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Non-Destructive Evaluation and Maintenance of Thermal Barrier Coatings Martin P University of Connecticut OpenCommons@UConn Master's Theses University of Connecticut Graduate School 8-5-2014 Non-Destructive Evaluation and Maintenance of Thermal Barrier Coatings Martin P. Hawron University of Connecticut - Storrs, [email protected] Recommended Citation Hawron, Martin P., "Non-Destructive Evaluation and Maintenance of Thermal Barrier Coatings" (2014). Master's Theses. 648. https://opencommons.uconn.edu/gs_theses/648 This work is brought to you for free and open access by the University of Connecticut Graduate School at OpenCommons@UConn. It has been accepted for inclusion in Master's Theses by an authorized administrator of OpenCommons@UConn. For more information, please contact [email protected]. Non-Destructive Evaluation and Maintenance of Thermal Barrier Coatings Martin Per Hawron B.S. B.S., Southern Arkansas University 2011 A Thesis Submitted in Partial Fulfillment of the Requirements for the Degree of Master of Science at the University of Connecticut 2014 APPROVAL PAGE Master of Science Thesis Non-Destructive Evaluation and Maintenance of Thermal Barrier Coatings Presented by: Martin Per Hawron B.S. Major Advisor:_________________________________________________________ Michael W. Renfro Associate Advisor:______________________________________________________ Eric H. Jordan Associate Advisor:______________________________________________________ Maury Gell University of Connecticut 2014 Acknowledgements Everywhere life has taken me, many have gone out of their way to help me along, and this university has been no exception. I am grateful to Mike Renfro for guiding my academic growth over the past two years, being an ever-approachable laser guru, and for convincing me to come to UConn in the first place. I am much indebted to Eric Jordan for the conversations in which he would communicate more knowledge about TBC’s than you could look up in a week. Thanks to Maury Gell for bringing his extensive knowledge on the subject to my thesis committee. I would have been lost without Jerod’s efforts in familiarizing me with the methodology and programming required for this work. To my lab-mates Kathryn, Chris, Marc and Stephen; Jason, George and Bikram: bouncing ideas off of you has been as useful as drinking with you has been, at times, necessary. I would like to thank Nick for his valuable assistance in developing software, as well as meticulous tinkering. Jonny is much appreciated for his contributions with POD and collection of LIBS references. Nirav deserves recognition as a veritable champion of IMS, and has been great to work with. My thanks go out to Tom Mealy for improving upon and fabricating a plethora of half-baked designs, Roger Ristau for allowing me to exploit his SEM expertise, to Jack Gromek for his instruction in XRD, and of course to Gary Lavigne for training and advice concerning the Ramascope. Finally, I would like to thank my family, who have been patient, supportive, and loving throughout the years I’ve been away. This research was funded by the Rolls Royce Corporation. i Table of Contents Acknowledgements .......................................................................................................................... i Table of Contents ............................................................................................................................ ii Table of Figures ............................................................................................................................. iv Abstract .......................................................................................................................................... 1 1 Introduction ................................................................................................................................ 2 2 Background ................................................................................................................................ 7 2.1 Thermal Barrier Coatings ...................................................................................................... 7 2.2.1 TBC Composition and Properties................................................................................... 7 2.1.2 TBC Spallation Causes and Prediction ........................................................................ 10 2.2 Remaining Life Non-Destructive Evaluation Method ........................................................ 11 2.2.1 Photo-Luminescence Piezospectroscopy ...................................................................... 12 2.2.2 CMAS and Interference with TBC Life Analysis .......................................................... 15 2.2.3 Laser-Induced Breakdown Spectroscopy ..................................................................... 17 2.3 Expansion to Mobile NDE System ..................................................................................... 22 2.3.1 Borescope NDE Concept .............................................................................................. 22 2.3.2 Laser Ablation for TBC Removal ................................................................................. 24 2.4 Optical Fiber Components for NDE Borescope Device ..................................................... 24 2.4.1 Coherent Fiber Bundles for LIF Scanning ................................................................... 25 2.4.2 Large-Core Optical Waveguides for Pulsed UV Laser ................................................ 25 2.5 Proper Orthogonal Decomposition for LIBS Spectra ......................................................... 26 2.5.1 LIBS Spectra for Coating Species Discrimination ....................................................... 28 2.5.2 Proper Orthogonal Decomposition .............................................................................. 28 3 Experimental Setup ................................................................................................................. 31 3.1 Laser Ablation and LIBS Setup ........................................................................................... 32 3.2 PLPS Setup and Raman Spectroscopy ................................................................................ 34 3.3 Optical Fiber Implementation Setup ................................................................................... 37 4 Improvements to NDE System ................................................................................................ 40 4.1 Orthogonal Spectral Modes for LIBS Analysis .................................................................. 42 4.1.1 POD for CMAS and TBC LIBS Spectral Ortho-modes ................................................ 43 4.1.2 Improved Laser Ablation Control................................................................................. 44 4.2 Beam Profile of Pulsed Quantel Nd:YAG Laser ................................................................ 46 ii 4.2.1 Non-Homogeneous Beam Energy Density ................................................................... 46 4.2.2 Optimization of Laser Operation Parameters .............................................................. 48 4.3 Improvements to PLPS Operation in Mobile Device.......................................................... 51 4.3.1 Increased Probe Area Versatility with New Objective Lens ........................................ 52 4.3.2 PLPS Signal Collection Expedited ............................................................................... 52 4.3.3 Extended Stress Domain for Engine-Run Blades ......................................................... 54 4.3.4 Potential Effect of Laser Heating on PLPS .................................................................. 61 4.4 Standard-Aero Field Demonstrations .................................................................................. 63 4.4.1 July 2012 Standard Aero Demonstration ..................................................................... 63 4.4.2 November 2012 Standard Aero Demonstration ........................................................... 66 5 Optical Fiber Components for in situ TBC Life Analysis .................................................... 70 5.1 Optical Fiber Bundles for PLPS Measurement Scans ......................................................... 70 5.1.1 Characteristics of Optical Fiber Bundle Types ............................................................ 72 5.1.2 Reliability of Fiber Bundle PLPS Measurements ......................................................... 76 5.2 LIBS Utilizing a Fiber Optic Waveguide ............................................................................ 79 5.2.1 Fused Silica Waveguide Damage Thresholds .............................................................. 80 5.2.2 LIBS Waveguide Performances .................................................................................... 83 6 Laser Ablation Thermal Barrier Coating Removal ............................................................. 90 6.1 Orthogonal POD Modes for LIBS Spectra ......................................................................... 90 6.1.1 Coating Species LIBS Spectra ...................................................................................... 91 6.1.2 Proper Orthogonal Decomposition of LIBS Spectra .................................................... 91 6.2 Ablation Drilling Stop Criterion ......................................................................................... 94 6.2.1 Threshold Algorithms ..................................................................................................
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