Low relative density yttria stabilized zirconia (YSZ) thermal barrier coatings have been deposited on NiCoCrAlY over-lay bond-coated Hastelloy-X substrates by an electron beam-directed vapor deposition (EB-DVD) method. The coatings have been applied to both roughened and smooth bond coat surfaces. During thermal cycling, those deposited on roughened surfaces spalled by delamination with the failure located in the YSZ layer close to the thermally-grown oxide (TGO). The cracks were initiated at “corn kernel” defects in the YSZ layer by a bond coat rumpling mechanism. Coatings applied to smooth bond coat surfaces had much longer (factor of two) spallation lifetimes and delamination occurred at the bond coat/TGO interface by the nucleation and coalescence of interfacial voids. In both cases, the delamination lifetime decreased with coating density and significantly exceeded the lifetimes of higher density coatings made by conventional electron beam deposition methods. The enhanced life of the more porous coatings is consistent with an increased compliance. This reduces the YSZ layers stored strain energy contribution to the driving force for interface delamination.

The influence of coating compliance on the delamination of thermal barrier coatings

The interface delamination plays an important role in failures of thermal barrier coatings. An axisymmetric finite element model was built for air plasma sprayed thermal barrier coatings. The model incorporated a Fortran subroutine developed for the TGO growth. It is found that the stress conversion happens in the top-coat at high temperature under isothermal exposure. A simple numerical method was proposed to calculate the normal and tangential stresses at the top-coat/TGO interface and the bond-coat/TGO interface. The bond-coat/TGO interface is less likely to separate during thermal exposure because the interfacial stresses are limited mostly by the high-temperature yield strength of the bond-coat. The delamination of the bond-coat/TGO interface happens on cooling, which is supported by the experimental observation. As a result, the delamination of the bond-coat/TGO interface could be appreciated based on the corresponding normal and tangential stresses.

Analysis of interface delamination in thermal barrier coating system with axisymmetric structure based on corresponding normal and tangential stresses

A parametric study of damage initiation and propagation in EB-PVD thermal barrier coatings

Delamination resistance of thermal barrier coatings containing embedded ductile layers

Dynamic crack growth mechanism and lifetime assessment in plasma sprayed thermal barrier system upon temperature cycling

Interactions have been calculated between cracks induced in thermal barrier coatings (TBCs) upon thermal cycling, motivated by displacement instability in the thermally grown oxide (TGO). The results indicate that the energy release rate G cycles as the temperature changes, with the largest value arising at ambient temperature. It increases on a cycle-by-cycle basis. The trends in G predict two responses. (i) Isolated cracks should be confined to the vicinity of the imperfection, as observed experimentally. (ii) Cracks that converge from neighboring imperfections exhibit a minimum G prior to convergence, providing the possibility that they might coalesce. Equating this minimum to the toughness of the TBC provides a criterion for coalescence and failure. Imposing this criterion allows the change in crack length upon cycling and the number of cycles to failure to be ascertained. The results are consistent with experimental measurements obtained from furnace cycle tests.

A Numerical Assessment of the Propagation and Coalescence of Delamination Cracks in Thermal Barrier Systems

Handle everyday research tasks with reliable, citation-backed results

Your personal Research Agent to handle research tasks with citation-backed results

Popular Tasks used by Researchers

How can I help with your research?

Meet SciSpace

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

M.Y. He

Author Tools

Chat about Author

Papers

A Numerical Assessment of the Propagation and Coalescence of Delamination Cracks in Thermal Barrier Systems