Study of oxidation behavior of TBCs with APS and HVOF CoNiCrAlY bond coatings

摘要

The use of Thermal Barrier Coatings (TBCs) has resulted in a significant improvement of the efficiency of gas turbines and diesel engines. A typical TBC is a multilayered coating system that comprises an oxidation resistant metallic bond coating (BC) and a thermally insulating ceramic top coating (TC). Under service condition an Al_2O_3 inter-layer, the Thermally Grown Oxide (TGO), forms in the interface between bond and top coating using aluminium from the BC material and oxygen that attains from the environment through pore channels of the TC. The aim of the present study is to describe the TGO formation on metallic bond coats deposited by different thermal spraying techniques. Therefore, TBCs that consist of a typical bond layer/top layer system (CoNiCrAlY bond layers and YSZ top layers) are deposited on Inconel 718 superalloy substrates. The metallic bond coatings are applied via Atmospheric Plasma Spraying (APS) and High Velocity Oxygen Fuel (HVOF); the ceramic top coatings via APS. Investigations are done concerning the oxidation behavior of this TBC system at 1100℃ in normal atmosphere for 8h, 24h, 50 h and 100 hours. The oxidation behaviour and microstructural properties during the oxidation test are evaluated and compared.