Hastelloy B vs. Hastelloy C

Attribute	Hastelloy B	Hastelloy C
Composition	Primarily composed of nickel, molybdenum, chromium, and iron	Contains nickel, molybdenum, chromium, and iron with additional elements such as tungsten and cobalt
Corrosion Resistance	High resistance to corrosion in various environments	Excellent resistance to corrosion in oxidizing and reducing environments
Temperature Resistance	Good resistance to high temperatures	Higher temperature resistance compared to Hastelloy B
Applications	Used in chemical processing, aerospace, and marine industries	Commonly used in chemical processing, petrochemical, and pharmaceutical industries

Composition

Hastelloy B and Hastelloy C are both nickel-based alloys that offer excellent corrosion resistance in a wide range of environments. However, they differ in their composition. Hastelloy B is primarily composed of nickel, molybdenum, and chromium, with small amounts of iron and tungsten. On the other hand, Hastelloy C contains nickel, molybdenum, and chromium as well, but with the addition of small amounts of iron and cobalt. This difference in composition gives each alloy unique properties that make them suitable for different applications.

Corrosion Resistance

Both Hastelloy B and Hastelloy C are known for their exceptional corrosion resistance, but they excel in different environments. Hastelloy B is particularly resistant to hydrochloric acid, sulfuric acid, and phosphoric acid, making it ideal for chemical processing applications. On the other hand, Hastelloy C offers superior resistance to oxidizing acids like nitric acid and chromic acid, as well as to chloride solutions. This makes it a preferred choice for applications in the chemical processing and petrochemical industries where exposure to harsh chemicals is common.

Temperature Resistance

When it comes to temperature resistance, both alloys can withstand high temperatures, but Hastelloy C has a higher temperature limit compared to Hastelloy B. Hastelloy B is suitable for use in temperatures up to 1300°F (704°C), while Hastelloy C can be used in temperatures up to 1900°F (1038°C). This higher temperature resistance of Hastelloy C makes it a better choice for applications where exposure to extreme heat is a concern, such as in aerospace and gas turbine components.

Strength and Toughness

While both alloys exhibit high strength and toughness, there are differences in their mechanical properties. Hastelloy B has a higher tensile strength and yield strength compared to Hastelloy C, making it a more suitable choice for applications that require high strength and resistance to mechanical stress. On the other hand, Hastelloy C offers better toughness and ductility, making it a preferred choice for applications that require good formability and weldability.

Cost

Cost is another factor to consider when choosing between Hastelloy B and Hastelloy C. Hastelloy C is generally more expensive than Hastelloy B due to its higher content of molybdenum and cobalt, which are more expensive metals compared to tungsten. This higher cost of Hastelloy C may influence the decision-making process, especially for applications where cost-effectiveness is a priority.

Applications

Due to their unique properties, Hastelloy B and Hastelloy C find applications in different industries. Hastelloy B is commonly used in chemical processing, pollution control, and pulp and paper industries where resistance to sulfuric acid and hydrochloric acid is crucial. On the other hand, Hastelloy C is preferred in applications such as chemical processing, aerospace, and gas turbine components where resistance to oxidizing acids and high temperatures is required.