Cr添加对Ni-Cr-Mo激光熔覆层在含氯硫代硫酸盐溶液中耐蚀性的影响

Effect of Cr Addition on Corrosion Resistance of Laser-Cladding Ni-Cr-Mo Coatings in Chloride Solution with Thiosulfate

摘要:

通过微观结构观察和电化学测量，在硫代硫酸盐氯化物溶液中评估了Cr的添加对Ni-Cr-Mo激光熔覆涂层耐腐蚀性的影响。通过扫描电子显微镜和X射线衍射观察到了非常相似的微观结构和相组成。涂层主要有共晶和枝晶，并由包含Cr、Mo、W、Fe的γ-Ni固溶体和Cr_0.19Fe_0.7Ni_0.11固溶体组成。电化学结果表明，添加一定Cr含量的激光熔覆层表现出更好的耐腐蚀性。C28涂层表现出较高的开路电位值和较低的钝化电流密度，并且具有更大的阻抗模量和电荷转移电阻。随着Cr含量的增加，在含氯的硫代硫酸盐溶液中钝化膜的厚度变厚，膜的缺陷变少。Mott-Schottky分析表明，溶液中激光熔覆层上表面形成的钝化膜表现为n型和p型半导体。

Abstract:

The effect of Cr addition on the corrosion resistance of the laser-cladding Ni-Cr-Mo coatings was evaluated in chloride solution with thiosulfate by microstructure observation and electrochemical measurements. Results show that very similar microstructures and phase compositions are tested by scanning electron microscope and X-ray diffraction. Both eutectic and dendrite structures are observed, and the coatings are mainly composed of the γ-Ni solid solution of Cr, Mo, W, Fe, and Cr0.19Fe0.7Ni0.11 solid solution. The electrochemical results confirm that the laser-cladding coating with the special Cr addition behaves better corrosion resistance. The coating C28 performs higher values in open circuit potential and lower passive current density, especially the larger modulus of the impedance and charger transfer resistance. With increasing Cr content, the passive film is much thicker and the defects of the films are less in chloride solution with thiosulfate. The Mott-Schottky reveals that the passive film formed on the top surface of the laser-cladding coatings in solution behaves as n-type and p-type semiconductors.