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Materials Research Science and Engineering Center
National Science Foundation
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Research Activities
| Microstructure and Defect
Characterization: Comprehensive efforts involving multidisciplinary characterization/scattering techniques along with property measurements have been employed for an integrated approach towards studying porosity in thermal sprayed coatings. While quantification / visualization of porosity have been obtained using high-resolution x-ray computed microtomography (CMT) studies, information regarding pore size distribution has been sought using ultra-small angle x-ray scattering (USAXS) technique, a novel direction towards characterization of plasma sprayed coatings Recent studies conducted in conjunction with the National Institute of Standards and Technology, combining well-established single and multiple small angle neutron scattering (SANS and MSANS) with other characterization and property measurement, have established a much improved understanding of the processing-microstructure- property correlations for several ceramic systems including YSZ.
(a) HVOF (b) Plasma Porosity: 4% 8% TC: 3 W/m K 5.3 W/m K Computer Microtomography of (a) HVOF and (b) plasma sprayed alumina coatings revealing anomalies in the pore structure within the coating and its effects on coating properties. (TC-Thermal conductivity)
Quantitative delineation of porosity in |
Process Science and
Maps: Significant progress has been made in process maps at the CTSR. Process maps not only provide a new scientific approach to analyzing complex phenomena, but also offer new technological insights into the process. The newly derived group parameter melting index (MI) along with Reynold’s number (Re), are used to provide a more complete assessment of a particle’s thermal history especially for refractory materials such as YSZ and can be used to distinguish splat morphology and assess deposit efficiency in a process map. Furthermore, both fundamental characteristics such as splat residual stress to practical attributes such as deposit efficiency can be correlated to the MI parameter.
Example of a 1st order process map representation for plasma sprayed YSZ with various nozzle dimensions, powder feedstock and process parameters.
Example of a second order process map representation for plasma sprayed Mo on steel identifying regimes of splat morphologies, substrate temperature effects on residual stresses and modulus vector. |
| 3D Simulations of Plasma
Spray: In conjunction with INEEL, CTSR has been very active in examining the three dimensional features of a plasma spray plume and particles through numerical simulations. Special attention has been directed to the efforts of injection carrier gases on the plasma jet and entrained multiple particle behavior. A database has been built based upon process conditions as well as particle behavior, such as temperature velocity and location. The 3D approach provides a more comprehensive assessment of the process through simulation.
Elastic Properties of Coatings: Example of stress-strain relationships in various Ni-Al coatings from instrumented spherical indentation.
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In-situ Sensing for Property
Determination: An in-situ sensor for measurement of modulus and stress has been developed through the CTSR, with the intention of connecting particle state with the deposit condition (e.g., stress state, imperfection structure). This sensor will enable determination of design relevant properties of coatings either in-situ or within minutes after processing. Furthermore this method may allow more quantitative assessment of process-structure-property relationship in aiding process/quality control. In situ measured properties in graded coatings
A schematic of a process control sensing apparatus under development by Integrated Coating Solution is shown below.
In-Situ Coating Property Sensor (ICP) |
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03/12/2005 SD and JQ
