等离子喷涂工艺对锅炉管束用Fe 基非晶涂层组织结构和耐蚀性能的影响

目的研究等离子喷涂功率和喷涂时间对锅炉管束用Fe基非晶涂层的相组成、微观组织结构及涂层耐蚀性能的影响。方法通过X射线衍射、扫描电子显微镜和三电极电化学研究进行分析。结果涂层主要由非晶相组成,表面较为平整致密;随着喷涂功率和喷涂时间的增加,涂层非晶相含量降低,孔隙率降低,致密性升高。非晶涂层在0.5mol/L H2SO4溶液和在3.5%(质量分数)NaCl溶液中均表现出良好的钝化作用,在0.5mol/L H2SO4溶液中钝化区较宽,在3.5%NaCl溶液中自腐蚀电流密度较低。随喷涂功率和时间的增加,阳极极化曲线钝化区加宽,电流密度降低。结论喷涂功率升高会导致涂层孔隙率下降,喷涂时间增加则致使涂层厚度增加,腐蚀介质渗透到基体的表面路径和阻力增加,从而可以进一步改善Fe基非晶涂层的耐蚀性能。

Effect of Spray Process on the Microstructure and Corrosion-resistance of Fe-based Amorphous Coatings Obtained by Plasma Spray on the Boiler Tubes

Objective To investigate the effects of plasma spray power and time on the phase, microstructure and corrosion-resistance of the amorphous coating on the boiler tubes. Methods XRD, SEM and electrochemical polarization research were adopted. Results The coating with high fraction of amorphous phase was obtained, which had a flat and compact surface. The amorphous fraction and porosity decreased and the density increased with the increasing spray power and time. The coatings exhibited an excellent ability to resist corrosion with wide passive region in 0. 5 mol/ L H2SO4 and 3. 5% NaCl solutions. And the coatings exhibited wider passive region and lower corrosion current density in 0. 5 mol/ L H2SO4 and 3. 5% NaCl solutions, respectively. With increase of the spray power and time, the anodic polarization curves of the amorphous coatings were passivated with wider passive region and lower passive current density. Conclusion The path and flow resistance that corrosive liquid permeated the substrate were increased, and the corrosion resistance of the coating was improved, owing to the decreased porosity and increased coating thickness with the increasing spray power and time.