球墨铸铁激光熔覆Hastelloy C276气孔缺陷与耐蚀性研究

Study on Porosity Defects and Corrosion Resistance of Laser Cladding Hastelloy C276 on Nodular Cast Iron

为替代价格高昂且难加工的整体镍基合金材料在腐蚀环境中的应用,采用激光熔覆技术在球墨铸铁QT500-7基体上制备Hastelloy C276合金涂层。研究了激光功率和扫描速度对涂层气孔率及稀释率的影响;采用光学显微镜(OM)、扫描电镜(SEM)、显微硬度计和电化学工作站对该涂层组织、硬度及耐蚀性能进行研究。结果表明:在所选工艺参数下,涂层与基体均能形成良好冶金结合,无裂纹缺陷。随着激光功率增大或激光扫描速度增大,该涂层稀释率及气孔率均呈增大趋势。该涂层组织以树枝晶为主,物相主要由γ-Ni固溶体及碳化物M_(23)C_(6)、M_(3)C_(7)、Ni_(6)Mo_(6)C组成。该涂层的平均硬度为379.38 HV,达到了基体的1.98倍。在3.5 wt%NaCl溶液中Hastelloy C276合金涂层自腐蚀电位高于球墨铸铁且自腐蚀电流密度低于球墨铸铁,线能量越低的工艺参数制备的涂层耐蚀性越好。

In order to replace the expensive and difficult-to-process overall nickel-based alloy materials used in corrosive working environments,Hastelloy C276 alloy coating on ball-milled cast iron QT500-7 substrate was prepared by using laser cladding technology.The effects of laser power and scanning speed on the porosity and dilution rate of the coating were studied.The structure,hardness and corrosion resistance of the coating were studied by OM,SEM and microhardness tester and electrochemical workstation.The results show that under the selected process parameters,both the coating and the substrate can form a good metallurgical bond without cracks.As the laser power increases or the laser scanning speed increases,the coating dilution rate and porosity both tend to increase.The coating structure is dominated by dendrites,and the phase is mainly composed ofγ-Ni solid solution and carbides M_(23)C_(6)、M_(3)C_(7)、and Ni_(6)Mo_(6)C.The average hardness of the coating is 379.38HV,which is 1.98 times than that of the substrate.In 3.5wt%NaCl solution,Hastelloy C276 alloy coating has a higher self-corrosion potential than ductile iron and a lower self-corrosion current density than ductile iron.The lower the heat input process parameters,the better the corrosion resistance of the coating.