【作者】 卓城之；

【导师】 徐江；

【作者基本信息】 南京航空航天大学 ， 材料加工工程， 2009， 硕士

【摘要】 本文研究了通过电刷镀制备三种纳米颗粒(n-SiO2、n-SiC和n-Al2O3)增强的复合镀层,然后再进行双辉Ni-Cr-Mo-Cu多元共渗,在316L不锈钢表面所制备的颗粒增强Ni基合金层的冲刷腐蚀性能;采用极化曲线、电化学交流阻抗谱(EIS)、开路电位和电流随时间变化关系以及冲刷腐蚀试验对比研究了三种复合镀渗层的耐蚀性与耐冲蚀性能,利用SEM对三种复合镀渗层的腐蚀形貌进行观察,并对复合镀渗层的冲蚀机理进行初步探讨。主要得出如下结论:(1)在静态(10wt.%HCl)、酸性流(10wt.%HCl)冲蚀和酸性料浆流(10wt.%HCl+10wt.%石英砂)冲蚀条件下的电化学测试结果表明:静态条件下,单一合金层的耐蚀性能最优;而两种动态条件(酸性流和料浆流),预镀Ni/SiO2的复合镀渗层的耐蚀性能最优,以下依次为单一合金层、预镀Ni/Al2O3的复合镀渗层、预镀Ni/SiC的复合镀渗层和316L不锈钢。对酸性流和酸性料浆流条件下的冲蚀试验结果表明:低旋转速度条件下(1.88m/s),单一合金层的耐冲蚀性能最好;高旋转速度条件下(2.51m/s、2.98 m/s和3.45 m/s),预镀Ni/SiO2的复合镀渗层的耐冲蚀性能明显优于单一合金层,而且随着旋转速度增大两者差距愈加明显。预镀Ni/Al2O3和Ni/SiC的两种复合镀渗层的耐冲蚀性能明显小于单一合金层,但都明显优于316L不锈钢。该结果证实不同颗粒特性对颗粒增强的复合镀渗层在酸性流动介质中冲蚀性能具有重要影响。(2)对单相流(不含砂的3.5wt.%NaCl溶液)和液固两相流(含砂的3.5wt.%NaCl溶液中)条件下,耐蚀性和耐冲蚀性能测试结果表明:旋转速度越大,预镀Ni/SiO2的复合镀渗层的耐蚀性能越好,耐冲蚀性能越优于其它合金层;预镀Ni/Al2O3的复合镀渗层与单一合金层之间存在临界速度(vk),旋转速度大于vk时,预镀Ni/Al2O3的复合镀渗层的耐冲蚀性能较优;预镀Ni/SiC的复合镀渗层由于耐蚀性能远低于单一合金层导致耐冲蚀性能大大降低,但仍然高于316L不锈钢基体。综合考虑电化学测试和冲蚀失重结果,SiO2颗粒增强复合层具有最好的耐冲蚀性能。更多还原

【Abstract】 In this paper, three kinds of nano-particles reinforced Ni-based composite alloying layers have been successfully prepared by a duplex surface treatment, consisting of Ni/nano–SiC, Ni/nano–SiO2 or Ni/nano–Al2O3 predeposited by brush plating, and a subsequent surface alloying with Ni–Cr–Mo–Cu by double glow process. The corrosion resistance and erosion–corrosion resistance of composite alloying layer were analysed by polarization curve, electrochemical impedance spectroscopy (EIS) OCP–t curve, current response at a potential of +0.2V and erosion–corrosion tests. The eroded surfaces of composite alloying layers were investigated by SEM. The erosion–corrosion mechanisms of composite alloying layers were also explored. The results of electrochemical tests and erosion–corrosion tests were as follows.(1) The results of polarization curves and EIS obtained under static state condition revealed that single Ni–based alloying layer possessed the best corrosion resistance. However, under hydrodynamic conditions (acidic flow and acidic slurry flow), composite alloying layer with brush plating Ni/nano–SiO2 particles interlayer exhibited the highest corrosion resistance, followed by single Ni–based alloying layer, composite alloying layer with brush plating Ni/nano–Al2O3 particles interlayer, composite alloying layer with brush plating Ni/nano–SiC particles interlayer and 316L stainless steel had the lowest corrosion resistance. Results of mass losses in acidic flow and acidic slurry flow showed that, at low rotational speed (1.88m/s), the erosion–corrosion resistance of single Ni–based alloying layer was higher than that of other tested materials. However, at high rotational speed (2.51m/s、2.98 m/s和3.45 m/s), the erosion–corrosion resistance of composite alloying layer with brush plating Ni/nano–SiO2 particles interlayer was higher than that of single Ni–based alloying layer, and the discrepancies of mass loss between composite alloying layer with brush plating Ni/nano–SiO2 particles interlayer and single Ni–based alloying layer increased with increasing rotational speeds and the tests time of erosion–corrosion. The erosion–corrosion resistances of composite alloying layer with brush plating Ni/nano–SiC and Ni/nano–Al2O3 particles interlayer were lower than that of single Ni–based alloying layer, but higher than that of 316L stainless steel. Thus it can be concluded that the erosion–corrosion resistances of composite alloying layers were associated with the characteristices of nano–particles.(2) Results of electrochemical tests and mass losses measurements obtained in liquid flow and liquid–solid slurry flow showed that the corrosion and erosion–corrosion resistances of composite alloying layer with brush plating Ni/nano–SiO2 particles interlayer was obviously higher than that of other investigated materials. Compared with single Ni–based alloying layer and composite alloying layer with brush plating Ni/nano–Al2O3 particles interlayer, there was a threshold of rotational speed (vk), above which the erosion–corrosion resistance of composite alloying layer with brush plating Ni/nano–Al2O3 particles interlayer were apparently lower than that of single alloying layer. Due to the poor corrosion resistance, the erosion–corrosion resistance of composite alloying layer with brush plating Ni/nano–SiC particles interlayer decreased dramatically compared to single Ni–based alloying layer, but was still higher than that of 316L stainless steel.In summary, composite alloying layer with brush plating Ni/nano–SiO2 particles interlayer was a good candidate material for erosion–corrosion environment.更多还原