CC BY
25XV International Symposium on Self-Propagating High-Temperature Synthesis
SHS POWDERS FOR THERMAL SPRAY COATINGS
A. Ph. Ilyushenko*", P. A. Vityaz", T. L. Talako", and A. I. Letsko"
aO.V. Roman Powder Metallurgy Institute, Minsk, 220005 Republic of Belarus *e-mail: alexil@mail.belpak.by
DOI: 10.24411/9999-0014A-2019-10052
Modern industrial technologies require development of novel materials with improved properties and lower cost. Surface engineering attempting to create functional layers is obviously the most economical way to provide high performance of machinery and equipment. Among the wide range of available methods, thermal spray (TS) coatings offer the most versatile solutions. Demand characteristics of thermal sprayed powders can be very different, depending on the spraying process, operating conditions, desired properties of final coatings, etc. Besides the intrinsic materials properties, technical requirements for TS feedstock powders include good flowability and sprayability. They are greatly affected by the particle shape and morphology as well as particle size distribution. That is why thermal spray feedstock powder production technology must be reliable, flexible, and inexpensive, if possible.
The prospects of manufacturing advanced powders for thermal spray coatings by the self-propagating high-temperature synthesis (SHS) have been discussed. Apart from important economical benefits, SHS allows production of powders with improved or unique structure and properties in size ranges and with an external morphology suitable for different thermal spray processes. With SHS, it is possible to manufacture composites via single-stage process even in systems of materials with significantly different properties (melting temperatures, etc.) as well as compositions that cannot be formed by the other methods. Different kinds of reaction mixtures and SHS processes activation play an important role in structure and phase formation mechanisms, providing good flexibility and reliability even for industrial-scale production.
At present, hundreds of different SHS powders have been investigated as feedstock materials for TS-coatings. Different methods of plasma spraying (air plasma spraying (APS), supersonic air plasma spraying (SAPS), low-pressure plasma spraying (LPPS), underwater plasma spraying (UPS)), detonation spraying (DS), flame spraying (FS), as well as high-velocity oxygen-fuel spraying (HVOF) have been approved for depositing protective coatings from SHS powders. The compositions of the most widely reported thermal sprayed SHS powders as well as methods of their deposition and properties of the coatings are presented.
SHS powders of carbides, nitrides and silicides have been endorsed for wear-resistant and high-temperature TS-coatings. Composite of type "refractory compound/metallic binder" are among the most widely used for thermal spraying SHS powders. The most popular compositions becoming widespread for thermal spray applications are titanium- and chromium carbide-based powders as well as titanium diboride-containing composites. Iron, nickel, cobalt, aluminium, copper and their alloys are usually used as binders. A big progress was achieved with composites having complex binders or solid lubricant phases. Principal advantages of the synthesized composite powders include fine distribution of carbide grains in the material volume and high cohesive bond strength between the components. These favor good coating properties. In general, deposition efficiency, density, hardness and wear resistance of TS-coatings from the composite SHS powders were better than that from similar plated or agglomerated ones.
Intermetallics, nickel, iron and titanium aluminides-based powders are currently used for thermal spray protective coatings. There is much interest in depositing thick ferrite and composite ceramic coatings for electromagnetic applications.
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A. Ph. Hyushenko et al.
iSHS 2019
Moscow, Russia
Some examples of original powders developed at the O.V. Roman Powder Metallurgy Institute are presented. The industrial-scale production of SHS powders has been established in the institute with good reproducibility of powders properties. Since 1996 O.V. Roman Powder Metallurgy Institute has been supplying SHS-powders under the contract to different thermal spray companies in USA, Sweden, Germany, India, Poland and etc.
A. Ph. Ilyushenko et al.
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