纳米颗粒增强Ni基复合镀渗层的腐蚀与

摘要:

采用复合镀渗工艺，对316L不锈钢表面刷镀的两种纳米陶瓷颗粒(非晶纳米SiO2(n-SiO2)和纳米SiC(n-SiC)颗粒)增强的复合镀层进行双辉Ni-Cr-Mo-Cu多元共渗处理，成功地在316L不锈钢表面制备了纳米颗粒增强Ni基合金层。利用XRD、SEM和TEM对两种复合镀渗层的微观组织进行观察，采用极化曲线、电化学阻抗谱(EIS)和冲刷腐蚀试验对两种复合镀渗层的耐蚀性和耐冲蚀性能进行研究。对两种颗粒增强的复合镀渗层的微观组织分析结果表明：在双辉多元共渗工艺(1000 ℃)条件下，电刷镀含n-SiO2颗粒的复合镀渗层中的SiO2颗粒仍保持非晶态；而电刷镀含n-SiC颗粒的复合镀渗层中的SiC颗粒已完全分解并与基体合金元素发生反应，导致在晶内析出三元硅化物Cr6.5Ni2.5Si和沿晶界析出碳化物Cr23C6。在3.5%NaCl(质量分数, 下同)溶液中的电化学腐蚀实验结果表明：SiO2颗粒增强的复合镀渗层存在明显的钝化区，点蚀电位和维钝电流密度与Ni基合金渗层的十分接近，而电刷镀含SiC颗粒增强的复合镀渗层处于活化状态，但其耐蚀性能仍略强于不锈钢；两种复合镀渗层的EIS图谱均呈现单容抗弧特征，与Ni基合金渗层相比，SiO2颗粒增强的复合镀渗层的容抗弧幅值略微减少，而SiC颗粒增强的复合层的容抗弧幅值明显下降，但仍略高于316L不锈钢。在液/固两相流(10%HCl+10%石英砂)条件下的冲刷腐蚀实验结果表明：SiO2颗粒增强的复合镀渗层具有最佳的耐冲蚀性能，而316L不锈钢的耐冲蚀性能最差

Abstract:

Two kinds of nanoparticles reinforced with Ni-based composite alloying layer were prepared by double glow plasma alloying on AISI 316L stainless steel surface, where Ni/amorphous nano-SiO2 and nano-SiC were firstly predeposited by brush plating. The microstructure of the two kinds of nanoparticles was investigated by XRD, SEM and TEM. Their corrosion resistance and erosion-corrosion resistance were analyzed by Tafel Plot, electrochemical impedance spectroscopy (EIS) and erosion-corrosion tests. The results indicate that under the alloying temperature (1000 oC) condition, the amorphous nano-SiO2 particles still kept the amorphous structure, whereas the nano-SiC particles was decomposed and Ni and Cr reacted with SiC to form Cr6.5Ni2.5Si and Cr23C6. The corrosion test results indicate that the alloying layer reinforced by amorphous nano-SiO2 particles display passivation, and the pitting potential (Epit) and passive current (ip) are slightly smaller than that of single alloying layer, whereas the Ni-based alloying layer reinforced by nano-SiC particles is active in 3.5% NaCl solution (mass fraction, similarly hereinafter). The results of impedance spectroscopy of measured samples show that the Nyquist plots of Ni-based alloying layers consisted of single capacitance arc. Compared with the single alloying layer, the capacitance arc of the amorphous nano-SiO2 particles reinforced by Ni-based composite alloying layer is slightly decreased. The capacitance arc of alloying layer reinforced by nano-SiC particle is lower than that of the single alloying layer and nano-SiO2 particles reinforced by Ni-based composite alloying layer, but still higher than that of 316L substrate. The erosion-corrosion results indicate that the alloying layer reinforced by amorphous nano-SiO2 particles show the highest erosive-corrosive resistance of the three alloying layers, while the 316L stainless steel is the worst