Using B2 Alloy And Studying Its Corrosion Resistance Ability

As a nickel-molybdenum alloy with superior resistance to the reducing environments containing acetic, phosphoric, and sulfuric acids along with hydrogen chloride gas, this alloy is used in a wide range of applications. The resistance to non-oxidizing acids and pure sulfuric acid is also known. However, the alloys cease to exhibit its abilities when used in those applications where iron and copper are present in a system along with hydrochloric acid. The resistance that this alloy shows to chloride-induced stress corrosion cracking and a wide range of organic acids are known across the industry.

Suitability of this alloy

It prevents the formation of carbide precipitates in the heat-affected zones of welding thereby making it one of the most suitable materials widely used in the chemical process applications. Due to the reduced carbide precipitates that can be seen in the heat-affected zones of welding, the corrosion resistance ability of this alloy comes into effect. The excellent resistance of the B2 alloy to stress corrosion cracking and pitting has made it popular for different types of applications that are more susceptible to corrosion.

Characteristics of B2

Being a solid-solution strengthened alloy, it is used in extreme reducing conditions. Compared to its predecessor, B2 contains less silicon, carbon, and iron making it less susceptible to reduced corrosion resistance in as-welded condition and the weld zone. A lot of chemistry control and years of development have led to the formation of the B2 alloy that is widely used today. With temperatures ranging from 1000 to 1600 degree Fahrenheit, this alloy must never be used as it leads to the formation of secondary phases that reduces the ductility of this alloy.

Heat treatment and fabrication

The welding of the B2 alloy can be performed using coated electrodes, MIG and TIG. However, the work piece is to be cleaned thoroughly with a suitable cleanser or acetone to ensure that all the markings and contaminants are removed. Prior to the process of welding, grinding can be performed with iron-based materials and an alumina wheel that has never been used before. Unless the work piece has been formed with any other means, there is no need to apply post or preheat treatment processes. For work pieces that have been formed, a full solution anneal may be needed. Before annealing, the cold-formed pieces must be shot-peened. On the other hand, hot working is to be performed when the range of temperature is extremely high. Performing a full solution anneal is necessary on all the hot-worked pieces. The Hastelloy B2 undergoes solution annealing at an extremely high temperature for about ten minutes which is then followed by water quench.

Corrosion resistance of B2

The high molybdenum content of B2 hastelloy bar alloy provides excellent resistance to this alloy to hydrochloric acid over a wide range of temperatures and concentrations. In the heat-affected zones, the alloy also shoes reasonably good resistance to hydrogen chloride, phosphoric and sulfuric acid, and is therefore resistant to different types of corrosion when the uniform rates of corrosion are similar but care has to be taken abstain the use of oxidizing media as it destroys the corrosion resistance ability of this alloy greatly.