Multilayer TBCs and EBCs: Integrating Design and Manufacturing Innovations for Multifunctional Performance

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Multifunctional thermal barrier coatings enabled by layered manufacturing

Majority of contemporary TBCs applied either via plasma spray or EB-PVD can typically be described as monolithic single layers, principally based on yttria stabilized zirconia (YSZ). Advent of new ceramic compositions has necessitated to some extent the need for double layers where the interfacial ceramic layer on the bond coat is often made of YSZ to prevent reaction of advanced compositions with TGO. Even in these situation the coating architecture is generally of a single variant. Since TBCs experience location specific performance needs (example interfacial oxidation, sintering resistance in the volume and need for distinct surface characteristics to mitigate against CMAS and erosion) there is an opportunity to engender unique microstructural and material characteristics. In this presentation, we will discuss the coupling of multilayer coating design to meet the disparate coating needs along with advanced layered manufacturing concepts. Plasma spray is uniquely capable of taking advantage of such layered design concepts as the coating itself is built in discrete layers of particle based assembly. Several variants of such multilayer, multifunctional coatings will be presented incorporating guidance from mechanics model, manufacturing advances and performance attributes

Segmentation cracks in plasma spray coatings: Formation dynamics and chracterization

Segmentation cracks in Air Plasma Sprayed (APS) Thermal Barrier Coatings (TBCs) have been recognized as crucial micro-structural asset for increasing the in-plane strain tolerance of the coatings and thus enhancing the TBC durability. These vertically cracked coatings also show excellent in-plane fracture toughness. This combination has allowed wide spread use of these coatings in gas turbine engines. Although industrially successful, there is limited scientific studies on the formation dynamics of such cracks, and their relationship to process conditions and performance. This is especially of importance as efforts are underway to find alternative to Yttria Stabilized Zirconias for higher temperature thermal barrier applications. Please click Additional Files below to see the full abstract

A Coupled Thermal and Mechanical Analysis of Sintering in Thermal Barrier Coatings Under Gradient Exposure

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A coupled thermal and mechanical analysis of sintering in thermal barrier coatings under gradient exposure

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Geodetic domination integrity in graphs

Reciprocal version of product degree distance of cactus graphs Let G be a simple graph. A subset S ⊆ V (G) is a said to be a geodetic set if every vertex u /∈ S lies on a shortest path between two vertices from S. The minimum cardinality of such a set S is the geodetic number g(G) of G. A subset D ⊆ V (G) is a dominating set of G if every vertex u /∈ D has at least one neighbor in D. The domination number γ(G) is the minimum cardinality of a dominating set of G. A subset is said to be a geodetic dominating set of G if it is both a geodetic and a dominating set. The geodetic domination number γg(G) is the minimum cardinality among all geodetic dominating sets in G. The geodetic domination integrity of a graph G is defined by DIg(G) = min{|S| + m(G − S) : S is a geodetic dominating set of G}, where m(G − S) denotes the order of the largest component in G−S. In this paper, we study the concepts of geodetic dominating integrity of some families of graphs and derive some bounds for the geodetic domination integrity. Also we obtain geodetic domination integrity of some cartesian product of graphs.Publisher's Versio

A comparative study of phase evolution in YSZ powders, pellets and free-standing air plasma sprayed thermal barrier coatings

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Optimizing Compliance and Thermal Conductivity of Plasma Sprayed Thermal Barrier Coatings via Controlled Powders and Processing Strategies

The properties and performance of plasma-sprayed thermal barrier coatings (TBCs) are strongly dependent on the microstructural defects, which are affected by starting powder morphology and processing conditions. Of particular interest is the use of hollow powders which not only allow for efficient melting of zirconia ceramics but also produce lower conductivity and more compliant coatings. Typical industrial hollow spray powders have an assortment of densities resulting in masking potential advantages of the hollow morphology. In this study, we have conducted process mapping strategies using a novel uniform shell thickness hollow powder to control the defect microstructure and properties. Correlations among coating properties, microstructure, and processing reveal feasibility to produce highly compliant and low conductivity TBC through a combination of optimized feedstock and processing conditions. The results are presented through the framework of process maps establishing correlations among process, microstructure, and properties and providing opportunities for optimization of TBCs