Discover the latest trends and innovations in the nickel alloy industry. We provide expert insights and in-depth analysis on the newest developments in nickel alloys.
Alloy 625 (Inconel 625, UNS N06625 / W.Nr. 2.4856) is a nickel-chromium-molybdenum superalloy stabilized with niobium and tantalum. It is specifically engineered to deliver a rare combination of exceptional corrosion resistance—particularly against pitting, crevice corrosion, and chloride stress corrosion cracking—alongside reliable mechanical strength from cryogenic temperatures up to 980°C (1800°F). Shanghai COCESS Special Alloys Co., Ltd supplies this critical alloy, ensuring your projects benefit from its proven dual-capability in the most demanding chemical and thermal environments.
Precise Chemical Composition & Mechanical Baseline
The superior performance of Alloy 625 is anchored in its strictly controlled chemistry, providing a balance of solid-solution strengthening and universal corrosion immunity.
Chemical Composition (wt.%): Ni ≥ 58.0 (Balance), Cr 20.0 – 23.0, Mo 8.0 – 10.0, Nb+Ta 3.15 – 4.15, Fe ≤ 5.0, C ≤ 0.10, Mn ≤ 0.50, Si ≤ 0.50, Al ≤ 0.40, Ti ≤ 0.40. The high Molybdenum and Nb content drive a Pitting Resistance Equivalent Number (PREN) typically > 45.
Mechanical Properties (Annealed / Solution Treated, Room Temp):
Tensile Strength (Rm): ≥ 830 MPa (typical 827–965 MPa / 120–140 ksi).
Yield Strength (Rp0.2): ≥ 414 MPa (typical 414–552 MPa / 60–80 ksi).
Elongation (A): ≥ 30% (typical 30–50%), ensuring high toughness and formability.
Hardness: Typically ≤ 220 HB (Annealed soft state for easy machining/formability).
Physical Properties: Density 8.44 g/cm³; Melting Range 1290 – 1350°C; Non-magnetic; Thermal Conductivity (100°C) ~9.8 W/(m·K).
High Temperature Performance & Oxidation Stability
Unlike many pure corrosion alloys, 625 retains significant structural integrity across a vast temperature spectrum, making it a go-to for thermal processing and aerospace.
Temperature Service Range: Performs reliably from -196°C (Liquid Nitrogen) up to 980°C (1800°F) for long-term service (short-term peaks to 1100°C). At 650°C, tensile strength remains approx. 735 MPa+ with yield ~380 MPa. Even at 800°C~980°C, it maintains useful load-bearing capacity and excellent resistance to oxidation.
Oxidation & Creep: Forms a stable, adherent Cr₂O₃-based scale. In static air at 900°C~1000°C, oxidation rates are very low (parabolic kinetics), preventing destructive scaling. It exhibits good creep-rupture strength (e.g., maintaining integrity at 650°C under sustained stress), suitable for intermediate high-heat applications, though for extreme 1000°C+ pure creep load, alloys like 617 or 718 might be assessed.
Thermal Cycling: The alloy handles thermal fatigue well, resisting cracking during repeated heating/cooling cycles (e.g., exhaust systems, furnace dampers).
Superior Corrosion Resistance Characteristics
The defining industrial advantage of Alloy 625 is its immunity to localized corrosion in halide-rich and aggressive chemical media.
Chloride Immunity: Exceptional resistance to Pitting and Crevice Corrosion in seawater, brine, and chemical process streams containing Cl⁻ ions (CPT often > 75°C in 3.5% NaCl). It is virtually immune to Chloride Stress Corrosion Cracking (Cl-SCC), a failure mode that destroys standard stainless steels.
Acid Resistance: Withstands reducing acids like Sulfuric (H₂SO₄), Phosphoric (H₃PO₄), and Hydrochloric (HCl) acids across various concentrations/temperatures, as well as oxidizing mixtures (e.g., Nitric + Hydrochloric). In 10% H₂SO₄, corrosion rates are extremely low (e.g., < 0.05–0.1 mm/year).
Sour Gas & Marine: Highly resistant to Sulfide Stress Cracking (SSC) and general corrosion in sour oil/gas (H₂S/CO₂) environments (NACE MR-01-75 compliant). Ideal for seawater piping, risers, and offshore platforms due to bio-fouling resistance and lack of pitting.
Industrial Applications & Supply Standards
Shanghai COCESS Special Alloys Co., Ltd supplies Alloy 625 to meet these critical sector needs:
Marine & Offshore: Seawater piping systems, propeller shafts, subsea wellhead components, firewater systems, and desalination plant evaporators.
Chemical Processing: Reactor vessels, heat exchanger tubing, transfer pipes, and agitators handling hot acids, halogens, and organic chlorides.
Aerospace & Energy: Aircraft ducting, exhaust systems, combustion liner components (up to 980°C), gas turbine seals, and nuclear fuel reprocessing equipment.
Relevant Standards: Sheet/Plate (ASTM B443 / ASME SB-443), Bar/Rod (ASTM B446 / ASME SB-446), Seamless Tube (ASTM B444 / ASME SB-444), Welded Tube (ASTM B704), Forgings (ASTM B564).
Every shipment includes an EN 10204 3.1 Material Test Certificate ensuring full traceability. For sourcing Alloy 625 with guaranteed high-temperature stability and corrosion data compliance, contact the technical sales team at Shanghai COCESS Special Alloys Co., Ltd.
Website: https://en.cocessalloys.com
Email: sales@cocessalloys.com
