Study On Interface Characteristics And Corrosion Resistance In LBE Of Al₂O₃-TiO₂ Composite Coatings

composite coatings were obtained on China Low Activation Martensitic ?CLAM? steel by thermal spraying-laser in-suit reaction compound technology with CrFe, FeAl and pure Ti powders in this thesis. The morphology, microstructure and properties of the Al₂O₃-TiO₂ composite coatings were characterized and tested mainly by optical microscopy ?OM?, X-ray diffraction ?XRD?, scanning electron microscopy ?SEM?, energy dispersive X-ray spectrometer ?EDS?, tension and pressure testing machine, Vickers hardness tester, etc. The main research results obtained are as follows:?1? The surface of the Al₂O₃-TiO₂ composite coatings prepared are smooth, the microstructure of coatings are both homogeneous and dense without defects such as cracks and pores, and the grain size is very small. Phase composition of the Al₂O₃-TiO₂ composite coatings were Al₂O₃, TiO₂, Fe2Ti05, Fe-Cr, ?Al948Cr.052?2O3, ?Al0.9Cr0.1?2O3. The categories of phase composition of the coatings are basically unchanged from the outside to the inside of the coatings, but phase content undulates.?2? The average micro-hardness value of the Al₂O₃-TiO₂ composite coatings near the intertface between the Al₂O₃-TiO₂ composite coatings and CLAM steel is 2219.7 HV0.1. Cracks generated around the indentation when the coating is very thin. However, when the coating is relatively thick, no crack generated around the indentation and the indentation outline is clear.?3? A shear strength test device for coatings/substrate interface was designed and developed according to GB/T6396-2008. The average shear strength of the interface beteween coatings and substrate was 280 MPa and the standard deviation was 5.5 MPa with deviation rate of 1.96% using method of average data measured multiple times, which indicates that the test value was stable. Metallurgical bond of interface between Al₂O₃-TiO₂ composite coatings and CLAM steel was well formed and the metallurgical bonded coatings had high bonding strength.?4?The Al₂O₃-TiO₂ composite coatings samples were grouped into 2 parts in the irradiation experiments, and the irradiation energy for both of them was 200 keV. However, the irradiation doses for them were 5×1016 ions/cm2 and 5×1017 ions/cm2 respectively. After irradiation, the coating samples were exposed to 550? lead bismuth eutectic ?LBE? for corrosion experiment, and the corrosion time was 200h,300h and 500h respectively. The diffusion depth of lead increases with the increases of corrosion time in CLAM steel and the diffusion depth of lead were 13 ?m, 18?m and 30?m respectively when the corrosion time were 200h,300h and 500h. However, there is no diffusion phenomenon of lead-bismuth for the Al₂O₃-TiO₂ composite coatings after irradiated with 200 keV He+ ion, even though the exposure time in 550? LBE is 500h. The Al₂O₃-TiO₂ composite coatings samples were still relatively intact after different exposure time in stagnant LBE and no obvious signs of corrosion attack by LBE were observed. The main reasons for that are the Al₂O₃-TiO₂ composite coatings have compact structure and ceramic layer structure which show good resistance to liquid metal wetting.