Self-propagating high-temperature synthesis for the deposition of thermal-sprayed coatings

Abstract

621.793The paper reviews the relevant literature and results of the author's research into self-propagating hightemperature synthesis (SHS) used to deposit protective thermal-sprayed coatings. The compositions of different SHS-produced powders, which are used to deposit thermal-sprayed coatings, are indicated. The combination of spraying and synthesis of the material to form coatings by the interaction of composite powder particles is considered. INTRODUCTIONOne of the main areas of Samsonov's scientific school is to ascertain the mechanism and features of solid-phase interactions. The first efforts focusing on the interaction of refractory compounds with refractory metals and the first degree theses devoted to these processes and supervised by G. V. Samsonov were initiated in the 1960s. The solid-phase interaction was further considered in studies intended to develop methods to combine dissimilar materials in a solid phase (diffusion welding), apply protective coatings, and ensure the high-temperature and high-load performance of parts with these coatings and also studies intended to find criteria for the compatibility of dissimilar materials that perform at high temperatures and loads (including the prevention of seizure in friction) and compatibility of composite material components (matrices with reinforcing fibers and inclusions).In 1967, A. G. Merzhanov and colleagues [1, 2] discovered a variety of contact solid-phase interaction, such as self-propagating high-temperature synthesis (SHS). The SHS process is as follows: an interaction reaction is locally initiated in a thin layer of a reactive mixture of reagents and then proceeds in a wave of gasless combustion that is selfpropagating over the entire system through heat transfer from hot interaction products to the next layer of the initial mixture. The thermal activity of the reaction is sufficient to further initiate the process. Reaction products both result from and further promote the process. Therefore, SHS is a highly exothermic interaction of chemical elements (or compounds) in a condensed phase that occurs in combustion conditions. Processes based on SHS are peculiar in that they have high temperatures, ensure rapid synthesis of new materials, are controllable, permit energy saving, ensure purity of the products, etc.The following processes based on self-propagating high-temperature synthesis are currently singled out [3]: SHS production of billets and powders; SHS sintering; power SHS compaction; SHS metallurgy; SHS welding; application of gas-transport SHS coatings.The SHS method was first used to obtain powders of refractory inorganic compounds (carbides, borides, nitrides, silicides, intermetallics, etc.) [4,5]. Figure 1 shows a general scheme for producing powders as SHS products. Such powders contain few admixtures and may be of both stoichiometric and variable composition. There are wide possibilities for producing various composite powders, for example, oxycarbides, carbosilicides, etc. The Institute of Structural Macrokinetics, USSR Academ...

Properties of intermetallic Ni–Al coatings deposited by high-velocity air–fuel spraying

“…The particle components interact to form an intermetallic phase through dissolution [11]. According to XRD, the amount of the intermetallic phase is somewhat higher in the coating than in the initial powder.…”

Current status and future directions of thermal spray coatings and techniques

“…The conventional values of drag and heat transfer coefficients must be corrected to account for various phenomena such as temperature gradients in the particle boundary layer (Pfender, 1999;Lee et al, 1985); noncontinuum effect (Knudsen effect) (Fauchais et al, 2008b;Lewis and Gauvin, 1973;Chen and Pfender, 1983a,b;Vardelle et al, 1997;Ganser, 1993;Chen and Ping, 1986a); vaporization effect (Vardelle et al, 1996); turbulence effect (Lee et al, 1985); particle shape effect, especially important for cold spray (Fukanuma et al, 2006) where particles do not melt; particle charging, which is no more negligible in VPS (Chen and Ping, 1986b); and thermophoresis effect, particularly for particles below 1 mm (Fauchais et al, 2008b). Chemical reactions between particles and ambient gas have also been considered with reactions due to diffusion (Vardelle et al, 1996) or convection (Neiser et al, 1998) and also reactions related to self-propagating high-temperature synthesis (Borisova and Borisov, 2008). Chemical reactions between particles and ambient gas have also been considered with reactions due to diffusion (Vardelle et al, 1996) or convection (Neiser et al, 1998) and also reactions related to self-propagating high-temperature synthesis (Borisova and Borisov, 2008).…”

D.C. Plasma Spraying

“…Besides the preceding nitridation of the starting powders, the reactive alloying with N can be achieved during vacuum plasma spraying by the exposure of the particles to a N 2 -rich plasma and by creating a N 2 -rich environment in the VPS chamber. Borisova and Borisov [192] have presented many carbide coatings that can be prepared by APS by selfpropagating high-temperature synthesis, SHS. SHS is accompanied by heat generation in composite powder particles (see Sect.…”