April_AMP_Digital

A D V A N C E D M A T E R I A L S & P R O C E S S E S | A P R I L 2 0 2 0 5 2 iTSSe TSS iTSSe TSS EXPERIMENTAL STUDY OF THE IMPACT OF SUBSTRATE SHAPE AND TILTING ON PARTICLE VELOCITY IN SUSPENSION PLASMA SPRAYING A. Dolmaire, S. Goutier, A. Joulia, P-M. Geffroy, M. Vardelle, and L. Bianchi Suspension plasma spraying has shown its capacity to deposit finely structured coatings with a wide range of mi- crostructures including columnar microstructures that are generally sought in thermal barrier coating applications for gas turbines. However, some challenges need to be resolved before the application of the technology is employed at an in- dustrial scale. One deals with the deposition of a uniform and reliable coating on a complex substrate shape. This work offers an experimental observation of submicron particle streams close to the substrate in order to understand mechanisms of deposition. Effects of the substrate shape and tilting were in- vestigated on particle velocity, direction, and coating growth. It was shown that particle velocities and directions are disrupt- ed by the substrate presence up to 10mmupstream. When the substrate is a cylinder or in a tilted orientation to the plasma jet, particle’s kinetic behavior is less affected. Finally, the ori- entationof the submicronparticle velocity vectors near impact greatly shapes the coating morphology. When impacting with a 40° angle of incidence, columns appeared on beads, contrary to submicron particle streams impacting orthogonally to the substrate surface. (Fig. 3) CFD SIMULATIONS OF FEEDER TUBE PRESSURE OSCILLATIONS AND PREDICTION OF CLOGGING IN COLD SPRAY NOZZLES Piotr Liebersbach, Alden Foelsche, Victor K. Champagne, Matt Siopis, Aaron Nardi, and David P. Schmidt Cold spray is an additivemanufacturingmethod inwhich powder particles are accelerated through a supersonic nozzle and impinged into a nearby substrate. This method produc- es deposits with advantageous attributes, namely with low porosity and low residual stresses, which nearly match those of the bulk material. One challenge with cold spray is nozzle clogging, which occurswhen particles bond to the inside of the nozzle, altering the cross-sectional area, increasing roughness on the nozzle inner surface, and causing a drop in the gas ve- locity, ultimately resulting in a lower quality deposit. Clogging puts certain combinations ofmaterials andoperational param- eters out of practical reach. A computational fluid dynamics (CFD) model of the cold spray nozzle is developed to study the flow of metal particles in the cold spray process. Through the study, researchers determine that the two-phase particle-lad- en flow from the feeder tube is inherently transient. CFD sim- ulations demonstrate that pressure fluctuations in the particle feed system can cause the particles to disperse in the nozzle and ultimately lead to some particles bonding with the nozzle wall. The degree of clogging is found to be strongly dependent on the amplitude of these upstream pressure fluctuations and seemingly independent of the pressure oscillation frequency. (Fig. 4) ADVANCES IN CORROSION-RESISTANT THERMAL SPRAY COATINGS FOR RENEWABLE ENERGY POWER PLANTS: PART I EFFECT OF COMPOSITION AND MICROSTRUCTURE AND PART II EFFECT OF ENVIRONMENT AND OUTLOOK Esmaeil Sadeghi, Nicolaie Markocsan, and Shrikant Joshi Renewable energy power plants suffer from severe Fig. 3 — Photograph of a spray during PIV measurements done in presence of a rotating cylindrical substrate and cooling air jets. Fig. 4 — Steady-state contours. SHARE ARTICLE FEATURE FROM JTST The Journal of Thermal Spray Technology (JTST) is pleased to bring your attention to SharedIt, a content sharing initiative from Springer Nature that allows authors and subscribers to easily and legally share links to free-to-read versions of research articles anywhere, including social media platforms, repositories, and personal websites. Authors and subscribers whowish to share JTST researchwith colleagues and friends are invited to use the “Share Article” tab to the right of any article on the JTST site on SpringerLink (springer.com/journal/11666) . Anyone who receives the link will be able to connect to a view-only version of the article for free. The editorial board hopes you find this tool helpful to learn and share the most recent advances in thermal spray research and technology development. 18 JTST HIGHLIGHTS