Oxidation Behavior and Oxide Transformation of a Pt-Modified Aluminide Coating at Moderate High Temperature

Yanyan Li,Shuai Li,Chao Zhang,Na Xu,Zebin Bao

doi:10.3390/cryst11080972

Yanyan Li, Shuai Li + Show 3 more

Open Access

https://doi.org/10.3390/cryst11080972

Copy DOI

Abstract

The oxidation performance of a single-phase Pt-modified aluminide coating was assessed in oxidation test at 980 °C in comparison with the single crystal superalloy. The results suggested that the Pt-modified aluminide coating exhibited superior oxidation resistance. During oxidation, the oxide scale formed on bare alloy changed constantly followed by the constitution of the multi-layer scale structure: An outer scale mainly consisted of Cr2O3 + NiCr2O4 + TiO2 with scarce protection, and an internal scale mainly consisted of Al2O3. The thickness of the outer oxide scale increased with time, where the scale became looser and more porous. Meanwhile, the internal scale was discontinuous. Oxygen and nitrogen inwardly diffused into substrate, forming Ta2O5 and TiN particles. In contrast to the complex constitution of oxide scale, a uniform and continuous Al2O3 scale formed on Pt-modified aluminide-coated samples after oxidation at 980 °C for 1500 h, which showed no spallation and cracking. Interestingly, θ-Al2O3 and α-Al2O3 phases remained after such a long oxidation time. It is the relatively lower temperature and the presence of Pt retarded θ-α transformation. The degradation rate from β-NiAl to γ′-Ni3Al was very slow in the coating. The various development of oxide scale on the coating and substrate was individually studied.

Highlights

IntroductionNickel-base single crystal (SX) superalloy series have been widely used as structural material in the hot-section components of aero, gas turbines, small type turbines and turboshaft engines [1,2], because of its satisfactory mechanical property (e.g., creep-resistance and rupture life) at high temperature
Accepted: 15 August 2021Nickel-base single crystal (SX) superalloy series have been widely used as structural material in the hot-section components of aero, gas turbines, small type turbines and turboshaft engines [1,2], because of its satisfactory mechanical property at high temperature
As serving in harsh oxygen-rich environment, the high-temperature oxidation performance plays a critical role in determining the service life of SX superalloys, which depends on the formation of a dense and protective oxide scale on the surface

Summary

Introduction

Nickel-base single crystal (SX) superalloy series have been widely used as structural material in the hot-section components of aero, gas turbines, small type turbines and turboshaft engines [1,2], because of its satisfactory mechanical property (e.g., creep-resistance and rupture life) at high temperature. Albeit holding excellent mechanical property, the oxidation rate of superalloy increases significantly once the temperature exceeds 900 ◦ C. As serving in harsh oxygen-rich environment, the high-temperature oxidation performance plays a critical role in determining the service life of SX superalloys, which depends on the formation of a dense and protective oxide scale (mainly refers to Al2 O3 or Cr2 O3 ) on the surface. Because the SX superalloys contain limited Al (

Methods

Results

Discussion

Conclusion