Splat interface bonding formation during plasma spraying of LZO coating

Plasma sprayed ceramic coatings of low thermal conductivity are becoming important candidates for next generation thermal barrier coatings. The rare earth ceramic materials are regarded as promising materials which can be applied by plasma spraying. However, the lower mechanical strength of these materials compared with YSZ limits their performance during thermal cycling. The interlamellar bonding of plasma sprayed ceramic coatings dominates their mechanical properties. In this study, the rare earth ceramic LZO splats were deposited on both YSZ and LZO surfaces at different surface temperatures to reveal the effect of the deposition temperature on the splat interface bonding formation. The bonding conditions between splat and different substrates were examined from the cross-sections by fracturing the splats. It is confirmed that at low surface temperature no effective splat bonding formed between the splat and the substrate surface. It is also observed that there was a critical surface temperature over which the interface bonding begins to form. The present results will benefit the control of splat interface bonding, and thus the properties of the coatings.