Abstract No.:
2842

 Title:
Iron-based arc-sprayed coatings for gas corrosion protection at elevated temperatures

 Authors:
Hanna Pokhmurska* / Institute of Composite Materials, Chemnitz University of Technology , Germany
Bernhard Wielage / Institute of Material Science and Engineering, Chemnitz University of Technology, , Germany
Vasyl Pokhmurskii/ G.V. Karpenko Physico-Mechanical Institute of the National Academy of Sciences of Ukraine, Ukraine
Mykhajlo Student/ G.V. Karpenko Physico-Mechanical Institute of the National Academy of Sciences of Ukraine, Ukraine
Volodymyr Gvozdeckii/ G.V. Karpenko Physico-Mechanical Institute of the National Academy of Sciences of Ukraine, Ukraine

 Abstract:
Electric arc spraying is an advantageous method in many applications due to its high deposition rate and economical operation. Recently a demand-driven development of Fe-based coatings that have a high resistance against erosion and corrosion at elevated temperatures has been observed. Such coatings can be an alternative for self-fluxing and cermet coatings for the protection of screen tubes of boilers of power stations.
In the present work, several cored powder wires of a diameter of 1.8 mm, filling coefficient 20-27 %, with 0.4 mm thick sheath made of low-carbon steel (0.08 % C) with additional alloying elements (Al, Cr, Mn, Ni, Si, B, etc) were developed. The kinetics of high-temperature oxidation of arc-sprayed 0.6-0.7 mm thick Fe-based coatings was investigated in the temperature range 20-700 °C during 1000 h in ambient air. Due to the high crystallisation rates during arc spraying, a large amount of supersaturated solid solution and even amorphous phases is observed in as-sprayed coatings. It has been shown that a formation of various dispersing phases such as intermetallics, carbides or borides, etc. takes place under the exposure temperature, which provides a respective increase of microhardness and resistance against gas-abrasive wear. At the same time an oxidation of coating takes place. It was established that the oxidation resistance of arc-sprayed coatings depends mostly on the coating microstructure and homogeneity of element distribution rather than on the general alloying level and microhardness of the coating. In the present work, the results concerning the influence of the chemical heterogeneity of element distribution as well as the evolution of stresses in thermally sprayed coatings during the exposure in elevated temperatures on the microstructure formation and coatings properties are discussed.



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