环境压力对Q345B激光填丝熔覆层的微观组织及性能影响研究

Influence of Environment Pressure on Microstructure and Properties of Q345BLaser Cladding with Filler Wire

以海洋工程应急修复为背景,使用高压焊接试验舱模拟水深压力,分别在0.1 MPa、0.2 MPa、0.3 MPa的环境压力下对Q345B低碳钢板材进行激光填丝熔覆试验,并对3种环境压力下的激光填丝熔覆层进行对比分析,以探索30 m水深范围内高压干法激光修复的可行性。通过光学显微镜、XRD、EDS分析了熔覆层的显微组织、化学成分和物相组成,采用显微硬度仪进行了硬度测试,利用动电位极化曲线研究了熔覆层的耐腐蚀性能。结果表明,0.1 MPa、0.2 MPa、0.3 MPa压力环境下熔覆层宏观成形良好,未发现明显缺陷;熔覆层主要由熔覆区、搭接区、相变影响区、熔合区、热影响区组成,显微组织主要由铁素体、珠光体和部分魏氏组织组成;随环境压力的增加,铁素体尺寸增大且魏氏组织增多;受微观组织的影响,三种环境压力下硬度变化趋势相同,均成阶梯状分布,且熔覆层整体硬度优于母材;在3.5%NaCl溶液中,熔覆层均呈现出明显的钝化行为,耐腐蚀性能均优于母材;随环境压力的增加,耐腐蚀性能有所降低。上述试验结果证明了激光填丝熔覆工艺在高压环境维修中有较好的适应性、可行性。

With the background of marine engineering emergency repair,the laser wire filling cladding experiment on Q345B low carbon steel plate was carried out by using hyperbaric welding test chamber to simulate water depth pressure under environmental pressures of 0.1MPa,0.2MPa,and 0.3MPa respectively.The laser cladding was compared and analyzed for exploring the feasibility of hyperbaric laser repair in 30mwater depth.The microstructure,chemical composition,and phase composition of the cladding layer were analyzed by optical microscope,XRD,and EDS.The hardness was tested by microhardness tester.The corrosion resistance of the cladding layer was studied by potentiodynamic polarization curve.The results show that the cladding layer is well formed under the pressure of 0.1MPa,0.2MPa,and 0.3MPa,and no obvious defects are found.The cladding layer is mainly composed of cladding zone,overlapping zone,phase transformation affected zone,fusion zone,and heat affected zone.The microstructure is mainly composed of ferrite,pearlite,and part of Widmanstatten structure.With the increase of environmental pressure,the size of ferrite and the number of Widmanstatten structure increases.With the influence of microstructure,the hardness variation trends are the same under the three environmental pressures,and the hardness of the cladding layer is better than that of the base metal.In 3.5%NaCl solution,the cladding layer exhibits obvious passivation behavior,and its corrosion resistance is better than that of the base metal.With the increase of environmental pressure,the corrosion resistance decreases.The experimental results show that laser wire filling cladding technology has good adaptability and feasibility for hyperbaric underwater repairment.