Protection offered by thermal barrier coatings to Al-Si alloys at high temperatures – A microstructural investigation

Publication date: Available online 22 August 2019Source: Materials Today: ProceedingsAuthor(s): V.R. Reghu, Kevin Lobo, Arhan Basha, Pramod Tilleti, V. Shankar, Parvati RamaswamyAbstractThermal barrier coatings, with ∼50 µm thick Nickel-Aluminide bond coat and ∼250 µm thick Yttria-Stabilized zirconia ceramic top coats were synthesized by Air Plasma Spray coating process on flat plates machined from Al-11Si alloy diesel engine pistons. Coating process parameters and qualifications that were followed were based on previous studies made on the same substrates. The ceramic coatings were subjected to various thermal treatments such as (a) thermal shock cycling tests and (b) continuous heating in a furnace. Uncoated Al-Si samples were simultaneously subjected to the same thermal treatments and used as reference to study the protection offered by the coatings to the base metal substrates. Thermal shock cycles tests involved subjecting the coated and uncoated Al-Si plates to oxy-acetylene flame to allow the ceramic surface to be maintained at 500 °C for 1000 cycles (one cycle comprised of heating for 60 s, withdrawal from flame and forced cooling in ambient air for 60 s) and similar thermal shock cycles in an electric furnace. The specimen were also heated in a furnace at 300 °C for 1000 continuous hours. Stresses induced during thermal shock cycles and oxidation of bond coat-ceramic coat interface during the exposure to heat are the main reasons for the coatingâ€...
Source: Materials Today: Proceedings - Category: Materials Science Source Type: research