GH3039大功率光纤激光焊接接头组织及力学性能研究

Microstructure and Mechanical Properties of GH3039 High Power Fiber Laser Welded Joints

对2 mm厚的高温合金GH3039薄板进行光纤激光焊接,采用光学显微镜、扫描电镜、显微硬度计以及拉伸试验机研究了焊接速度对焊缝成形的影响以及焊接接头的微观组织和力学性能。结果表明：在聚焦距离250 mm、输出功率2500 W、离焦量0 mm、斑点直径0.42 mm、波长1060 nm和焊接速度为4 m/min情况下,可获得成形良好且无宏观缺陷的焊接接头。在焊接接头凝固初期,靠近熔合线附近的熔化区形成胞晶组织,随着凝固过程的进行,焊缝组织以柱状晶的形式向焊缝中心生长。焊接接头中心区域会出现一定程度上的软化,焊缝区域显微硬度的平均值高于母材。接头抗拉强度最高可达到母材的93.7%,伸长率最高可达母材的58%,焊缝中心为接头的薄弱部位。焊接接头的断裂形式为脆性和韧性混合断裂,并没有在晶界析出大量的难熔Nb、Mo等元素的脆性化合物。

The fiber laser welding of high temperature alloy GH3039 sheet with thickness of 2 mm was carried out. The effect of welding speed on the weld formation, microstructure and mechanical properties of the joints were studied by using optical microscope, scanning electron microscope, microhardness tester, tensile testing machine. The results show that the welded joint with good formation and no macroscopic defects was obtained under the focusing distance of 250 mm, output power of 2500 W, defocusing amount of 0 mm, spot diameter of 0.42 mm, wavelength of 1060 nm and welding speed of 4 m/min. In the initial period of solidification of welded joint, cellar microstructure forms in the molten zone near fusion line.The microstructure of the welding seam grows in the form of columnar crystals towards the center of the welding seam with the prolonging of solidification process. Softening occurs in the center of the welded joint to some extent, the microhardness of the welded joint is bigger than that of the base metal. The tensile strength of the welded joint is up to 93.7% of that of the base metal, and the elongation is up to 58% of that of the base metal, the weld center is the weak part of the welded joint. The fracture from of the welded joint is the mixed mode of brittle and ductile fracture, no brittle compounds containing Nb and Mo precipitate at grain boundary.