Hastelloy G-30
Introduction to Hastelloy G-30
Hastelloy G-30 is a nickel-based corrosion-resistant alloy with enhanced resistance to oxidizing acids, particularly nitric, phosphoric, and mixtures of strong acids and oxidizing salts. It was developed to upgrade to Hastelloy G, with improved thermal stability and a broader corrosion resistance range. Key alloying elements—chromium, iron, cobalt, and copper—optimize the material’s performance in complex chemical environments.
G-30 is especially favored for CNC-machined parts used in fertilizer production, pickling operations, and process streams involving strong oxidizers and mineral acids. Its formability, mechanical strength, and corrosion resistance make it an ideal material for high-precision components in aggressive service conditions.
Chemical, Physical, and Mechanical Properties of Hastelloy G-30
Hastelloy G-30 (UNS N06030 / ASTM B582 / B619 / B622 / B626) is engineered for maximum corrosion resistance in oxidizing acidic environments, offering significant performance gains over G and other high-chromium alloys.
Chemical Composition (Typical)
Element | Composition Range (wt.%) | Key Role |
|---|---|---|
Nickel (Ni) | Balance (≥43.0) | Base alloy for corrosion resistance |
Chromium (Cr) | 28.0–31.5 | Provides resistance to oxidizing agents like nitric and sulfuric acid |
Iron (Fe) | 13.0–17.0 | Improves structural strength |
Cobalt (Co) | 1.0–5.0 | Enhances corrosion resistance in acidic chloride media |
Molybdenum (Mo) | 4.0–6.0 | Resists localized corrosion |
Copper (Cu) | 0.5–2.4 | Increases resistance to phosphoric and sulfuric acids |
Tungsten (W) | ≤1.5 | Aids pitting resistance |
Manganese (Mn) | ≤1.5 | Supports hot working |
Silicon (Si) | ≤0.8 | Minimizes intergranular corrosion |
Carbon (C) | ≤0.03 | Reduces carbide precipitation during welding |
Sulfur (S) | ≤0.02 | Controlled to prevent hot cracking during machining |
Physical Properties
Property | Value (Typical) | Test Standard/Condition |
|---|---|---|
Density | 8.22 g/cm³ | ASTM B311 |
Melting Range | 1355–1410°C | ASTM E1268 |
Thermal Conductivity | 10.0 W/m·K at 100°C | ASTM E1225 |
Electrical Resistivity | 1.18 µΩ·m at 20°C | ASTM B193 |
Thermal Expansion | 12.0 µm/m·°C (20–300°C) | ASTM E228 |
Specific Heat Capacity | 400 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 | 655–760 MPa | ASTM E8/E8M |
Yield Strength (0.2%) | 275–345 MPa | ASTM E8/E8M |
Elongation | ≥35% (25mm gauge) | ASTM E8/E8M |
Hardness | 180–220 HB | ASTM E10 |
Impact Toughness | High ductility at sub-zero and ambient temperatures | ASTM E23 |
Key Characteristics of Hastelloy G-30
Superior Oxidizing Acid Resistance: Withstands 65% nitric acid, 75% sulfuric acid, and mixed acid systems with oxidizing salts such as ferric and cupric chlorides.
Thermal and Microstructural Stability: Resists intergranular corrosion even after extended thermal exposure between 500–900°C.
Enhanced Formability and Weldability: Suitable for precision CNC work, welding, and forming with minimal carbide sensitization or grain boundary attack.
Corrosion Performance: Corrosion rates <0.015 mm/year in 75% H₃PO₄ and <0.02 mm/year in nitric + chloride mixed acid streams per ASTM G31.
CNC Machining Challenges and Solutions for Hastelloy G-30
Machining Challenges
Moderate Work Hardening
While less severe than C-series Hastelloys, G-30 still exhibits surface hardening that can impair tool life and surface quality.
Heat Retention
Limited thermal conductivity accumulates heat in the cutting zone, causing accelerated tool wear.
Edge Wear and Galling
Tool adhesion and material smearing can reduce dimensional precision, especially in dry or low-pressure coolant environments.
Optimized Machining Strategies
Tool Selection
Parameter | Recommendation | Rationale |
|---|---|---|
Tool Material | PVD-coated carbide (K20–K30) or ceramic inserts | Good resistance to work hardening and thermal load |
Coating | AlTiN, TiAlCrN (3–5 µm) | Enhances heat and wear resistance |
Geometry | Positive rake (10°–12°), honed edge radius 0.03 mm | Minimizes cutting pressure and chip adhesion |
Cutting Parameters (ISO 3685)
Operation | Speed (m/min) | Feed (mm/rev) | DOC (mm) | Coolant Pressure (bar) |
|---|---|---|---|---|
Roughing | 15–22 | 0.20–0.30 | 2.0–3.5 | 90–120 |
Finishing | 25–35 | 0.05–0.10 | 0.5–1.0 | 120–150 |
Surface Treatment for Machined Hastelloy G-30 Parts
Hot Isostatic Pressing (HIP)
HIP enhances fatigue life and removes internal voids in cast or AM parts using 100–200 MPa pressure at 1150°C.
Heat Treatment
Heat Treatment involves solution annealing at 1120°C to restore corrosion resistance post-machining and welding.
Superalloy Welding
Superalloy Welding using ERNiCrMo-3 filler maintains corrosion performance with minimal heat input and controlled interpass temperatures.
Thermal Barrier Coating (TBC)
TBC Coating is ideal for parts exposed to 850–1000°C in nitric or sulfur-based chemical environments.
Electrical Discharge Machining (EDM)
EDM enables precise feature definition down to ±0.005 mm and Ra <0.6 µm in tight geometries.
Deep Hole Drilling
Deep Hole Drilling ensures accurate bore alignment and finish in L/D >30:1 configurations.
Material Testing and Analysis
Material Testing includes ASTM G31 immersion tests, tensile (E8), hardness (E18), and metallographic inspection.
Industry Applications of Hastelloy G-30 Components
Fertilizer Production
Acid-resistant piping and tanks used in phosphoric and nitric acid processes.
Pickling Equipment
CNC-machined parts for acid regeneration and pickling line circulation systems.
Pollution Control
Scrubber internals, ducts, and mist eliminators handling hot acidic gases and chemical slurries.
Pharmaceutical and Agrochemical
Components for process vessels, heat exchangers, and mixing systems require ultra-high corrosion resistance and cleanliness.
FAQs
What CNC tolerances and surface finishes can be achieved with Hastelloy G-30?
How does Hastelloy G-30 perform in nitric/phosphoric acid and mixed acid systems?
What machining strategies help avoid work hardening and galling on G-30 parts?
Is Hastelloy G-30 suitable for welded pressure systems in fertilizer or pickling operations?
What documentation and testing reports are provided with G-30 precision machined parts?
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