Abstract
Multilayer, graded ceramic/metal coatings were prepared by an air plasma spray method on Ti-6Al-4V, 4140 steel and graphite substrates. The coatings were designed to provide thermal barriers for diesel engine pistons to operate at higher temperatures with improved thermal efficiency and cleaner emissions. A systematic, progressive variation in the mixture of yttria-stabilized zirconia and bondcoat alloys (NiCoCrAlYHfSi) was designed to provide better thermal expansion match with the substrate and to improve thermal shock resistance and cycle life. Heat transfer through the layers was evaluated by a flash diffusivity technique based on a model of one-dimensional heat flow. The aging effect of the as-sprayed coatings was captured during diffusivity measurements, which included one heating and cooling cycle. The hysteresis of thermal diffusivity due to aging was not observed after 100-h annealing at 800 °C. The measurements of coatings on substrate and freestanding coatings allowed the influence of interface resistance to be evaluated. The microstructure of the multilayer coating was examined using scanning electron microscope and electron probe microanalysis.
| Original language | English |
|---|---|
| Pages (from-to) | 371-378 |
| Number of pages | 8 |
| Journal | Journal of Thermal Spray Technology |
| Volume | 27 |
| Issue number | 3 |
| DOIs | |
| State | Published - Feb 1 2018 |
Funding
Acknowledgments This work was conducted through a Corporate Research and Development Agreement (CRADA) project with Cummins Engine Company. This work is sponsored by the assistant secretary for Energy Efficiency and Renewable Energy of the Department of Energy and the Propulsion Materials program under the Vehicle Technologies program and Oak Ridge National Laboratory managed by UT-Battelle LLC under Contract DE-AC05000OR22725.
Keywords
- TBC
- thermal barrier coatings
- thermal diffusivity