Tailored TBC for Resistance to CMAS, Erosion, and Impact (07-Apr-2008)
An article has a thermal barrier coating (TBC). The TBC has a layered architecture providing one or more of the following benefits: (1) alternating TBC compositions having CMAS resistance (such as Gd-zirconate) with compositions having high toughness (such as 7YSZ) to functionalize the TBC coating to simultaneously possess CMAS resistance and durability. (2) alternating TBC compositions having high toughness with compositions having high-temperature phase stability (such as higher/modified zirconia stabilizer compositions) to functionalize the TBC coating to simultaneously possess durability and phase stability. (3) engineering interfaces within the TBC that provide sacrificial failure planes as may be obtained for the above-mentioned architectures so that the TBC is engineered to withstand impact and/or CMAS damage without catastrophic loss of the entire TBC. Such coating may blanket the article, or may be selectively applied to locations especially prone to CMAS attack or to locations that operate at particularly high surface temperatures.
Title: Tailored TBC for Resistance to CMAS, Erosion, and Impact
Abstract: An article has a thermal barrier coating (TBC). The TBC has a layered architecture providing one or more of the following benefits: (1) alternating TBC compositions having CMAS resistance (such as Gd-zirconate) with compositions having high toughness (such as 7YSZ) to functionalize the TBC coating to simultaneously possess CMAS resistance and durability. (2) alternating TBC compositions having high toughness with compositions having high-temperature phase stability (such as higher/modified zirconia stabilizer compositions) to functionalize the TBC coating to simultaneously possess durability and phase stability. (3) engineering interfaces within the TBC that provide sacrificial failure planes as may be obtained for the above-mentioned architectures so that the TBC is engineered to withstand impact and/or CMAS damage without catastrophic loss of the entire TBC. Such coating may blanket the article, or may be selectively applied to locations especially prone to CMAS attack or to locations that operate at particularly high surface temperatures.
Background: While today's 7YSZ TBCs provide a good balance of thermal resistance and durability, the coatings are subject to failure by solid-particle impact/erosion and CMAS infiltration. Since failure due to CMAS and impact damage is unpredictable in current applications, this prevents full design reliance on the TBCs, therefore limiting the benefits. Additionally, as advanced TBC applications continue to raise the surface temperature, coating failure modes related to phase destabilization and tetragonal-to-monoclinic phase transformation are anticipated. No solutions have satisfactorily addressed this problem. However, studies are being conducted by a number of entities to identify TBC microstructures, compositions, and overlay coatings to improve impact/erosion resistance and prevent CMAS attack. Recent findings by one such entity...
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