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Zhang K.,Southwest Jiaotong University | Ning S.-H.,Southwest Jiaotong University | Luo X.-W.,Southwest Jiaotong University | Dong L.-X.,Southwest Jiaotong University | And 3 more authors.
Cailiao Rechuli Xuebao/Transactions of Materials and Heat Treatment | Year: 2015

Al2O3/YSZ-Al2O3 coatings with spatial-network structure have been prepared by thermal pressure and filtration of sol-gel paint(TPFSP). To further improve high-temperature oxidation resistance of the coatings, process chemical densification(PCD) for different cycles was applied to the as-prepared coatings in this study. Cyclic high-temperature oxidation test demonstrates that their high-temperature oxidation resistance is improved with increasing cycles of the PCD. However, the impovement on high-temperature oxidation resistance decaies after 12 cycles of the PCD. Morphology of the coatings before and after cyclic high-temperature oxidation test shows that the number of bulges on the coatings decreases with increasing cycles of the PCD. At the same time, the thickness of thermally grown oxide (TGO) layer under the coatings and the degree of internal oxidation of metallic substrate near the TGO layer also decreases with increasing cycles of the PCD. Morphology change of the coatings made by PCD agrees well with the change of cyclic oxidation kinetics curves. © 2015, Editorial Office of TRANSACTIONS OF MATERIALS AND HEAT TREATMENT. All right reserved.

Zhang K.,Southwest Jiaotong University | Ning S.,Southwest Jiaotong University | Ren C.,Taiyuan Weitai New Material Technology Company Ltd | Luo X.,Southwest Jiaotong University | And 3 more authors.
Surface and Coatings Technology | Year: 2015

In our previous study, spatial-network Al2O3/YSZ composite coatings have been prepared by modified sol-gel techniques. It demonstrated that the structure of YSZ particles covered with a spatial-network Al2O3 blanket was beneficial to oxidation and spallation resistance of the ceramic coatings. To further improve oxidation resistance of the ceramic coatings, filling and sealing processes of chemical densification (FSPCD) were applied for as-prepared coatings in the present study. Cyclic oxidation test at 1050°C demonstrates that their oxidation resistance is greatly enhanced due to the FSPCD. To understand the mechanisms underlying the improvement of oxidation resistance of the coatings by the filling and sealing processes, a concept analogous to calculation of electrical resistance of a composite material has been utilized to analyze diffusion resistance of the coatings against oxygen. The relationship between reduced oxygen diffusion rate and the micro-structure changed by the chemical densification is discussed by means of the novel theoretical model. © 2015 Elsevier B.V.

Cheng C.-M.,Taiyuan University of Technology | Xing Y.-T.,Taiyuan Weitai New Material Technology Company Ltd | Shi J.-Y.,Taiyuan University of Technology | Wang B.-C.,Taiyuan University of Technology | Li T.-B.,Taiyuan Weitai New Material Technology Company Ltd
Corrosion and Protection | Year: 2013

Using urotropin as pickling inhibitor, the acid pickling recipe was improved, and the optimum technological parametess were obtain by orthogonal test. The results show that after acid pickling, a qualified compact passive film was formed on the surface of 44660 ultra-pure ferrite stainless steel, and the corrosion resistance was improved. The process solved the technological problem of under-pickling and over-pickling of 44660 ultra-pure ferrite stainless steel in actual production and thus may provide referential meaning for solving the problems about pickling of various ultra-pure ferrite stainless steel.

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