Imaging Profilometry For In Situ Measurement of Plasma Spray Coating Thickness

Persistent Link:
http://hdl.handle.net/10150/560844
Title:
Imaging Profilometry For In Situ Measurement of Plasma Spray Coating Thickness
Author:
Trail, Nicholas
Issue Date:
2015
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Embargo:
Release after 01-Jun-2017
Abstract:
Thermal Barrier Coatings (TBCs), and plasma spray coatings in general, require critical control over the deposited thickness to achieve reliable coating performance. Currently, the plasma spray industry quantifies thickness by sampling the part before and after TBC deposition. Approximate thickness is thus inferred from previous runs. However, process variability can allow errors to propagate in this result that leads to wasted time and resources, and can ultimately lead to non-reliant coatings. To this end, an in situ optical fringe profilometer is developed that enables coating thickness measurements across a 2-dimensional surface. The initial profilometer concept is explored through requirements and trade studies, leading to a hardware and algorithm design family and prototype build to capture and compare real-world data to simulation and model predictions. This initial result shows a viable path-forward and the ability to achieve micrometer-scale depth resolution. Modifications and alterations to the in situ profilometer are then explored to improve the performance limits achievable. In specific, industrial spray coatings operate by dropping fine-grain media into a high pressure gas line aimed through a plasma torch to impart enough thermal and kinetic energy to stick to the part surface. This presents a challenging operational environment for an optical depth measurement sensor, working with a variable high-temperature blackbody stray light source; constant part rotation and plasma gun movement; and a non-isolated vibration environment. As such, the concept of the profilometer is further adapted specific to this end-purpose, by developing and reviewing both dual-fringe projection and plenoptic imaging. These techniques allow an improvement to both the system micro- and macroscopic depth retrieval limits, allowing a method to solve for an extended range of phase ambiguities and relax object focus requirements (respectively). The end result is a system concept and algorithm design that presents a feasible manner for automated in situ geometry and depth measurements in the plasma spray industry. The in situ fringe profilometer work described herein allows a flexible path to recover object depth information remotely, and is especially relevant for asymmetric and complex non-planar geometries, which are experiencing renewed interest with additive manufacturing processes and generally quite common to the thermal spray industry.
Type:
text; Electronic Dissertation
Keywords:
plasma spray; profilometry; projection; Optical Sciences; fringe
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Optical Sciences
Degree Grantor:
University of Arizona
Advisor:
Dereniak, Eustace L.

Full metadata record

DC FieldValue Language
dc.language.isoen_USen
dc.titleImaging Profilometry For In Situ Measurement of Plasma Spray Coating Thicknessen_US
dc.creatorTrail, Nicholasen
dc.contributor.authorTrail, Nicholasen
dc.date.issued2015en
dc.publisherThe University of Arizona.en
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en
dc.description.releaseRelease after 01-Jun-2017en
dc.description.abstractThermal Barrier Coatings (TBCs), and plasma spray coatings in general, require critical control over the deposited thickness to achieve reliable coating performance. Currently, the plasma spray industry quantifies thickness by sampling the part before and after TBC deposition. Approximate thickness is thus inferred from previous runs. However, process variability can allow errors to propagate in this result that leads to wasted time and resources, and can ultimately lead to non-reliant coatings. To this end, an in situ optical fringe profilometer is developed that enables coating thickness measurements across a 2-dimensional surface. The initial profilometer concept is explored through requirements and trade studies, leading to a hardware and algorithm design family and prototype build to capture and compare real-world data to simulation and model predictions. This initial result shows a viable path-forward and the ability to achieve micrometer-scale depth resolution. Modifications and alterations to the in situ profilometer are then explored to improve the performance limits achievable. In specific, industrial spray coatings operate by dropping fine-grain media into a high pressure gas line aimed through a plasma torch to impart enough thermal and kinetic energy to stick to the part surface. This presents a challenging operational environment for an optical depth measurement sensor, working with a variable high-temperature blackbody stray light source; constant part rotation and plasma gun movement; and a non-isolated vibration environment. As such, the concept of the profilometer is further adapted specific to this end-purpose, by developing and reviewing both dual-fringe projection and plenoptic imaging. These techniques allow an improvement to both the system micro- and macroscopic depth retrieval limits, allowing a method to solve for an extended range of phase ambiguities and relax object focus requirements (respectively). The end result is a system concept and algorithm design that presents a feasible manner for automated in situ geometry and depth measurements in the plasma spray industry. The in situ fringe profilometer work described herein allows a flexible path to recover object depth information remotely, and is especially relevant for asymmetric and complex non-planar geometries, which are experiencing renewed interest with additive manufacturing processes and generally quite common to the thermal spray industry.en
dc.typetexten
dc.typeElectronic Dissertationen
dc.subjectplasma sprayen
dc.subjectprofilometryen
dc.subjectprojectionen
dc.subjectOptical Sciencesen
dc.subjectfringeen
thesis.degree.namePh.D.en
thesis.degree.leveldoctoralen
thesis.degree.disciplineGraduate Collegeen
thesis.degree.disciplineOptical Sciencesen
thesis.degree.grantorUniversity of Arizonaen
dc.contributor.advisorDereniak, Eustace L.en
dc.contributor.committeememberSchwiegerling, James T.en
dc.contributor.committeememberKudenov, Michael W.en
dc.contributor.committeememberDereniak, Eustace L.en
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