Inconel 625 vs Inconel 718: Corrosion Resistance, Strength and Cost

Introduction

When comparing Inconel 625 vs Inconel 718, buyers should choose Inconel 625 when corrosion resistance, seawater performance, weldability and resistance to pitting or crevice corrosion are the main requirements. Choose Inconel 718 when very high mechanical strength, fatigue resistance, creep resistance and high-temperature strength are more important than maximum corrosion resistance. In simple terms, Inconel 625 is usually the better choice for corrosion service, while Inconel 718 is usually the better choice for high-strength aerospace, turbine, spring, fastener and pressure-load applications.

Both Inconel 625 and Inconel 718 are nickel-based superalloys used in oil and gas, aerospace, marine engineering, chemical processing, power generation and high-temperature equipment. However, they are designed for different engineering priorities. Alloy 625 is a solid-solution strengthened nickel-chromium-molybdenum-niobium alloy, while Alloy 718 is a precipitation-hardenable nickel-chromium alloy strengthened mainly by niobium, titanium and aluminum through heat treatment.

For industrial procurement, buyers should compare corrosion environment, strength requirement, working temperature, welding process, heat treatment condition, product form, applicable ASTM or ASME standard, EN 10204 3.1 MTC, heat number control, PMI testing, UT testing, third-party inspection, export packaging and delivery capability before selecting Inconel 625 or Inconel 718.

What Are Inconel 625 and Inconel 718?

Inconel 625, also known as Alloy 625 or UNS N06625, is a nickel-chromium-molybdenum-niobium alloy known for excellent corrosion resistance, high strength without age hardening and good weldability. It is commonly supplied as Inconel 625 pipe, tube, bar, plate, sheet, flange, fitting, forging, wire and welding consumable.

Inconel 718, also known as Alloy 718 or UNS N07718, is a precipitation-hardenable nickel-chromium alloy with very high strength, excellent fatigue resistance and good performance at elevated temperatures. It is widely used for aerospace fasteners, turbine components, high-strength bolts, springs, shafts, oilfield tools, cryogenic parts and precision machined components.

Fast Buyer Recommendation

Application Condition	Recommended Alloy	Reason
Seawater, offshore and chloride corrosion service	Inconel 625	Higher molybdenum content provides stronger resistance to pitting and crevice corrosion
High-strength bolts, fasteners and aerospace parts	Inconel 718	Precipitation hardening provides very high strength and fatigue resistance
Welded piping, overlay and corrosion-resistant fabrication	Inconel 625	Good weldability and strong corrosion performance after welding
Turbine, compressor and high-load rotating components	Inconel 718	Excellent strength, creep resistance and fatigue performance after heat treatment
Chemical processing with aggressive media	Inconel 625 or higher corrosion alloy	Better corrosion resistance than Inconel 718 in many chemical and chloride environments

Chemical Composition Comparison

The chemical composition explains the main performance difference between Inconel 625 and Inconel 718. Inconel 625 contains higher molybdenum, which improves corrosion resistance in chloride and seawater environments. Inconel 718 contains niobium, titanium and aluminum for precipitation hardening, which gives it much higher strength after proper heat treatment.

Element	Inconel 625 / UNS N06625 Typical Range (%)	Inconel 718 / UNS N07718 Typical Range (%)	Material Selection Note
Nickel (Ni)	Minimum 58.00	50.00 – 55.00	Base element for corrosion resistance and high-temperature stability
Chromium (Cr)	20.00 – 23.00	17.00 – 21.00	Improves oxidation resistance and general corrosion resistance
Molybdenum (Mo)	8.00 – 10.00	2.80 – 3.30	Higher Mo content makes Inconel 625 better for chloride pitting and crevice corrosion resistance
Niobium + Tantalum (Nb + Ta)	3.15 – 4.15	4.75 – 5.50	Key strengthening element, especially important in Inconel 718
Titanium (Ti)	Max 0.40	0.65 – 1.15	Supports precipitation hardening in Inconel 718
Aluminum (Al)	Max 0.40	0.20 – 0.80	Contributes to precipitation strengthening in Inconel 718
Iron (Fe)	Max 5.00	Balance / significant content	Must match the applicable specification and MTC values
Carbon (C)	Max 0.10	Max 0.08	Controlled for weldability, hot workability and microstructure stability

Mechanical Properties and Heat Treatment

Mechanical properties are a major reason buyers compare Inconel 625 and Inconel 718. Inconel 625 provides good strength through solid-solution strengthening without aging treatment. Inconel 718 can achieve much higher tensile strength and yield strength after solution treatment and precipitation hardening, making it suitable for aerospace fasteners, turbine parts, springs and high-load components.

Property	Inconel 625	Inconel 718	Buyer Selection Note
Strengthening Method	Solid-solution strengthened	Precipitation hardenable	Choose 718 when high strength after heat treatment is required
Tensile Strength	High, but generally lower than aged 718	Very high after precipitation hardening	Confirm actual condition, bar size and heat treatment on MTC
Yield Strength	Good for corrosion-resistant structures and piping components	Much higher in aged condition	Important for bolts, shafts, springs, aerospace and high-load parts
Fatigue Resistance	Good	Excellent for high-strength applications	718 is commonly selected for cyclic load and rotating components
Weldability	Very good	Good, but heat treatment and cracking sensitivity must be managed	625 is often preferred for weld overlay and corrosion-resistant fabrication
Machinability	Difficult compared with stainless steel, but workable with proper tooling	Difficult, especially after aging due to high strength	Confirm machining allowance, condition and hardness before production

Applicable Standards and Equivalent Grades

Inconel 625 and Inconel 718 are supplied according to different standards depending on product form. A correct quotation should clearly state whether the buyer needs bar, plate, sheet, pipe, tube, wire, forging, flange, fitting or machined part. Using the wrong standard can create certificate problems during project inspection.

Item	Inconel 625	Inconel 718	Common Product Scope
UNS	N06625	N07718	International material identification
EN / W.Nr.	2.4856 / NiCr22Mo9Nb	2.4668 / NiCr19Fe19Nb5Mo3	European drawings and project specifications
Bar / Rod Standard	ASTM B446	ASTM B637	Round bar, rod, forging stock and machined parts
Plate / Sheet Standard	ASTM B443	ASTM B670 or project-specific specification depending on product requirement	Plate, sheet, strip and cut-to-size material
Pipe / Tube Standard	ASTM B444, ASTM B704, ASTM B705	Project-specific or aerospace/oilfield specifications depending on form and condition	Seamless tube, welded tube, pipe and precision tubing
Forging Standard	ASTM B564	AMS / ASTM / customer project specification depending on application	Forged rings, blocks, discs, shafts, flanges and high-strength components
Common Aerospace Specification	AMS 5599, AMS 5666 and other product-specific requirements	AMS 5662, AMS 5663, AMS 5664 and other heat-treatment-specific requirements	Aerospace bars, forgings, sheet, plate and high-performance components

Quality Testing and Material Traceability

For nickel alloy procurement, traceability is critical because Inconel 625 and Inconel 718 are high-value materials with different chemical designs and heat treatment requirements. The heat number on the product marking, label, packing list and EN 10204 3.1 MTC should match. For critical applications, PMI testing, UT testing, dimensional inspection and third-party inspection should be confirmed before shipment.

Certificate and Inspection Checklist

Inspection / Document Item	What to Check	Why It Matters
EN 10204 3.1 MTC	Grade, UNS number, standard, heat number, chemical composition, mechanical properties and condition	Confirms batch-specific quality and supports project documentation
Heat Number Control	Heat number on material, tag, packing list and MTC must be consistent	Prevents mixed material supply and supports full traceability
PMI Testing	Verify Ni, Cr, Mo, Nb and alloy identity	Helps distinguish Inconel 625 from Inconel 718 and avoid wrong-grade supply
UT Testing	Check internal defects for bars, plates, forgings and critical components	Important for aerospace, high-load, pressure and machining applications
Heat Treatment Report	Especially important for Inconel 718 solution treated and aged condition	Determines final strength, hardness, fatigue performance and service reliability
Dimensional Inspection	Diameter, thickness, OD, WT, width, length, straightness, flatness and tolerance	Ensures machining, welding, assembly and installation requirements are met
Third-party Inspection	SGS, BV, TUV, Intertek or customer-appointed inspection before shipment	Provides additional confidence for export orders and critical engineering projects

Comparison With Similar Nickel Alloys

Inconel 625 and Inconel 718 are often compared with Inconel 600, Inconel 601, Inconel X-750, Hastelloy C-276, Incoloy 825 and Monel 400. The correct grade depends on the balance between corrosion resistance, high-temperature oxidation resistance, strength, weldability and cost.

Material	Corrosion Resistance	Strength	Cost Level	Best-use Recommendation
Inconel 625	Excellent in seawater, chloride and many chemical environments	High	High	Offshore, seawater systems, chemical processing, weld overlay and corrosion-resistant piping
Inconel 718	Good, but not as corrosion-focused as 625	Very high after aging	High	Aerospace fasteners, turbine parts, high-strength bolts, springs and oilfield tools
Inconel 600	Good general corrosion and oxidation resistance	Medium	Medium to high	Heat treatment equipment, furnace parts and general nickel alloy service
Inconel X-750	Good oxidation and corrosion resistance	High after precipitation hardening	High	Springs, fasteners, turbine parts and high-temperature mechanical components
Hastelloy C-276	Excellent in many severe chemical environments	Medium to high	Very high	Strong acids, chemical reactors, pollution control and severe corrosion service

Industrial Applications of Inconel 625 and Inconel 718

Both alloys are used in demanding industries, but their application focus is different. Inconel 625 is more often used where corrosion resistance, seawater resistance and weldability are critical. Inconel 718 is more often used where very high strength, fatigue resistance and creep resistance are required.

Industry / Application	Recommended Alloy	Common Products	Selection Reason
Offshore and Marine Engineering	Inconel 625	Pipes, tubes, flanges, fittings, bolts, shafts and weld overlay parts	Excellent resistance to seawater, chloride pitting and crevice corrosion
Aerospace	Inconel 718	Fasteners, turbine discs, shafts, rings, springs and structural components	Very high strength, fatigue resistance and elevated-temperature performance
Chemical Processing	Inconel 625	Heat exchangers, process piping, reactors, tube sheets and fittings	Better corrosion resistance in many acidic and chloride-containing media
Oil and Gas	625 or 718 depending on service	Downhole tools, fasteners, valves, piping, springs and high-pressure parts	625 for corrosion; 718 for high-strength mechanical components
Power Generation	625 or 718 depending on part design	Turbine parts, fasteners, heat-resistant components and corrosion-resistant piping	625 for corrosion/oxidation; 718 for strength and fatigue performance
Welding and Cladding	Inconel 625	Welding wire, overlay wire, clad plates and corrosion-resistant weld deposits	Excellent weldability and corrosion-resistant overlay performance

Why Choose Inconel 625 or Inconel 718?

The correct selection depends on whether the buyer needs corrosion resistance or mechanical strength as the main priority. Inconel 625 is usually selected for corrosion service, weld overlay, seawater piping and chemical environments. Inconel 718 is usually selected for high-strength fasteners, aerospace parts, springs, turbine components and high-load machined parts.

Corrosion, Strength and Cost Comparison

Selection Factor	Inconel 625	Inconel 718	Buyer Decision
Corrosion Resistance	Excellent in seawater, chloride, pitting and many chemical environments	Good, but generally not as corrosion-focused as 625	Choose 625 when corrosion resistance is the first priority
Mechanical Strength	High strength without aging	Very high strength after precipitation hardening	Choose 718 when high strength, fatigue and load capacity are critical
Weldability	Excellent and widely used for weld overlay	Good, but heat treatment and cracking control are more important	Choose 625 for corrosion-resistant weld fabrication and cladding
Heat Treatment	No age hardening required for standard strength	Requires solution treatment and aging for maximum strength	Confirm final condition carefully for 718
Cost	High due to Ni and Mo content	High due to alloying elements and heat treatment requirements	Total cost depends on market price, size, condition, testing and machining difficulty

Common Buyer Mistakes

A common mistake is selecting Inconel 718 only because it is stronger, even when the part will be exposed to severe seawater or chemical corrosion where Inconel 625 may perform better. Another mistake is selecting Inconel 625 for a high-load fastener or spring application where aged Inconel 718 would provide much higher strength. Buyers should also avoid accepting unclear certificates, mixed heat numbers, missing heat treatment condition or material without PMI verification.

Surface Finish, Processing and Export Packaging

Inconel 625 and Inconel 718 can be supplied with different surface conditions according to product form and application. Common bar finishes include black surface, peeled surface, turned surface, ground surface and polished surface. Plate and sheet products can be supplied hot rolled, cold rolled, solution annealed, pickled or polished. Pipes and tubes may be supplied pickled, bright annealed or mechanically polished depending on service requirements.

Because nickel alloys are high-value materials, export packaging should protect the material from scratches, moisture, deformation and contamination. SASA ALLOY can provide seaworthy wooden cases, wooden pallets, plastic wrapping, end caps for pipes and tubes, steel strip bundling, clear labels and shipping marks. Heat number, grade, size and quantity should be clearly marked for warehouse receiving and project inspection.

Related Nickel Alloy Products

SASA ALLOY supplies Inconel 625 and Inconel 718 in different product forms for oil and gas, offshore, aerospace, chemical processing, power generation and industrial manufacturing projects. Product links can help buyers quickly confirm whether they need bars, plates, pipes, tubes, wire, flanges, fittings or forgings.

Product	Common Grades	Typical Use
Inconel Alloy Bar	Inconel 600, 601, 625, 718, X-750, 725	Shafts, fasteners, valve stems, springs, machining parts and aerospace components
Inconel Alloy Plate	Inconel 600, 601, 625, 718, 690	Pressure parts, chemical equipment, heat-resistant plates and corrosion-resistant structures
Inconel Alloy Pipe and Tube	Inconel 600, 601, 625, 690, 718	Seawater piping, heat exchangers, chemical transfer lines and high-temperature systems
Nickel Alloy Flanges	Inconel 625, Inconel 718, Hastelloy C-276, Monel 400, Incoloy 825	Oil and gas, chemical piping, offshore systems and pressure equipment connections
Nickel Alloy Fittings	Inconel 625, Hastelloy C-276, Monel 400, Incoloy 825, Alloy 20	Elbows, tees, reducers, stub ends and customized corrosion-resistant piping fittings

FAQ About Inconel 625 vs Inconel 718

1. Which is better, Inconel 625 or Inconel 718?

Neither alloy is universally better. Inconel 625 is better when corrosion resistance, seawater performance and weldability are the main priorities. Inconel 718 is better when very high strength, fatigue resistance and high-temperature mechanical performance are required.

2. Is Inconel 718 stronger than Inconel 625?

Yes, Inconel 718 can achieve much higher strength after proper solution treatment and aging. It is commonly used for high-strength bolts, fasteners, springs, turbine components and aerospace parts. Inconel 625 has high strength, but it is selected more often for corrosion resistance and weldability.

3. Is Inconel 625 more corrosion resistant than Inconel 718?

In many chloride, seawater and chemical environments, Inconel 625 offers better corrosion resistance because of its higher molybdenum content. Inconel 718 still has good corrosion resistance, but its main advantage is high mechanical strength after precipitation hardening.

4. Which alloy is better for welding?

Inconel 625 is generally easier to use for corrosion-resistant welding, overlay and fabrication. Inconel 718 can be welded, but heat treatment condition, cracking control and post-weld performance must be managed carefully for critical parts.

5. Which alloy is more expensive?

Both Inconel 625 and Inconel 718 are high-cost nickel alloys. The final cost depends on nickel, molybdenum and niobium market prices, product form, size, heat treatment, testing requirements, machining difficulty and delivery time. In many cases, Inconel 625 has high raw material cost due to molybdenum content, while Inconel 718 may have additional cost from heat treatment and high-strength processing requirements.

6. How can buyers verify whether the material is Inconel 625 or Inconel 718?

Buyers should review the EN 10204 3.1 MTC, heat number, product marking and chemical composition. PMI testing is strongly recommended for high-value nickel alloy orders because it can verify nickel, chromium, molybdenum and niobium content and help identify the correct alloy grade.

7. What information is needed for a fast quotation?

A complete inquiry should include alloy grade, UNS number, product form, ASTM or AMS standard, size, quantity, condition, heat treatment requirement, surface finish, tolerance, testing requirement, MTC requirement, destination port and packing requirement. For example: ASTM B637 UNS N07718 Inconel 718 round bar, solution treated and aged, diameter 25 mm, length 3000 mm, EN 10204 3.1 MTC and PMI testing required.

Conclusion

The choice between Inconel 625 and Inconel 718 should be based on the real working condition. Inconel 625 is usually the preferred alloy for corrosion resistance, seawater service, offshore piping, chemical processing, weld overlay and chloride-containing environments. Inconel 718 is usually the preferred alloy for high-strength fasteners, aerospace components, turbine parts, springs, oilfield tools and load-bearing components requiring precipitation-hardened strength.

Before ordering, buyers should confirm the correct UNS number, ASTM or AMS standard, product form, heat treatment condition, mechanical property requirement, corrosion environment, EN 10204 3.1 MTC, PMI testing, UT testing, dimensional inspection and export packaging. A professional nickel alloy supplier should help buyers compare corrosion resistance, strength and cost to select the most suitable material for the project.