THERMAL RESPONSE OF VARIOUS THERMAL BARRIER COATINGS IN A HIGH HEAT-FLUX ROCKET ENGINE

Traditional APS ZrO2-Y2O3 thermal barrier coatings (TBCs) formed by air plasma spraying (APS) and low pressure and air plasma sprayed ZrO2-Y2O3/NiCrAlY cermet coatings werre tested in an H2-O2 rocket engine located at the NASA Lewis Research Center. The test cycle was approximately 1.2 s at 1400-degrees-C in a hydrogen-rich environment. During testing, the maximum metal temperature without a coating was 1310-degrees-C. The traditional ZrO2-Y2O3 TBCs with a 100-125-mu-m thick ceramic layer reduced the maximum metal temperature by approximately 350-degrees-C. Increasing the ceramic layer thickness to 200-225-mu-m resulted in an additional metal temperature reduction of 100-degrees-C. However, the cermet coatings, consisting of a ceramic and metal mixture, exhibited a much lower thermal protection capability by reducing the maximum metal temperature by approximately 100-degrees-C. It was also found that the surface roughness of the traditional TBCs had little effect on the thermal response.