GH4169 is one of the most widely used nickel-based superalloys in high-temperature and high-stress applications. It corresponds to Inconel 718, UNS N07718, and W.Nr. 2.4668, and is specified in aerospace, oil and gas, nuclear, and cryogenic engineering. Despite its popularity, procurement teams and design engineers often struggle to compare offers because suppliers quote different standards, different heat treatment conditions, and different levels of documentation.
This guide is written from the perspective of a special steel trading company - Sichuan Liaofu Special Steel Trading Co., Ltd. which sources GH4169 round bar, forged bar, and plate from approved Chinese mills such as Fushun Special Steel, Baosteel, and Xining Special Steel. We do not melt steel and we do not operate a laboratory. All chemical and mechanical data below reflects typical mill-published values and should be confirmed against the actual mill test certificate for each heat.
What Is GH4169 / Inconel 718? Equivalent Standard Overview
GH4169 is the Chinese designation defined in GB/T 14992. It is a precipitation-hardenable nickel-chromium-iron alloy with niobium and molybdenum additions. The most common international equivalents are:
- Inconel 718-trade name, Special Metals Corporation
- UNS N07718-unified numbering system
- W.Nr. 2.4668-DIN/EN designation
- AMS 5662 / AMS 5663 / AMS 5664-aerospace material specifications for bar, forging, and ring
- ASTM B637-standard specification for nickel-chromium-iron alloy bar, forgings, and rings
- API 6ACRA-oil and gas applications
- GB/T 14992 / GB/T 30568-Chinese standards
These designations are not automatically interchangeable. A heat certified to GB/T may not satisfy an AMS 5662 requirement without additional testing and documentation. When you issue an inquiry, always state the exact standard, product form, heat treatment condition, and any customer-specific specification.
Chemical Composition & Key Mechanical Properties
Nominal Chemistry of GH4169 / Inconel 718
The table below shows typical mill-published chemistry ranges. Actual values must be taken from the original mill test certificate.
| Element | Typical Range (wt.%) |
|---|---|
| Ni | 50.0 – 55.0 |
| Cr | 17.0 – 21.0 |
| Fe | Balance |
| Nb + Ta | 4.75 – 5.50 |
| Mo | 2.80 – 3.30 |
| Ti | 0.65 – 1.15 |
| Al | 0.20 – 0.80 |
| C | ≤ 0.08 |
| Mn | ≤ 0.35 |
| Si | ≤ 0.35 |
| S | ≤ 0.015 |
| P | ≤ 0.015 |
| B | ≤ 0.006 |
The niobium content is what drives the precipitation hardening reaction. If Nb is on the low side, the alloy may not reach the specified yield strength after aging. This is one reason why chemistry verification on the MTC matters more than a generic "Inconel 718" label.
Typical Mechanical Properties in Aged Condition
For GH4169 round bar in the solution-annealed and double-aged condition (typically 720℃ ± 10℃ for 8 hours, furnace cool to 620℃ ± 10℃, hold 8 hours, air cool), typical room-temperature properties are:
- Tensile strength: ≥ 1,240 MPa
- Yield strength (0.2% offset): ≥ 1,030 MPa
- Elongation: ≥ 12%
- Reduction of area: ≥ 15%
- Hardness: typically 36 – 44 HRC
These values are typical for small-to-medium section bar. Large forgings may show slightly lower values due to section size effects. Always confirm the exact acceptance criteria in the applicable standard.
Fatigue & High-Temperature Performance (650℃ Service Limit)
Why 650℃ Is the Practical Ceiling
GH4169 is often described as having a service limit of approximately 650℃. Above this temperature, the strengthening phase begins to coarsen and transform, and creep resistance drops rapidly. For applications above 650℃, other alloys such as Waspaloy, René 41, or Inconel 625 may be more appropriate depending on the stress and environment.
At or below 650℃, GH4169 offers an excellent combination of:
- High yield strength
- Good fatigue resistance
- Excellent creep rupture strength
- Resistance to oxidation and corrosion
- Weldability (unlike many other high-strength superalloys)
Where Fatigue Data Comes From and What a Trader Can Legitimately Provide
Fatigue data for GH4169 originates from the steel mill or from independent testing laboratories. It is tied to a specific heat, product form, surface condition, and test standard. A trading company such as Sichuan Liaofu does not generate fatigue data and does not operate a fatigue testing machine.
If your design requires fatigue data, the correct approach is:
- Ask your supplier to request the mill's fatigue report for the relevant heat or production campaign.
- If no mill data exists, commission independent fatigue testing on a sample cut from the actual heat you will purchase.
- Use published handbook data (e.g., MMPDS, ASM) only for preliminary design, never for final qualification.
We can provide the original mill MTC and, when available, mill-issued test reports. We cannot and do not create N-value curves or S-N curves ourselves.
Machining & Welding Challenges for GH4169 Round Bar / Forgings
Machining Recommendations
GH4169 is known for work hardening and low thermal conductivity, which makes machining difficult. Key recommendations:
Use carbide tools with sharp edges and positive rake angles
Maintain constant feed - do not dwell or rub
Use high-pressure coolant directed at the cutting zone
Expect lower cutting speeds than for alloy steel or stainless steel
Consider ceramic or CBN tools for finishing operations
Perform a stress-relief anneal before final machining if the part is distortion-sensitive
Welding and Post-Weld Heat Treatment
GH4169 is more weldable than many nickel superalloys. Common processes include TIG, MIG, and electron beam welding. However:
Pre-weld cleaning is critical to avoid sulfur and lead contamination
Post-weld heat treatment (solution anneal + age) is required to restore properties in the weld zone
Filler metal should match the base alloy or be specified by the design authority
Welding should be avoided on material in the fully aged condition
Material Traceability: Heat Number & MTC / MTR Document Checklist
Every shipment of GH4169 from Sichuan Liaofu includes the original mill test certificate. Before you accept the material, verify:
Mill name and logo are visible and match the supplier's claim
Heat number on the certificate matches the heat number stamped on the bar or forging
Chemical composition includes Nb, Mo, Ti, Al, and all specified residuals
Mechanical properties include tensile, yield, elongation, and reduction of area
Heat treatment condition is stated (solution annealed + aged, or as-specified)
Applicable standard is listed (GB/T 14992, ASTM B637, AMS 5662, etc.)
Issue date is recent and consistent with the shipment
No signs of alteration, overwriting, or inconsistent fonts
If any of these items are missing or inconsistent, stop and request clarification before processing the material.
Typical Applications & Common Grade Pitfalls
Applications by Industry
- Aerospace: turbine discs, compressor blades, fasteners, casings
- Oil and gas: downhole tools, valves, wellhead components, subsea hardware
- Power generation: gas turbine components, nuclear reactor parts
- Cryogenic: storage tanks, piping, and valves for LNG
- Automotive and motorsport: exhaust valves, turbocharger components
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Three Grade Pitfalls to Avoid
- Assuming GH4169 = Inconel 718 = AMS 5662. They are related but not identical. Always specify the standard and condition.
- Buying solution-annealed material for a part that requires aged properties. If you machine and install without aging, the part will be significantly weaker than designed.
- Accepting a certificate without a heat number. Without heat traceability, you cannot prove the material meets the specification, and your customer may reject the entire lot.
Contact Sichuan Liaofu Special Steel for Stocked GH4169 Round Bar & Forgings
Sichuan Liaofu Special Steel Trading Co., Ltd. supplies GH4169 / Inconel 718 round bar, forged bar, and plate from approved Chinese mills. We provide:
- Original mill test certificates with every shipment
- Cutting-to-size service for trial and production quantities
- Export packaging and documentation
- Support for small trial orders and large batch orders
We are a trader, not a mill. We do not claim to manufacture GH4169 or to generate independent fatigue data. Our role is to connect overseas buyers with reliable Chinese mill sources and to ensure every shipment is fully traceable.