Hastelloy B
Introduction to Hastelloy B
Hastelloy B is a corrosion-resistant, nickel-molybdenum alloy developed specifically for use in strong reducing environments, particularly hydrochloric acid. With exceptional resistance to hydrogen chloride, sulfuric, acetic, and phosphoric acids—even under severe conditions—Hastelloy B is a preferred material for CNC-machined components used in chemical reactors, heat exchangers, and acid recovery systems.
Hastelloy B maintains excellent ductility and mechanical properties across a wide temperature range and is typically CNC machined in the annealed condition. Its resistance to stress corrosion cracking and pitting makes it ideal for applications involving aggressive media and high purity processing.
Chemical, Physical, and Mechanical Properties of Hastelloy B
Hastelloy B (UNS N10001 / ASTM B333 / B335) is a wrought, solid-solution-strengthened alloy. It is available in hot-rolled, cold-drawn, and annealed bar, sheet, and plate forms. The material is best known for its extreme resistance to hydrochloric acid and non-oxidizing media.
Chemical Composition (Typical)
Element | Composition Range (wt.%) | Key Role |
|---|---|---|
Nickel (Ni) | Balance (≥65.0) | Base element; corrosion resistance in reducing media |
Molybdenum (Mo) | 26.0–30.0 | Primary alloying element; enhances resistance to pitting and crevice corrosion |
Iron (Fe) | 2.0–4.0 | Balances mechanical strength |
Carbon (C) | ≤0.02 | Controlled to reduce carbide precipitation during welding |
Manganese (Mn) | ≤1.0 | Enhances hot workability |
Silicon (Si) | ≤0.10 | Kept low to avoid susceptibility to intergranular attack |
Chromium (Cr) | ≤1.0 | Low content avoids oxidation-prone behavior |
Cobalt (Co) | ≤1.0 | Impurity limited for property stability |
Sulfur (S) | ≤0.03 | Minimized to reduce hot cracking during machining and welding |
Physical Properties
Property | Value (Typical) | Test Standard/Condition |
|---|---|---|
Density | 9.22 g/cm³ | ASTM B311 |
Melting Range | 1330–1380°C | ASTM E1268 |
Thermal Conductivity | 10.2 W/m·K at 100°C | ASTM E1225 |
Electrical Resistivity | 1.23 µΩ·m at 20°C | ASTM B193 |
Thermal Expansion | 12.3 µm/m·°C (20–300°C) | ASTM E228 |
Specific Heat Capacity | 390 J/kg·K at 20°C | ASTM E1269 |
Elastic Modulus | 200 GPa at 20°C | ASTM E111 |
Mechanical Properties (Annealed Condition)
Property | Value (Typical) | Test Standard |
|---|---|---|
Tensile Strength | 690–760 MPa | ASTM E8/E8M |
Yield Strength (0.2%) | 275–345 MPa | ASTM E8/E8M |
Elongation | ≥40% (25mm gauge) | ASTM E8/E8M |
Hardness | 180–220 HB | ASTM E10 |
Impact Toughness | Excellent at cryogenic and ambient conditions | ASTM E23 |
Key Characteristics of Hastelloy B
Extreme Corrosion Resistance: Demonstrates corrosion rates <0.02 mm/year in boiling 20% HCl and <0.05 mm/year in 50% acetic acid at 80°C (ASTM G31).
Low Carbon Formulation: Reduced carbide precipitation during welding or thermal cycles, maintaining corrosion resistance in heat-affected zones.
Stress Cracking Resistance: Resists stress corrosion cracking in both chloride and fluoride ion environments common in chemical reactors.
Fabrication Compatibility: Maintains dimensional stability during CNC machining, forming, and thermal processing.
CNC Machining Challenges and Solutions for Hastelloy B
Machining Challenges
Work Hardening
The alloy work-hardens rapidly under tool engagement, leading to increased tool wear if inappropriate feeds are used.
Thermal Control
Low thermal conductivity results in heat buildup at the cutting edge, increasing tool failure risk under dry machining conditions.
Chip Formation
Produces continuous, tough chips with poor breakability, requiring aggressive chip-breaking geometries.
Optimized Machining Strategies
Tool Selection
Parameter | Recommendation | Rationale |
|---|---|---|
Tool Material | PVD-coated carbide (K20–K40) or ceramic inserts | Maintains cutting edge at high temperatures |
Coating | TiAlN or AlCrN (3–4 µm) | Minimizes flank wear and built-up edge |
Geometry | 10–15° positive rake, honed edge (~0.02 mm radius) | Reduces cutting forces and delays surface hardening |
Cutting Parameters (ISO 3685)
Operation | Speed (m/min) | Feed (mm/rev) | DOC (mm) | Coolant Pressure (bar) |
|---|---|---|---|---|
Roughing | 10–20 | 0.20–0.30 | 2.0–3.0 | 100–120 |
Finishing | 20–35 | 0.05–0.10 | 0.5–1.0 | 120–150 |
Surface Treatment for Machined Hastelloy B Parts
Hot Isostatic Pressing (HIP)
HIP densifies cast or additively manufactured parts to enhance fatigue strength and remove internal porosity.
Heat Treatment
Heat Treatment includes annealing at 1150°C ±15°C followed by rapid quenching to avoid sensitization and retain corrosion resistance.
Superalloy Welding
Superalloy Welding requires low-heat-input GTAW with ERNiMo-7 filler to minimize heat-affected zone corrosion.
Thermal Barrier Coating (TBC)
TBC Coating may be applied for indirect acid vapor protection or thermal insulation in reactor assemblies.
Electrical Discharge Machining (EDM)
EDM supports precision geometry creation without inducing mechanical stress or heat-affected distortion.
Deep Hole Drilling
Deep Hole Drilling enables formation of cooling or acid flow passages up to L/D ratios of 30:1.
Material Testing and Analysis
Material Testing includes corrosion immersion testing (ASTM G31), sensitization testing (ASTM A262), and hardness profiling (ASTM E18).
Industry Applications of Hastelloy B Components
Chemical Processing
Acid pump bodies, heat exchanger tubes, and reaction vessels.
Maintains performance in HCl concentrations >40% at 100°C.
Pharmaceutical Equipment
Reactor linings, mixers, and seals for high-purity acid environments.
Non-contaminating and corrosion-resistant even in trace halides.
Metal Pickling and Recovery
Nozzles, pipe fittings, and heat exchanger baffles in nitric and sulfuric acid recovery units.
Resists localized attack during acid circulation.
Pulp and Paper
Digesters and black liquor evaporator tubes exposed to acid bleaching agents.
FAQs
How does Hastelloy B perform in concentrated hydrochloric and sulfuric acid environments?
What machining techniques reduce tool wear when cutting Hastelloy B?
Can Hastelloy B be used in welded acid systems without post-weld heat treatment?
What surface treatments enhance the longevity of Hastelloy B components?
What standards and certifications are used to validate Hastelloy B for chemical equipment?
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