Inconel 600, 625 & 718 Comparison | High-Performance Fasteners

Selecting the right Inconel alloy is critical for engineers, procurement managers, and decision-makers in aerospace, marine, energy, and industrial applications. High-performance alloys such as Inconel 600, 625, and 718 are nickel-based superalloys engineered for extreme environments, including high temperature, corrosive conditions, and high-stress operations. Making the wrong choice can lead to material failure, downtime, or regulatory non-compliance.

This guide provides a comprehensive technical comparison of Inconel grades, covering chemical composition, mechanical properties, density, hardness, yield strength, thermal performance, machining challenges, surface treatment, industry applications, technical standards, and supplier considerations. It addresses common customer pain points, helping you make informed decisions backed by ISO 9001, IATF 16949, AS9100, and NADCAP certifications.

Understanding Inconel 600, 625, and 718

Inconel 600 – Chemical Composition, Properties, and Fabrication vs Stainless Steel

Composition: Approximately 72% nickel, 14–17% chromium, with minor iron, manganese, silicon, and carbon.

Properties: Excellent oxidation and corrosion resistance up to 1093°C. Mechanical properties include:

• Hardness: 160–220 HB

• Tensile strength: 515–827 MPa

• Yield strength: 180–310 MPa

Applications: Metal stampings, heat exchangers, chemical processing components, industrial ducting.

Fabrication & Machining: Inconel 600 supports metal stamping, CNC machining, and moderate welding. Surface finishing such as electropolishing or passivation improves corrosion resistance. For stamping, typical sheet thicknesses range 0.5–3 mm, with feed rates adjusted to minimize work hardening.

Supplier & Certification Notes: Certified suppliers provide custom Inconel 600 metal stampings in bulk or precision parts for aerospace, marine, and industrial applications.

Inconel 625 – Mechanical Performance, Machining Challenges, and Corrosion Resistance

Composition: Nickel (58%), chromium (20–23%), molybdenum (8–10%), niobium (3–4%).

Properties:

• Hardness: 200–300 HB

• Yield strength: 414–827 MPa

• Tensile strength: 827–1,034 MPa

• Excellent fatigue and corrosion resistance, especially in seawater and chemically aggressive environments

Machining & Fabrication: Compared to 600, Inconel 625 is more challenging to machine, requiring:

• Specialized tooling (carbide or coated tools)

• Controlled cutting speed and feed rates (recommended 30–60 m/min for roughing, 15–25 m/min for finishing)

• Low heat input during welding; preheating generally not required, but post-weld stress relief may be applied

• Slow feed rates in CNC milling to reduce work hardening

Surface Treatment: Passivation or electropolishing improves corrosion resistance for marine and chemical applications.

Applications: Offshore platforms, chemical plants, marine structures, aerospace components.

Supplier & Testing: Certified suppliers and hardness testing labs in the USA provide compliance with ISO 9001 and IATF 16949 standards.

Inconel 718 – Precipitation-Hardened Superalloy for High-Load Applications

Composition: Nickel-based, strengthened with chromium, niobium, molybdenum, and titanium.

Properties:

• Hardness: 330–410 HB after aging

• Yield strength: up to 1,270 MPa

• Tensile strength: 1,380–1,510 MPa

• Density: 8.19 g/cm³

Applications: Aerospace turbine disks, high-pressure valves, fasteners in high-load and high-temperature environments.

Machining & Fabrication:

• Requires precision CNC machining, carbide tooling, and post-machining stress-relief heat treatment

• Welding feasible but demands strict pre- and post-heat treatment to maintain mechanical properties

• Recommended cutting speeds: 10–30 m/min; feed rates: 0.05–0.2 mm/rev for turning; lower for finishing

Supplier & Certification Notes: Components from NADCAP-approved suppliers meet AS9100/IATF 16949 standards.

Technical Comparison of Inconel Grades – Mechanical and Corrosion Properties

Analysis:

• Inconel vs Stainless Steel: Inconel alloys maintain strength and corrosion resistance at high temperatures; stainless steel may fail in marine or chemical environments.

• 625 vs 718: Use 625 for marine or chemically aggressive conditions; choose 718 for high-load and high-temperature structural components.

• Cost Considerations: 718 is most expensive due to complex processing; 600 and 625 allow cost-efficient bulk production.

Fabrication and Surface Treatment – CNC, Stamping, Welding, and Finishing

• Inconel 600: Metal stamping, CNC machining, moderate welding; electropolishing reduces corrosion points.

• Inconel 625: Controlled machining, slow feed rates, heat input management; passivation or coatings enhance seawater durability.

• Inconel 718: Precision CNC, carbide tooling, post-aging heat treatment; surface finishing improves fatigue resistance.

Selecting the right combination of alloy, machining parameters, heat treatment, and surface finishing is essential for meeting aerospace, marine, and energy technical standards

Real-World Applications: Case Stories

Aerospace Precision in Germany
In Germany, a leading aerospace manufacturer faced a critical challenge: producing turbine fasteners capable of withstanding extreme temperatures and high mechanical stress. Traditional materials risked premature wear and potential safety issues. The company turned to Welle Inspection for a solution. Our engineers supplied precision-machined Inconel 718 fasteners, rigorously tested for yield strength and corrosion resistance. Over the next 18 months, these components performed flawlessly, exceeding AS9100 standards and ensuring zero in-service failures, giving the manufacturer confidence in both safety and reliability.

Marine Reliability in Houston, USA
On the Gulf Coast in Houston, an offshore platform struggled with fastener corrosion due to constant seawater exposure. Downtime and maintenance costs were mounting. Welle Inspection recommended Inconel 625 fasteners, known for their superior corrosion resistance in marine environments. Each batch underwent certified hardness testing before deployment. The results were immediate: the fasteners resisted the harsh marine conditions, eliminated unplanned maintenance, and guaranteed operational safety, allowing the platform team to focus on production rather than repairs.

FAQ / People Also Ask

Is Inconel stronger than stainless steel?
Yes, Inconel alloys like 718 and 625 offer higher yield strength and corrosion resistance at elevated temperatures.

Which Inconel grade is best for marine applications?
Inconel 625 resists seawater; 718 is suitable for high-load structural applications.

Can Inconel 718 be welded easily?
Welding 718 requires controlled pre- and post-heat treatment to maintain strength and fatigue resistance.

How hard is Inconel 625 compared to stainless steel?
Brinell hardness: 200–300 HB, generally higher than most stainless steels.

What industries use Inconel 600 metal stampings?
Aerospace, marine, chemical processing, and high-temperature industrial applications.

Where to buy Inconel 718 fasteners with NADCAP approval?
Certified suppliers like Welle Inspection provide traceable, high-performance components in USA, UK, India, and UAE.

CTA 

Ensure your project’s success with the right Inconel grade. Order custom Inconel 600, 625, or 718 components from certified suppliers. Consult our experts today for precision machining, hardness testing, and corrosion-resistant solutions to prevent material failure.

For Further Reading

1.Why Is Inconel So Expensive?

2.High Tensile Inconel 718 Bolts

3.Inconel Bolts: High-Temperature, Corrosion-Resistant Solutions

4.Nickel vs AL6XN vs Monel vs Hastelloy vs Inconel