Mechanical Properties of LaTi_2Al_9O_(19) and Thermal Cycling Behaviors of Plasma-Sprayed LaTi_2Al_9O_(19)/YSZ Thermal Barrier Coatings

摘要

Recently, extensive efforts have been made to develop new thermal barrier coating (TBC) materials which can operate at temperatures above 1523 K over a long term. In this article, LaTi_2Al_9O_(19) (LTA) was synthesized by solid-state reaction at 1773 K, and the mechanical properties of the LTA bulk were evaluated. The microhardness is about 14 GPa, comparable to that of YSZ bulk, whereas the Young's modulus is about 44 GPa, lower than the value of YSZ. However, the fracture toughness of 0.8-1 MPa m~(1/2) is much lower than that of bulk YSZ. A double-ceramic-layer LTA/YSZ TBC structure was proposed and the TBC sprayed by plasma spraying. Thermal cycling tests of the TBC specimens were performed at 1373 K with a dwell time of 10 min. The LTA remained good stability with ZrO_2 and Al_2O_3. However, the single layer LTA TBC was cracked at the LTA/bond coat interface after about 300 cycles, due to its poor thermal shock resistance, while the YSZ TBC yielded a lifetime of about 1000 cycles. The LTA/YSZ TBC remained intact even after 3000 cycles, exhibiting a promising potential as new TBC materials.