Ultimate Guide to Inconel 625

Glance

UNS Designation	N06625
Werkstoff Number	2.4856
Alloy Type	Nickel-Chromium-Molybdenum-Niobium (Ni-Cr-Mo-Nb) Solid-Solution Strengthened Superalloy
Nickel Content	58.0% minimum (balance)
Density	8.44 g/cm³ (0.305 lb/in³)
Melting Range	1290–1350°C (2350–2460°F)
Tensile Strength (Annealed)	827–1034 MPa (120–150 ksi)
Yield Strength (Annealed, 0.2% Offset)	414–655 MPa (60–95 ksi)
Maximum Service Temperature	~980°C (1800°F) — oxidizing; ~815°C (1500°F) — reducing
PREN (Pitting Resistance)	≥ 45 (excellent seawater corrosion resistance)
Common Product Forms	Pipe, Tube, Plate, Sheet, Bar, Forgings, Wire, Welding Wire/Filler Metal
Key Standards	ASTM B443/B444/B446/B704/B705; AMS 5599/5666; ASME SB-443; NACE MR0175

Avaliable Product Forms

Designated as UNS N06625 / W.Nr. 2.4856, it is globally recognized and available in virtually all mill forms: pipe, tube, plate, sheet, bar, forged fittings, BW fittings, fasteners, and flanges, etc.

What Is Inconel 625?

Inconel 625 is a nickel-chromium-molybdenum-niobium superalloy renowned for its outstanding combination of corrosion resistance, high-temperature strength, and excellent fabricability.

Originally developed in the 1960s for supercritical steam-line piping, it has since become the go-to material for demanding environments in aerospace, marine engineering, chemical processing, nuclear power, and oil & gas.

What makes it unique: solid-solution strengthening via niobium and molybdenum — meaning it does not require precipitation hardening to achieve its remarkable properties.

Withstands continuous service up to 980°C (1800°F) in oxidizing atmospheres and resists a wide spectrum of corrosive media — from seawater to sulfuric acid.

Inconel 625 Chemical Composition

The exceptional performance of Inconel 625 begins with its controlled chemical composition. Each alloying element plays a specific role, working together to create a material that is simultaneously strong, tough, and corrosion-resistant in conditions that would defeat most other metals.

Nominal Chemical Composition (Weight %)

Nickel (Ni)	58.0% min — Balance (typically 61–63%)
Chromium (Cr)	20.0–23.0%
Molybdenum (Mo)	8.0–10.0%
Niobium + Tantalum (Nb+Ta)	3.15–4.15%
Iron (Fe)	5.0% max
Carbon (C)	0.10% max
Manganese (Mn)	0.50% max
Silicon (Si)	0.50% max
Phosphorus (P)	0.015% max
Sulfur (S)	0.015% max
Cobalt (Co)	1.0% max (if specified)
Aluminum (Al)	0.40% max
Titanium (Ti)	0.40% max

Nickel (Ni) — The Foundation
At approximately 62% of the alloy by weight, nickel provides the austenitic (face-centered cubic) crystal structure that gives Inconel 625 its metallurgical stability from cryogenic temperatures to its melting point. Unlike ferritic or martensitic steels, this structure does not undergo a ductile-to-brittle transition at low temperatures, and it resists sigma-phase embrittlement in service. Nickel also provides the basis for resistance to chloride stress-corrosion cracking (SCC).

Chromium (Cr) — Oxidation Resistance
The 20–23% chromium content provides the alloy's primary defense against oxidizing environments. At elevated temperatures, chromium forms a dense, adherent oxide layer (Cr₂O₃) on the surface that acts as a diffusion barrier, slowing further oxidation. This is why Inconel 625 can operate continuously at temperatures up to 980°C in oxidizing atmospheres — a regime where 316L stainless steel would catastrophically oxidize. In aqueous environments at lower temperatures, chromium contributes to the passive film that imparts corrosion resistance.

Molybdenum (Mo) — The Corrosion Warrior
With 8–10% molybdenum, Inconel 625 significantly outclasses standard stainless steels in resistance to pitting and crevice corrosion. Molybdenum enhances the stability of the passive film in chloride-containing environments, directly contributing to the alloy's high PREN (Pitting Resistance Equivalent Number) of approximately 45 or higher. It also provides resistance to reducing acids — an area where the chromium oxide film alone would be insufficient. In practice, this means Inconel 625 resists seawater, brine, and many concentrations of sulfuric and hydrochloric acids at moderate temperatures.

Niobium (Nb) + Tantalum (Ta) — The Strengtheners
The 3.15–4.15% combined addition of niobium and tantalum is what makes Inconel 625 a solid-solution strengthened alloy rather than one that requires precipitation hardening. Niobium atoms, being significantly larger than nickel atoms (atomic radius mismatch of approximately 15%), introduce lattice strain that impedes dislocation movement. This strengthening effect persists at elevated temperatures where precipitation-hardened alloys would overage and lose their strength. During welding, niobium also acts as a stabilizer against sensitization, tying up carbon and preventing chromium carbide precipitation at grain boundaries.

Iron (Fe) — The Balancer
Iron is present at up to 5.0% maximum, primarily as a cost-control element introduced during melting. At this level, iron does not negatively affect the alloy's corrosion resistance or mechanical properties. However, tight control is exercised because excessive iron could dilute the nickel content and compromise the austenitic structure.

Inconel 625 Mechanical Properties

One of the defining characteristics of Inconel 625 is its ability to maintain useful strength across an extraordinarily wide temperature range — from -196°C to well above 800°C. The table below summarizes typical mechanical properties for annealed Inconel 625 at room temperature, as specified by ASTM B443 (plate/sheet/ strip) and ASTM B444 (pipe/tube).

Room-Temperature Mechanical Properties

Tensile Strength (Rm)	827 MPa (120 ksi) minimum; typically 860–1034 MPa
Yield Strength (Rp0.2)	414 MPa (60 ksi) minimum; typically 450–655 MPa
Elongation in 50 mm	30% minimum; typically 35–60%
Hardness	Rockwell B 90–100 (typical annealed); ≤ HRB 100 (per ASTM)
Modulus of Elasticity	207 GPa (30 × 10⁶ psi) at 20°C
Shear Modulus	79 GPa (11.5 × 10⁶ psi)
Poisson's Ratio	0.31

Elevated-Temperature Strength

Unlike carbon steels and many stainless steels, which lose a significant fraction of their strength above 500–600°C, Inconel 625 retains useful mechanical properties at much higher temperatures. The niobium and molybdenum in solid solution continue to impede dislocation movement even as thermal energy activates additional slip systems. Typical elevated-temperature tensile properties for annealed material are:

• At 540°C (1000°F): Tensile strength ~ 760 MPa, Yield strength ~ 310 MPa

• At 650°C (1200°F): Tensile strength ~ 655 MPa, Yield strength ~ 280 MPa

• At 760°C (1400°F): Tensile strength ~ 415 MPa, Yield strength ~ 240 MPa

• At 870°C (1600°F): Tensile strength ~ 240 MPa, Yield strength ~ 170 MPa

For applications requiring guaranteed elevated-temperature strength, the material can be ordered to the 'Grade 1' (solution-annealed) or 'Grade 2' (solution-annealed + aged) conditions per ASTM B443/B444. Grade 2 material, which undergoes a controlled aging treatment at approximately 730°C (1350°F), can achieve yield strengths exceeding 760 MPa at room temperature through precipitation of gamma-double-prime (γ″) — a metastable Ni₃Nb phase — though this treatment is generally used for applications below 650°C to avoid overaging in service.

Cryogenic Toughness

Inconel 625 retains excellent ductility and impact toughness at cryogenic temperatures. At -196°C (-320°F), the alloy exhibits Charpy V-notch impact values typically exceeding 100 J (74 ft-lb), with no evidence of ductile-to-brittle transition. This makes it suitable for liquefied natural gas (LNG) processing equipment, cryogenic valves, and other low-temperature applications where austenitic stainless steels would also perform well but may lack the required corrosion resistance in subsequent service.

Inconel 625 Corrosion Resistance

Inconel 625 alloy's combination of high nickel, chromium, and molybdenum content provides defense against virtually every common corrosion mechanism. Below, we detail each category of resistance and the environments where it applies.

Pitting and Crevice Corrosion Resistance

Inconel 625's PREN (Pitting Resistance Equivalent Number) — calculated as %Cr + 3.3 × %Mo + 16 × %N — typically exceeds 45 when using nominal composition values. For comparison, 316L stainless steel has a PREN of approximately 24–26, while duplex 2205 reaches 34–36.

In practical terms, this means Inconel 625 exhibits a critical pitting temperature well above 85°C in neutral chloride solutions compared to approximately 15–25°C for 316L. It is considered essentially immune to pitting and crevice corrosion in seawater at ambient temperatures.

Chloride Stress-Corrosion Cracking (SCC) Resistance

The 300 series austenitic stainless steels are susceptible to chloride SCC at temperatures above approximately 60°C. Inconel 625 is highly resistant to this failure mechanism. The threshold nickel content for immunity to chloride SCC in boiling magnesium chloride tests (ASTM G36) is approximately 45%; Inconel 625 sits comfortably above this threshold. This is why Inconel 625 heat exchanger tubing and process piping are standard choices in applications where hot chloride-containing media contact metal surfaces.

Acid Resistance

Inconel 625 resists a comprehensive range of acids under moderate conditions:

•Sulfuric acid (H₂SO₄): Resistant at all concentrations up to approximately 40°C; lower concentrations tolerated at higher temperatures. Not recommended for hot concentrated sulfuric acid.

•Hydrochloric acid (HCl): Resistant at room temperature up to approximately 10% concentration. Not recommended for hot HCl service — Hastelloy C276 is typically preferred in those conditions.

•Phosphoric acid (H₃PO₄): Excellent resistance at all concentrations up to boiling point. This makes Inconel 625 a popular choice for phosphoric acid evaporators and heat exchangers.

•Nitric acid (HNO₃): Very good resistance at all concentrations and temperatures, though at extreme conditions (>90%, boiling) specialized stainless steels may be preferred for economic reasons.

•Organic acids (acetic, formic, etc.): Excellent resistance at all concentrations and temperatures. It's a critical property for pharmaceutical and food-processing equipment.

High-Temperature Oxidation and Carburization

At elevated temperatures, Inconel 625 forms a protective chromium oxide (Cr₂O₃) scale that inhibits further oxidation.

In cyclic oxidation testing, the alloy shows negligible weight change at 980°C even after 1,000 hours. Additionally, the alloy resists carburization which is critical in petrochemical furnace applications. The nickel content reduces carbon solubility compared to iron-based alloys, while the chromium and niobium tie up any carbon that does enter as stable carbides.

Inconel 625 Temperature Range

The effective temperature range of Inconel 625 is one of the widest of any alloy. This section summarizes the critical temperature thresholds that designers and engineers should consider.

Cryogenic Service: -196°C (-320°F) and below

As noted in Section 2.3, Inconel 625 remains ductile and tough at LNG temperatures. There is no ductile-to-brittle transition temperature (DBTT), and Charpy impact values remain high. No special heat treatment or processing is required for cryogenic service beyond standard solution annealing.

Continuously Oxidizing Service: up to 980°C (1800°F)

The chromium oxide protective scale remains effective in clean oxidizing atmospheres up to approximately 980°C. Above this temperature, the scale can spall during thermal cycling, leading to progressive metal loss. For continuous service at the upper end of this range, design allowances for section loss should be considered.

Reducing / Sulfidizing Service: up to 815°C (1500°F)

In reducing atmospheres — particularly those containing hydrogen sulfide (H₂S) — the protective chromium oxide scale is less stable. The service limit drops to approximately 815°C. For applications in sulfidizing environments above this temperature, higher-nickel alloys such as Inconel 601 or 617 may provide better performance.

Creep-Limited Applications: 650–815°C (1200–1500°F)

While tensile properties at temperature are impressive, long-term creep resistance becomes the limiting factor in pressure-boundary applications above approximately 650°C.

The ASME Boiler and Pressure Vessel Code (Section II, Part D) provides time-dependent allowable stress values for Inconel 625 (SB-443) that account for creep rupture life. For high-temperature pressure vessels operating above 650°C, consult the relevant code case for Grade 2 material or consider precipitation-hardened alternatives such as Inconel 718.

Inconel 625 Heat Treatment

The standard heat treatment for Inconel 625 and the condition in which the vast majority of the material is supplied is solution annealing.

Solution Annealing (Grade 1)

Solution annealing dissolves the carbides and intermetallic phases that may have formed during hot working or previous processing, homogenizes the alloying elements, and produces a uniform equiaxed austenitic grain structure. The standard parameters are:

•Temperature: 1095–1205°C (2000–2200°F) — the specific temperature within this range depends on the product form and thickness.
•Holding Time: Typically 1 hour per 25 mm (1 inch) of thickness, with a minimum of 15–30 minutes for thin sections.
•Cooling: Rapid air cooling or water quenching from the annealing temperature. Water quenching is required for sections over approximately 50 mm (2 inches) to prevent re-precipitation of carbides during slow cooling through the 540–870°C (1000–1600°F) range — the 'sensitization' window.

Annealed + Aged (Grade 2)

When higher strength is required for applications operating below 650°C, Inconel 625 can be ordered to Grade 2. This involves an additional aging treatment at approximately 730°C (1350°F) for 8–10 hours, followed by furnace cooling or air cooling.

During aging, gamma-double-prime (γ″ — a metastable Ni₃Nb phase with a body-centered tetragonal crystal structure) precipitates finely and uniformly throughout the matrix, increasing yield strength by 200–300 MPa over the annealed condition.

Important caveat: Grade 2 material should not be exposed to service temperatures above approximately 650°C for extended periods. The γ″ phase overages at these temperatures, transforming to the stable orthorhombic delta (δ — Ni₃Nb) phase, which does not provide significant strengthening. For applications above 650°C, Inconel 718 (which uses γ″ as its primary strengthening phase but with a different alloy design for better stability) or solid-solution strengthened alternatives may be more appropriate.

Stress Relieving After Welding

For most applications, Inconel 625 welded fabrications can be placed in service without post-weld heat treatment (PWHT).

The alloy's resistance to sensitization and excellent as-welded mechanical properties mean PWHT is rarely required for structural integrity. However, when dimensional stability or residual stress relief is necessary. For example, in components that will be machined to tight tolerances after welding — a stress-relief treatment at 870–980°C for 1 hour per 25 mm of thickness can be applied without significant loss of tensile properties.

Inconel 625 Welding Guide

Unlike some nickel alloys that are prone to hot cracking, solidification cracking, or post-weld heat-treatment cracking, Inconel 625 can be welded using virtually all common arc welding processes. This section summarizes the essential principles. A dedicated article in this hub series, 'Inconel 625 Welding Guide,' provides the complete procedure qualification details.

Recommended Welding Processes

•Gas Tungsten Arc Welding (GTAW/TIG) — Preferred for root passes, thin sections, and applications requiring the highest quality. Provides excellent control of heat input and weld pool.
•Gas Metal Arc Welding (GMAW/MIG) — Suitable for thicker sections where higher deposition rates are needed. Pulsed-spray transfer mode is recommended for out-of-position welding.
•Shielded Metal Arc Welding (SMAW/Stick) — Acceptable for field fabrication and repair where gas shielding is impractical. Requires careful moisture control of electrodes to prevent hydrogen-induced porosity.
•Flux-Cored Arc Welding (FCAW) — Increasingly used for weld overlay (cladding) applications where Inconel 625 is deposited onto carbon steel substrates for corrosion protection.

Filler Metal Selection

The standard filler metal for joining Inconel 625 to itself is ERNiCrMo-3 (GTAW/GMAW wire) or ENiCrMo-3 (SMAW electrode), per AWS A5.14/A5.11.

This filler metal is also the standard choice for dissimilar-metal welding — joining Inconel 625 to carbon steel, stainless steel, or other nickel alloys. The over-alloyed chemistry of ERNiCrMo-3 compensates for dilution from the base metal and ensures the weld deposit retains the required corrosion resistance.

Key Welding Parameters

•Interpass Temperature: 150°C (300°F) maximum to prevent grain growth and maintain corrosion resistance.
•Heat Input: Low to moderate — typically 0.5–1.5 kJ/mm. Excessive heat input promotes grain growth and can degrade toughness.
•Shielding Gas (GTAW): 100% argon or argon-helium mixtures for improved wetting. Nitrogen additions (1–2%) are not recommended, as they can increase the risk of porosity.
•Backing Gas (for root passes): 100% argon; flow until the root pass has cooled below 250°C to prevent oxidation (sugaring).

Dissimilar Metal Welding

Inconel 625 is the industry standard for dissimilar-metal welds between nickel alloys and carbon steels, low-alloy steels, or stainless steels. The ERNiCrMo-3 filler metal provides a weld deposit with an intermediate coefficient of thermal expansion, reducing thermal fatigue stresses in service. No preheat is required for the Inconel 625 side, though preheat may be applied to the carbon steel side (typically 100–150°C) and must not exceed the interpass temperature limit on the Inconel side.

Inconel 625 Product Forms and Standards

Inconel 625 is available in virtually every wrought product form used in industrial fabrication. The table below summarizes the key ASTM/ASME specifications for each product form, all under the UNS N06625 designation.

Pipe (Seamless & Welded)	ASTM B444 / ASME SB-444; NACE MR0175 compliant
Tube (Seamless & Welded)	ASTM B444 / B704 / B705; ASME SB-444
Plate, Sheet & Strip	ASTM B443 / ASME SB-443; AMS 5599 (sheet/strip)
Bar, Rod & Wire	ASTM B446 / ASME SB-446; AMS 5666 (bar/forging)
Forgings	ASTM B564 / ASME SB-564 (nickel alloy forgings)
Welding Wire / Filler Metal	AWS A5.14 ERNiCrMo-3; AWS A5.11 ENiCrMo-3
Fittings (Butt-Weld)	ASTM B366 / ASME SB-366 (factory-made wrought fittings)
Bolts & Fasteners	ASTM F467 / F468; commonly manufactured per customer drawing

For pressure-boundary applications, Inconel 625 components are typically ordered to ASME Section II (Materials) specifications, with ASME Section VIII Division 1 (Pressure Vessels) or ASME B31.3 (Process Piping) governing the design rules.

The allowable stress values for ASME code construction are tabulated in ASME Section II, Part D, for both annealed (Grade 1) and annealed-plus-aged (Grade 2) conditions.

Inconel 625 Applications

The following is a summary overview of Inconel 625's application areas.

Inconel 625 for Offshore Oil & Gas

Inconel 625 is the benchmark material for sour service (H₂S-containing) environments in offshore production. Hydraulic control lines, chemical injection lines, subsea umbilical tubing, and wellhead components are routinely manufactured from Inconel 625 per NACE MR0175/ISO 15156, which lists the alloy as acceptable for all sour service conditions at any temperature. Its combination of chloride SCC resistance and H₂S resistance makes it uniquely suited for deepwater and ultra-deepwater production.

Inconel 625 for Marine Engineering

From seawater pump shafts and fasteners to propeller blades and heat exchanger tubing, Inconel 625 provides the crevice corrosion resistance that stainless steels cannot deliver in stagnant or low-flow seawater conditions. Wire rope, springs, and bellows manufactured from Inconel 625 wire are standard in naval and offshore mooring applications. The alloy is also widely used for seawater piping systems on naval vessels and offshore platforms, particularly in the form of Inconel 625-clad carbon steel pipe, which combines the corrosion resistance of the alloy with the structural strength and lower cost of carbon steel.

Inconel 625 for Aerospace

Inconel 625 is used extensively in aerospace gas turbine engines for thrust-reverser components, turbine shroud rings, bellows, expansion joints, and ducting systems that operate in the 600–980°C temperature range. It is also the standard material for engine exhaust systems in military aircraft and spacecraft, where the combination of high-temperature strength, thermal fatigue resistance, and weldability is essential. The AMS 5599 (sheet/strip) and AMS 5666 (bar/forging) specifications are the primary procurement documents for aerospace-grade Inconel 625.

Inconel 625 for Chemical Processing

In the chemical process industries, Inconel 625 is specified for heat exchangers, reactors, columns, and piping systems handling mixed acids, chlorinated organics, or hot chloride-containing process streams. The alloy's resistance to chloride SCC allows it to be used at temperatures where 316L stainless steel would fail within hours. Specific applications include phosphoric acid evaporator tubes, sulfuric acid coolers, and organic acid reactors in pharmaceutical manufacturing.

Inconel 625 for Nuclear Power

Inconel 625 is used in nuclear power plants for reactor-core components, control-rod drive mechanisms, and primary coolant piping. The alloy's resistance to irradiation-assisted stress-corrosion cracking (IASCC) and its compatibility with the high-temperature water chemistry of pressurized water reactors (PWRs) make it a standard material for critical service in nuclear steam-supply systems.

Inconel 625 for LNG and Cryogenic Processing

Main heat exchangers in LNG liquefaction plants often use Inconel 625 tubing, taking advantage of the alloy's combination of cryogenic toughness and corrosion resistance to aggressive amine-based acid-gas removal (AGR) solvents used upstream of the liquefaction cold box.

Inconel 625 vs Other Alloys

Inconel 625 vs Inconel 718

The difference is strength versus corrosion-temperature.

Inconel 718, an age-hardenable alloy, reaches yield strength above 1,034 MPa, making it suitable for aerospace turbine disks and jet engine fasteners.

Inconel 625, solid-solution-strengthened, has a far wider operating window: superior pitting and chloride resistance, while its non-age-hardened microstructure retains useful strength to approximately 980°C, well beyond 718's 650–700°C degradation limit.

So, choose 718 when strength governs; choose 625 when corrosion or sustained high temperature does.

Inconel 625 vs Hastelloy C276

The decision depends on whether the environment is reducing or oxidizing.

Hastelloy C276, with PREN exceeding 65, outperforms Inconel 625 decisively in reducing acids—hydrochloric, hot sulfuric, and wet chloride gases—where its unmatched localized corrosion resistance justifies a 30–50% cost premium.

Inconel 625, carrying 20–23% chromium to C276's 14.5–16.5%, reverses the advantage in oxidizing conditions above 600°C by forming a more stable chromia scale, sustaining oxidation resistance to approximately 980°C with half-again higher yield strength.

Practically: concentrated reducing acid streams demand C276; oxidizing, high-temperature, or strength-critical service favors 625.

Inconel 625 vs Incoloy 825

Incoloy 825 is the economical baseline; Inconel 625 is the performance extension.

With 38–46% nickel, 2.5–3.5% molybdenum, and deliberate copper addition (1.5–3%), Incoloy 825 handles sulfuric and phosphoric acid service below 500°C at roughly 40–50% lower material cost than 625—sufficient for pickling tanks, chemical heat exchangers, and fertilizer production.

Inconel 625 doubles the nickel (≥58%), triples the molybdenum (8–10%), and adds niobium (3.15–4.15%), extending corrosion resistance into seawater, sour H₂S streams, and high-chloride brines while raising the service ceiling by 200–300°C.

The choice of 625 is warranted the moment chlorides, sulfides, or temperatures above 500°C enter the specification.

Inconel 625 vs Monel 400

The distinction is binary: Monel 400 owns seawater and HF acid below 400°C; Inconel 625 owns everything hotter, stronger, or more corrosive.

Monel 400's nickel-copper chemistry (63%+ Ni, 28–34% Cu) delivers decades-proven performance in marine propeller shafts, pump components, and HF alkylation units, yet its lack of chromium precludes any meaningful oxidation protection above 500°C.

Inconel 625 has 20–23% chromium for oxidation resistance to 980°C, plus 8–10% molybdenum and niobium for chloride pitting immunity and yield strength of 414 MPa—73% higher than Monel 400's 240 MPa.

For ambient seawater or HF, Monel 400 is cost-effective and proven; for any scenario involving elevated temperature combined with strength or oxidizing conditions, Inconel 625 is the only defensible choice.

Inconel 625 vs Stainless Steel 316L

Inconel 625 is the answer when 316L's corrosion and temperature limits are exceeded—at 5–10× the cost.

316L serves food processing, architecture, and pharma well with a PREN of approximately 24 but fails predictably above 400°C under load and in any chloride-rich environment where pitting and stress corrosion cracking occur.

Inconel 625 eliminates these failure modes: 58%+ nickel provides SCC immunity; 20–23% chromium and 8–10% molybdenum raise the PREN to approximately 50; niobium solid-solution strengthening sustains ASME design allowables to 980°C with triple the elevated-temperature yield strength of 316L.

The selection guideline is simple: specify 316L for ambient, low-chloride, non-structural service; specify 625 once the process stream introduces seawater, brine, H₂S, or sustained temperatures above 500°C.

Inconel 625 Buying Guide

Inconel 625 Equivalent Grades Chart

Country / Organization	Standard	Designation
United States (ASTM / ASME)	ASTM B443 / ASME SB-443	N06625 Grade 1 or Grade 2
United States (ASTM / ASME)	ASTM B446 / ASME SB-446	N06625 Grade 1 (annealed)
United States (ASTM / ASME)	ASTM B564 / ASME SB-564	N06625
United States (ASTM / ASME)	ASTM B704 / ASME SB-704	N06625
United States (ASTM / ASME)	ASTM B705 / ASME SB-705	N06625
United States (ASTM / ASME)	ASTM B829 / ASME SB-829	N06625
United States (AMS)	AMS 5599	Inconel 625
Germany (DIN / WNr)	DIN 2.4856	NiCr22Mo9Nb
Germany (EN / DIN)	EN 10095 / 2.4856	NiCr22Mo9Nb
Germany (DIN)	DIN 17744	NiCr22Mo9Nb
United Kingdom (BS)	BS 3072 / BS 3074	NA43 (approx.)
France (AFNOR)	AFNOR NC22DNb	NC22DNb
Japan (JIS)	JIS NCF 625	NCF 625
China (GB/T)	GB/T 15007	NS336 / 0Cr20Ni65Mo3Nb2
China (YB)	YB/T 5354 / 5355	NS336
Russia (GOST)	GOST 5632	ХН65МВБ (KhN65MVB)
Russia	GOST 22442	EP814
European Union (EN)	EN 10095 / 2.4856	NiCr22Mo9Nb
India (IS)	IS 10095	~N06625
ISO (International)	ISO 6208	NiCr22Mo9Nb
ISO (International)	ISO 9723 / 9724	N06625

Frequently Asked Questions

Q: Is Inconel 625 magnetic?
No. Inconel 625 has a fully austenitic (face-centered cubic) crystal structure at room temperature, which is non-magnetic. It will not attract a magnet in the annealed condition. However, cold working can induce trace amounts of martensite, producing very slight magnetic permeability — this effect is minimal and does not affect the alloy's suitability for non-magnetic applications.

Q: What is the difference between Inconel 625 and Inconel 625 LCF?
Inconel 625 LCF (Low Cycle Fatigue) is a variant of the standard alloy with tighter controls on chemistry and grain size, specifically optimized for aerospace rotating components subjected to cyclic thermal and mechanical loading. The LCF designation is not an official ASTM grade but rather a supplier-specific terminology. For most industrial applications, standard Inconel 625 (Grade 1) provides adequate fatigue performance.

Q: Can Inconel 625 be machined?
Yes, but with difficulty. Inconel 625 work-hardens rapidly during machining, which accelerates tool wear. Recommended practices include: use carbide or ceramic cutting tools; maintain rigid tool setups to minimize vibration; use low cutting speeds (15–25 m/min for carbide tools); use positive-rake tool geometries; and apply chlorinated or sulfurized cutting fluids. For production machining, ceramic inserts running at 200–300 m/min can be cost-effective.

Q: What is the maximum pressure rating for Inconel 625 pipe?
Pressure ratings are not determined solely by the material — they depend on pipe diameter, wall thickness, service temperature, and the applicable design code (ASME B31.3 for process piping, ASME VIII for pressure vessels).
Inconel 625 pipe to ASTM B444 typically follows the same dimensional standards (ANSI/ASME B36.10M or B36.19M) as stainless steel pipe, and pressure ratings are calculated using the allowable stress values from ASME Section II, Part D.

Q: Does Inconel 625 rust?
No. Under normal conditions, Inconel 625 does not rust (form iron oxide) because of its high nickel and chromium content.
However, under certain conditions — such as exposure to reducing acids at elevated temperatures — the passive film may break down, leading to uniform or localized corrosion. This is not 'rusting' in the conventional sense (hydration of iron oxide) but rather a loss of passivity. For environments where this is a concern, refer to the corrosion data in Section 3 or consult our technical team for a material recommendation.

Q: What is the shelf life of Inconel 625 welding consumables?
ERNiCrMo-3 welding wire and ENiCrMo-3 electrodes, when stored in their original sealed packaging in a clean, dry environment, have an indefinite shelf life in terms of metallurgical properties.
However, electrodes (SMAW) can absorb moisture over time if the packaging is damaged, leading to hydrogen-induced porosity during welding. It is standard practice to re-dry SMAW electrodes at 250–300°C for 2 hours before use if they have been exposed to ambient humidity.

Q: Is Inconel 625 suitable for 3D printing / additive manufacturing?
Yes. Inconel 625 is one of the most widely used alloys in laser powder bed fusion (LPBF) and directed energy deposition (DED) additive manufacturing.
AMS 7000 and AMS 7001 provide specifications for additively manufactured Inconel 625. The rapid solidification inherent in LPBF produces a finer grain structure than wrought material, which can enhance strength but may require post-process hot isostatic pressing (HIP) to eliminate internal porosity for critical applications.