Oxidation Behavior of Al-Y Coating on γ-TiAl at 900°C

Yang Z G,Miao Q,Liang W P,Song Y P,Hu R Y

doi:10.1590/s1517-707620190001.0649

Yang Z G, Miao Q + Show 3 more

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https://doi.org/10.1590/s1517-707620190001.0649

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Abstract

In this study, an Al-Y coating was applied to enhance the property of oxidation resistance on the surface of γ- TiAl alloys by rf magnetron sputtering. The isothermal oxidation tests were investigated at 900 °C for 100 h. The coating characteristics and microstructure of coating after isothermal oxidation were inspected by XRD and SEM methods respectively, and coating bonding strength was investigated by scratch tester. Results show that Al2O3 and Y2O3 were produced on the surface of γ-TiAl alloys to enhance oxidation resistance during the isothermal oxidation test. Diffusion layer with rich element of Al provides abundant Al to surface for formation of a continuous Al2O3 layer which increases oxidation resistance effectively. Oxides of YAlO3 and YAG were formed during the oxidation tests, which were beneficial for the strength, hardness and fracture toughness of crystal grain of Al2O3. Furthermore, Element of Ti diffused into surface from substrate was restrained by Al because of the formation of TiAl3 and TiAl, which avoid the layer-broken by titanium oxides with porous structure Keywords: Oxidation behavior; Magnetron sputtering; High temperature; Al-Y coating; γ-TiAl alloy; Diffusion

Highlights

Γ-TiAl alloys are widely used in aero engines and automotive components due to the outstanding creep properties, high melting point which is more than 1450 °C, and the preeminent specific modulus that is around 160 GPa to 180 GPa [1]
Results show that Al2O3 and Y2O3 were produced on the surface of γ-TiAl alloys to enhance oxidation resistance during the isothermal oxidation test
Ceramic coatings were used in TiAl alloy to improve the property of oxidation resistance

Summary

Introduction

Γ-TiAl alloys are widely used in aero engines and automotive components due to the outstanding creep properties (more than 900 °C), high melting point which is more than 1450 °C, and the preeminent specific modulus that is around 160 GPa to 180 GPa [1]. Surface modification technique can be an excellent method which contributes to form steady oxide scales to increase oxidation resistance of γ-TiAl alloys, and make sure it can be used steadily in high temperature environment. M Taheri et al [11] have been succeeded in forming NiCrAlY or CoNiCrAlYSi coating on the surface of TiAl alloy to improve the oxidation resistance. Ceramic coatings were used in TiAl alloy to improve the property of oxidation resistance. Such as Cr2O3 and Al2O3, which have been used to enhance the long time steady application in high temperature environment [16-22]. A preeminent coating was applied on the surface of TiAl alloy to improve the property of oxidation resistance. The aim of the study is to reveal Al-Y coating and demonstrate the effect of Al-Y layer on surface of γ-TiAl in oxidation resistance

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