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Remanufacturing and Advanced Machining
Similarly, Mahade et al. (2020) describe coatings deposited by simultaneous
spraying of T-400 (Tribaloy-400) powder and Cr 3 C 2 suspension. The as-obtained
coating revealed a lamellar microstructure with distributed fine carbides, showing
the presence of original feedstock constituents, along with some oxides of chromium. Hardness of the as-sprayed coatings is higher than in the pure T-400 coating.
Moreover, the hybrid coatings possess excellent wear and scratch resistance, superior
compared to the pure T-400 coating, which is important for durability improvement
of engineering components operating under severe wear conditions. The authors
believe that the hybrid approach is easily extendable to other material systems and
can contribute to fabrication of next-generation wear-resistant coatings.
Solution precursor plasma spraying (SPPS) allows for manufacturing coatings
with submicrometer and nanometer structures. Examples of the coatings obtained
with SPPS include thermal barrier coatings (Yang et al., 2020), nanostructural photocatalytic coatings (Dom et al., 2012), hydrophobous rare earth coatings (Xu et al.,
2021), coatings for solid oxy-fuel cells (Shri Prakash et al., 2017), environmental
barrier coatings (Darthout et al., 2016), bioactive glass coatings (Canas et al., 2019;
Garrido et al., 2021), coatings for gas sensors (Yu et al., 2017), etc. The precursors
applied to spraying are generally mixtures of compounds, such as salts, acetates, or
nitrates, dissolved in a solvent (usually an organic liquid or water) to form a final
solution (Łatka et al., 2020).
There are also reports on hybridizing the conventional atmospheric plasma
spraying (APS) technique with the solution precursor plasma spray (SPPS) route.
This way, Joshi et al. (2014) produce thermal barrier coatings (TBCs) with tailored
configurations. The authors claim that such a hybrid process can be conveniently
adopted for forming composite, multilayered and graded coatings, yielding distinct
TBC microstructures with extended coating durability. Comparing TBC specimens
generated using the conventional APS technique, the SPPS method, and APS-SPPS
hybrid processing, the authors demonstrate advantages of the hybrid processing. A
similar hybrid APS-SPPS route with simultaneous feeding of an appropriate solution
precursor and commercially available spray-grade powder feedstock is reported to
enable fabrication of microstructures with nanostructured and micron-sized features
(Lohia et al., 2014). Hou et al. (2019) propose a hybrid suspension-solution precursor
plasma spray process with a radio-frequency thermal plasma torch and demonstrate
it is feasible to deposit Ba(Mg 1/3 Ta 2/3 )O 3 (BMT) nanostructured coatings.
In high velocity oxy-fuel (HVOF) and high velocity air-fuel spraying (HVAF),
gas combustion serves as an energy source for melting and accelerating powder particles. The HVOF process enables reaching higher particle velocity and lower particle
temperature than APS and thus high deposition efficiency, good adhesion of coatings with a low content of oxides and low porosity (Łatka et al., 2020). Functionally
graded coatings (FGCs) with gradually changing coefficient of thermal expansion
and Young’s modulus, which decreases stress and increases bond strength, may be
obtained by HVOF in two ways (Mamun and Stokes, 2014):
1. Using premixed powders
2. Co-injection of different powders
Remanufacturing and Advanced Machining
Similarly, Mahade et al. (2020) describe coatings deposited by simultaneous
spraying of T-400 (Tribaloy-400) powder and Cr 3 C 2 suspension. The as-obtained
coating revealed a lamellar microstructure with distributed fine carbides, showing
the presence of original feedstock constituents, along with some oxides of chromium. Hardness of the as-sprayed coatings is higher than in the pure T-400 coating.
Moreover, the hybrid coatings possess excellent wear and scratch resistance, superior
compared to the pure T-400 coating, which is important for durability improvement
of engineering components operating under severe wear conditions. The authors
believe that the hybrid approach is easily extendable to other material systems and
can contribute to fabrication of next-generation wear-resistant coatings.
Solution precursor plasma spraying (SPPS) allows for manufacturing coatings
with submicrometer and nanometer structures. Examples of the coatings obtained
with SPPS include thermal barrier coatings (Yang et al., 2020), nanostructural photocatalytic coatings (Dom et al., 2012), hydrophobous rare earth coatings (Xu et al.,
2021), coatings for solid oxy-fuel cells (Shri Prakash et al., 2017), environmental
barrier coatings (Darthout et al., 2016), bioactive glass coatings (Canas et al., 2019;
Garrido et al., 2021), coatings for gas sensors (Yu et al., 2017), etc. The precursors
applied to spraying are generally mixtures of compounds, such as salts, acetates, or
nitrates, dissolved in a solvent (usually an organic liquid or water) to form a final
solution (Łatka et al., 2020).
There are also reports on hybridizing the conventional atmospheric plasma
spraying (APS) technique with the solution precursor plasma spray (SPPS) route.
This way, Joshi et al. (2014) produce thermal barrier coatings (TBCs) with tailored
configurations. The authors claim that such a hybrid process can be conveniently
adopted for forming composite, multilayered and graded coatings, yielding distinct
TBC microstructures with extended coating durability. Comparing TBC specimens
generated using the conventional APS technique, the SPPS method, and APS-SPPS
hybrid processing, the authors demonstrate advantages of the hybrid processing. A
similar hybrid APS-SPPS route with simultaneous feeding of an appropriate solution
precursor and commercially available spray-grade powder feedstock is reported to
enable fabrication of microstructures with nanostructured and micron-sized features
(Lohia et al., 2014). Hou et al. (2019) propose a hybrid suspension-solution precursor
plasma spray process with a radio-frequency thermal plasma torch and demonstrate
it is feasible to deposit Ba(Mg 1/3 Ta 2/3 )O 3 (BMT) nanostructured coatings.
In high velocity oxy-fuel (HVOF) and high velocity air-fuel spraying (HVAF),
gas combustion serves as an energy source for melting and accelerating powder particles. The HVOF process enables reaching higher particle velocity and lower particle
temperature than APS and thus high deposition efficiency, good adhesion of coatings with a low content of oxides and low porosity (Łatka et al., 2020). Functionally
graded coatings (FGCs) with gradually changing coefficient of thermal expansion
and Young’s modulus, which decreases stress and increases bond strength, may be
obtained by HVOF in two ways (Mamun and Stokes, 2014):
1. Using premixed powders
2. Co-injection of different powders