Inconel 625: Complete Properties & Application Guide

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Overview

Inconel 625 (UNS N06625 / W.Nr. 2.4856) is a nickel-chromium-molybdenum alloy with an addition of niobium that acts with the molybdenum to stiffen the alloy's matrix and thereby provide high strength without a strengthening heat treatment. The alloy resists a wide range of severely corrosive environments and is especially resistant to pitting and crevice corrosion. Inconel 625 is widely used in aerospace, chemical processing, marine engineering, and nuclear applications.

Chemical Composition (ASTM B446 / AMS 5666)

The chemical composition of Inconel 625 is carefully controlled to achieve its unique combination of high strength and excellent corrosion resistance. The niobium content is particularly important for stabilizing the alloy against sensitization during welding.

Element	Min %	Max %
Nickel (Ni)	Balance	Balance
Chromium (Cr)	20.0	23.0
Molybdenum (Mo)	8.0	10.0
Niobium + Tantalum (Nb+Ta)	3.15	4.15
Iron (Fe)	—	5.0
Aluminum (Al)	—	0.40
Titanium (Ti)	—	0.40
Carbon (C)	—	0.10
Silicon (Si)	—	0.50
Manganese (Mn)	—	0.50
Phosphorus (P)	—	0.015
Sulfur (S)	—	0.015

Physical Properties

Inconel 625 exhibits a face-centered cubic (FCC) crystal structure, which contributes to its excellent ductility and toughness at both room and cryogenic temperatures. The alloy's low thermal expansion coefficient and high thermal conductivity make it suitable for thermal cycling applications.

Property	Value	Unit
Density	8.44	g/cm3
Melting Point	1350	°C
Specific Heat (21°C)	410	J/kg·K
Thermal Conductivity (21°C)	9.8	W/m·K
Electrical Resistivity (21°C)	1.29	μΩ·m
Modulus of Elasticity (21°C)	205.8	GPa
Mean Coefficient of Thermal Expansion (21-93°C)	12.8	μm/m·°C
Curie Temperature	< -196	°C

Mechanical Properties at Room Temperature

The mechanical properties of Inconel 625 vary depending on the product form and heat treatment condition. The data below represents typical values for solution-annealed bar and forgings per ASTM B446.

Property	Value
Tensile Strength	930 MPa (135 ksi)
Yield Strength (0.2% offset)	517 MPa (75 ksi)
Elongation in 2 inches	42.5%
Reduction of Area	56%
Hardness (Rockwell B)	85-95 HRB
Impact Strength (Charpy V-notch, room temp)	260 J

High-Temperature Mechanical Properties

Inconel 625 maintains excellent strength at elevated temperatures. The alloy's strength is derived from the solid-solution hardening effect of the refractory metals (Mo, Nb) and chromium, rather than from precipitation hardening. This means it does not require aging heat treatment to achieve high strength.

Temperature (°C)	Tensile Strength (MPa)	Yield Strength (MPa)	Elongation (%)
21 (Room)	930	517	42.5
316	862	448	45
427	838	414	43
538	793	379	42
649	724	345	44
760	552	310	48
871	345	276	62
982	172	138	85

Corrosion Resistance

Inconel 625 exhibits outstanding corrosion resistance in a wide range of severe environments. The high chromium content provides resistance to oxidizing conditions, while the molybdenum content provides resistance to reducing conditions. The niobium content prevents sensitization and intergranular corrosion after welding.

Resistance to Specific Media:

• Seawater and Marine Environments: Excellent resistance to pitting and crevice corrosion in seawater at temperatures up to 40°C. Widely used in propeller blades, submarine components, and offshore platform equipment.
• Acid Environments: Good resistance to nitric, phosphoric, and sulfuric acids. Excellent resistance to hydrochloric acid at moderate concentrations and temperatures.
• Oxidation Resistance: Forms a protective chromium oxide scale that provides excellent resistance to oxidation at temperatures up to 980°C (1800°F).
• Chloride Stress Corrosion Cracking: Highly resistant to chloride-induced stress corrosion cracking, making it ideal for heat exchangers and chemical processing equipment.

Applications

The unique combination of high strength, excellent corrosion resistance, and good fabricability makes Inconel 625 suitable for a wide range of demanding applications:

• Aerospace: Jet engine exhaust systems, thrust reverser systems, ducting, and bellows. Turbine shroud rings, combustion chambers, and afterburner components.
• Chemical Processing: Reaction vessels, distillation columns, heat exchangers, and transfer piping in environments containing aggressive chemicals including sulfuric, phosphoric, and hydrochloric acids.
• Marine Engineering: Propeller blades, submarine propulsion motors, seawater piping, and offshore platform risers. The alloy's resistance to seawater corrosion and biofouling is exceptional.
• Nuclear Industry: Reactor core components, control rod mechanisms, and waste reprocessing equipment. The alloy's resistance to radiation damage and high-temperature water corrosion is critical.
• Oil and Gas: Downhole equipment, wellhead components, and subsea manifolds. Sour gas service (H2S-containing environments) is a primary application due to the alloy's resistance to sulfide stress cracking.
• Power Generation: Boiler tubes, superheater tubing, and flue gas desulfurization equipment. The alloy withstands high-temperature flue gases containing sulfur oxides and chlorides.

Available Product Forms

Hangbo Alloy Group manufactures and supplies Inconel 625 in the following product forms, conforming to ASTM, AMS, and ASME specifications:

• Round Bars: ASTM B446, AMS 5666, diameters from 6 mm to 300 mm, hot-finished or cold-drawn, solution annealed.
• Seamless Tubes & Pipes: ASTM B444, ASTM B829, sizes from 6 mm OD to 219 mm OD, various wall thicknesses.
• Plates & Sheets: ASTM B443, AMS 5599, thicknesses from 0.5 mm to 50 mm, hot-rolled or cold-rolled.
• Forgings: ASTM B564, ASTM B366, custom flanges, rings, discs, and complex shapes per customer drawing.
• Welding Wire: AWS A5.14 ERNiCrMo-3, diameters 0.8 mm to 5.0 mm, precision-wound coils and spools.

Related Standards

Standard	Description
ASTM B443	Plate, Sheet, and Strip
ASTM B446	Bar and Rod
ASTM B444	Seamless Pipe and Tube
ASTM B564	Forgings
ASTM B366	Fittings
AMS 5599	Sheet, Strip, and Plate
AMS 5666	Bar, Forging, and Ring
AWS A5.14	Welding Wire (ERNiCrMo-3)
ASME SB-443	Boiler and Pressure Vessel Code

Contact Us for Inconel 625

Hangbo Alloy Group maintains extensive inventory of Inconel 625 in all standard product forms. We can provide mill test certificates, third-party inspection reports (SGS, TUV), and custom processing services including cutting, machining, and surface finishing.

For quotations, material certifications, or technical consultation, contact our sales team or call +86-136-1165-6360. We typically respond within 10 minutes.