A Critical Assessment of Particle Temperature Distributions During Plasma Spraying: Experimental Results for YSZ

Abstract

Plasma sprayed coatings of Yttria Stabilized Zirconia (YSZ) have been studied extensively through the years to understand variations in coating properties as well as to achieve control on microstructure of the coatings. The requirement for microstructural control and reliability have become all the more important as coatings have now become part of an integrated "prime reliant" design strategy aimed at increasing turbine inlet temperature and associated efficiencies. One of the important thrusts in monitoring and controlling the process has been the application of process sensors that measure spray stream characteristics, notably particle temperature and velocity. Although single particle-based measurements have been available for some time, in general control strategies based on particle state rely on average values of temperature and velocity. In this study, a detailed examination of particle temperature distributions is presented. When systematically examined over a wide range of operating conditions of the resulting range of particle temperatures, a significant structure in the statistical distribution has been observed. A close inspection of the data indicates that this distribution can be interpreted as melting state indicator for YSZ. A characteristic peak at the melting point of ZrO 2 (error in absolute T -measurement is ≈ ±10%) can be used as an indicator for re-solidified particles. In the past, control strategies based on process diagnostic sensors have been based on average particle temperatures and velocities. Although the average values seem to be promising as control parameters, it has been shown through our results that different melting states could be demonstrated for the same average T and V settings. The melting state in turn has an important bearing on the coating structure and properties. It therefore implies that a process control strategy (to maintain coating quality) based on in flight particle sensors will have to take these findings into account. As an example, one strategy of process control would not only define the process in terms of the average particle temperature and velocity but also include the effect that parameter changes have on distributions.

Combustion Flame Spray of CoNiCrAlY & YSZ coatings

“…This proven superior performance of HOSP-produced powders in respect to other types of traditional materials (e.g. agglomerated, crushed) confirms similar findings on APS depositions of the same materials [19] Finally, it is worth mentioning that by separate tests on CFS deposition by using HOSP-produced Metco 204B-NS (D, Tab. 1), also employed in this study to spray the APS topcoat layer and of considerable higher nominal size distribution than powders E-F-G-H, no material sticking was observed, again likely due to size-dominant effects as described by Eq.…”

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

“…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. Además, las características del recubrimiento final dependerán del comportamiento de las partículas durante el vuelo (11,12). No obstante, la naturaleza, morfología, tamaño de partícula, etc.…”

Plasma Sprayed Bioceramic Coatings on Ti-Based Substrates: Methods for Investigation of Their Crystallographic Structures and Mechanical Properties

“…For this purpose, new techniques for visualisation and diagnostics of the injected powder particles during their flight to the coated surface have been developed (Moreau et al, 2005;Srinivasan et al, 2006;Streibl et al, 2006). New methods for non-destructive control, including statistical evaluation of the collected data, together with prognosis of the coating parameters as a function of the technological conditions have been offered as well (Zhu & Ding, 2000).…”

“…New methods for non-destructive control, including statistical evaluation of the collected data, together with prognosis of the coating parameters as a function of the technological conditions have been offered as well (Zhu & Ding, 2000). Some work has already been done to characterise the following main dependencies that play an important role for successful performance of the discussed biomedical coatings (Azarmi et al, 2008;Boulos et al, 1993;Celik et al, 1999;Chen et al, 1993;Choi et al, 1998;Dyshlovenko et al, 2005;Fan et al, 2005;Gueorguiev et al, 2008aGueorguiev et al, , 2008cIordanova & Forcey, 1997;Khor et al, 2004;Kreye et al, 2007;Kuroda & Clyne, 1991;Leigh & Berndt, 1997;Li & Khor, 2002;Liu et al, 2005;Lugscheiber et al, 1993;Mawdsley et al, 2001;Montavon et al, 1997;Moreau et al, 2005;Neufuss et al, 2001;Ohmori & Li, 1991;Parizi et al, 2007;Sampath et al, 2003;Sarikaya, 2005;Srinivasan et al, 2006;Staia et al, 2001;Streibl et al, 2006;Toma et al, 2003;Tong et al, 1996;Wallace & Ilavsky, 1998;Zhu & Ding, 2000):…”