钎焊WC-Ni基复合涂层的耐腐蚀性能

Corrosion Resistance of Brazed Tungsten Carbide- Nickel Composite Coatings on Carbon Steel

钎焊法制备WC复合涂层可以克服热喷涂层的许多缺点,但目前对其在中性NaCl介质中的腐蚀行为研究不多。在碳钢表面真空钎焊制备了WC-Ni复合涂层,采用X射线衍射(XRD)分析了WC-Ni复合涂层表面的物相;通过动电位极化曲线考察了其在3%NaCl溶液中的腐蚀电化学行为;通过场发射扫描电镜(FEGSEM)结合EDX能谱仪观察了不同极化电位处理的涂层的表面形貌和化学组成;采用电感耦合等离子体发射光谱分析了不同极化电位下溶解的金属离子浓度。结果表明:钎焊WC-Ni复合涂层主要是由WC,Ni,NiW,Ni2W4C,Cr3NiB6等物相组成,没有W2C等脆性相;阳极极化曲线上出现2个电流密度平台,分别对应Ni,Cr的氧化物膜的形成和W氧化形成WO3膜层,低电位时主要存在Ni的活性溶解,高电位时同时存在Ni,Cr,W等元素的活性溶解;该涂层耐腐蚀性能较好,硬质相WC的脱落减少,耐磨性提高。

WC- Ni composite coatings were prepared on mild steel substrates by high- temperature sinter- brazing in vacuum.The phases on the surface of the coatings were characterized by X-ray diffraction.The corrosion behavior and electrochemical behavior of the composite coatings in 3%NaCl solution(mass fraction) were evaluated based on measurements of potentiodynamic polarization curves.The morphology and elemental composition of the brazed composite coatings after constant potential polarization were analyzed by field emission scanning electron microscopy and energy dispersive spectrometry.Moreover,the concentration of the metal ions immersed under different polarization potentials was measured by inductively coupled plasma atomic emission spectrometry.Results showed that the brazed WC-Ni composite coatings mainly consisted of WC,Ni,NiW,Ni_2W_4C,and Cr_3NiB_6 phases and did not contain brittle phase like W_2C.Besides,two current density platforms emerged in the anodic polarization curves of the brazed composite coatings,corresponding to the formation of Ni and Cr oxide film and WO_3film.At a low polarization potential,the brazed composite coatings were dominated by active dissolution of Ni,while they were dominated by simultaneous dissolution of Ni,Cr and W at higher anodic potentials.In one word,as- prepared brazed WC-Ni composite coatings showed good corrosion resistance.