X-RAY STRESS MEASUREMENTS ON PLASMA-SPRAY ED ZIRKONIA THERMAL BARRIERCOATINGS

Turbine blades for acro engines with plasma sprayed zirconia thermal b arrier coatings were subjected to typical component loads as thermal f atigue and creep. Before and after testing residual surface stresses i n the coatings were determined by X-ray stress measurements. Different substrate temperatures during the plasma spraying process caused tens ile or compressive stresses on the surfaces of the thermal barrier coa tings. Coatings with compressive stresses failed after only a few ther mal cycles whereas those with tensile stresses sustained 700 to 1500 c ycles without visible damage. Thermal fatigue and creep tests lead to stress changes reducing tensile stresses and increasing compressive st resses.