resistance to reduction.

The optimized Hastelloy B-3 alloy performs very satisfactorily in practical applications. As a result, this alloy is still used today.

In summary, Hastelloy B, Hastelloy B-2 and Hastelloy B-3 are all nickel-molybdenum alloys that have been developed to better suit applications in reducing environments. Originally, Hastelloy B-2 was an upgraded version of Hastelloy B. However, the unsatisfactory performance of Hastelloy B-2 eventually led to the emergence of Hastelloy B-3 as a performance-optimized version of Hastelloy B-2.

Currently Hastelloy B and Hastelloy B-2 have been replaced by Hastelloy B-3. As a result the first two alloys are much more rare as raw materials and have resulted in them being more expensive instead. If you are torn between which material to choose for your project, we do not hesitate to recommend Hastelloy B-3.

Hastelloy B was invented to better suit applications in reducing environments.

Hastelloy B-2 pursued a more extreme resistance to reduction corrosion. However, defects were found in practical use.

Hastelloy B-3 optimized the chemical composition of Hastelloy B-2. It has become the most widely used Hastelloy B series alloy today.

AEETHER CO., LIMITED is committed to supplying high quality Hastelloy alloys. Please contact us if you have any purchasing needs.