Inconel625等离子弧焊接头组织与接头性能研究

Research on Inconel625 Plasma Arc Welding Joint Microstructure and Joint Performance

摘要:

对4mm镍基高温合金Inconel625薄板进行等离子弧焊实验,对比研究了3种不同焊接热输入下焊接接头各部分的微观组织、接头力学性能、断口形貌以及母材和焊缝的高温腐蚀行为。结果表明Inconel625等离子焊接接头组织是由母材的奥氏体等轴晶、焊缝融合线附近的胞状晶以及焊缝中心的树枝晶组成；在焊缝处有大量的碳化物和少量Laves相析出,使得焊接接头力学性能降低,韧性下降,焊缝成为接头薄弱环节；在焊接热输入为10.175KJ/cm时接头力学性能最优,抗拉强度为765.3MPa与母材的785.4MPa相当,延伸率为31.9%相较于母材的42.8%有所下降,试样断裂方式为发生在焊缝处的韧性断裂；母材和焊缝金属在750℃下24h熔盐腐蚀后腐蚀产物基本相同,主要为外层颗粒状NiO和Cr₂O₃以及NiCr₂O₄腐蚀层。

Abstract:

Plasma arc welding experiments were performed on 4mm nickel-based superalloy Inconel625 thin plates, and the microstructure of each part of the welded joint under three different welding heat inputs, the mechanical properties of the joint, the fracture morphology, and the high-temperature corrosion behavior of the base metal and the weld were compared.The results show that the structure of Inconel625 plasma welded joint is composed of the austenite equiaxed crystal of the base material and the cell crystal near the weld fusion line and the dendritic crystal in the center of the weld.There is a large amount of carbide and a small amount of Laves phase precipitation at the weld, making the mechanical properties of the welded joint reduced, the toughness of the weld becomes a weak link in the joint.In the welding heat input of 10.175KJ/cm when the mechanical properties of the joint is optimal, the tensile strength of 765.3MPa and the parent material of 785.4MPa equivalent, elongation of 31.9% compared to 42.8% of the parent material has decreased.Specimens fracture by ductile fracture occurring at the weld seam.Base metal and weld metal at 750°C after 24h molten salt corrosion corrosion products are basically the same: the outer layer of granular NiO and Cr2O3 and NiCr2O4 corrosion layer.