Abstract: A superalloy turbine blade (10) has a MCRALY bond coating (22) and a thermal barrier coating (24). The thermal barrier coating (24) comprises a plurality of alternate layers (25, 27) which have different structure to produce a plurality of interfaces (26) substantially parallel to the metallic substrate (20)/ bond coating (22) interface. These interfaces (26) provide paths of increased resistance to heat transfer to reduce thermal conductivity of thermal barrier coating (24). The structure in the alternate layers (25, 27) of the thermal barrier coating (24) is columnar (28), or segmented, to ensure that the strain tolerance of the thermal barrier coating (24) is not impaired. The columnar grains (28) in the layers (25, 27) extend substantially perpendicular to the metallic substrate (20)/ bond coating (22) interface. This enables thermal barrier coating (24) of reduced thickness and weight to be used.