The influence of the in-situ formed and added carbon on the formation of metastable Ni-based phases during detonation spraying

Detonation (D-gun) spraying uses detonation of hydrocarbon fuel to heat and accelerate the powder particles. Spraying using incomplete combustion can lead to changes in the composition of the sprayed material due to the presence of the in-situ formed carbon particles in the spraying atmosphere. In this work, we have studied the phase formation of the deposits obtained by D-gun spraying of Ni and "Ni-amorphous carbon mixtures". It was found that solid solutions based on metastable hcp-Ni and fcc-Ni form in detonation deposits at O-2/C2H2=0.7 and explosive charges of 50-70%. No metastable phases were found in the coatings sprayed at O-2/C2H2 greater than 1.1. Microstructural and elemental analyses confirmed that the in-situ formed carbon is preferentially incorporated in molten Ni particles. Carbon ex situ introduced into the feedstock powder changes the sprinkling conditions of the melt over the substrate surface and lowers the cooling rate of the molten particles. As a result, deposits obtained at an explosive charge of 60% and 70% from powders containing added carbon tend to show lower concentrations of the hcp phase compared with deposits obtained from Ni. (C) 2016 Elsevier B.V. All rights reserved.