Abstract No.:
3633

 Scheduled at:
Friday, May 23, 2014, Hall H3 9:20 AM
New Processes


 Title:
Reduction, oxidation and interfacial reactions in detonation sprayed powders as tools of coating design

 Authors:
Dina Dudina / Lavrentyev Institute of Hydrodynamics SB RAS, Russia
Igor Batraev/ Lavrentiev Institute of Hydrodynamics SB RAS, Russia
Vladimir Ulianitsky*/ Lavrentiev Institute of Hydrodynamics SB RAS, Russia

 Abstract:
This presentation is concerned with the chemical aspects of detonation spraying. Conducting experiments on a Computer-Controlled Detonation Spaying CCDS2000 facility developed in Lavrentiev Institute of Hydrodynamics SB RAS, we have found that as the spraying conditions are varied, flexibly and in a wide range allowed by the technical capabilities of the facility, new phases can appear in the coatings in substantial quantities as a result of chemical reactions of reduction or oxidation as well as interfacial interactions in the case of spraying of composite powders. The key advantage of the CCDS2000 is the possibility of varying and precisely controlling the quantity of the explosive gaseous mixtures and their stoichiometry. The carrier gas can be chosen to be inert or reactive. We have studied the chemical behavior of TiO2 during detonation spraying with CCDS2000 and found that it experiences reduction to titanium suboxides, their content in the coatings depending on the stoichiometry of the O2+C2H2 mixtures rich in C2H2. During detonation spraying of titanium aluminides (Ti3Al, TiAl3, TiAl) their oxidation can be prevented by creating reducing conditions of spraying. In oxidizing conditions, complete oxidation of Ti3Al can occur resulting in the formation of a mixture of oxide phases in the coatings. Interfacial reactions have been studied on the Ti3SiC2-Cu composite, in which de-intercalation of Si can be prevented in relatively cold conditions of spraying. At higher temperatures, coatings of unusual phase composition form: carbon-deficient TiCx particulate inclusions are distributed in the Cu matrix that has been modified by dissolution of Si in it. The composites having the Cu(Si) matrix showed higher hardness compared to those in which the reaction did not occur. The formation of new phases in the coatings affects their microstructure development and results in the new microstructural features.

<= go back