Design, manufacturing, and utilization of efficient heating systems for pipelines and closed-pressure equipment are necessary for cold regions to compensate for heat loss and prevent damages that are caused by freezing of the enclosed liquid. Given large-scale financial losses that stem from failure and bursting of the pipes, the development of novel, efficient, and affordable heaters, which can lead to improved efficiency, cost savings, and environmental benefits across various industries and applications, is of crucial importance. Heating systems have already been produced via different high-temperature thermal spraying techniques to achieve higher efficiency compared to conventional heating cables. In this study, tin, as the heating element, was deposited by using the cold spray process onto alumina coating that was fabricated by flame spraying (FS) to provide electrical insulation. Techno-economic assessment of fabrication and utilization of the coating-based heaters was conducted. It was found that cold-sprayed heater coatings exhibit improved performance compared to other thermally sprayed heater coatings and conventional heater cables. Further, their fabrication and utilization were more economically feasible. The results suggest that the new generations of coating-based heating systems may be competitive with conventional heat tracers that are widely used in industry.

This study deals with the deposition of coating materials that can be difficult to process by plasma spraying, including lanthanum and gadolinium zirconate, two pyrochlores of interest for thermal barrier applications, and lanthanum strontium cobalt ferrite (LSCF), a perovskite of interest for gas separation membranes. In addition to conventional atmospheric plasma spraying (APS), the feedstock powders were applied by suspension plasma spraying (SPS) and plasma spray-physical vapor deposition (PS-PVD). The spraying processes are described in detail along with the characteristics of the powders and coatings and the effects of various spray parameters on splat behavior and coating composition and structure.

Oxide compounds basically composed of calcium, magnesium, aluminum and silicon cations also known as CMAS, can be deposited on the surface of thermal barrier coatings (TBC) of gas turbine blades. Under certain operation conditions these compounds have been found to aggressively degrade the TBC, hence affecting the thermo-mechanical properties of the underlying component. Detailed investigation on the interaction of CMAS and the atmospheric plasma sprayed (APS) yttria-stabilized zirconia (YSZ) TBC was performed in a burner rig test facility under thermal gradient cycling conditions and at the same time CMAS deposition. This novel and unique test approach promises a coating screening and characterization test under service conditions. Variable exposure times at approximately 1250°C/1050°C surface/substrate temperatures were applied. The lifetime of the TBC was indicated by the number of thermal cycles until significant spallation occurred. X-ray spectroscopy and microstructural analyses were conducted on the cycled samples to determine the effect of thermo-chemical interactions. It was found that with extended heating period of 10 times the standard cycle, the number of sustainable load alternations heating/cooling was reduced. Interaction of CMAS and YSZ induces formation of glassy soda-silicate phase. Thermal cycling of thermo-physically mismatched TBC and glass melt causes crack formation and coating failure.

Fracture toughness and phase stability are crucial properties of thermal barrier coatings (TBC) during highly loaded thermomechanical operations in gas turbines. While several alternative TBC materials have exhibited excellent thermal resistance, their potential applicability has been limited due to poor endurance to cyclic stresses. The addition of TiO 2 to the non-transformable tetragonal t´-YSZ has been found to effectively enhance the fracture toughness and phase stability of YSZ at high temperature exposures. Thermal cycling tests in a burner rig were conducted on TBCs prepared from atmospheric plasma sprayed titania-doped YSZ to verify this phenomena. Exposure temperature was 1400°C at the surface and thermal gradient across the sample was provided by simultaneous back-cooling treatment. Cycling tests reveal that the slight increase in the tetragonality of the deposited coatings with increasing amount of dopant did not cause a significant effect to the lifetime of the TBCs. Moreover, increasing amount of Ti-substitution did not influence the fracture toughness of the bulk YSZ.