摘要
采用超音速火焰喷涂(high velocity oxy-fuel,HVOF)技术在Q235钢基体上制备了Cr3C2-Ni Cr涂层,借助X射线衍射(XRD)和扫描电镜(SEM)等方法分析了涂层的相组成和微观组织,研究涂层与镀铬层在质量分数为3.5%Na Cl溶液中的腐蚀性能.结果表明,涂层主要由Cr3C2,Cr7C3和Ni Cr等相组成,涂层的致密度高,层状结构明显,含少量孔隙.阻抗谱曲线表明,Cr3C2-Ni Cr涂层对基体的保护作用良好,在Na Cl溶液中浸泡时间40 d后,极化电阻为2.8 kΩ,而镀铬层失效严重,极化电阻为300Ω.极化曲线表明,Cr3C2-Ni Cr涂层在浸泡周期内腐蚀电位平稳,腐蚀电流缓慢增加.镀铬层的腐蚀电位下降较快,腐蚀速率成倍增加.孔洞是影响Cr3C2-Ni Cr涂层耐蚀性的重要原因,影响镀铬层耐蚀性的主要原因是裂纹.
Cr_3C_2-NiCr coating was prepared on Q235 steel by high velocity oxy-fuel(HVOF) thermal spraying.The phase composition and microstructures of the coating were analyzed by X-ray diffraction(XRD) and scanning election microscopy(SEM).The corrosion resistance of the as-sprayed hard chromium coating immersed in 3.5%NaCl solution for several days was evaluated by immersion and electrochemical method.The results show that the Cr_3C_2-NiCr coating exhibits a layered structure with low porosity.The coating is composed of Cr_3C_2,Cr_7C_3 and NiCr phases.The electrochemical impedance spectroscopy(EIS) data indicates that Cr_3C_2-NiCr coating protects the base steel well,and the total impedance is 2.8 kΩ after 40 d immersion in 3.5%NaCl solution.The hard chromium coating becomes invalid and the total impedance is 300Ω.The polarization curve shows a stable corrosion potential and the current increases slowly with the immersion time.For hard chromium coating,corrosion potential decreases quickly and the rate of corrosion multiplies as the immersion time increasing.Pores strongly affect the corrosion resistance of the Cr_3C_2-NiCr coating,and cracks are the main influencing factor for hard chromium coating.
出处
《焊接学报》
EI
CAS
CSCD
北大核心
2015年第2期109-112,118,共5页
Transactions of The China Welding Institution
关键词
超音速火焰喷涂
涂层
镀铬层
耐蚀性能
电化学阻抗谱
high velocity oxy-fuel
coating
chromium coating
corrosion resistance
electrochemical impedance spectroscopy
