Cost Effective Testing of Coatings

Transcription

1 Cost Effective Testing of Coatings Mark Gee National Physical Laboratory 9 th March 2010

2 NPL Today World leading National Measurement Institute 600+ specialists in Measurement Science State-of-the-art standards facilities The heart of the UK s National Measurement System to support business and society Experts in Knowledge Transfer To deliver the highest economic and social impact as a world-leading National Measurement Institute through excellent, responsive science and knowledge services 2

3 The growing demand for better measurements Environment Communications Healthcare It is estimated that in Europe today we measure and weigh at a cost equivalent to 2-7% of GDP Industry Food Science You and I Doctors Regulators Metrology influences, drives and underpins much of what we do and experience in our everyday lives, though often unseen. Industry, trade, regulation, legislation, quality of life, science and innovation all rely on metrology Health & safety Transport 3

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7 Materials Team Advanced Engineered Materials Innovative Metals Engineering Liquid Metal Processing, Residual Stress and Strain, High Temperature Degradation Performance of Engineered Surfaces Nano Mechanics, Tribology, Powder Route Materials (PRM), Microscopy Thermal & Electrochemistry Thermal Performance of Materials & Structures Thermal Properties of Structures, Dynamic Thermal Evaluation Electrochemistry Environment Induced Cracking (EIC), Fuel cells, Photovoltaics, Nanoscale EC Electronics & Modelling Materials Modelling Thermodynamics (MTDATA), Structural Health Monitoring, FE, FD & Genetic Modelling Electronics Interconnect circuit cleanness (SIR, SEC), solder reliability, component mounting Nano- & Multifunctional Materials Nanomaterials material characterisation, micro-fluidic studies, modelling Multifunctional Materials Multiphysics coupling in Multiferroic/functional materials (includes magnetic and organic electronics) Bio, Polymeric & Composite Materials Polymeric Materials Micro-processing and reduced length scale properties Composites SHM, Nanocomposites, Complex geometries & multiaxial properties Biomaterials Cellular interactions with materials and fluid flow through complex porous structures 7

8 Measurement Why do we do it? Reasons Provide information for materials development (can we make it) Provide information on likely performance (will it work) Provide information for input into modelling (can we predict if it will work) Other factors Cost of testing versus field trials Need for simple and quick QC tests Need for high quality data for modelling Need for the right information for production As close to shop floor as possible Increasing range of coatings Increasing possibility of combining different functionality through nanostructuring (layered, particulate etc) 8

9 Coatings Measurement Wide range of measurement methods available Adhesion, thickness, composition, hardness, mechanical properties, residual stress, wear, friction Aim is to make measurements simpler, more relevant, cheaper, more robust Guidance available NPL Good Practice Guide No 83, An Introduction to the Mechanical Testing of Coatings, M G Gee and N M Jennett Measurement standards in many ASTM, CEN and ISO committees Metallic and other inorganic coatings, BS STI/33, CEN 262, ISO TC 107 Ceramic coatings, BS RPI/13, CEN 184 WG5, ISO TC 206 Thermal sprayed coatings, BS STI/40, CEN 240 9

10 Bend Testing for Coating Integrity Testing Context Need to provide information on integrity of coatings under mechanical loading Science Use instrumented bend testing Acoustic emission Video to detect cracking Future Vision Is being taken forward into work to provide simple test for near shop floor environment Proposal for standardisation in CEN Acoustic emission Video Strain gauge Rollers Displacement Sensor Load cell Motor drive 10

11 Bend Testing Force displacement curves Acoustic emission 11

12 Bend Testing - Comparison of Samples Hydroxyapatite Chromium Carbide: Fine Ground Chromium Carbide: Coarse Ground Tungsten Carbide: Fine Ground Tungsten Carbide: Coarse Ground Codeposited Electroplate Hard Chrome 12

13 Bend Testing - Case Study Coated tube Force vs displacement summary (all pipes) Compare performance of oxidised and unoxidised tube Force (N) Coated 1 Coated 2 Coated 3 Ox Ox Ox Ox Ox b 200 Uncoated Uncoated 2 Uncoated Displacement (mm) 13

14 Coupon Bending for Residual Stress Measurement Residual stress from thermal expansion mismatch and processing effects For thin coatings Stoney formula; thick coatings more complex formula Methods for measurement Profilometry Flexus Optical microscope LVDT 14

15 Coupon Bending for Residual Stress Measurement Substrate Finish and Thickness Fine, 1.2 Fine, 2 Fine, 3 Coarse, 1.2 Coarse, 2 Coarse, Optical Flexus Height, mm Deflection, μm Distance,mm Optical microscope measurements on thermally sprayed coatings Profilometer measurements on Fecralloy Sample (574 MPa) Distance, mm Comparison between optical and profilometer measurements Residual Stress, MPa Coarse Freund Fine Freund Coarse Stoney Fine Stoney Substrate Thickness, mm Comparison between Stoney and Freund analysis LVDT jig 15

16 Rockwell Indentation Adhesion Test: Drory and Hutchinson Analysis MCrAlY Coating on Mar M002 Substrate Γ C = 680 J m -2 Γ C =1470 J m -2

17 Scratch Testing Friction Force, N AE Signal, db Load, N Applied load, N L c = 21.3 N load acoustic emission tangential force optical inspection of failure modes 18

18 Scratch Testing - Tranverse Normal Load (10 to 80 N) Direction of Travel 10 N 10 N Substrate Direction of Travel Coating Substrate 80 N Rockwell Indenter 50 N Coating 1000 Crack length, µm Critical Load (Lc) 80 N Indenter Load, N 19

19 Pulsed Thermography Flash lamp IR radiation Bond-coat delamination on power turbine vane Thermal camera to PC Heat conduction Type of failure prevented Saving on power disruption, downtime, cost 20

20 Coating Measurement Using SAWs Non-contact measurement method using high power laser Short (400ps) laser pulse is adsorbed by material Thermo-elastic expansion generates wide bandwidth SAW packets SAWs detected by piezo-wedge Velocity used to calculate Elastic Modulus, Poisson s ratio, Film thickness, Porosity & Density 3220 Phase Velocity, c (m/s) µm TiN on Steel Movie from Steel Frequency, f (MHz) 21

21 Impact Excitation Apparatus Context Need for simple measurement of coating modulus Modulus can be measure of quality and integrity of coating Science Use impact excitation where transducer measures the resonant frequency f. Modulus E is function of geometry and resonant frequency Future Vision Develop into portable easy to use apparatus for shop floor use Resonant Frequencies 22

22 Modulus against Frequency for TiN coated steel 1200 Extrapolation back to Zero khz gives a value for the modulus of the coating. Modulus E (GPa) Results from Euler- Bernoulli analysis of frequency shift Accurate film thickness is crucial (fourth power) Intercept A = 425 GPa Intercept B = 427 GPa Intercept C = 440 GPa Specimen A (0.87mm substrate, 950nm coating) Specimen B (0.87mm substrate, 2280nm coating) Specimen C (0.87mm substrate, 2660nm coating) Frequency (khz) 23

23 3D Optical Microscopy for Wear Measurement Before Wear Similar to confocal microscopy Height data combined with image data Dataset correlation Real volume measurement Before Wear After Wear Correlated and Subtracted Images After Wear After Wear Profile from above 24

24 Gas Borne Particle Erosion Stepwise Analysis Gas blast erosion test Supply tube Mixing chamber Gas supply M4 M6 Nozzle tube Working distance Nozzle length Abrasive reser voir Mass Loss, g Specimen Schematic diagram of gas blast erosion test system, ASTM G 76 (11) 75 ms μm sand Normal incidence 20 mm stand-off 5 mm nozzle Increments from 0.1 gm to 4 or 15 gm (later stages) Mass of Erodant, g Area Examined Erosion Damage 25

25 Stepwise Erosion Large Grain WC/Co Hardmetal 27.5 g 33.5 g 8 μm 26

26 Monitoring Degradation of Surfaces Due to Wear Develop sensors that give signature that can be related to wear processes Setting up four different approaches Electrostatic probe Electromagnetic probe Chromatic aberration probe Reflectivity Distance Real time video of moving surface through linescan camera system Booth et al, Tribology International 39 (2006)

27 Chromatic Aberration Probe Uses optics giving enhanced chromatic aberration Different wavelengths are focussed at different depths Measuring colour of reflected light gives measure of distance Non-contact Fast Arm Displacement(micrometres) Displacement-sd 7.87 Opto Probe Time (s) Optical Probe Output (V) 28

28 New In-situ Micro-tribology Test System A new micro-tribology test system has been designed and fabricated (within the SEM) to perform tests on a range of low friction coatings. The test system is being applied to three initial areas: 1. A study of the abrasion resistance of tool materials such as WC/Co 2. Examination of the tribological performance of low friction carbon based coatings 3. Tribological assessment of Inorganic Fullerene Like coatings: EU project Friction with time for micro-tribology experiment on CP x films from Linköping University 29

29 To Sum Up Wide range of measurement methods available Range of accessibity Need to think about relevance of measurements to applications NPL is available to help 30