A novel approach to coating for improving the comprehensive high-temperature service performance of TiAl alloys

Abstract

TiAl alloys, with half the density of nickel-based superalloys, are highly suitable for aerospace applications requiring lightweight materials. However, they tend to form a nonprotective mixed oxide film on their surface at high temperatures. This oxide film is prone to cracking, which can lead to long-term high-temperature oxidation surface degradation, thereby reducing their high-temperature creep and fatigue resistance. Surface cracks on the oxide film further aggravated the brittleness of the TiAl intermetallic compounds after high-temperature exposure. While coatings are typically applied to promote the formation of dense oxides for surface protection, they primarily enhance oxidation resistance. However, this improvement comes at the cost of reducing the high-temperature creep and fatigue resistance and the room-temperature plasticity of TiAl alloys. This study introduced an electroless coating method to deposit a Pt coating, approximately 200 nm thick, on the surface of TiAl alloys. During high-temperature applications, the Pt dispersed as nanoparticles within the oxide layer, enhancing the oxide's plasticity. This oxide structure considerably improved the high-temperature creep and fatigue properties of TiAl alloys, while enhancing their room-temperature tensile properties after oxidation. This approach offers a novel strategy for designing surface coatings for high-temperature components.