When sourcing nickel-based superalloys for aerospace, oil & gas, or high-temperature structural components, hardness is a critical indicator of strength, wear resistance, and service performance. Among these alloys, Inconel® 718 (UNS N07718) stands out for its exceptional hardness after heat treatment, combined with excellent corrosion resistance and fatigue strength.
What is Inconel 718 alloy bar?
Inconel 718 is a precipitation-hardened nickel-chromium alloy, primarily strengthened by γ'' (Ni₃Nb) and γ' (Ni₃(Al,Ti)) phases. Unlike many high-temperature alloys, it maintains high strength and hardness at temperatures up to 650 °C (1200 °F) while also possessing good weldability. It is suitable for applications such as aircraft engine turbine discs and shafts, oil and gas downhole tools, nuclear reactor components, high-strength fasteners, and structural components.
Reasons for the high hardness of Inconel 718
The high hardness of Inconel 718 does not stem from cold working, but rather from controlled precipitation hardening.
Key strengthening mechanisms:
1. Niobium-rich γ'' phase → the main contributor to hardness
2. Aluminum and titanium γ' phase → secondary strengthening effect
3. Fine, stable precipitates → inhibit dislocation movement at high temperatures
4. This mechanism makes Inconel 718 superior to solid solution alloys such as Inconel 625 in terms of hardness and yield strength.
What is the hardness of Inconel 718?
Hardness of Inconel 718 (By Condition)
| Condition | Typical Hardness |
|---|---|
| Solution Annealed | HRC 20 – 25 |
| Solution Treated + Aged (Standard AMS 5662 / 5663) | HRC 36 – 45 |
| Peak Aged (High Strength Condition) | Up to HRC 46 |
| Brinell Hardness (Aged) | HB 331 – 418 |
| Vickers Hardness (Aged) | HV 350 – 450 |
Inconel 718 Temperature Performance
| Temperature | Hardness Stability |
|---|---|
| Room temperature | Excellent |
| 400–600 °C | Very stable |
| Up to 650 °C | Retains majority of hardness |
| Above 700 °C | Gradual degradation |
Inconel 718 vs. Inconel 600,Inconel 625：Hardness
| Material | Typical Hardness (HRC) |
|---|---|
| Stainless Steel 316 | 15 – 20 |
| Inconel 600 | 20 – 25 |
| Inconel 625 | 25 – 32 |
| Inconel 718 (Aged) | 36 – 45 |
What are the differences in hardness between Inconel 718 and Inconel 625?
Inconel 718 is significantly harder and stronger than Inconel 625, especially when aged, due to its precipitation hardening (gamma prime/double-prime) for high strength, while 625 relies on solid solution strengthening (molybdenum/niobium) for excellent corrosion resistance, making 718 better for high-stress, high-temp parts and 625 for marine/chemical environments, even though 625 has good strength too.
Inconel 718 suppliers
At GNEE, Inconel 718 is available in various forms to meet diverse industrial needs:
Plates and Sheets (cold rolled and hot rolled)
Bars and Rods (round, square, hexagonal)
Tubes (seamless and welded)
Wires and Strips (for springs, fasteners, electrical applications)
Forgings and Custom Parts (according to drawings or specifications)
Specifications: UNS NO7718, WNR 2.4668, AFNOR NC19FeNb, JIS NCF 718, GOST ХН75МБТЮ, EURONORM NiCr22Mo9Nb, OR ЭИ602, BS NA 21.
Temperature Range: -423°F to 1300°F.
Testing and Documentation: Mill Test Certificates, EN 10204 3.1, Chemical Reports, Mechanical Reports, Destructive Testing Reports, Non-Destructive Testing Reports, PMI Test Reports, Visual Inspection Reports, Third-Party Inspection Reports, NABL Certified Laboratory Reports.
Packaging: Wooden crates, bubble wrap, steel strapping, or packaged according to customer requirements.
