| 摘要 |
An abradable ceramic coated turbine shroud structure (1) includes a grid of slant-steps (3) isolated by grooves (14) in a superalloy metal shroud substrate. A thin NiCrAlY bonding layer (8) is formed on the machined slant-steps. A stabilised zirconia layer (19) is plasma sprayed on the bonding layer (8) at a sufficiently large spray angle (18) to cause formation of deep shadow gaps (22) in the zirconia layer (19). The shadow gaps (22) provide a high degree of thermal strain tolerance, avoiding spalling. The exposed surface of the zirconia layer (19) is machined nearly to the shadow gap ends. The turbine blade tips (4) are treated to minimise blade tip wear during initial abrading of the zirconia layer (19). The procedure results in very close blade tip-to-shroud tolerances after the initial abrading. |
