45钢表面PII-DGPSM复合强化层的耐腐蚀性能研究

Investigation of corrosion resistance of PII-DGPSM composite strengthened layer on the surface of 45 steel

摘要:

针对海工装备中常用45钢表面耐腐蚀性不足的问题，采用离子注入技术(PII)注Al和双辉等离子表面冶金技术(DGPSM)渗Cr复合，在基体45钢表面制备Al-Cr复合强化层。利用X射线衍射(XRD)、光电子能谱(XPS)、原子力显微镜(AFM)、扫描电镜(SEM)和能谱(EDS)等对试样的元素分布、物相结构进行表征。并采用极化曲线和电化学阻抗谱，对比分析Al-Cr复合涂层、注Al涂层和基体在3.5wt%NaCl溶液中的耐腐蚀性，研究其腐蚀机理。研究表明，采用复合技术制备所得Al-Cr涂层的耐腐蚀性最佳，其表面形成Cr2O3和Al2O3复合钝化膜，和涂层内部形成具有优异耐腐蚀性Fe2AlCr和Al8Cr5相，阻碍Cl-的腐蚀作用；注Al层耐腐蚀性次之，其表面形成致密Al2O3钝化膜，延缓了Cl-对基体的腐蚀作用；基体耐腐蚀性最差。

Abstract:

Aiming at improving the corrosion resistance of 45 steel used in maritime works, an Al-Cr composite alloyed layer is deposited on the surface of 45 steel via a composite technique of plasma ion implantation (PII) and double glow plasma surface metallurgy (DGPSM). Element distributions and phase structures of the Al-Cr composite alloyed layer are investigated via X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Atomic force microscope (AFM), Scanning electron microscope (SEM) and Energy dispersive spectroscopy (EDS). Polarization curves and electrochemical impedance spectroscopy (EIS) are used to study the corrosion resistance and the corrosion mechanisms of the Al-Cr composite alloyed layer, the Al implanted layer and 45 steel in 3.5 wt% NaCl solution. The results show that the Al-Cr composite alloyed layer reveals the best corrosion resistance. The formation of Cr2O3 and Al2O3 as passive films on the surface of the Al-Cr composite alloyed layer, and the inner Fe2AlCr and Al8Cr5 phases with excellent corrosion resistance, hindering the corrosion of Cl- ions effectively. The Al implanted layer exhibits moderate corrosion resistance due to the formation of Al2O3 passive film. The substrate of 45 steel shows the worst corrosion resistance.