汽轮机转轴表面CMT修复层微观组织及力学性能对比研究  

Comparative Study of Microstructure and Mechanical Properties in CMT Repair Layers on Surface of Steam Turbine Rotor

作　　者：邵光辉 杨克 邹晓东 易江龙 刘俊建 SHAO Guang-hui;YANG Ke;ZOU Xiao-dong;YI Jiang-long;LIU Jun-jian(Datang Boiler and Pressure Vessel Inspection Centre Co.,Ltd.,Hefei 231200,China;Guangdong Key Laboratory of Modern Welding Technology,China-Ukraine Institute of welding,Guangdong Academy of Science,Guangzhou 510650,China)

机构地区：[1]大唐锅炉压力容器检验中心有限公司,合肥231200 [2]广东省科学院中乌焊接研究所广东省现代焊接技术重点实验室,广州510650

出　　处：《精密成形工程》2023年第9期99-107,共9页Journal of Netshape Forming Engineering

基　　金：广东省科技计划(2022A0505050052);广州市科技计划(201604046026);广东省科学院发展专项(2022GDASZH-2022010203)。

摘　　要：目的针对汽轮机Cr12NiWMoV转轴在高温环境下的磨损失效问题,对失效部位进行堆焊修复。方法选用Inconel625合金和316L不锈钢2种材料,利用冷金属过渡(CMT)技术在汽轮机转轴表面进行堆焊修复再制造。利用光学显微镜、扫描电子显微镜、维氏硬度计和万能试验机等手段,对2种堆焊修复材料和母材的结合情况进行测试和分析,探究其微观组织和力学性能的差异。结果光学显微镜结果表明,Inconel625合金和316L不锈钢的熔覆层与基体具有良好的冶金结合,修复试样无缺陷。316L不锈钢修复层组织为奥氏体+δ-铁素体,而δ-铁素体的形成会导致修复层硬度降低、塑性下降;Inconel 625合金修复层的微观组织以奥氏体为基体,具有典型的柱状晶结构,且在枝晶间区域观察到Nb、Mo元素的大量偏聚,这会导致不规则形状的Laves相和细小的MC碳化物在枝晶间区域大量析出。Laves相为脆性相,在室温拉伸过程中易成为裂纹的主要形核点,造成裂纹的产生与扩展,使修复层的延伸率降低。结论与316L不锈钢相比,Inconel625合金修复层具有更高的强度和硬度,更适合成为汽轮机转轴表面的堆焊修复材料。The work aims to address the issue of high-temperature wear of Cr12NiWMoV steam turbine rotors by surfacing of the failure part.Inconel 625 alloy and 316L stainless steel were used as raw materials for repairing and remanufacturing on the surface of steam turbine rotors by cold metal transfer(CMT)arc surfacing.Optical microscope,scanning electron micro-scope,Vickers hardness tester and universal testing machine were employed to test and analyze the bonding status between the base metal and the two surfacing repair materials, to explore the variations in their microstructure and mechanical properties. The results revealed that both the Inconel 625 and 316L stainless steel repair layers were free from defects and flawlessly bonded with the substrate. Furthermore, the microstructure of the 316L stainless steel repair layer consisted of austenite and a large amount of δ-ferrite. The formation of δ-ferrite led to a decrease in the hardness and ductility of 316L stainless steel repair layer. The microstructure of the Inconel 625 repair layer exhibited a typical columnar structure based on austenite. In addition, the segregation of Nb and Mo elements occurred in the interdendritic region, resulting in the precipitation of a large number of irregularly shaped Laves phase and some fine MC carbides. It was well-known that Laves phases were easy to break up and they were the main nucleation points for the formation of microscopic holes during the room temperature tensile process, leading to a reduction in the ductility of the repair layer. In comparison with the 316L stainless steel repair layer, Inconel 625 alloy repair layer has higher hardness and strength, making it more suitable for repairing the surface of steam turbine rotors.

关 键 词：Inconel625 316L不锈钢 汽轮机转轴 修复再制造 CMT 

分 类 号：TG455[金属学及工艺—焊接]