| Efficiency of applying the fossil fuel require to be improved,as a result of the increasing demand for the energy all around the world.As for gas turbine engines,improving the apply efficiency of fossil fuel means to increasing the working temperature.The working temperature of turbine engines are above 1000℃ and still increasing.Super alloys normally applied as the substrate of blade on the turbine engines,are incapable of function regularly at this temperature.Thermal barrier coatings(TBCs)are developed to protect super alloys under high temperature.Several factors including growth rate of oxide on the bond coat,thickness and composition of oxide may have a influence on the service lifetime of the thermal barrier coatings.Pt,Hf and Re(react elements)are often added to the bond coat so as to extend the service lifetime of bond coat.However,Pt would interact with the bond coat,and the mechanism about how the Pt affect the thermal growth oxide is still debatable.Moreover,the mechanism with how the water vapor affect the Pt modified bond coat oxidation procedure is still not class.This article investigate two methods of Pt addition to bond coat,which are Pt modified NiCoCrAl and Pt addition to the oxide grow from the bond coat,and their influence to the microstructure and inner stress within the bond coat in air and water vapor atmosphere.Compared to the Pt modified NiCoCrAl,oxide additional Pt have a significantly influence to the surface morphology of the specimen.OM,SEM,EDS were allied to investigate the oxide in bond coat and its microstructure,morphology and composition.After 500 hours oxidation in air and water vapor separately,the results can be summarized as follows:Regardless how the Pt added to the NiCoCrAl,Pt modified NiCoCrAl and Pt insert within the oxide of NiCoCrAl are all exhibit a better anti high temperature oxidation behavior than NiCoCrAl.Pt has a different diffuse rate in different phases of NiCoCrAl due to the different lattice structure within the phases.Inner stress is initiated by different growth rate of the oxide in β-NiAl and γ’-Ni3Al due to existence water vapor.The oxide product change significantly due to the water vapor in Pt containing oxide.Cr2O3 and Ni/CoPt are generated in water vapor.Water vapor promote the formation of Cr2O3 due to the decrease of oxygen pressure in water vapor,and enable to encourage the uphill diffusion of Ni and Co to the surface of NiCoCrAl and combine with Pt to create totally different oxidation products which are never observed in previous research. |
