High Temperature Oxidation Behavior Of Hf/Pt Modified Al₂O₃ Layer On Nickel-based Alloy Surface

At present,with the development of thrust-weight ratio and fuel consumption over the world,lead the combustion chamber temperature rising,the super-temperature alloy has been impossible to meet the higher service temperature.In thermal barrier system,MCrAlY can be used as a bond coating.The quality,thickness,composition and roughness of the interface produced by the bond coating have a decisive impact on the service life of TBC.The growth of the thermal growth oxide（TGO）on the bonding coating can be improved by adding elements platinum（Pt）,hafnium（Hf）and rhenium（La）.The complicated interaction will occurred between the Hf and alumina,effect of distribution on high temperature growth of Hf layer growth mechanism of micro heat are still controversial,especially in the addition of water bearing gas atmosphere,the oxidation mechanism of Hf/Pt modified adhesive layer is still not very clear.In addition,platinum coating is obtained through heat treatment.There is still insufficient research on the influence of Hf/Pt on oxidation behavior in oxide.In this paper,different modification ways of Hf/Pt were studied:（1）directly doped Hf to CoNiCrAl alloy;（2）modified oxides by Hf/Pt on the surface of NiCoCrAl alloy.The Hf modified CoNiCrAl alloy by smelting alloy doped active elements to achieve Hf;adding Hf/Pt oxide is by magnetron sputtering Hf/Pt samples right after heat treatment,heat treatment process is a process of pre-oxidation of the alloy surface,the surface of Hf/Pt and generation of alumina interaction,thus affecting the alumina layer the growth and the phase composition of alumina layer because of surface active element sputtering（Hf/Pt）are different,and the order of sputtering effect of the oxide layer and defects（oxide and alloy）surface undulation.The main results are as follows:（1）The distribution of reactive elements oxide（HfO₂）in the oxide layer is distinctly different after 600 hours oxidation of CoNiCrAlHf alloy coating in air and water vapor.The distribution of reactive elements oxide（HfO₂）within oxide layer is more uniform during the water vapor plus air.The bonding property is better than that of CoNiCrAl Hf alloy samples in high temperature oxidation in air.There is more spallation and more defects in the oxide layer that oxidation in air.（2）In the experiment of single sputtering Hf/Pt modified alumina layer of NiCoCrAl alloy,the unmodified Ni CoCrAl alloy samples showed poor oxidation resistance at the early stage of oxidation,and the defects of the oxide layer appeared the fastest;the NiCoCrAl+Hf alloy sample surface produced a large number of spinel（Ni Cr2O4）due to the induction of Hf over doping.The oxide layer of NiCoCrAl+Pt alloy appeared cracking and falling off at the later stage of oxidation.（3）In the experiment of Co-doped Hf/Pt modified lumina layer of NiCoCrAl alloy,the surface of NiCoCrAl+Hf+Pt alloy did not appear more obvious cracks and holes after 72h hours,the oxide layer was more compact,and the surface of NiCoCrAl+Pt+Hf alloy appeared to fall off after the oxidation of 72h,because Pt promotion was promoted.The uphill diffusion of Al resulted in obvious holes in the interface of alumina and alloy.