If you’re dealing with mixed acids, high temperatures, or harsh industrial environments, choosing the right material is key. UNS N06985 Hastelloy G3—a versatile nickel alloy—shines with its all-around corrosion resistance and strong mechanical performance. This guide covers everything you need to know, from its core properties to real-world uses, so you can pick the best material for your project.
1. Material Properties of UNS N06985 Hastelloy G3
Hastelloy G3’s strength comes from its well-balanced composition and standout traits. Let’s break them down simply.
1.1 Chemical Composition
Every element in this alloy plays a role in boosting performance. Here’s its typical makeup (by weight):
| Element | Content Range (%) | Key Role |
|---|---|---|
| Nickel (Ni) | 48–58 | Base metal—provides ductility and protects against stress cracking |
| Chromium (Cr) | 21–25 | Enhances oxidation resistance and fights pitting in acidic liquids |
| Molybdenum (Mo) | 6–8 | Boosts resistance to strong acids (like sulfuric and hydrochloric acid) |
| Iron (Fe) | 13–19 | Adds strength without reducing flexibility |
| Carbon (C) | Max 0.015 | Minimizes carbide formation (prevents intergranular corrosion) |
| Manganese (Mn) | Max 1.0 | Aids in manufacturing processes (e.g., welding and casting) |
| Silicon (Si) | Max 0.8 | Reduces oxidation at high temperatures |
| Phosphorus (P) | Max 0.04 | Controlled to avoid brittleness in the alloy |
| Sulfur (S) | Max 0.03 | Kept low to prevent corrosion in harsh chemical environments |
| Copper (Cu) | 1.5–2.5 | Improves resistance to sulfuric acid and acidic brines |
1.2 Physical Properties
These traits make Hastelloy G3 easy to design with for tough jobs:
- Density: 8.3 g/cm³ (lighter than many other superalloys, like Hastelloy B2)
- Melting Point: 1330–1380°C (2425–2525°F) – handles high-heat industrial processes
- Thermal Conductivity: 14.0 W/(m·K) at 20°C (68°F) – transfers heat evenly, avoiding hotspots
- Thermal Expansion Coefficient: 13.2 μm/(m·K) (20–100°C) – doesn’t warp much when heated or cooled
- Electrical Resistivity: 125 Ω·mm²/m at 20°C – works for electrical parts in harsh areas
- Magnetic Properties: Non-magnetic – ideal for medical equipment or electronics where magnetism is a problem
1.3 Mechanical Properties
Hastelloy G3 balances strength and flexibility, even at high temperatures. All values below are for the annealed (heat-treated) version:
| Property | Value (Room Temperature) |
|---|---|
| Tensile Strength | Min 650 MPa (94 ksi) |
| Yield Strength | Min 275 MPa (40 ksi) |
| Elongation | Min 45% (in 50 mm) |
| Hardness | Max 200 HB (Brinell) |
| Fatigue Resistance | 220 MPa (10⁷ cycles) |
| Creep Resistance | Maintains strength up to 700°C (1290°F) |
1.4 Other Properties
- Corrosion Resistance: Excellent in mixed acids (e.g., sulfuric + hydrochloric) and salty environments—outperforms stainless steel.
- Oxidation Resistance: Resists scaling in air up to 1000°C (1830°F) for short periods.
- Stress Corrosion Cracking (SCC) Resistance: Unaffected by SCC in chloride-rich solutions (a common issue for 316 stainless steel).
- Pitting Resistance: High resistance to pitting in seawater or acidic brines.
- Hot/Cold Working Properties: Easy to forge (hot working at 1050–1150°C) and bend (cold working) without losing strength.
2. Applications of UNS N06985 Hastelloy G3
Thanks to its all-around performance, Hastelloy G3 is used across many industries. Here are the most common uses, with real-world examples:
2.1 Chemical Processing Equipment
- Use Case: A chemical plant in China used Hastelloy G3 for mixers that handle a blend of sulfuric and nitric acid. The old mixers (made of 316 stainless steel) failed after 2 years—this one has lasted 6 years with no corrosion.
- Other Uses: Acid storage tanks, heat exchangers, and pipe systems.
2.2 Oil and Gas Industry
- Use Case: An offshore oil rig in the Gulf of Mexico uses Hastelloy G3 for wellhead valves. The alloy resists salty seawater and high-pressure natural gas, cutting maintenance costs by 35%.
2.3 Acid Handling Systems
- Use Case: A wastewater treatment plant in Australia uses Hastelloy G3 for pumps that move hydrochloric acid. The pumps run 3x longer than those made of carbon steel, saving the plant $50,000 yearly in replacements.
2.4 Pollution Control Systems
- Use Case: A power plant in Germany uses Hastelloy G3 for flue gas desulfurization (FGD) systems. The alloy resists the acidic byproducts of FGD, avoiding frequent part changes.
2.5 Pharmaceuticals & Food Processing
- Why It Works: Non-toxic and easy to clean (meets FDA standards). Used for mixing tanks that handle acidic ingredients (like vinegar or fruit juices).
3. Manufacturing Techniques for UNS N06985 Hastelloy G3
To get the best performance from Hastelloy G3, manufacturers use specific methods tailored to its properties:
- Casting: Investment casting (using a wax mold) is best for complex shapes (e.g., valve bodies). The low carbon content prevents defects during casting.
- Forging: Hot forging (at 1050–1150°C) shapes the alloy into strong parts like pump impellers. Cold forging (at room temperature) is used for small parts (e.g., bolts) to boost hardness.
- Welding: Gas Tungsten Arc Welding (GTAW) is recommended. Use matching filler metals (e.g., ERNiCrMo-19) to maintain corrosion resistance. Clean the metal first (remove oil or dirt) to avoid weak welds.
- Machining: Use carbide tools (they stay sharp longer). Add coolant (like mineral oil) to prevent overheating—Hastelloy G3 can work-harden if cut too quickly.
- Heat Treatment: Annealing (heat to 1065–1120°C, then cool fast) softens the alloy for forming and restores corrosion resistance after welding.
- Surface Treatment: Passivation (soak in nitric acid) creates a thin protective layer—this boosts pitting resistance. No painting is needed; the alloy’s surface resists rust on its own.
4. Case Study: Hastelloy G3 in a Chemical Reactor
A pharmaceutical company in the UK needed a reactor to make a new drug. The reactor uses a mix of sulfuric acid and ethanol at 90°C—their old reactor (made of Inconel 625) failed after 3 years due to corrosion.
They switched to a Hastelloy G3 reactor. Here’s the result:
- Lifespan: The reactor has been in use for 7 years with no signs of corrosion.
- Cost Savings: Maintenance costs dropped by 60% (no need for frequent part replacements).
- Performance: The alloy’s even heat transfer improved drug production efficiency by 12%.
This case shows why Hastelloy G3 is a reliable choice for mixed-acid environments.
5. Comparative with Other Materials
How does UNS N06985 Hastelloy G3 stack up against other common materials? The table below compares key properties:
| Material | Corrosion Resistance (Mixed Acids) | Tensile Strength (MPa) | Max Service Temp (°C) | Cost (Relative) |
|---|---|---|---|---|
| Hastelloy G3 | Excellent | 650 | 700 | High |
| Stainless Steel 316 | Poor | 515 | 870 | Low |
| Titanium Alloy Ti-6Al-4V | Good (chlorides) | 860 | 400 | Very High |
| Inconel 625 | Very Good (high temps) | 930 | 980 | High |
| Monel 400 | Fair (seawater) | 550 | 480 | Medium |
| Hastelloy C22 | Excellent (acids) | 690 | 650 | High |
| Hastelloy B2 | Good (pure HCl) | 690 | 600 | High |
| Carbon Steel | Very Poor | 400 | 425 | Very Low |
Key Takeaways:
- Hastelloy G3 outperforms stainless steel and carbon steel in mixed-acid environments.
- It’s more affordable than titanium alloys and offers better high-temperature resistance than Hastelloy B2.
- Inconel 625 works better at extreme temps, but Hastelloy G3 is superior in mixed-acid corrosion resistance.
Yigu Technology’s Perspective
At Yigu Technology, we recommend UNS N06985 Hastelloy G3 for clients in chemical processing, oil and gas, and pollution control. Its all-around corrosion resistance and easy manufacturability make it a cost-effective choice for harsh environments. Our team provides custom machining for Hastelloy G3 components, ensuring they meet strict industry standards. For projects needing a balance of acid resistance and high-temperature performance, Hastelloy G3 is a top pick.
FAQ
1. Can UNS N06985 Hastelloy G3 handle mixed acids?
Yes! It’s designed for this—even blends of sulfuric and hydrochloric acid won’t corrode it. This makes it way better than stainless steel or carbon steel for mixed-acid tasks.
2. Is Hastelloy G3 suitable for marine applications?
Absolutely. Its high pitting resistance and resistance to seawater corrosion make it ideal for marine parts like propeller shafts or hull components—outperforming materials like Monel 400 in long-term use.
3. What’s the typical lifespan of Hastelloy G3 parts in chemical processing?
In harsh environments (e.g., mixed acids), Hastelloy G3 parts last 7–10 years—3–4 times longer than stainless steel parts. Proper maintenance (like annealing) can extend this lifespan even further.
