The Process And Performance Of Platinum Modified Aluminide Coatings Deposited By CVD Method

In order to adapt the harsh working environment of turbine blade,the chemical vapor deposition?CVD?method can effectively prepare the corrosion-resistant aluminide coating on the surface of the turbine blade.In order to further improve the service life of the turbine blade,the aluminide coating needs to be modified.Firstly,the different thicknesses Pt plating on the surface of nickel-based superalloy Inconel 718 by electroplating.And simple aluminide coating,?-?Ni,Pt?Al coating and PtAl₂+?-?Ni,Pt?Al dual phase coating were prepared by CVD method.The simple aluminide coating and the?-?Ni,Pt?Al coating exhibit a two-layer microstructure in which the outer layer consists of single-phase?and the inner layer is the IDZ.The PtAl₂+?-?Ni,Pt?Al dual phase coating have a three-layer structure consisting of a two-phase PtAl₂+?-?Ni,Pt?Al,an intermediate layer and an inner interdiffusion zone?IDZ?,and PtAl₂ is diffusely distributed in the?phase.In this paper,the cyclic oxidation tests of three kinds of coatings at 1100°C show that the?-?Ni,Pt?Al coating of 6?m Pt exhibits the best resistance to cyclic oxidation,the best spallation resistance of oxide scale and the lowest maginkude of surface rumpling.Pt might be enhancing selective oxidation of Al resulting in the formation of comparatively purer oxide which resists oxidation better.The presence of Pt improve the adhesion of the oxide scale by reducing the formation of voids at the coating/oxide scale interface.In the high temperature oxidation process,the addition of Pt can effectively hinder the diffusion of Ti.For the Pt modified aluminide coating,the spallation of the oxide scale is mainly caused by the increase of surface rumpling during cyclic oxidation.And different Pt content affects the surface rumpling of the coating.It is proved that the difference of surface rumpling,in which an interaction existed among phase transformation and oxide scale spallation of the coating itself during the high temperature exposures.The oxidation resistance and performance of?Ni.Pt?Al coating are determined by the aspects mentioned above.??The hot corrosion test of three kinds of coatings in 95%Na₂SO₄+5%NaCl mixed salt?mass fraction?at 900°C shows that the?-?Ni,Pt?Al coating exhibits the best resistance to hot corrosion.The hot corrosion resistance of PtAl₂+?-?Ni,Pt?Al dual phase coating decreased,mainly due to the large degree of surface rumpling lead to oxide scale spalling.The surface of the?-?Ni,Pt?Al coating forms a higher density of equiaxed Al₂O₃particles,while the surface of the simple aluminide coating and the the PtAl₂+?-?Ni,Pt?Al dual phase coating form poor density elongated oxides.