In this study, a multi-chamber detonation sprayer is used to deposit cermet coatings on flat specimens of corrosion-resistant steel. It is shown that the sprayer provided conditions for the formation of dense WC-CoCr, CrC-NiCr, and CrC-TaC-NiCr layers, ranging in thickness from 80-375 μm, with low porosity, high microhardness, and low wear rates.

This work assesses the influence of powder characteristics on the deposition efficiency, microstructure, and tribological properties of Cr 3 C 2 -NiCr coatings. Four commercial powders prepared by different methods were used for the study. All have a spherical morphology but vary in terms of porosity, carbide grain size, and flowability. The feedstocks were deposited on flat low-carbon steel substrates using a liquid-fueled HVOF torch mounted on an industrial robot. Deposition efficiency was measured along with coating hardness, Young’s modulus, and abrasive wear resistance. In addition, some of the coatings were heat treated and changes in microstructure and hardness were recorded.

The composition of the cored wires is inhomogeneous and contains solid velum as well as a powder filling which strongly influences the particle formation, in-flight particle behavior, the coating microstructure, and consequently the behavior of the desired coating. To study the effect of particle size distribution of the filling powder in cored wires the parameters of the twin wire arc spraying process such as current, voltage, and atomization air pressure are changed for different intervals of particle size distributions (-45µm+25µm, and -95µm+63µm). Fluctuations in arc voltage and current are measured and found to be higher at smaller particle sizes. The characteristics of inflight particles showed a higher particle velocity in case of smaller particle sizes. The particle temperature is higher in case of bigger particle sizes. The splats tend to form a pancake shape in case of smaller particle sizes. Therefore, the lamellas are more homogenous and the porosity is low. This investigation is important for deep understanding of twin wire arc spraying with cored wires.

This study examines the fundamental reactions that, in the solution plasma spraying process, lead to the conversion of the precursor salts to solid material that is deposited onto the substrate. The study specifically focused on the phenomena occurring in-flight and the effect of plasma jet treatment on the mechanical and thermal treatment of the solution injected in the form of a liquid jet. The evolution of precursor droplets in the plasma flow was investigated “in situ” using a shadowgraphy technique. The morphology and structure of material deposited onto smooth stainless steel substrates during single scan experiments were characterized by SEM, GI-XRD and micro-Raman spectroscopy and were correlated to the in-flight observations, in order to evaluate the effect of the plasma-forming gas and solution solvent.

Hollow spherical (HOSP) powders of metals, metal alloys and oxide ceramics are of great interest for thermal spraying, powder metallurgy and material science. For the last decade due to constant rise of interest in HOSP powders and expansion of areas of their application, the efforts of researchers, including authors of present paper, are focused on developing methods of producing the hollow microspheres, based on processing of agglomerated powders in thermal plasma. Exists a range of methods of producing the agglomerated powders with size of dozens of microns, which particles consist of several uniformly mixed nano- submicron- and micron sized powder components: 1) spray drying, 2) processing of atomized suspensions; 3) mechanical treatment of powder mixtures in high-energy planetary mills, etc. A brief overview the results of R&D directed to production of various HOSP oxide and metallic powders (α-alumina, zirconia stabilized by yttria, quartz, nickel allow) by the use of DC torches with interelectrode inserts (cascade torches) and twin torch is presented. In particular, the theoretical approach providing the requirements to plasma flow in criterion view have been developed. A physical and mathematical model of hollow particle behavior in plasma flow is developed and discussed.