Technical Overview: Inconel 718 / UNS N07718 / GH4169 Round Bar

Description:

Material Name: Inconel 718 (Nickel-Chromium Alloy)

UNS Number: N07718

Chinese Alloy Code: GH4169

Form: Round Bar / Rod

Key Properties:

High strength at cryogenic to ~700°C (1290°F)

Excellent corrosion and oxidation resistance

Good creep and fatigue resistance

Can be solution-annealed and age-hardened for high mechanical strength

Applications:

Aerospace turbine engines (discs, shafts, fasteners)

Gas turbine components

High-temperature chemical processing equipment

Oil & gas downhole applications

Standards & Specifications:

ASTM B637, AMS 5662, AMS 5383, ASME SB637

Typical diameters: 10 mm – 500 mm (custom sizes available)

5 Questions & Answers About Inconel 718 / UNS N07718 / GH4169 Round Bar

1. What makes Inconel 718 / GH4169 suitable for high-temperature applications?

Answer:

Inconel 718 contains nickel, chromium, and niobium, giving it precipitation hardening capability.

Maintains high tensile, yield, and creep strength up to 700°C.

Excellent oxidation and corrosion resistance, even in acidic or saline environments.

Ideal for aerospace turbines, high-temperature valves, and nuclear applications.

2. How does UNS N07718 (Inconel 718) differ from GH4169?

Answer:

UNS N07718 is the standard international designation (ASTM / ASME).

GH4169 is the Chinese national code for the same material.

Both have identical chemical composition and mechanical properties.

Selection depends on project specification or regional standards.

3. What heat treatments are typically applied to Inconel 718 round bars?

Answer:

Solution annealing: ~980–1,020°C, followed by rapid quenching to dissolve precipitates.

Aging / precipitation hardening: double-stage aging (720°C for 8 hours, cool, then 620°C for 8 hours) to achieve maximum tensile and yield strength.

Proper heat treatment ensures creep, fatigue, and tensile performance for high-temperature service.

4. What inspections are commonly done on Inconel 718 bars?

Answer:

Chemical composition analysis (PMI or spectroscopy)

Tensile test (yield, ultimate strength, elongation)

Hardness test (Rockwell or Brinell)

Non-destructive testing (NDT): ultrasonic or magnetic particle testing

Dimensional checks: diameter, roundness, straightness, and surface finish

These ensure compliance with AMS 5662 / ASTM B637 / SB637 standards.

5. What are the typical applications of high-temperature Inconel 718 round bars?

Answer:

Aerospace: turbine disks, blades, shafts, fasteners

Energy: gas turbines, heat exchangers, nuclear reactors

Oil & Gas: high-pressure valves, downhole equipment

Chemical Industry: high-temperature pumps, mixers, reactor internals

General: any component requiring strength and corrosion resistance up to ~700°C