CMAS resistance characteristics of multi-components rare earth phosphate materials at 1250 °C and 1350 °C

Calcium-magnesium-alumina-silicate (CMAS) attack is a major challenge for thermal barrier coatings (TBCs) during the application. In this work, four rare earth phosphates materials including (La0.2Nd0.2Sm0.2Eu0.2Gd0.2)PO4, (La0.5Nd0.5)PO4, (La0.5Gd0.5)PO4 and (Nd0.5Gd0.5)PO4 were synthesized by chemical co-precipitation. The resistance behaviors to CMAS of the materials were investigated at 1250 °C and 1350 °C for 5 h, 10 h and 20 h, respectively. Results show that the main corrosion products are the apatite compounds (Ca2+xRe8-x(PO4)x(SiO4)6-xO2) and the Ca3(PO4)2. Increasing the corrosion temperature from 1250 °C to 1350 °C will promote the penetration of the melted CMAS. It would not lead to the more serious corrosion by prolonging the corrosion time at 1250 °C and 1350 °C. The P–Ca layer composed by the Ca3(PO4)2, which relates to the rare earth elements compositions, prevent the CMAS corrosion to the materials effectively. Preparing multi-components rare earth phosphates and optimizing their element compositions will be a new way to improve the resistance to the CMAS for these materials.