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 (La 0.2 Nd 0.2 Sm 0.2 Eu 0.2 Gd 0.2 )PO 4 , (La 0.5 Nd 0.5 )PO 4 , (La 0.5 Gd 0.5 )PO 4 and (Nd 0.5 Gd 0.5 )PO 4 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 (Ca 2+ x Re 8- x (PO 4 ) x (SiO 4 ) 6- x O 2 ) and the Ca 3 (PO 4 ) 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 Ca 3 (PO 4 ) 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.