Assessing Process and Coating Reliability Through Monitoring of Process and Design Relevant Coating Properties

Abstract

Thermal spray in general, plasma spray in particular, is a highly complex process with numerous interacting variables associated with generation of the spray stream, deposit formation dynamics, and the resultant property linkages. Compounding this variability further are both the spatial (different booths and different locations) and temporal (process start-stops, hardware degradation, operator etc.) effects. As such, an understanding of process and coating consistency and variability offers significant challenges. Recent scientific advances as well as measurement tools have enabled elucidation of the intrinsic variabilities associated with each of the process sub-steps; however, integrated understanding of the system level reliability is still lacking. This article seeks an integrated assessment of process and coating reliability through systematic measurements of variabilities during each stage of the process subjected to different operating parameters. Through critical examination of first-order process maps, the influence of process parameters on particle state is reviewed for repeated spray runs with a single parameter effect as well as across a spectrum of process parameters. In addition, influence of these changes on designrelevant coating properties were obtained for plasma-sprayed zirconia through recourse to novel in situ and ex situ substrate curvature measurements. Finally, the implications of such integrated reliability studies have been explored through collaborative experiments conducted in the industrial sites.

Influencia de los parámetros de proyección por plasma atmosférico en recubrimientos de YSZ obtenidos a partir de polvos micro y nanoestructurados

“…Son multitud los trabajos que han estudiado la influencia de los parámetros de la proyección por plasma en las características del recubrimiento final (7)(8)(9). Desde hace ya bastantes años, se dispone de equipamiento que permite monitorizar el comportamiento que experimenta el material en el interior del plasma (10). Estos equipos se han utilizado para conocer la influencia que ejercen los parámetros de proyección en la velocidad y temperatura de las partículas en el interior del plasma.…”

Particle in-flight behavior and its determining the microstructure and mechanical properties of zirconia based thermal barrier coatings

“…Although many reports which associated with the effect of microstructure on the properties of as-sprayed coatings can be found [12][13][14][15], the detailed information on the relationship between particle in-flight behavior, defect and mechanical properties of YSZ coatings is still scarce. In view of the above, the correlation between particle in-flight behavior and coating defects was established and the influence of defects on the mechanical properties of assprayed coatings was further studied.…”

Effect of Microstructure on the Thermal Conductivity of Plasma Sprayed Y₂O₃ Stabilized Zirconia (8 %YSZ)

“…The thermal conductivity of monoclinic zirconia is higher than the tetragonal and cubic phases [11][12][13] . Some studies investigated the relationship between the spray process and the microstructure of the thermal barrier coating 14,15 . It was found that with increasing particle velocity and temperature the coating is densified and the thermal conductivity increases 14,15 .…”

“…Some studies investigated the relationship between the spray process and the microstructure of the thermal barrier coating 14,15 . It was found that with increasing particle velocity and temperature the coating is densified and the thermal conductivity increases 14,15 . The quantitative effect of grain boundaries on the thermal conductivity was analyzed which shows that the thermal conductivity of small grains is lower compared to large grains [16][17][18] .…”