Influence of impact parameters of zirconia droplets on splat formation and morphology in plasma spraying

Abstract

In this study, the effects of the impact parameters, namely, the diameter d0, velocity V0, and temperature T0, of an impacting droplet of yttria-stabilized zirconia (YSZ) on splat morphology have been investigated systematically under plasma spraying conditions. In particular, fully molten droplets of 30–90μm in d0 that impact on a preheated quartz glass substrate at V0 of 10–70m∕s have been examined via hybrid plasma spraying. The degree of flattening of final splat morphology, ξ, was found to be predicted by the relationship ξ=0.43Re1∕3, where Re is the Reynolds number. The dimensionless spreading time of droplets, ts*=tsV0∕d0, was distributed around 2.7, where ts is the spreading time of the droplet. The ideal maximum spread factor derived from the splat height was approximately proportional to Re1∕4. The latter two findings suggest that the analytical model developed by Pasandideh-Fard et al. [Phys. Fluids 8, 650 (1996)] can be applied to the droplet impact in plasma spraying especially for the case of YSZ. In addition, the thermal contact resistance of disk shaped splats decreased with the increase of V0 within the range of 10−5–10−6m2K∕W.