No abstract

This study presents significant advantages of coldspraying in performance of coatings based on Al matrix reinforced by metastable nano-and submicrosized quasicrystalline particles as compared to those processed by thermal spraying and, in particular, by high velocity oxy-fuel (HVOF) spraying technique.Two kinds of feedstock powders with nominal compositions Al^J^C^ and Al94Fe2.5Cr2.5Ti1 were employed in spraying the coatings on cold rolled steel substrate. Microstructure and key mechanical characteristics of feedstock powders and coatings performed by coldspraying and HVOF process were studied and discussed.The main benefit of cold-spraying as opposed to HVOF spraying was that the composite quasicrystalline structure of initial feedstock powders is retained in the interior of flattened particles heavily deformed under impact in solid state. Strain hardening of coating and substrate is resulted from impact during cold-spraying.The results showed that unlike to HVOF sprayed coatings important advantage of cold-sprayed quasicrystalline coatings is referred to combination of increased hardness with ductility indicated by plasticity characteristic just about critical value δ Η « 0.9, which is quite enough for preventing brittle failure of material during particle impact onto substrate or previously deposited particles.

The paper examines the phase formation of detonation coatings sprayed from mechanically alloyed . It is shown that coatings with different phase compositions and functional properties can be consolidated from this activated powder by varying process conditions (including gas composition during detonation spraying). Three types of composite coatings with different structures are obtained: TiB and TiB 2 inclusions are distributed in an intermetallic matrix (Al 3 Ti, γ-TiAl); inclusions of oxides and oxynitrides are additionally present in the same structure; inclusions of borides, Al, and Ti are distributed in a mixture of intermetallic and nitride (TiN, AlN) phases.