RE-,x-O-,y-改性滲層鋁組織及性能研究.pdf

1、Aluminide coatings are widely used to provide protection for the surface of metallic components because of their excellent resistance to oxidation and corrosion. Pack cementation is a coating technique which is frequentl

2、y used to apply protective coatings on metal surfaces to protect them from high temperature oxidation and corrosion. It has very important meaning to the property of the coating to use the especial effect of rare earth t

3、o improve the coating’s microstructure. A RExOy-modified aluminide coating has been developed on 20 steel samples in a process of two steps: the first was composite electro-deposition of Ni and RExOy particles on 20 stee

4、l, followed by the way of aluminizing on the Ni-RExOy composite coating using pack cementation method at 900℃ for 4 hours. For comparison, aluminizing was also performed on the 20 steel and the one with electroplate Ni f

5、ilm but without RExOy addition. The samples with different coating we studied from CO2 corrosion resistance experiment, H2S corrosion resistance experiment and oxidation resistance experiment. The layer’s growth kinetics

6、 curve equation was obtained with computer fitting from measuring the thickness of the layer. The optical microscope (OM), the scanning electronic microscope (SEM) and X-ray energy dispersive analysis (EDS) and the trans

7、mission electron microscope (TEM) we used to analyze the microstructure and component of the layer and the effect of RExOy was also discussed in this work.The results show a fine grain layer rich with RExOy dispersion wa

8、s obtained using the method of electro-deposition and aluminizing in the condition of this experiment. The content of CeO2 is up to 5.21Wt% in the rich area of aluminized coatings, which strain the interdiffusion between

9、 the coating and the base during the oxidation process at high temperature; The out layer of the coating was mainly composed of β-NiAl phase and spinodal decomposition was found in the surface; Amorphous and nano-crystal

10、line we found in the surface of the layer. When the wavelengths of spinodal decomposition got to the level of nanometers, the nano-crystalline were easy to form; The growth kinetics curve equation of the modified coating

11、 was δ=-1.2t2+41.0t+22.0, of which the fitting rate with experimental data was up to 99.5%; The RExOy-modified coating’s corrosion resistance was superior to that of the other two RExOy-free coatings, which was 2-4 times

12、 as that of the pure aluminum coating on the 20 steel. The analysis of surface indicated that pitting was occurred on the NiAl coating while uniform corrosion was occurred on the modified coating; the results of high tem

13、perature oxidation experiment indicated the oxidation resistance of the RExOymodified coating is obvious better than that of the other two coatings, which is 2-3 times than the pure aluminum coating. Meanwhile, the effec

14、t of RExOy during the process of the whole experiment was analyzed: during the process of aluminizing, RExOy played a part of refining grain size and improving the uniform of microstructure; during the corrosion process,

15、 RExOy took part in the reaction with the corrosive mediums, making the coating at the same potential, uniform corrosion was occurred, and then decreased the corrosion rates; during the corrosion process, the RExOy which