PERFORMANCE OF THERMAL BARRIER COATINGS IN HIGH HEAT-FLUX ENVIRONMENTS

Thermal barrier coatings were exposed to the high temperature and high heat flux produced by a 30 kw plasma torch. Analysis of the specimen heating rates indicates that the temperature drop across the thickness of the 0. 038 cm ceramic layer was about 1100 degree C after 0. 5 s in the flame. An as-sprayed ZrO//2-8wt%Y//2O//3 specimen survived 3000 of the 0. 5 s cycles without failing. A coated specimen with no surface modification but which was heat treated in argon also did not surface spall. Heat treatment in air led to spalling in as early as one cycle from heating stresses. Failures at edges were investigated and shown to be a minor source of concern.