Hastelloy (Ni-Cr-Mo Alloy) (Ni+Cr+Mo)
Hastelloy is a family of nickel-chromium-molybdenum superalloys developed by Haynes International, engineered for extreme corrosion resistance in the most aggressive chemical environments. Where standard stainless steels and even duplex grades fail — concentrated acids, mixed acid-chloride environments, and high-temperature oxidizing/reducing conditions — Hastelloy alloys provide reliable service. They are the last line of defense in chemical processing.
Properties
- Density
- 8,690–9,220 kg/m³
- Melting Point
- 1,260–1,370 °C
- Boiling Point
- ~2,700 °C
- Thermal Conductivity
- 9.1–11.5 W/(m·K)
- Electrical Resistivity
- 1.30 × 10⁻⁶ Ω·m
- Tensile Strength
- 690–900 MPa
- Yield Strength
- 310–420 MPa
- Hardness
- 180–240 HB
- Elongation
- 40–60%
- Crystal Structure
- FCC (Austenite)
Common Grades
- Hastelloy C-276 (N10276): The most versatile grade — 16% Cr, 16% Mo, 4% W. Resists pitting, crevice corrosion, and stress corrosion cracking in chloride environments.
- Hastelloy C-22 (N06022): Improved version of C-276 with better resistance to oxidizing acids and mixed-acid environments. Often the default choice for new designs.
- Hastelloy B-3 (N10675): Molybdenum-rich grade (28% Mo) for hydrochloric acid at all concentrations and temperatures. No chromium — not for oxidizing environments.
- Hastelloy X (N06002): High-temperature alloy for gas turbine components, furnace parts. Service up to 1,200°C.
Applications
- Chemical Processing: Reactors, heat exchangers, piping, and valves handling HCl, H₂SO₄, HF, and mixed acids
- Flue Gas Desulfurization: Scrubber systems, absorber towers, reheaters in coal-fired power plants
- Pharmaceutical: Reactor vessels, agitators, and piping for active pharmaceutical ingredient synthesis
- Oil & Gas: Sour gas (H₂S) wellhead components, downhole tools, subsea flow control equipment
- Waste Treatment: Incineration systems, waste acid recovery, hazardous waste processing equipment
FAQ
What is the difference between Hastelloy and Inconel?
Hastelloy alloys (C-276, C-22, B-3) are optimized for chemical corrosion resistance at moderate temperatures — they excel in acid environments. Inconel alloys (625, 718) are designed for high-temperature strength and oxidation resistance — they excel in jet engines and gas turbines. Some overlap exists (Inconel 625 has good acid resistance), but the design philosophies differ.
When should I use Hastelloy instead of duplex stainless steel?
Choose Hastelloy when: chloride concentrations exceed duplex limits (>1000 ppm Cl⁻ at elevated temperatures), reducing acids are present (HCl, H₂SO₄), temperatures exceed 300°C in corrosive service, or mixed oxidizing-reducing conditions exist. Duplex is preferred when its corrosion limits are adequate, as it costs 70–85% less.
Why is Hastelloy so expensive?
Hastelloy's cost reflects its high nickel content (50–65%), substantial molybdenum (15–28%), and chromium additions. These are all expensive raw materials. Additionally, complex melting processes (VIM/VAR), strict quality control requirements, and relatively low production volumes compared to stainless steel contribute to the premium pricing.