High Temperature Oxidation and Thermal Shock Properties of La2Zr2O7 Thermal Barrier Coatings Deposited on Nickel-Based Superalloy by Laser-Cladding

Kaijin Huang,Wei Li,Kai Pan,Aihua Wang,Xin Lin

doi:10.3390/coatings10040370

Abstract

In order to reduce the difficulty and cost of manufacturing and improve the high temperature oxidation and thermal shock properties of nickel-based superalloy, a thin La2Zr2O7 thermal barrier coating without bond coat was successfully prepared by laser-cladding using La2Zr2O7 powders on a nickel-based superalloy substrate. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) methods were used to characterize the microstructure of the coating. The high temperature oxidation and thermal shock properties of the coating were evaluated by the air isothermal oxidation method at 1100 °C for 110 h and thermal cycling method at 25~1100 °C, respectively. The results show that the coating is mainly composed of La2Zr2O7 phase. The oxidation weight gain rate of the coating is about two-thirds of that of the substrate, and the first crack thermal shock lifetime of the coating is about 1.67 times of that of the substrate. The oxidation products of the coating are mainly Fe2O3, Cr2O3, NiCr2O4, Nb2O5 and La2Zr2O7. The existence of La2Zr2O7 phase in the coating is the main reason for the improvement of its oxidation resistance at 1100 °C and its thermal shock resistance at 25~1100 °C.

Highlights

With the development of modern industrial technology, nickel-based superalloys are widely used in aerospace, petrochemical and energy industries [1]
After oxidation at 1300 ◦ C for 25 h, they found that the LZ was prone to fall off, while yttria-stabilized zirconia (YSZ) had no mixed oxides compared with LZ/YSZ
The thermal shock property was tested according to the following method: First, the sample was put into an electric furnace at 1100 °C and kept at this

Summary

Introduction

With the development of modern industrial technology, nickel-based superalloys are widely used in aerospace, petrochemical and energy industries [1]. After oxidation at 1300 ◦ C for 25 h, they found that the LZ was prone to fall off, while YSZ had no mixed oxides compared with LZ/YSZ It is well-known that the main practical methods for preparing thermal barrier coatings are plasma spraying (PS) and EB-PVD. The former has the advantages of a simple, economical and practical, good thermal insulation effect, but poor stress tolerance and corrosion resistance. Laser-cladding can automatically stratify the composition and columnar structure of the gradient thermal barrier coatings, improving the high temperature oxidation and thermal shock properties of the coatings.

Othickness

Macroscopic

Microstructure

High Temperature Oxidation Properties

Thermal Shock Properties

Conclusions