Microstructure and thermal analysis of APS nano PYSZ coated aluminum alloy piston

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Journal Article
Journal of Alloys and Compounds, 2020, 812
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© 2019 Elsevier B.V. Aluminium alloys in internal combustion (IC) engines may suffer from heat damage. Such heat damage can be mitigated using thermal barrier coatings (TBCs). In this study, the TBC Nano yttria partially stabilized zirconia (PYSZ) is applied as an aggregated powder to an aluminum alloy piston using an atmospheric plasma spray (APS) method. The preparation and application of the Nano PYSZ aggregated powder are critical to its effectiveness as a TBC. IC engine bench experiments were undertaken to provide a baseline against which the effectiveness of the TBC could be judged. The microstructure of the Nano PYSZ aggregated powder and thermal barrier coatings were examined using three instruments: scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM) and X-ray powder diffraction (XRD). Results from this study show that the Nano PYSZ ceramic TBCs, applied to the aluminum alloy piston using a plasma spraying technique, (a) has a high quality Nano-structure, (b) can effectively resist the thermal shock of high temperature gas in the cylinder and (c) maintains both stable macro characteristics and micro structure during the working cycle of the IC engine. The thermal insulation properties of TBCs were also examined. The thermal analyses describe the distribution of temperature across both the piston and the aluminum alloy substrate. Results desmonstrate the effectiveness of the TBCs in reducing the temperature of the aluminium alloy substrate at the top of piston. One benefit is that the piston can operate effectively at higher temperatures. Specifically, as the thickness of ceramic coating increased from 0.1 mm to 1.4 mm, the maximum temperature of the pistons coated with the TBCs increased from 399 °C to 665 °C. The maximum temperature of the aluminum alloy substrates simultaneously decreased from 336 °C to 241 °C. This study clearly demonstrates the excellent thermal insulation properties of the TBCs and shows that the thermal insulation performance can be significantly enhanced by increasing the thickness of the ceramic layer.
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