超超临界锅炉水冷壁MIG堆焊修复工艺研究OA

To address the thinning failure of water wall tubes in coal-fired power plant boilers,this study proposes a repair method using MIG vertical-down overlay welding with ERNiCrMo-3 filler wire.The influence of welding parameters was systematically investigated to optimize the process.The welding stability was verified through visual inspection(VT),radio-graphic testing(RT),mechanical testing,and metallographic analysis.Key findings include:The corrosion depth was mea-sured at approximately 450μm.The similar thermal expansion coefficients between the filler wire and base metal(15CrMoG)prevented interfacial delamination.Both VT and RT results met Class I acceptance criteria.The shear strength reached 491 MPa,exceeding the standard value(440 MPa)of 15CrMoG base material.No cracks were observed in side bend tests.Micro-structural characterization revealed:Weld zone:γ solid solution with precipitated phases.Overheated zone:Bainite.Normal-ized zone:Bainite with minor pearlite.Partially normalized zone:Ferrite,bainite,and pearlite.A slight hardness peak in the coarse-grained zone was attributed to bainite formation.This study provides technical support for overlay welding repair of water wall tubes and offers a new approach for practical maintenance applications.