激光熔覆Ni_(31)Si_(12)/FeNi金属硅化物复合材料涂层显微组织与耐蚀性研究

Microstructure and Corrosion Resistance of Laser Clad Ni_3 1Si1_2/FeNi Silicides Composite Coating

以Ni、Si元素粉末为原料,利用激光熔覆技术在A3钢表面制得了Ni_(31)Si_(12)/FeNi金属硅化物复合材料涂层。分析了该涂层显微组织,采用测定阳极极化曲线的方法评价了该涂层在0.5mol/l H_2SO_4水溶液中的耐蚀性能,考察了添加少量合金元素Cr对涂层耐酸腐蚀性能的影响。结果表明:激光熔覆Ni_(31)Si_(12) /12/FeNi金属硅化物复合材料涂层组织由带状Ni31Si12初生相及带间FeNi/Ni_(31)Si_(12)/12共晶组成,涂层表面平整、组织细小、与基体间为完全冶金结合;涂层组织显微硬度在HV650—75O之间,沿层深分布均匀;涂层组织组成相Ni_(31)Si_(12)/FeNi本身具有良好的耐酸腐蚀性能,具有快速凝固成分均匀的显微组织,激光熔覆Ni_(31)Si_(12)//FeNi金属硅化物复合材料涂层在H_2SO_4水溶液中表现出良好的耐蚀性。合金元素Cr的添加进一步提高了涂层的耐酸腐蚀性能。

A corrosion resistant Ni31 Si12/FeNi silicides composite coating was fabricated on substrate of a low carbon steel A3 by laser cladding using the Ni, Si powders. The laser clad silicides composite coating, which is met-allurgically bonded to the steel substrate, has a rapidly solidified microstructure consisting of belt-shaped Ni31 Si12 primary phase and small amount of FeNi/N31Si12 eutectics. The average microhardness of the laser clad silicide alloy coating ranges from HV650 to HV750. The corrosion resistances of the nickel silicides composite coating as the content of alloyed-element Cr in the water solutions of 0. 5mol/l H2SO4 were evaluated utilizing the anodic polarization electrochemical corrosion-test method. Because of the inherent excellent corrosion-resisting properties of the constituting phases of Ni31 Si12 and FeNi, and the rapidly solidified homogeneous microstructure, the laser clad nickel silicides composite coating exhibits excellent corrosion resistance. Meantime it is indicated that the corrosion resistances of laser clad Ni31 Si12/FeNi silicides composite coating are enhanced with the increasing chromium content.