Research on the welding process of Inconel 718 and Inconel 600
Research on the welding process of Inconel 718 and Inconel 600
Due to their different compositions, welding Inconel 718 and Inconel 600 requires specialized techniques. Friction stir welding (FSW) and transient liquid phase (TLP) bonding techniques have achieved great success in joining these two alloys, avoiding the Laves phase defects commonly found in fusion welding. While standard fusion welding methods such as TIG are also used for welding similar alloys, welding dissimilar alloys requires precise control, focusing on minimizing crack formation by controlling heat input and precipitates in the heat-affected zone (HAZ).
At what temperature does Inconel 718 oxidize?
Inconel 718 begins to deform under its own weight at approximately 1540 K. At 1560 K, noticeable grooves appear on the material's surface. At temperatures of 1173 K and below, Inconel 718 undergoes a brief oxidation process after approximately 24 hours of exposure to air.
The main welding processes and research findings for Inconel 718 and 600 alloys are presented
Friction Stir Welding (FSW):
Successes: Effectively joins Inconel 718 and 600 alloys, forming high-strength joints free from harmful Laves or δ phases commonly found in fusion welding.
Microstructure: The interface shows a fine-grained region with high hardness, and the heat-affected zone (HAZ) exhibits slight grain coarsening, but overall mechanical properties are good.
Transient Liquid Phase Diffusion Bonding (TLP):
Method: Uses an interlayer (e.g., BNi-2) and specific heat treatment (isothermal solidification/homogenization) to create high-strength, defect-free joints.
Results: High shear strength (e.g., 568 MPa) was achieved after appropriate post-weld heat treatment.
Fusion Welding (TIG/GTAW):
Inconel 718 (homogeneous welding): Inconel 718 exhibits excellent TIG welding performance, typically using Inconel 718 filler metal and post-weld aging treatment, thanks to its slow aging response.
Dissimilar material welding (Inconel 600/718): More challenging; requires careful control of welding parameters to prevent cracking, typically using TIG welding, but FSW or TLP welding methods are superior for this specific combination.
Electron Beam Welding (EBW) and Laser Beam Welding (LBW):
Advantages: Low heat input, minimizing deformation and defects; EBW can typically weld thick sections without cracking.
Challenges and Considerations
Inconel 718: Its strength derives from γ' (gamma phase) precipitation, but unwanted Laves/σ phases can form during fusion welding, leading to cracking.
Inconel 600: TIG/MIG welding can be used, but unlike Inconel 718, it is susceptible to strain-age cracking due to the rapid formation of the γ phase.
Dissimilar Material Joints: The compositional differences between 718 and 600 alloys (especially in Al/Ti/Nb content) necessitate special welding methods, such as friction stir welding (FSW) or transient liquid phase diffusion bonding (TLP), to control microstructural changes and prevent heat-affected zone (HAZ) failure.
Summary
For joining Inconel 718 and 600, solid-state FSW and TLP welding are the preferred methods, as they avoid fusion welding-related defects and thus achieve superior mechanical properties; while standard fusion welding techniques (TIG) require precise control to prevent cracking.
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Gnee Steel is a supplier of inconel 600 alloy, offering a wide range of products including: seamless pipe (sizes: 4-219 mm; thickness: 0.5-20 mm); welded pipe (sizes: 5.0-1219.2 mm; thickness: 0.5-20 mm); plates (thickness: 0.1 to 100 mm; width: 10-2500 mm); strips; alloy round bars (diameter: 3-800 mm); flat bars (thickness: 2-100 mm; width: 10-500 mm); hexagonal bars (size: 2-100 mm); wire rods; and extruded profiles. We collaborate with steel mills to provide our customers with inconel 600 alloy products that meet or exceed numerous leading industry standards, including ASTM, ASME, SAE, AMS, ISO, DIN, EN, and BS standards.
Gnee Steel stocks and sells inconel 600, pipes, plates, strips, round bars, flat bars, forged billets, hexagonal steel, wire rods, and extruded profiles. Please feel free to contact us at ss@gneesteel.com for a quote.
