Effects of Heat and Momentum Gain Differentiation during Gas Detonation Spraying of FeAl Powder Particles into the Water

Abstract

In this paper, dynamic interactions between the FeAl particles and the gaseous detonation stream during supersonic D-gun spraying (DGS) conditions into the water are discussed in detail. Analytical and numerical models for the prediction of momentum and complex heat exchange, that includes radiative effects of heat transfer between the FeAl particle and the D-gun barrel wall and phase transformations due to melting and evaporation of the FeAl phase, are analyzed. Phase transformations identified during the DGS process impose the limit of FeAl grain size, which is required to maintain a solid state of aggregation during a collision with the substrate material. The identification of the characteristic time values for particle acceleration in the supersonic gas detonation flux, their convective heating and heat diffusion enable to assess the aggregation state of FeAl particles sprayed into water under certain DGS conditions.

Synthesis, Properties and Applications of Intermetallics, Ceramic and Cermet Coatings

“…This Special Issue is focused on various conventional synthesis methods of different intermetallic, ceramic, and composite coatings obtained by thermal (D-gun and Arc) spraying [ 6 , 7 ], the CVD process [ 8 , 9 , 10 ], magnetron sputtering [ 11 ], anodization [ 12 ], and during the sintering of aluminum, iron and particulate mullite ceramic powders using self-propagated high-temperature synthesis (SHS) [ 13 ].…”

“…With regard to FeAl-type intermetallic materials, the main challenge is the brittleness of the FeAl (B2) phase due to their long-range ordered (LRO) crystal structure which limits the plastic deformation of the formed material. Therefore, a unique problem involves the analysis of the synthesis conditions’ effect on the deformation and strengthening mechanisms of the nominally brittle intermetallic and ceramic alumina phases formed in situ during the powder particle synthesis processes at the supersonic jet flow in the D-gun spraying (DGS) process [ 3 , 6 ]. This description requires a deep understanding of both the elementary structural transformations of the FeAl powder particles sprayed in the D-gun process into the water and the grain structure in the synthesized intermetallic coating sprayed into the steel substrate [ 6 , 14 ].…”

“…Therefore, a unique problem involves the analysis of the synthesis conditions’ effect on the deformation and strengthening mechanisms of the nominally brittle intermetallic and ceramic alumina phases formed in situ during the powder particle synthesis processes at the supersonic jet flow in the D-gun spraying (DGS) process [ 3 , 6 ]. This description requires a deep understanding of both the elementary structural transformations of the FeAl powder particles sprayed in the D-gun process into the water and the grain structure in the synthesized intermetallic coating sprayed into the steel substrate [ 6 , 14 ]. On the other hand, the effects of synthesis conditions such as the impact of particle velocity, the temperature, and dynamic pressure of the gaseous stream on the chemical and phase, composition, crystallographic and morphological microtexture, size of the crystallites, and the state of the grain boundaries in the particles and obtained coatings, as well as the degree of superstructure disorder with the identification of nano/ultrafine grain and subgrain areas, dislocation, and antiphase domains, are discussed in detail [ 6 , 14 ].…”

“…It should be mentioned that during the thermophysical analysis of both the feedstock powder material and coatings, different phenomena were considered. These include the exchange of momentum and convective heat transfer, as well as the thermal effects of phase changes after the melting of powder particles, and additional analytical and numerical analysis [ 3 , 6 , 14 ]. It was found in [ 6 ] that the gas parameters and thermodynamic state of combustion products at the time of a detonation explosion of the gas mixture in the C–J plane are sufficient to melt FeAl powder particles up to 5 µm in diameter.…”

“…These include the exchange of momentum and convective heat transfer, as well as the thermal effects of phase changes after the melting of powder particles, and additional analytical and numerical analysis [ 3 , 6 , 14 ]. It was found in [ 6 ] that the gas parameters and thermodynamic state of combustion products at the time of a detonation explosion of the gas mixture in the C–J plane are sufficient to melt FeAl powder particles up to 5 µm in diameter. However, under conditions of thermal forcing in the C–J plane, when a shock wave passes through the powder particles, the changes in particle velocity are much faster than the particle temperature changes caused by convective heating.…”