Aerospace welding demands joints that maintain their strength at both cryogenic and elevated temperatures, resist fatigue over thousands of flight cycles and remain dimensionally stable through machining and assembly. Filler metal selection becomes critical when the base material is a precipitation-strengthened superalloy like Inconel 718, as a mismatched filler can leave the joint weaker than its parent metal or prone to cracking during heat treatment. Inconel 718 filler wire, classified as ERNiFeCr-2 under AWS A5.14, is built to weld and repair 718 components used in engine casings, disks and structural fittings.
What Makes Inconel 718 Suitable for Aerospace Welding?
Inconel 718 (UNS N07718) is a nickel-chromium-iron superalloy strengthened through precipitation hardening. Two intermetallic phases, gamma double prime (Ni₃Nb) and gamma prime (Ni₃(Al,Ti)), form during ageing and give the alloy tensile strength above 1,240 MPa while retaining ductility. The alloy holds this strength from cryogenic temperatures up to around 650°C, a range that includes most turbine engine sections outside the hottest combustion zones. A protective chromium oxide layer resists oxidation and corrosion in fuel, exhaust and marine environments. These properties make 718 a standard choice for rotating and static engine hardware and any filler wire used to join or fix it needs to fit the same combination of strength, oxidation resistance and metallurgical stability.
Why Inconel 718 Filler Wire Is Used for High-Strength Joints
Filler wire exists to rebuild the joint zone with material that responds to heat treatment the way the surrounding base metal does. ERNiFeCr-2 filler wire has a chemistry similar to wrought 718, with nickel, chromium, iron, niobium, and molybdenum in the same proportions, so the weld deposit age-hardens with the parent structure during post-weld treatment. Nickel-based filler also resists solidification cracking better than many alternatives, provided welders control heat input, interpass temperature and contamination from sulfur, lead, or other low-melting elements that promote micro-fissuring.
Joint Design Considerations for Inconel 718 Welding
Joint geometry decides how much filler the joint takes, how heat spreads through the section and how much residual stress builds up as the weld cools. Fit-up gaps should stay tight and consistent, since wide or uneven gaps force extra passes and raise total heat input. Section thickness and accessibility determine whether a single-V, double-V, or U-groove preparation better fits the joint, particularly on thick-walled casings where full penetration from one side is difficult. Distortion control matters as well: symmetric weld sequencing and controlled pass order limit angular and longitudinal shrinkage on precision-machined aerospace parts.
Managing Heat Input and Distortion
Heat input controls the metallurgical changes that determine whether a weld cracks or performs. Excess heat coarsens the grain structure in the heat-affected zone and can trigger liquation of low-melting phases at grain boundaries. Welders control the heat input through the stringer bead technique, moderate travel speed, and interpass temperatures held below 93°C, limiting the time the surrounding material spends at elevated temperature during multi-pass welding.
Strength Requirements for Aerospace Welded Joints
Aerospace structures carry static tensile loads and cyclic fatigue loads across a variety of pressurisation and thermal cycles, so a joint has to meet minimum tensile strength and resist crack initiation under repeated stress. AWS A5.14 specifies a minimum tensile strength of 165,000 psi (about 1,138 MPa) for ERNiFeCr-2 weld deposits after proper heat treatment, which serves as a baseline in procedure qualification. Where components operate above ambient temperature, such as compressor and turbine sections, the joint must also retain strength and creep resistance at service temperature. Filler selection has to align with these design requirements from the outset, and every welding procedure intended for flight hardware requires qualification testing that confirms tensile, bend and where applicable, fatigue performance before production welding begins.
Post-Weld Heat Treatment of Inconel 718 Welds
Post-weld heat treatment restores the precipitation-hardened condition that as welded Inconel 718 lacks. As weld metal is stored in a solution-annealed-like state, it remains soft and ductile until heat treatment develops the gamma double prime and gamma prime phases that provide the alloy’s strength. A solution anneal near 980°C followed by a two-step age around 720°C for 8 hours, furnace cooled to 620°C for a further 8 hours, is a method commonly used for new fabrication, considering the applicable material specification, prior component condition and welding procedure governs the exact cycle for a given part.
| Consideration | Why It Matters |
| Heat-treatment condition | Influences final mechanical properties |
| Welding procedure | Controls weld quality and thermal exposure |
| Component geometry | Affects heating uniformity |
| Required properties | Determines the appropriate treatment route |
| Applicable specification | Ensures process compliance |
Aerospace Applications of Inconel 718 Filler Wire
Gas turbine engine manufacturing and repair account for a large share of demand for Inconel 718 filler wire, since compressor casings, turbine disks, shafts and combustor components rely on the alloy’s strength at elevated temperature. Structural fittings, engine mounts and fastener assemblies that see high static and cyclic loads also requires 718 joints where weight savings matter more than in heavier steel designs. Repair welding differs from new fabrication in scope: a repair typically targets a localized crack, worn surface, or dimensional correction on an in-service part and the heat treatment route has to work around features already machined or coated on the component.
Key Factors When Selecting Inconel 718 Filler Wire
Match the wire to the joint’s required strength and expected service temperature, since not every application calls for the same heat-treated condition. Account for the welding process, whether GTAW or GMAW and choose wire diameter based on joint thickness and the deposition rate needed. Review joint geometry and section thickness to confirm the selected diameter and process combination will achieve full penetration without excess heat input. Check that the filler meets the aerospace specification called out on the drawing, such as AMS 5832, and that a qualified welding procedure exists for the joint configuration. Verify the supplier provides material certification and full traceability, since flight-critical components require a documented chain of custody from heat lot to finished weld.
Conclusion
Filler selection, joint design, strength requirements and post-weld heat treatment all work together to determine whether an Inconel 718 weld performs in service. Inconel 718 filler wire should match the base material chemistry, meet the service conditions the component will experience, and follow a qualified welding procedure. Process control at every stage, from joint preparation through final heat treatment, is what keeps aerospace welds within specification. Metracore Alloys supplies Inconel 718 filler wire with material certification and traceability for aerospace and industrial welding applications. Explore our Inconel 718 Filler Metal today to get high-grade materials for your critical welding applications!