Al基金属玻璃涂层孔隙特性的精确表征及对其腐蚀行为的影响规律

The Accurate Characterization for Pores’ Properties of Aluminum-based Metallic Class Coating and the Influence of Corrosion Behavior from Pores to Coating

摘要:

选用Al86Ni6Y4.5Co2La1.5铝基非晶粉体材料，采用自研的低温超音速喷涂系统，在ZM5表面制备了具备良好耐蚀性能的铝基金属玻璃涂层，分析了涂层的孔隙类型及成因，优选出X射线三维成像法测定了涂层孔隙率，表征了涂层孔隙几何特征，阐明了孔隙对涂层腐蚀行为的影响规律。结果表明，涂层主要包含宏观型、层间型、微球型和微细型四类常规孔隙缺陷；涂层孔隙率基本小于1%且沿厚度方向上变化不大，孔隙呈近球形，尺寸均小于10μm，尤以5μm左右居多；不同孔隙率的涂层均呈现出较宽的自钝化区间，自腐蚀电位较为接近，腐蚀电流密度与孔隙率正相关，大尺寸、贯穿型、边界处的个别特殊孔隙是导致涂层腐蚀失效的根本原因。

Abstract:

Choosing Al86Ni6Y4.5Co2La1.5 amorphous powder and adopting self-developed low-temperature supersonic spray system, the paper has prepared the aluminum-based metallic glass coating on ZM5 surface with good corrosion resistance, analyzed the pores’ types and causes in the coating, selected the X-ray three-dimensional imaging method for the determination of the coating’s porosity and the characterization of the pores’ geometry features, clarified the influence of pores on the corrosion behavior of the coating. The results show that the coating consists mainly of four types of conventional porosity defects，which are macro-type、layer-type、 microsphere-type and microscopic-type; The porosities are substantially less than 1% and have little change along the thickness direction, the pores are nearly spherical, and their average sizes are less than 10μm, especially about 5μm; different porosities in the coating are shown a wide range of self passivation interval, closer self corrosion potentials and positive correlation between the corrosion current densities and porosities. Individual special pores with the characteristics of large-size, through-type and at the border are the root cause of coating’s corrosion failure.