Presently, the self-propagating high-temperature synthesis (SHS) has found wide use in the production of compacts and powder materials, and also in the fabrication of end products. Yet, a disadvantageous feature of the standard SHS process, which can be overcome in part by running the synthesis reaction under pressure, is that it fails to provide the possibility of obtaining high-density materials and products. It is therefore of interest to develop a combined process which would allow one to apply a two-component Ni-Al coating with prescribed stoichiometric composition by cold spraying of a nickel-aluminum powder mixture followed by self-propagating high-temperature synthesis of a target intermetallide (Ni3Al or NiAl) by treating the surface layer of the cold sprayed coating with a highly-concentrated energy flux (argon plasma jet). Preparation methods for nickel-aluminum powder mixtures (in particular, mechanochemical activation) intended for cold spraying process are discussed. Computational experiments were performed to substantiate the choice of stationary, traveling and pulsed energy sources for subsequent initiation of SHS in the heterogeneous layer deposited onto a steel substrate. A model was developed to predict the local phase state of the material synthesized in the coating; this model involves the state diagram of the Ni-Al system. The characteristics of sprayed coatings were examined. The developed approach is shown to offer much potential in practical applications.

To enhance the efficiency of computational experiment covering all links of a technological chain ‘generation of plasma jet – injection of particles – formation of dust-laden plasma jet – coating deposition from drops of a melt’ it is very attractive to integrate the experimentally tested analytical solutions characterizing splats formation along with 2-D/3-D models describing dust-laden technological flow. The authors of the present paper carried out a computer simulation of a plasma spraying process from zirconia particles injection to a coating formation conducted by integrating particle-laden plasma flow, metal oxide splat formation and coating formation models with reference to the thermal barriers. The velocity and temperature of both plasma flow and zirconia particles under an applied RF electromagnetic field were clarified by using the first model. Radial distributions of particle impact location, velocity and temperature were obtained based on both an unsteady effect of a plasma flow and distributions of particle size and injection velocity. Secondly, splat thickness and diameter after zirconia droplets impact onto substrate were clarified by using the earlier experimentally probated analytical solution. Finally, the coating thickness distributions were evaluated by using the last model. Abstract only; no full-text paper available.