基于Incoloy800H钨极氩弧焊接头组织及其性能分析

在2 mm厚800H合金钨极氩弧焊试验的基础上,研究焊接接头的微观组织和析出相成分,并分析焊接接头的力学性能和抗晶间腐蚀性能,观察拉伸断口和晶间腐蚀试样的形貌。结果表明:焊缝组织为柱状晶和等轴晶,热影响区晶粒明显长大,焊接接头中有少量的TiN和富Cr相(Fe,Cr)_(23)C_6析出相存在;母材、热影响区和焊缝的HV硬度分别为1730、1526和1590 MPa;室温抗拉强度和延伸率分别为565.0 MPa、31.8%,均超过ASME标准关于800H合金规定值(450.0 MPa和30.0%),拉伸断裂为韧性断裂;焊接接头高温(650℃)抗拉强度和延伸率分别为394.5 MPa、15.5%,其断口是混合型断口;较接头组织,母材腐蚀更为严重,表面晶界开裂并伴有少量且尺寸较小的腐蚀坑,基体中TiN缺陷处易引起点蚀。

Microstructure and Properties of Welded Joint of Incoloy800H Alloy by Tungsten Argon Arc Welding

The microstructure and properties of the welded joint were studied based on the tungsten argon arc welding of 2 mm thick alloy 800H. The characteristics of microstructure, mico-hardness, room-temperature and high-temperature tensile strength, fractography and intergranular corrosion of samples were analyzed. Results show that the crystallizing morphology on the weld seam is of columnar crystals and equiaxed grains, the grains of heat-affected zone (HAZ) grows bigger, and a small amount of TiN and (Fe,Cr)23C6 phases precipitate in the welded joint. The average hardness of base metal, HAZ and welding seam is 1730, 1526 and 1590 MPa, respectively. Moreover, room temperature tensile strength and elongation for alloy 800H is 565.0 MPa and 31.8%, respectively, which are both higher than the ASME standard requirement (tensile strength 450.0 MPa and elongation 30.0%), and ductile fracture happens at room temperature. The high temperature (650 °C) tensile strength and elongation of alloy 800H welding joints is 394.5 MPa and 15.5%, respectively, and the fracture is mixed mode at 650 °C. In comparison with welded joint of alloy 800H, the corrosion of base metal are much severer, with intercrystalline fracture of base metal and a few corrosion pits on the surface. The TiN precipitates in the base metal could result in pitting.