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.

The molybdenum content of the nickel-molybdenum (B-type) alloys is such that there is a strong tendency for phases other than the desirable (face-centered cubic) gamma phase to form in the microstructure, particularly in the temperature range 500°C to 900°C. The most deleterious of these alternate phases is Ni4Mo, which forms quickly at certain temperatures, affects ductility, and reduces resistance to stress corrosion cracking.

The chief attribute of B-3 alloy, as compared with other modern B-type materials, is its greatly improved structural stability (in particular its reduced susceptibility to Ni4Mo).