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In this investigation, aluminide coatings used to protect industrial components at high temperature and corrosive environments were modified with silicon addition and the microstructural features and formation mechanism were evaluated. The coating on the nickel-based superalloy IN738LC was carried out by a two stage process including siliconizing at first and aluminizing thereafter. Pack cementation siliconizing performed at 950C for 2, 4 and 6 hours in several powder mixtures of Si, A12O3 and NHiCl, then aluminum was diffused into the surface of the specimens by an industrial aluminizing process. The modified coatings were characterized by means of standard metallography, scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction methods. The results show that Si in the coatings mainly presents in the form of secondary phases including Cr3Si, Mo5Si3 and Nii6Ti6Si7, well distributed within the NiAl matrix. The advantages of this two stage modified coating is discussed.
In this investigation, aluminide coatings used to protect industrial components at high temperature and corrosive environments were modified with silicon addition and the microstructural features and formation mechanism were. The coating on the nickel-based superalloy IN738LC was carried out by a two stage process including siliconizing at first and aluminizing thereafter. Pack cementation siliconizing performed at 950C for 2, 4 and 6 hours in several powder mixtures of Si, A12O3 and NHiCl, then aluminum was diffused into the surface of the specimens by an industrial aluminizing process. The modified coatings The results show that Si in the coatings mainly presents in the form of secondary phases including Cr3Si, Mo5Si3 and Nii6Ti6Si7, well distributed within the NiAl matrix. The advantages of this two stage modified coating is dis cussed