High Temperature Protective Bond Coats:Development and Effect of Reactive Element

Abstract

High temperature protective coatings, mostly metal-based, are widely utilized for protecting key components (such as gas turbine blades) serving in areo- or land-based turbine engines. By forming a slow-growing dense oxide scale (Al2O3, Cr2O3 and SiO2 etc.), these coatings offer reliable protection, and prevent the underlying substrate alloy from aggressive invasion at high temperature. The paper reviews the developing history of bond coats, mainly aluminide diffusion coating and MCrAlY overlay. Modification of these coatings has been mainly related to increasing Al content for achieving a proper distribution, while the refrainment of element inter-diffusion between coating and substrate alloy is a worrying concern. Then, the attention is transferred to reactive element effects (REEs), including how REE was observed in history, mechanisms explaining REE and recent investigations on the doping-effect of RE. In summary, the challenges to achieve an ideal protective metal coating are presented, in which the possible solutions to overcome these challenges are mentioned.

Keywords

• aluminide coating
• MCrAlY overlay coating
• high temperature oxidation
• hot corrosion
• reactive element effect