GdPO4: CMAS-phobic and infiltration-inhibiting protective layer material for thermal barrier coatings

摘要

Calcium–magnesium–alumina–silicate (CMAS) which wets, spreads and infiltrates into thermal barrier coatings (TBCs) at high temperatures during the operation of aero engines, seriously jeopardizes the performance and lifetime of TBCs. Here, we proposed a promising protective layer material of GdPO4 for TBCs, which has excellent CMAS-phobicity and infiltration -inhibiting ability. The CMAS wetting behavior and its i nterfacial reaction with GdPO4 were investigated and compared to Gd2Zr2O7 and YSZ. The results showed that the contact angle between CMAS and GdPO4 was the highest, indicating the best CMAS-phobicity of GdPO4. An apatite reaction layer with a bilayer structure was formed at the interface between CMAS and GdPO4 after corrosion at 1250 ° C for 1 h, effectively inhibiting CMAS wetting and infiltration, mainly attributable to the fact that the needle -like structure of the upper sublayer helps pin the three -phase contact line of molten CMAS, which can inhibit CMAS wetting, and the compact lower sublayer inhibits CMAS infiltration. First - principles calculations revealed that GdPO4 and its interfacial reaction layer had lower surface energy and smaller adhesion work between the interfacial reaction layer and CMAS, and these material properties all favor the CMAS-phobicity of GdPO4. It is thus concluded that GdPO4 is of excellent CMAS-phobicity and infiltration-inhibiting ability.