采用超音频感应熔覆技术获得高质量具有冶金结合的感应重熔超音速火焰喷涂(HVOF)铁基涂层.借助XRD、SEN/EDS、显微硬度计、极化曲线和交流阻抗手段综合分析涂层微观形貌、物相组成、显微硬度分布以及耐蚀性能.研究结果表明,感应重熔处理后涂层孔隙率从5.74％大幅降低至0.43％,感应重熔HVOF铁基涂层由γ-Fe、硼化物(Cr,Fe)2B以及少量的共晶体γ-Fe/(Cr,Fe)2B组成.在模拟海水溶液电化学测试结果显示,感应重熔HVOF铁基涂层极化曲线呈现典型活化-钝化特征,感应重熔涂层自腐蚀电流密度比HVOF铁基涂层明显降低.交流阻抗结果显示感应重熔HVOF铁基涂层的容抗弧半径相对HVOF铁基涂层更大.感应重熔后涂层内部富氧夹杂物以及孔隙率显著减少,有效阻隔氯离子通过孔隙连接形成的扩散通道进入涂层内部形成腐蚀原电池,涂层耐蚀性能显著提高2.74倍.
Induction remelting high velocity oxy-fuel (HVOF) sprayed Fe-based coatings were conducted by using ultrasonic frequency induction device.X-ray diffraction (XRD),scanning electron microscopy (SEM) and energy-dispersive spectrometer (EDS) analysis,microhardness test,polarization curve and electrochemical impedance spectroscopy technique were used to examine the microstructure,microhardness and corrosion resistance of the coatings.The results show that the porosity is reduced from 5.74％ to 0.43％ after the induction remelting.The phases of γ-Fe,(Cr,Fe)2 B and γ-Fe/(Cr,Fe)2B eutectics are identified in the induction remelted HVOF sprayed Fe-based coatings.Electrochemical test results in simulated sea water show that the polarization curve exhibits an activepassivation charicteristic.The corrosion current density of the induction-remelted coating is lower than that of the HVOF sprayed Fe-based coating due to the reduction of porosity and oxide inclusion content in the remelted coatings,by which the penetration of chloride ions through the pores to form inner galvanic couple is impeded.Electrochemical impedance spectroscopy results show capacitive reactance arc of the induction remelted HVOF sprayed Fe-based coating is larger than that of the HVOF sprayed Fe-based coating,the corrosion resistance increases by 2.74 times.
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