Aluminized coatings prepared on nickel-based superalloys can provide good protection against high temperature oxidation and hot corrosion.This study investigated the simple aluminized and silicon-aluminized coatings on nickel-based superalloy K4104.The simple aluminized coating was prepared by pack cementation and the Al-Si coating was prepared by slurry aluminizing,respectively.The microstructure of simple aluminized and Al-Si coating was analyzed by means of scanning electron microscope (SEM),X-ray diffraction (XRD) and electron probe microanalysis (EPMA).And the formation mechanism of simple aluminized and Al-Si coatings was discussed.The results showed that the simple aluminized coating was about 49 um thick and consisted of three layers.The outer layer mainly consisted of Al-rich β-NiAl.The intermediate layer consisted of Ni-rich β-NiAl and Cr-rich.The inner diffusion layer consisted of Cr-rich and y-Ni3Al.The microstructure of Al-Si coating showed that the coating was about 70 um thick and consisted of five layers.The Al-Si coating consisted of CrxSiy,Al-rich β-NiAl,Ni-rich β-NiAl,Cr-rich and Y-Ni3Al.The microstructure of simple aluminized coating was compared with that of Al-Si coating in order to find out the effect of Si.Owing to the effect of Si,there was a Transition layer in Al-Si coating.The Al-Si coating was thicker than simple aluminized coating.The declining trend of the aluminum concentration in the Al-Si coating was smoother than that of the simple aluminized coating.