Corrosion behavior and mechanism of NiCrAl–NiC abradable sealing coating system in NaCl solution

Abstract

As an important component of aviation turbine engines, abradable sealing coatings have the function of protecting turbine blades and improving engine efficiency. However, Abradable Sealing Coating systems (ASCs) are often damaged by corrosion in their applications, which may cause safety accidents. This article uses atmospheric plasma spraying technology to prepare NiCrAl–NiC ASC system, which is divided into three layers with a porous structure on the top. In order to fully explore the corrosion behavior of NiCrAl–NiC ASC system, corrosion tests were conducted on the ASC system using immersion method. The corrosion potential of this coating system is −0.96V, and a low corrosion potential indicates that the coating is more prone to corrosion. On the other hand, its current density is 51.64 × 10−6 A cm−2, indicating a slower corrosion rate of the coating. After immersion for 600 h, the corrosive medium Penetrated into the interior of the coating, forming interlayer corrosion. The electrochemical impedance results showed that the corrosion process of the coating was divided into three stages, and the impedance fitting results were consistent with the changes in coating porosity during the immersion process. The corrosion products of the coating are oxygen-containing compounds of various metal elements, including Al2O3, Al (OH)3, NiO, Ni(OH)2, and Cr2O3. The porous, multi-layered, and multiphase characteristics of coatings result in their unique corrosion behavior.