Nickel-based alloys are widely used in extreme environment fields such as aerospace, chemical industry, nuclear energy, and marine engineering due to their excellent high-temperature strength, corrosion resistance, and oxidation resistance. However, due to their complex composition and strong thermal sensitivity, cracks, porosity, and softening of the heat-affected zone are prone to occur during the welding process. Therefore, the correct selection of welding methods is crucial for ensuring the quality of the weld joints of nickel-based alloys.



First, the welding characteristics of nickel-based alloys



The welding performance of nickel-based alloys is greatly influenced by their composition, especially the presence of elements such as chromium, molybdenum, and iron, which significantly alter their welding behavior. Overall, nickel-based alloys have the following welding characteristics:



1. High thermal crack sensitivity: Nickel-based alloys are prone to produce solidification cracks and liquefaction cracks during the welding process.



2. Sensitive to impurities: Elements such as sulfur and phosphorus are prone to cause brittleness or cracks in the weld.



3. Low thermal conductivity and high expansion coefficient: this is easy to cause welding deformation and residual stress concentration.



4. The weld joint is prone to uneven performance: especially softening phenomena may occur in the heat-affected zone.

　　Two, Analysis of Common Welding Methods and Their Suitability



# 1. Tungsten Inert Gas Welding (TIG)



TIG welding is a high-quality welding process suitable for thin plates and welding situations with high precision. Its advantages are controllable heat input, beautiful weld bead formation, and less spatter, especially suitable for materials that are sensitive to heat input, such as nickel-based alloys. However, TIG welding has low production efficiency and is suitable for small batch or precision welding.



# 2. Gas Tungsten Arc Welding (MIG)



MIG welding has high welding efficiency and is suitable for welding medium and thick plate structures. It has high deposition rate and flexible operation, but attention should be paid to controlling heat input when welding nickel-based alloys to prevent grain coarsening in the heat-affected zone and the thermal cracking tendency of the weld metal.

　　# 3. Submerged Arc Welding (SAW)



Submerged arc welding is mainly used for large-scale welding of thick plate structures, with the characteristics of large penetration depth and high efficiency. However, due to its large heat input, it is prone to thermal cracks and tissue deterioration when welding nickel-based alloys, so welding parameters need to be strictly controlled, and preheating and layer temperature control should be配合.



# 4. Electron Beam Welding (EBW) and Laser Welding (LW)



These two welding methods have the advantages of energy concentration, large depth-width ratio, and narrow heat-affected zone, which are particularly suitable for high-precision and high-strength nickel-based alloy connections. However, due to their high cost and complex processes, they are usually used in high-end manufacturing fields such as aeroengine blades.

　　# 5. Plasma Arc Welding (PAW)



Plasma arc welding integrates the advantages of TIG and laser welding, has good weld bead formation and stable arc characteristics, and is suitable for thin plate welding with high requirements for weld quality.



Three, Key Factors in Welding Method Selection



When selecting a welding method, the following aspects should be considered comprehensively:



- Material type and thickness: Nickel-based alloys with different compositions (such as Inconel 625, Inconel 718, etc.) have different sensitivities to heat input and cooling speed, and thickness affects the selection of heat input.



- Joint form and welding position: Different types of joints such as butt joints, corner joints, and lap joints have different adaptability to welding methods; full-position welding often uses TIG or MIG.



- Quality requirements and production efficiency: For high-precision parts, TIG and laser welding are preferred; for mass production, MIG or submerged arc welding can be considered.



- Cost and equipment conditions: High-end welding methods such as electron beam welding have a large investment and need to be selected in combination with the actual capabilities of the enterprise.



Four, Conclusion



Welding of nickel-based alloys is a highly technical task. Choosing the appropriate welding method not only relates to the quality and efficiency of welding but also directly affects the service performance of the components. Therefore, in practical applications, it should be comprehensively evaluated according to factors such as material characteristics, working conditions, and economy, and scientific welding processes should be selected, supplemented by reasonable welding parameters and process control measures to ensure the high performance and high reliability of the weld joints.