UNS N07718 Inconel Bars DIN 2.4668

Product Description

UNS N07718 (commonly known as Inconel 718 / DIN 2.4668 / NiCr19Fe19Nb5Mo3) is a high-strength, corrosion-resistant nickel-chromium superalloy. Unlike the cast-focused Inconel 713C, Inconel 718 is exceptionally versatile because it combines extreme high-temperature strength with excellent fabricability, weldability, and resistance to post-weld cracking.

It is primarily strengthened by precipitation hardening via the formulation of gamma double prime $\gamma''$ ($\text{Ni}_3\text{Nb}$) and gamma prime $\gamma'$ ($\text{Ni}_3(\text{Al}, \text{Ti})$) precipitates.

Technical Specifications & International Equivalents

Chemical Composition (Weight %)

The high Niobium (Nb) content is the defining feature that slows down the precipitation kinetics, allowing it to be welded and cooled without immediate strain-age cracking.

• Nickel (Ni): 50.0 55.0%

• Chromium (Cr): 17.0 21.0%

• Iron (Fe): Balance (~17%)

• Niobium + Tantalum (Nb + Ta): 4.75 5.50% (Key strengthening element)

• Molybdenum (Mo): 2.80 3.30%

• Titanium (Ti): 0.65 1.15%

• Aluminum (Al): 0.20 0.80%

• Carbon (C): 0.08% Max

Supply Forms: Round, Hex, & Flat Bars

Because of its superb hot-working characteristics, UNS N07718 bars are widely produced across multiple profiles, typically supplied in either the solution-annealed condition (ready for fabrication/machining and subsequent aging) or the fully age-hardened condition (maximum strength).

1. Round Bars & Rods

• Dimensions: Available from small diameter wire-rod sizes (~3mm) up to large forged shafts over 300mm.

• Finishes: Centerless ground, peeled, smooth turned, or black hot-rolled.

• Applications: Heavy-duty rotating shafts, aerospace turbine blades, high-strength downhole tool joints, and specialized industrial fasteners (J-bolts, 12-point flange bolts).

2. Flat Bars & Hex Bars

• Hex Bars: Highly sought after for machining into high-pressure fluid headers, fittings, and heavy-duty nuts/clamping hardware.

• Flat Bars: Frequently deployed in high-temperature structural framing, tooling fixtures, and furnace components where massive structural loads are sustained up to 700C (1300F).

Mechanical Properties & Heat Treatment Conditions

The mechanical behavior of DIN 2.4668 depends drastically on its heat-treated state:

1. Solution Annealed (e.g., AMS 5662): Yield strength is relatively low (~350550 MPa), which maximizes ductility and allows for easier machining, forming, and welding.

2. Precipitation Hardened / Aged (e.g., AMS 5663): After a two-stage aging cycle (typically heating to ~718C, furnace cooling to ~620C, and holding), the yield strength skyrockets to $\ge$ 1030 MPa (150 ksi) with outstanding creep-rupture strength up to 650C (1200F).

Fabrication, Machining, & Welding

• Welding: Unlike many other aluminum-titanium hardened superalloys, 718 can be readily welded using gas tungsten arc (GTAW), plasma arc, or electron beam methods. Use matching filler metal (Inconel 718 / ERNiFeCr-2).

• Machining: Work-hardens aggressively. It is best machined in the solution-annealed state using rigid setups, heavy-duty carbide tooling, a constant feed rate, and copious amounts of coolant to avoid glazed surfaces.