Views: 2 Author: Wang Publish Time: 2024-07-02 Origin: Site
Overview
Hastelloy B-3 is a nickel-molybdenum alloy with excellent resistance to pitting, corrosion, and stress-corrosion cracking plus, thermal stability superior to that of alloy B-2. In addition, this nickel steel alloy has great resistance to knife-line and heat–affected zone attack. Alloy B3 also withstands sulfuric, acetic, formic and phosphoric acids, and other non-oxidizing media. Furthermore, this nickel alloy has excellent resistance to hydrochloric acid at all concentrations and temperatures. Hastelloy B-3’s distinguishing feature is its ability to maintain excellent ductility during transient exposures to intermediate temperatures. Such exposures are routinely experienced during heat treatments associated with fabrication.
Alloy B3 has poor corrosion resistance to oxidizing environments, therefore, it is not recommended for use in oxidizing media or in the presence of ferric or cupric salts because they may cause rapid premature corrosion failure. These salts may develop when hydrochloric acid comes in contact with iron and copper. Therefore, if this nickel steel alloy is used in conjunction with iron or copper piping in a system containing hydrochloric acid, the presence of these salts could cause the alloy to fail prematurely.
HASTELLOY B3 alloy (UNS N10675) 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. HASTELLOY B3 alloy is available in the form of plates, sheets, strips, billets, bars, wires, pipes, tubes, and coated electrodes. It is used in numerous chemical process industry (CPI) applications, especially in the construction of reaction vessels for pure, reducing acid service.
Hastelloy B3 Chemical Composition
Hastelloy B3 is an iron-based superalloy with nickel and molybdenum as its primary elements. The exact composition varies slightly depending on the manufacturer, but typically it consists of between 57% and 60% nickel, up to 29% chromium, up to 4% cobalt, up to 4% tungsten, up to 8% molybdenum, 0.5%-2% manganese, less than 1% silicon and phosphorus each, 0.03%-0.10% carbon, 2%-4% iron and trace amounts of sulfur and other elements. The following table shows the chemical composition of HASTELLOY(r) B-3.
Element | Content (%) |
Nickel, Ni | 65 min |
Molybdenum, Mo | 27-32 |
Cobalt, Co | 3 max |
Manganese, Mn | 3 max |
Tungsten, W | 3 max |
Iron, Fe | 1-3 |
Chromium, Cr | 1-3 |
Aluminum, Al | 0.5 max |
Copper, Cu | 0.2 max |
Niobium, Nb | 0.2 max |
Tantalum, Ta | 0.2 max |
Titanium, Ti | 0.2 max |
Vanadium, V | 0.2 max |
Zirconium, Zr | 0.1 max |
Phosphorus, P | 0.03 max |
Sulfur, S | 0.01 max |
Carbon, C | 0.01 max |
Key Properties of Hastelloy B3
Superior Corrosion Resistance: Hastelloy B3 is highly resistant to various corrosive environments, including hydrochloric and sulfuric acids. Its unique combination of nickel and molybdenum provides outstanding resistance to both localized and general corrosion, making it a preferred choice for harsh environments.
Excellent Thermal Stability: This alloy b3 exhibits remarkable thermal stability, withstanding temperatures up to 1500°F (816°C). Its ability to maintain its mechanical properties at high temperatures makes it ideal for applications where elevated temperatures are a factor, such as heat exchangers and reactors.
Enhanced Fabricability: Hastelloy B3 displays improved fabricability compared to its predecessor, Hastelloy B2. It can be readily formed, welded, and machined using conventional techniques, making it a versatile material for various applications.
Resistance to Hydrogen Embrittlement Unlike many other nickel alloys, Hastelloy B3 is highly resistant to hydrogen embrittlement, ensuring the material’s longevity and reliability in hydrogen-rich environments.
Fabrication of Hastelloy B3 is relatively straightforward and can be achieved using standard fabrication techniques for nickel-based alloys. This alloy is both formable and weldable, making it a versatile option for a wide range of applications. Cold working is possible with Hastelloy B3, although intermediate annealing may be necessary to avoid work hardening. Forging should be performed at a temperature between 1750°F and 2050°F, followed by rapid cooling.
Heat treatment of Hastelloy B3 is also relatively straightforward, with annealing performed at a temperature range between 2020°F and 2150°F, followed by a rapid quench. Cooling at an accelerated rate is important to avoid the formation of detrimental phases that may form between 400°F and 1800°F. Welding can be performed using gas tungsten-arc, gas metal-arc, and shielded metal-arc processes.
Hastelloy B3 is a specific type of Hastelloy alloy known for its excellent resistance to hydrochloric acid at all concentrations and temperatures. Here are some common applications where Hastelloy B3 is particularly useful:
1. Chemical Processing: Acetic Acid Production: Hastelloy B3 is often used in the production of acetic acid where resistance to acetic anhydride and acetic acid mixtures is critical.
Phosphoric Acid Production: It is also employed in the production of phosphoric acid due to its resistance to acid mixtures containing phosphoric acid.
2. Petrochemical Processing:Sulfuric Acid Production: Hastelloy B3 is resistant to sulfuric acid solutions and can be used in environments where sulfuric acid is present. Gas Scrubbers: It is used in gas scrubbers where acidic gases are treated and neutralized.
3. Power Generation: Nuclear Reactor Components: Hastelloy B3 is used in nuclear reactors for its resistance to corrosion in reactor core environments.
4. Oil and Gas Industry: Downhole Applications: In environments with high chloride content, such as deep well drilling, Hastelloy B3's resistance to chloride stress corrosion cracking is beneficial. Offshore Platforms: It is used in offshore platforms where exposure to seawater and various corrosive chemicals is a concern.
5. Industrial Manufacturing: Heat Exchangers: Hastelloy B3 is used in heat exchangers where corrosive fluids are cooled or heated. Reactors and Mixers: It finds applications in reactors and mixers used in various industrial processes involving corrosive chemicals.
6. Environmental Protection: Pollution Control Equipment: Hastelloy B3 is employed in pollution control equipment such as scrubbers and stacks where it encounters aggressive chemical environments.
The key advantage of Hastelloy B3 in these applications is its resistance to a wide range of corrosive environments, particularly those involving acids, while maintaining mechanical strength and stability at elevated temperatures. Its versatility makes it a preferred choice in industries where corrosion resistance is critical to operational reliability and safety.