Investigating thermal shock and corrosion resistance of Inconel 601 super alloy after thermal barrier coating with %8 YSZ powder

Abstract

Superalloys, which are categorized in three groups as iron-based, nickel-based and cobalt-based, are used especially in high temperature applications. Inconel 601 alloy, a nickel-based superalloy, is widely used in applications such as chemical processing, aerospace, power generation, heat treatment, chemical refining and gas turbine engines. Although the mechanical properties of superalloy materials and their resistance to wear, corrosion and oxidation are better than other metallurgical materials, these properties are not satisfactory in some applications. In such cases, the desired properties can be obtained by applying heat treatment and coating processes to superalloys. In this study, approximately 100, 200 and 300 µm ceramic top coat thickness thermal barrier coating system with NiCrAlY and 8%YSZ powder coating materials, were created for the Inconel 601 substrate material and SEM, EDS and XRD datas are given. Then, electrochemical corrosion test with 3.5% NaCl solution and 8 cycles of thermal shock test at 1200 °C using FCT thermal shock method were applied to the samples. Considering the corrosion rate values and SEM images after the electrochemical corrosion test, it was determined that the sample with the highest corrosion resistance was the sample with a ceramic top coating thickness of 100 µm. The reason for this is that as the coating thickness increases in thermal barrier coatings, the tension increases and accordingly, a change in pore and crack density occurs. The fact that the samples with a ceramic top coating of 100 µm thickness have the highest corrosion resistance can be explained in this way. Considering that the pore and crack ratio decreases due to the sintering effect in the SEM images of the samples after the thermal shock test, but considering that the TGO layer thickness will increase at higher temperatures and longer service conditions, in regards to thermal barrier coating deformation, it was concluded that the samples with 100 and 200 µm ceramic top coating thicknesses were safer in terms of thermal shock.