Gradient　thermal　cycling　test　was　performed　on　atmospheric　plasma　sprayed　(APS)　thermal　barrier　coatings　(TBCs)　to　examine　the　influence　of　the　bond　coat　temperature　on　the　thermal　cyclic　lifetime.　The　TBC　system　consisted　of　Inconel　738　substrate,　cold-sprayed　NiCoCrAlTaY　bond　coat　(BC)　and　plasma-sprayed　yttria-stabilized　zirconia　(YSZ)　top　coat.　Every　thermal　cycling　test　included　70s　heating,　50s　holding　and　120s　cooling.　The　temperature　of　top　YSZ　surface　was　about　1150　°C,　while　the　bond　coat　temperatures　were　900°C,　950°C　and　1000°C,　respectively.　Results　indicated　that　the　lifetime　of　APS　TBCs　is　significantly　affected　by　bond　coat　temperature.　A　model　to　predict　the　relative　thermal　cyclic　lifetime　of　TBCs　at　different　bond　coat　temperature　was　established　by　taking　account　of　main　factors　affecting　the　lifetime　of　TBCs.　It　was　found　that　the　predicted　results　are　consistent　with　the　observed　results.　As　a　result,　the　change　of　lifetime　of　APS　TBCs　mainly　depends　on　the　growth　rate　of　thermally　grown　oxide　(TGO),　elastic　modulus　of　YSZ　and　thermal　expansion　mismatch　difference　between　YSZ　and　substrate　caused　by　different　bond　coat　temperature.　©　(2015)　by　ASM　International　All　rights　reserved.