Abstract
Inconel 718 alloy laser-welded joints have poor mechanical properties due to the presence of Laves phases and liquation cracks. This paper intends to solve the above problems by high-frequency micro-vibration-coupled bead-on-plate laser welding. According to the shape of the weld beam, the upper part of the weld is defined as the nail head, and the lower part is the nail body. The results showed that high-frequency micro-vibration can achieve grain refinement. The micro-vibration could break the primary dendrite arm to form secondary dendrite and reduce epitaxial growth of the cellular crystal region. Micro-vibration exacerbated the flow of Niobium (Nb) elements surrounded by dendrites and reduced dendritic segregation, which decreased the formation of Laves phases. The combination of interdendritic Nickel (Ni), Titanium (Ti), and Nb and the precipitation of strengthening phases γ′ and γ″ were promoted. When the vibration acceleration was 50.10 m/s2, it could inhibit the formation of Laves phases among dendrites and the size of the bulk Laves phase was effectively reduced. The cracks generated in the Inconel 718 alloy were distributed at three locations including the nail-head, the nail-body, and the junction of nail-head and nail-body. When the vibration frequency was 919 Hz, the length of the liquation crack reduced from 180 to 110 μm. While under 1331 Hz, the expansion of the liquation crack was extended, with the length of 200 μm.
Highlights
Inconel 718 nickel-based alloy has superior oxidation resistance, thermal stability, corrosion resistance, and high temperature strength in a high temperature environment from 650 to 1000 ◦ C
Most previous researchers used ultrasonic vibration-assisted welding to reduce defects in the welding of Inconel 718 alloy, such as Laves phase and liquation crack, but this technique is difficult to apply in practice
High-frequency micro-vibration-assisted bead-on-plate laser welding of Inconel 718 alloy is used, which reduces the formation of Laves phases and inhibits the expansion of liquation cracks
Summary
Inconel 718 nickel-based alloy has superior oxidation resistance, thermal stability, corrosion resistance, and high temperature strength (high temperature fatigue strength, high temperature tensile strength, creep resistance) in a high temperature environment from 650 to 1000 ◦ C. The γ0 phase showed a dispersed distribution at the same time They believed that the vibration-caused generation of free crystals was the main mechanism of grain refinement. The test found that the dendrite length decreased from 1256 to 89 μm, and the thermal crack sensitivity decreased from 47.5% to 13.3% They believed that dendritic fragmentation and grain size refinement were the main reason for reducing the tendency of hot cracking. Most previous researchers used ultrasonic vibration-assisted welding to reduce defects in the welding of Inconel 718 alloy, such as Laves phase and liquation crack, but this technique is difficult to apply in practice. High-frequency micro-vibration-assisted bead-on-plate laser welding of Inconel 718 alloy is used, which reduces the formation of Laves phases and inhibits the expansion of liquation cracks
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