Hastelloy B-3
Introduction to Hastelloy B-3
Hastelloy B-3 is a nickel-molybdenum alloy engineered for exceptional resistance to hydrochloric acid, acetic acid, and other strongly reducing chemicals. As the latest evolution in the Hastelloy B family, B-3 addresses the limitations of previous grades by offering significantly improved thermal stability, enhanced resistance to stress corrosion cracking, and reduced sensitivity to heat-affected zone (HAZ) corrosion after welding.
Due to its excellent formability and corrosion performance, Hastelloy B-3 is widely used in CNC-machined components within the chemical processing, pharmaceutical, and waste treatment industries. The alloy's robust structure ensures dimensional stability and longevity under aggressive service conditions, particularly where both high temperatures and reducing acids are present.
Chemical, Physical, and Mechanical Properties of Hastelloy B-3
Hastelloy B-3 (UNS N10675 / ASTM B333 / B335) is a solid-solution-strengthened alloy designed to combat the shortcomings of earlier B-series alloys in heat-affected zones. It features improved processability and performance in welded conditions.
Chemical Composition (Typical)
Element | Composition Range (wt.%) | Key Role |
|---|---|---|
Nickel (Ni) | Balance (≥65.0) | Base element; provides corrosion resistance in reducing media |
Molybdenum (Mo) | 28.5–30.5 | Enhances resistance to hydrochloric and other non-oxidizing acids |
Iron (Fe) | 1.5–3.0 | Improves mechanical properties |
Cobalt (Co) | 1.0–3.0 | Enhances thermal stability |
Chromium (Cr) | ≤1.5 | Controls grain boundary corrosion |
Manganese (Mn) | ≤3.0 | Assists in hot working |
Carbon (C) | ≤0.01 | Minimizes carbide precipitation during welding |
Silicon (Si) | ≤0.1 | Reduced to lower the risk of intergranular attack |
Aluminum (Al) | ≤0.5 | Controlled to ensure structural stability |
Sulfur (S) | ≤0.02 | Prevents hot cracking in CNC and welding operations |
Physical Properties
Property | Value (Typical) | Test Standard/Condition |
|---|---|---|
Density | 9.24 g/cm³ | ASTM B311 |
Melting Range | 1350–1400°C | ASTM E1268 |
Thermal Conductivity | 10.4 W/m·K at 100°C | ASTM E1225 |
Electrical Resistivity | 1.29 µΩ·m at 20°C | ASTM B193 |
Thermal Expansion | 12.2 µm/m·°C (20–300°C) | ASTM E228 |
Specific Heat Capacity | 390 J/kg·K at 20°C | ASTM E1269 |
Elastic Modulus | 195 GPa at 20°C | ASTM E111 |
Mechanical Properties (Annealed Condition)
Property | Value (Typical) | Test Standard |
|---|---|---|
Tensile Strength | 690–770 MPa | ASTM E8/E8M |
Yield Strength (0.2%) | 275–350 MPa | ASTM E8/E8M |
Elongation | ≥45% (25mm gauge) | ASTM E8/E8M |
Hardness | 180–220 HB | ASTM E10 |
Impact Toughness | Excellent at room and cryogenic temperatures | ASTM E23 |
Key Characteristics of Hastelloy B-3
Enhanced Thermal Stability: Resists intermetallic phase formation during exposure to 500–900°C, which is a major improvement over B-2 and B alloys.
Superior Weldability: Maintains corrosion resistance in the HAZ without requiring post-weld heat treatment, reducing fabrication complexity.
High Corrosion Resistance: Demonstrates corrosion rates <0.02 mm/year in boiling 20% HCl and acetic acid at 80°C, confirmed by ASTM G31 immersion testing.
CNC Machining Compatibility: Stable microstructure allows high-precision machining with tolerances within ±0.01 mm and fine surface finish below Ra 1.0 µm.
CNC Machining Challenges and Solutions for Hastelloy B-3
Machining Challenges
Work Hardening
The material exhibits a strain hardening exponent (n ≈ 0.35), leading to increased surface hardness and reduced tool life if shallow cuts are used.
Thermal Retention
Poor thermal conductivity causes cutting temperatures to exceed 600°C, making high-pressure, through-tool coolant essential.
Chip Management
Produces long, continuous chips that are difficult to evacuate in confined geometries or high-feed scenarios.
Optimized Machining Strategies
Tool Selection
Parameter | Recommendation | Rationale |
|---|---|---|
Tool Material | CVD/PVD-coated carbide (K20–K30) or ceramic inserts | Withstand elevated cutting temperatures |
Coating | AlCrN or TiAlN (3–5 µm) | Improves chip shedding and reduces flank wear |
Geometry | Positive rake angle (10–12°), 0.02–0.05 mm edge hone | Balances cutting force and chip control |
Cutting Parameters (ISO 3685)
Operation | Speed (m/min) | Feed (mm/rev) | DOC (mm) | Coolant Pressure (bar) |
|---|---|---|---|---|
Roughing | 10–18 | 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-3 Parts
Hot Isostatic Pressing (HIP)
HIP applies uniform pressure up to 100–200 MPa at temperatures around 1150°C, eliminating internal voids and increasing fatigue strength by over 25% for critical components.
Heat Treatment
Heat Treatment involves annealing at 1065–1100°C for 1–2 hours, followed by rapid quenching to suppress phase separation and restore corrosion resistance to <0.01 mm/year in HCl.
Superalloy Welding
Superalloy Welding uses GTAW with ERNiMo-10 filler and controlled interpass temperatures <100°C to avoid sensitization in the HAZ and preserve ductility >40%.
Thermal Barrier Coating (TBC)
TBC Coating provides up to 200 µm of YSZ ceramic protection for components operating above 800°C in acidic or vapor-laden environments.
Electrical Discharge Machining (EDM)
EDM supports micro-feature formation with dimensional accuracy ±0.005 mm and surface finish Ra <0.8 µm, especially in hard-to-reach geometries.
Deep Hole Drilling
Deep Hole Drilling allows drilling up to 30× diameter using internal coolant-fed tools, critical for forming acid flow paths in pump housings and reactor components.
Material Testing and Analysis
Material Testing includes intergranular corrosion testing (ASTM A262 Prac. C), mechanical validation (ASTM E8/E18), and microstructure analysis with SEM and EDS.
Industry Applications of Hastelloy B-3 Components
Chemical Reactors and Vessels
Used in HCl vapor environments up to 100°C, where typical stainless steels fail due to localized attack.
Pharmaceutical Systems
Ideal for sealed mixing components in acetic/formic acid processes with low tolerance for contamination.
Waste Acid Recovery Units
Performs reliably in hot acid regeneration loops with alternating exposure to chlorides and sulfates.
Semiconductor Equipment
Acid-resistant chamber linings and precision valve seats operating under ultra-pure chemical streams.
FAQs
What advantages does Hastelloy B-3 offer over Hastelloy B-2 and B in CNC machining and corrosion performance?
How should cutting tools and coatings be selected for optimal machining of Hastelloy B-3?
Is post-weld heat treatment necessary for maintaining corrosion resistance in Hastelloy B-3?
What industries benefit most from using Hastelloy B-3 components?
What testing methods are used to verify corrosion and thermal stability of Hastelloy B-3 parts?
Explore Related Blogs
