Comprehensive Guide to Nickel-Based Alloys: Hastelloy B2 (UNS N10665)
What is Hastelloy B2?
Hastelloy B2 (UNS N10665/W.Nr. 2.4617/Alloy B2) is a solid solution strengthened nickel-molybdenum alloy with small additions of carbon, silicon, and iron. It has good resistance to hydrogen chloride, sulfuric acid, and phosphoric acid, and excellent resistance to stress corrosion cracking and pitting at elevated temperatures. The significantly reduced carbon content makes Hastelloy B2 less susceptible to reduced corrosion resistance in the weld zone under welded conditions. It can be used in reducing chemical environments and in the chemical processing industry. However, Hastelloy B2 should not be used at temperatures between 1000°F and 1600°F, nor in oxidizing media.
Hastelloy B-2 (UNS N10665) is a solid solution strengthened nickel-molybdenum alloy that is typically used in extreme reducing conditions. Compared to its predecessor, Hastelloy B (UNS N2), Hastelloy B-10001 has significantly lower carbon, silicon, and iron contents, making the alloy less susceptible to degradation of weld zone corrosion resistance in the as-welded condition. Control of other alloying elements, such as iron and chromium, addresses other issues related to fabricability. Tight chemical control and years of development have resulted in the alloys used today, either Hastelloy B-2 or Hastelloy B-3, with limited chemistry that allows Hastelloy B-2 to be used in the welded condition and is less susceptible to SCC in many conditions. As always, care must be taken in selecting the appropriate alloy for the desired application.
Hastelloy B-2 should not be used at temperatures between 1000°F and 1600°F because the alloy forms secondary phases that reduce the ductility of the material.
Types of Hastelloy Alloys
Hastelloy B-2 nickel-molybdenum alloy has excellent corrosion resistance in reducing environments
An upgraded version of Hastelloy B-3: B-2 has excellent corrosion resistance to hydrochloric acid at any temperature and concentration
Hastelloy C-4: Good thermal stability, good toughness and corrosion resistance at 650-1040℃
Hastelloy C-22: Better uniform corrosion resistance and excellent local corrosion resistance than C-4 and C-276 in oxidizing media
Hastelloy C-276: Good resistance to oxidation and moderate reductive corrosion, excellent resistance to stress corrosion
Hastelloy C-2000: The most comprehensive Corrosion-resistant alloy with excellent uniform corrosion resistance in oxidizing and reducing environments
Hastelloy G-35: An upgraded product of G-30, it has better corrosion resistance and thermal stability, and has excellent performance in highly oxidizing mixed acid media with high chromium content such as phosphoric acid
Hastelloy X: Combining the characteristics of high strength, oxidation resistance and easy processing, the above grades have their specific chemical composition, mechanical properties and advantages, so we cannot generalize the characteristics of Hastelloy
Hastelloy is mainly divided into three series: B, C, and G, and is mainly used in iron-based CrNi or CrNiMo stainless steel, non-metallic materials and other highly corrosive media.
To improve the corrosion resistance and hot and cold processing properties of Hastelloy, three major improvements have been made to Hastelloy:
B series: B → B-2 (00ni70mo28) → B-3
C series: C → C-276 (00cr16mo16w4) → C-4 (00cr16mo16) → C-22 (00cr22mo13w3) → C-2000 (00cr20mo16)
G series: G → G-3 (00cr22ni48mo7cu) → G-30 (00cr30ni48mo7cu)
The most widely used materials are N10665 (B-2), N10276 (C-276), N06022 (C-22), N06455 (C-4) and N06985 (G-3)
Annealing of Hastelloy B2
Through 1950°F Cold working by soaking and rapid quenching, resulting in extensive work hardening followed by annealing. Note that bright finish parts must be solution annealed and rapidly cooled in an inert (argon) or reducing (hydrogen) atmosphere to prevent surface oxidation during heating and cooling.
Heat Treatment Hastelloy B2
Solution treated at 1950 F and rapidly quenched. This is normal for the product form supplied and used. Bright annealed product forms (plate and strip) are solution treated at 2100 F and then cooled in a hydrogen atmosphere to prevent bright surface oxidation.
