Study On High Temperature Oxidation And Molten Salt Corrosion Behavior Of Platinum Modified Aluminide Coating On Ni-base Superalloy

Directionally solidified Ni-base superalloys are widely used in hot-end components such as aero-engines and gas turbines due to their excellent mechanical properties at high temperature.Before the superalloys is in service,a high-temperature protective coatings is usually applied on the surface of the alloy to prolong the service life.Aluminide coating has good protective effect,strong anti-oxidation ability,simple preparation and low cost,and is a widely used high-temperature protective coating.However,prolonged exposure to hot air can cause coating degradation,wrinkling,and spalling problems during alloy service.The emergence of modified aluminide coatings solves this problem well.β-（Ni,Pt）Al/Ni composite coating was prepared on the surface of directionally solidified superalloy by electroplating-hot dipping method.Meanwhile,Si-dopedβ-（Ni,Al）Al andβ-（Ni,Al）Al/Ni coatings were obtained with a certain Si content.The effects of pre-plating Ni on the high temperature oxidation of the coating,the corrosion behavior of molten salt and the content of Si in the molten pool on the cyclic oxidation behavior of the coating were studied.The phase and morphology of the coating were characterized by XRD and SEM,and the oxidation and corrosion behavior of the coating were dynamically analyzed according to the oxidation and corrosion weight gain data.The major outcomes of this study are listed below:（1）Compared withβ-Ni Al coating andβ-（Ni,Pt）Al coating,the element interdiffusion behavior betweenβ-（Ni,Pt）Al/Ni composite coating and substrate is weakened,the thickness of secondary reaction zone with acicular TCP phase is smaller,and the amount of precipitated TCP is significantly reduced.It shows better high temperature oxidation resistance.（2）Compared withβ-（Ni,Pt）Al coating,β-（Ni,Pt）Al/Ni composite coating has more complete surface oxide film,lower degree of internal oxidation and better corrosion resistance after etching in the environment of 25wt.%Na Cl+75wt.%Na₂SO₄ mixed salt at 900℃for 100 h.（3）Compared with the coating without Si,the oxidation resistance ofβ-（Ni,Pt）Al coating decreased with the increase of Si content when 1wt.%Si,3wt.%Si.（4）The oxidation resistance ofβ-（Ni,Pt）Al/Ni composite coating decreased after adding Si into the molten pool.