GH4169 is the Chinese national standard designation for the globally renowned Inconel 718 (UNS N07718, W.Nr. 2.4668) precipitation-hardening nickel-based superalloy. This alloy delivers exceptional comprehensive performance across a wide temperature range from -253°C to 700°C, with its yield strength below 650°C ranking first among all wrought superalloys. It exhibits outstanding fatigue resistance, radiation tolerance, oxidation resistance, corrosion resistance, and excellent weldability. GH4169/Inconel 718 is widely used in aerospace, nuclear energy, petroleum industries, and extrusion tooling for manufacturing complex-shaped components.

1. Chemical Composition of GH4169 (Inconel 718 / UNS N07718)

GH4169 and Inconel 718 share nearly identical chemical compositions, with nickel content around 50–55%, chromium 17–21%, and niobium 4.75–5.5%. The alloy is strengthened by γ′ (Ni₃(Al,Ti)) and γ″ (Ni₃Nb) precipitates formed during aging treatments. Below is the complete chemical composition range for GH4169 (mass fraction %):

Element	Min (%)	Max (%)
Nickel (Ni)	50.0	55.0
Chromium (Cr)	17.0	21.0
Iron (Fe)	Balance	Balance
Molybdenum (Mo)	2.8	3.3
Niobium (Nb)	4.75	5.5
Titanium (Ti)	0.65	1.15
Aluminum (Al)	0.2	0.8
Carbon (C)	—	0.08
Silicon (Si)	—	0.35
Manganese (Mn)	—	0.35
Phosphorus (P)	—	0.015
Sulfur (S)	—	0.015
Copper (Cu)	—	0.30
Cobalt (Co)	—	1.00
Boron (B)	—	0.006
Magnesium (Mg)	—	0.01

2. Mechanical Properties of GH4169 (Inconel 718)

GH4169/Inconel 718 exhibits outstanding mechanical performance across a broad temperature spectrum from cryogenic to 700°C. The following tables summarize the instantaneous tensile properties at various test temperatures:

2.1 Instantaneous Tensile Properties – Room Temperature

Diameter (mm)	Test Temp.	Tensile Strength (MPa)	Yield Strength (MPa)	Elongation (%)	Reduction of Area (%)	Hardness (HBW)	Impact KV₂ (J)
16–115	Room Temp	≥1275	≥1035	≥12	≥15	≥331	≥32
16–115	Room Temp	≥1275	≥1030	≥12	≥15	≥331	≥39
—	Room Temp	≥1225	—	≥15	≥30	341–477	≥39
—	Room Temp	≥1225	—	≥15	≥30	341–477	≥39

2.2 Instantaneous Tensile Properties – Elevated & Cryogenic Temperatures

Diameter (mm)	Test Temp.	Tensile Strength (MPa)	Yield Strength (MPa)	Elongation (%)	Reduction of Area (%)
16–115	650°C	≥1000	≥860	≥12	≥15
16–115	-196°C	≥1470	—	≥12	≥20
—	800°C	≥540	—	≥15	≥25
—	600°C	≥1080	—	≥12	≥20
—	400°C	≥1130	—	≥12	≥20
—	-196°C	≥1470	—	≥12	≥20

2.3 Stress-Rupture Properties

Diameter (mm)	Test Temp.	Stress (MPa)	Life (hours)
16–115	650°C	690	≥25
—	800°C	390	≥30
—	600°C	880	≥50

Note: Values shown are minimum requirements per GB/T and ASTM standards. Actual properties may vary by heat treatment and product form. Typical room-temperature tensile strength for Inconel 718 can reach 1375 MPa with yield strength of 1100 MPa.

3. Microstructure & Strengthening Mechanism

GH4169/Inconel 718 has an austenitic structure. After precipitation hardening, the γ″ phase (Ni₃Nb) forms, imparting excellent mechanical properties. During heat treatment, the δ phase precipitates at grain boundaries, contributing to optimal plasticity. The alloy is strengthened through a combination of solid-solution strengthening and precipitation hardening via γ′ and γ″ phases.

4. Industrial Applications of GH4169 / Inconel 718

GH4169/Inconel 718 is one of the most widely used nickel-based superalloys across multiple high-tech industries:

Aerospace & Aviation: Turbine disks, blades, shafts, compressor disks, casings, rings, fasteners, elastic components, gas conduits, and rocket engine components.
Nuclear Energy: Elastic components, grid structures, and reactor internal components requiring radiation resistance.
Petroleum & Chemical: Corrosion-resistant equipment, downhole tools, subsea components, and extrusion dies.
Power Generation: Gas turbine hot-section components, steam turbine blades, and nozzles.

5. Processing & Heat Treatment Parameters

5.1 Machining Characteristics

Challenge	Description	Recommended Practice
Thermal Conductivity	Extremely poor, leading to high cutting temperatures	Use carbide tooling; apply adequate coolant
Cutting Force	High alloying content results in high cutting forces	Optimize cutting parameters; use rigid setups
Work Hardening	Severe work-hardening tendency during machining	Maintain sharp cutting edges; avoid dwell
Tool Wear	Hard particles in the alloy cause rapid wear	Use premium carbide or ceramic inserts; centerless grinding for tight tolerances

5.2 Hot Heading (Forging) Parameters

Parameter	Value / Requirement
Heading (forming) temperature	1040 – 1090°C
Final heading (finish) temperature	930 – 950°C
Grain size (standard strength)	Grade 4 – 6
Grain size (high strength)	Grade 8

5.3 Heat Treatment Schedules & Achievable Properties

Condition	Heat Treatment Parameters	Achievable Performance
Solution + Aged	Solution: 950 – 980°C; Double Aging: 720°C × 8h + 620°C × 8h	Tensile Strength ≤ 1700 MPa; Hardness ≤ 450 HBW
Solution + Cold Work + Aged	Cold work prior to aging; subsequent aging schedule same as above	Enhanced yield strength with moderate ductility

Different heat treatment schedules can be employed to control grain size, δ phase morphology, distribution, and quantity, thereby achieving different levels of mechanical properties.

6. Selection Recommendations

GH4169/Inconel 718 is recommended for applications meeting the following criteria:

Selection Parameter	Requirement / Range
Tensile Strength (max)	Up to 1700 MPa
Shear Strength (min)	≥ 780 MPa
Service Temperature Range	-200°C to +700°C
Environmental Resistance	Oxidation and corrosion resistance required
Typical Product Forms	Bolts, screws, pins, washers, high-lock fasteners, and special-purpose parts

Note: GH4169 follows Chinese GB/T and HB standards, while Inconel 718 follows ASTM and AMS international standards. GH4169 is typically more cost-effective with shorter supply lead times for domestic Chinese projects, whereas Inconel 718 is preferred for international programs and high-precision applications.

7. Global Grade Equivalents

Country / Region	Standard	Grade Designation
China	GB/T	GH4169 (formerly GH169)
USA	UNS	N07718
USA	ASTM / AMS	Inconel 718 / Alloy 718
Germany / Europe	EN / DIN	W.Nr. 2.4668 / NiCr19Fe19Nb5Mo3
France	NF	NC19FeNb
UK	BS	NA 51

8. Conclusion

GH4169 (Inconel 718 / UNS N07718) is a premier precipitation-hardening nickel-based superalloy that delivers unmatched comprehensive performance from cryogenic to high-temperature environments. With its exceptional strength below 650°C, outstanding corrosion and oxidation resistance, and excellent fabricability, this alloy remains the material of choice for critical aerospace, nuclear, and petroleum applications. Understanding its chemical composition, mechanical properties, and processing parameters is essential for engineers and procurement professionals seeking reliable, high-performance materials for demanding service conditions.

Key takeaway: GH4169 and Inconel 718 are essentially the same alloy under different national standards – choose GH4169 for domestic Chinese projects and Inconel 718 for international applications, always verifying compliance with your specific project requirements and standards.