Effect of TiC self healing coatings on the cyclic oxidation resistance and lifetime of thermal barrier coatings
Abstract Thermal barrier coatings (TBC) are getting great importance in industry as the inlet temperature of advanced gas turbine engines is continuously being pushed higher in order to improve efficiency. It is well known that the thermal growth oxide (TGO) could decrease the durability of the TBC. In order to slow the growth rate of TGO, oxidation barrier coatings were designed and fabricated. Among these coatings, self healing coating is the most promising. The present study shows that TiC acts as a self healing agent releasing its oxide (TiO 2 by reaction with oxygen in air and heals the cracks/pores present in the coatings. A TiC self healing coating after pre oxidation treatment in the furnace at 600 degC could suppress the growth of the detrimental oxides by the formation of a low porosity self healing layer at the top coat (TC)/bond coat (BC) interface. The porosity of healed coatings decreased three times from 12% to 3% as compared to the as sprayed coating. This lower porosity could attribute to the lower growth rate of self healing TBC. The gained weight versus the development of the TGO exhibited 30% slower oxidation rate than the conventional TBC while less than 10% oxide area percentage in BC of TiC self healing. The treated coatings demonstrated better oxidation resistance up to 28.8% than the conventional coatings. TiC self healing coatings reduce the growth rate of TGO which promote the TBC to survive twice thermal cycles at higher temperature of 1000 degC. TiC self healing TBCs could be considered as a promising TBC with better oxidation resistance and thermal cycle resistance.