Oxidation Resistance of NiCrAl with CeO2 Addition for Thermal Barrier Coating System

Abstract

The thermal barrier coating (TBC) system, including a bond coat and a top coat, was developed to enhance the service life of components functioning at elevated temperatures in gas turbines. Research on the bond coat layer for the creation of high-temperature resistance materials includes the addition of 0.4 wt.% CeO2 into the NiCrAl layer was conducted. The assessment of NiCrAl and NiCrAlCe is conducted to evaluate the performance of the bond coat layer. These coating materials were produced using mechanical milling. High-velocity oxygen fuel (HVOF) was used to apply the metallic layer onto the Inconel 625 substrate. A zirconia ceramic layer stabilized with 8 mol% yttria (8YSZ) was subsequently placed to the metal binder layer via air plasma spraying (APS). The coated samples underwent oxidation testing under equilibrium conditions at 1000° for 100 hours. The microstructure and phases present in the coating layer were analyzed utilizing field-emission scanning electron microscopy (FE-SEM) and x-ray diffraction (XRD). The findings indicate that TBC with NiCrAlCe bond coat exhibited superior oxidation resistance. Adding CeO2 as an active-controlled element significantly enhanced the growth of protective oxides after coating, which led to a reduction in layer porosity. The oxidation kinetic showed a parabolic curve, characterized by minimum mass change and oxidation rate of 0.9751 mg/cm2 and 2.64 × 10-12 g2/cm4s, respectively. Moreover, the t’-ZrO2 phase in NiCrAlCe-8YSZ possesses better thermal stability than NiCrAl-8YSZ, attributed to its consistent crystallite size and microstrain under thermal exposure.