Manufacturers recognize superalloys for their excellent performance even at temperatures near the melting point. For this reason, nickel-based superalloys are particularly desirable in the aerospace and nuclear industries. However, meeting design criteria can be difficult due to the significant challenges of welding nickel-based superalloys.
To ensure reliable, high-quality welds, manufactures and technicians should explore the unique properties of nickel, its alloys, and their weldability.
Most nickel-based superalloys combine nickel with other metallic or non-metallic alloying elements such as iron (Fe), cobalt (Co), chromium (Cr), molybdenum (Mo), tungsten (W), aluminum (Al), titanium (Ti), carbon (C), niobium (Nb), and more. Nickel-based alloys can either be solid solution strengthened or precipitate strengthened. The solid solution strengthened sheet alloys such as Hastelloy X are generally used for moderate strength applications and have Cr, Mo, W, and Fe as alloying elements. The primarily used precipitate strengthened Ni-based alloys have Ti and Al as essential solutes with 10-20% Cr content and small amounts of Zr, C, Mo, B, and W.
To ensure pipe welding consistency, operators should weld continuously around the pipe with controlled arc, feed, heat input, and speed. However, even for welders with years of experience, “human error” is possible. Additionally, large-diameter, thick-wall piping is impossible to weld in one continuous pass. Resulting inconsistencies can give rise to weld defects such as lack of penetration, inclusions, cracks, porosity, undercutting, splattering, and more. Factors that contribute to manual pipe welding challenges include:
When compared to other metals, nickel-based superalloys provide an excellent response against high temperatures. This trait, combined with their inherent strength, makes nickel-based superalloys a standard choice in aerospace and power generation turbines. However, the weldability of this alloy can be a serious problem, especially for precipitate strengthened alloy.
Tungsten Inert Gas (TIG) welding is the most suitable process for welding nickel-based superalloys. The excellent heat input control minimizes the HAZ, which reduces the risk of grain growth and, consequently, the risk of cracking. Further, inert gas shielding can prevent oxidation while forming the pure weld. Compatible filler materials containing Ti, Al, and Nb with TIG welding can further minimize the risk of cracking or the development of pores. These positive results can be further enhanced with orbital welding.
Superalloys with high-end performance ability require a welding solution that can foster its properties and boost efficiency. Automated welding techniques like orbital welding can ensure that welding procedures are properly implemented. The control, consistency, and repeatability available with an orbital welding process ensure a high-quality weld with each pass. The orbital weld head enables proper weld penetration while the remote monitoring system allows weld parameter optimization for welding nickel-based superalloys. By maintaining the corrosion resistance and strength of nickel-based superalloys, orbital TIG welding helps manufacturers achieve productivity gains and consistent, reliable results.
Arc Machines, Inc., with decades of expertise in creating high-quality, precision welds, can provide you with a high-end solution for welding nickel-based superalloys. Arc Machines welcomes you to explore our advanced welding technology processes and equipment. Contact us to arrange a meeting to discuss how we can address your welding needs.
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