Effect of Cyclic Oxidation Exposure on Tensile Properties of a Pt-Aluminide Bond-Coated Ni-Base Superalloy

Abstract

The tensile behavior of a directionally solidified (DS) Ni-base superalloy, namely, CM-247LC, was evaluated in the presence of a Pt-aluminide bond coat. The effect of the thermal cycling exposure of the coated alloy at 1373 K (1100°C) on its tensile properties was examined. The tensile properties were evaluated at a temperature of 1143 K (870°C). The presence of the bond coating caused an approximately 8 pct drop in the strength of the alloy in the as-coated condition. However, the coating did not appreciably affect the tensile ductility of the substrate alloy. The bond coat prevented oxidation-related surface damage to the superalloy during thermal cycling exposure in air at 1373 K (1100°C). Such cyclic oxidation exposure (up to 750 hours) did not cause any further reduction in yield strength (YS) of the coated alloy. There was a marginal decrease in the ultimate tensile strength (UTS) with increased exposure duration. Because of the oxidation protection provided by the bond coat, the drastic loss in ductility of the alloy, which would have happened in the absence of the coating, was prevented.

Microstructural evolution and cyclic oxidation of Pt-Al-YSZ coating under thermal shock

“…It seems that PtAl 2 particles spalled along with the oxide scale. Similar results have been reported by Zafir Alam et al during the cyclic oxidation of Pt-Al coatings [27]. The decrease in Al concentration in the Pt-Al layer has resulted in β to γ′ phase transformation in some regions ( figure 11(b)).…”

On the Thermal Shock Resistance and Failure Mechanism of the Pt-Modified Aluminide Bond Coating

“…Currently, the Pt-Al bond coating is widely utilized in TBC systems for turbine components, including blades and nozzle guide vanes, due to its exceptional performance. The protection of Pt-Al bond coating is primarily due to the formation of a continuous α-Al 2 O 3 regenerated layer on the surface [7], which offers comprehensive support against high-temperature oxidation and hot corrosion for the entire TBC [8,9]. Meanwhile, the Pt-Al bond coating exhibits superior mechanical properties and excellent oxidation and corrosion resistance [10,11].…”

“…On the one hand, Pt can enhance the oxidation resistance by increasing the diffusion coefficient of Al in the alloy, and it enhances the adhesion of the protective layer to the substrate [14]. On the other hand, Pt can increase the modulus of elasticity of β-NiAl and also improve its creep resistance, preventing a significant decline in alloy ductility [7]. Researchers are also working on improvements to the wrinkle resistance and oxidation resistance of Pt-Al coatings [15][16][17][18].…”