Study On The Organization And Thermal Protection Properties Of Ce-Y Modified Silicide Co-deposition Coating On The Surface Of TiAlNb9 Alloy

In order to improve the high temperature service performance of TiAlNb9 alloy,Si-Ce-Y co-deposition coating was prepared on the surface of TiAlNb9 alloy by using powder embedding infiltration technique.The influence of catalyst type,difference in holding time and addition of rare earth elements on the microstructure of the co-deposition coating was characterised and analysed by scanning electron microscopy,energy spectrometer and X-ray diffractometer,and the formation mechanism of the layer was analysed to evaluate the The formation mechanism of the seep layer was analyzed,and the thermal shock resistance,high temperature oxidation resistance and friction wear resistance of TiAlNb9 substrate and Si-Ce-Y co-deposition coating were evaluated to reveal their failure mechanism.The results show that the structure and phase composition of the Si-Ce-Y co-deposition coating are influenced by the catalyst type,holding time and the amount of rare earth elements added.After optimizing the process parameters,the Si-Ce-Y co-deposition coating was prepared by using a permeate component of15Si-3Ce O₂-3Y₂O₃-2Na F-77Al₂O₃（wt.%）,a holding temperature of 1080℃and a holding time of 3 h.The Si-Ce-Y co-deposition coating had a multilayer structure,from the outer layer to the inner layer in the order of（Ti,Nb）Si₂,（Ti,Nb）₅Si₄and（Ti,Nb）₅Si₃outer layer,（Ti,Nb）₅Si₄and（Ti,Nb）₅Si₃intermediate layer,and Ti Al₂inner layer.Thermal shock experiments showed that penetration cracks appeared in the TiAlNb9substrate after 47 thermal shocks,while penetration cracks appeared in the Si-Ce-Y co-deposition coating after 57 thermal shocks.Compared with the TiAlNb9 substrate,the Si-Ce-Y co-deposition coating showed penetration cracks more slowly,indicating that the Ce-Y modified silicide infiltration layer can effectively improve the thermal shock resistance of the TiAlNb9 substrate.High-temperature oxidation experiments show that the oxidation weight gain rate of Si-Ce-Y co-deposition coating at 1000℃is much lower than that of TiAlNb9 substrate,and the oxide film composed of Al₂O₃and Ti O₂formed during the oxidation process of TiAlNb9 substrate is easy to crack and peel off,which cannot play a protective role for the substrate.Ti O₂,Si O₂and Al₂O₃oxide film,which has a continuous and dense oxide film structure and can hinder the internal diffusion of oxygen elements,effectively improving the high temperature oxidation resistance of the TiAlNb9 substrate.With the prolongation of oxidation time,the Si element within the seepage layer underwent internal/external diffusion,while the Ti element underwent significant external diffusion,leading to cracks in the seepage layer and eventually causing the failure of the Si-Ce-Y co-deposition coating.The friction and wear experiments show that the Si-Ce-Y co-deposition coating has a certain friction reduction effect on the TiAlNb9 substrate when the GCr15 ball is used as the friction substrate,and the Si-Ce-Y co-deposition coating has a certain frictional reduction effect on the TiAlNb9 substrate below 300°C when the WC ball is used as the friction substrate.In all the frictional wear experiments carried out,the friction wear resistance of the Si-Ce-Y co-deposition coating was significantly better than that of the TiAlNb9 substrate.When mated with GCr15 ball,the wear mechanisms of TiAlNb9substrate at 20°C are abrasive wear and ploughing wear,at 300°C the main wear mechanisms are ploughing wear,abrasive wear and slight oxidation wear,at 600°C the wear mechanisms are mainly ploughing wear,oxidation wear,abrasive wear and adhesion wear;The wear mechanism of the Si-Ce-Y co-deposition coating at 20°C is mainly grain pull-out and crystal fracture,while the wear mechanism of the Si-Ce-Y co-deposition coating at 300°C and 600°C is the smearing of GCr15 on top of it.When mated with WC balls,the wear mechanism of the TiAlNb9 substrate at 20°C is abrasive wear and ploughing wear,at 300°C is ploughing wear,abrasive wear and slight oxidation wear,and at 600°C is mainly oxidation wear,ploughing wear and abrasive wear;The wear mechanism of the Si-Ce-Y co-deposition coating at 20°C is chipping wear,and at 300°C and 600°C are abrasive wear,chipping wear and oxidation wear.