Facilitating Sustainability through Surface Engineering by Measurement and Standards M G Gee National Physical Laboratory 14 th June 2011 IMF Fair Thursday, 02 June 2011 1
Sustainability and Surface Engineering Surface engineering can help with the sustainable use of materials and resources by e.g.: Enabling the use of lightweight materials in transport applications leading to fuel efficiency Development of low friction in power plant and transmissions giving improved fuel efficiency Improved durability of components and systems Improved manufacturing efficiency Lower materials use To design effective surface engineering solutions we require good data for design 2
Sustainability and Measurement Three approaches to measurement Assess operating conditions in application, extract key conditions, model and then measure important parameters to achieve prediction of performance Issues: reliability of extracting key parameters, difficulty in modelling, choice of important parameters, extrapolation is difficult, but can be much cheaper Reproduce operating conditions exactly so that good reliable simulation performance can be achieved Issues: can we reproduce operating conditions well enough, can be very expensive Try it and see (field testing) Issues: Often doesn t work, so repeated iterations are expensive, in many cases you cannot do this for safety etc reasons 3
Coatings Measurement Measurements needed in areas such as: Thickness Chemistry Strength and adhesion Hardness and elastic properties Measuring wear and friction Durability Residual stress Aim is to make measurements simpler, more relevant, cheaper, more robust Standardisation can give improved framework for measurements 4
Measuring Coating Integrity by Bend 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 Video Strain gauge Acoustic emission Rollers Displacement Sensor Load cell Motor drive 5
Bend Testing Force displacement curves Acoustic emission 6
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 7
Bend Testing - Case Study Coated tube Compare performance of oxidised and unoxidised tube 900 800 700 Force vs displacement summary (all pipes) Coated 1 Coated 2 Coated 3 600 Ox 1000 1 Force (N) 500 400 300 Ox 1000 2 Ox 1000 3 Ox 1100 1 Ox 1100 1b 200 Uncoated 1 100 0 Uncoated 2 Uncoated 3-2 0 2 4 6 8 Displacement (mm) 8
Rockwell adhesion test Load Rockwell C indent made into coated specimen Fracture and delamination around indent indicates adhesion properties Radius of indenter, a Radius of delamination, r 9
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
Scratch Testing 40 80 70 Friction Force, N 30 20 10 AE Signal, db 60 50 40 30 0 0 20 40 60 80 100 Load, N 20 0 20 40 60 80 100 Applied load, N L c = 21.3 N load acoustic emission tangential force optical inspection of failure modes 11
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 800 600 400 200 Critical Load (Lc) 80 N 0 0 20 40 60 80 100 120 140 160 180 200 Indenter Load, N 12
Fracture Analysis in Scratch Testing First principle stress 13
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 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 15
Coupon Bending for Residual Stress Measurement 2.0 1.5 Substrate Finish and Thickness Fine, 1.2 Fine, 2 Fine, 3 Coarse, 1.2 Coarse, 2 Coarse, 3 0-50 Optical Flexus Height, mm 1.0 0.5 Deflection, μm -100-150 -200 0.0-60 -50-40 -30-20 -10 0 Distance,mm Optical microscope measurements on thermally sprayed coatings 1200 1100 1000 900 Profilometer measurements on Fecralloy Sample (574 MPa) -250-20 -10 0 10 20 30 Distance, mm Comparison between optical and profilometer measurements Residual Stress, MPa 800 700 600 500 400 300 200 100 Coarse Freund Fine Freund Coarse Stoney Fine Stoney 0 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 Substrate Thickness, mm Comparison between Stoney and Freund analysis LVDT jig 16
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) 3200 3180 3160 3140 3120 3100 3µm TiN on Steel Movie from http://www.novelengineers.com/lawave.ppt 3080 3060 Steel 0 20 40 60 Frequency, f (MHz) 17
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 18
Modulus against Frequency for TiN coated steel 1200 Extrapolation back to Zero khz gives a value for the modulus of the coating. 1000 Results from Euler- Bernoulli analysis of frequency shift Accurate film thickness is crucial (fourth power) Modulus E (GPa) 800 600 400 200 0 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) 0 5 10 15 20 25 30 35 40 Frequency (khz) 19
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 20
Gas Borne Particle Erosion Stepwise Analysis Ga s blast erosion test Supply tube Mixing chamber Ga s supply 0.020 M4 M6 Nozzle tube Working distance Nozzle le ngth Ab ra sive re se r voir Mass Loss, g 0.015 0.010 Specimen 0.005 Schematic diagram of gas blast erosion test system, ASTM G 76 (11) 75 ms -1 200 μm sand Normal incidence 20 mm stand-off 5 mm nozzle Increments from 0.1 gm to 4 or 15 gm (later stages) 0.000 0 50 100 150 200 250 300 Mass of Erodant, g Area Examined Erosion Damage 21
Stepwise Erosion Large Grain WC/Co Hardmetal 27.5 g 33.5 g 8 μm 22
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) 1564 1575 23
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 15 7.96 7.95 Arm Displacement(micrometres) 10 5 0 7.94 7.93 7.92 7.91 7.89-5 7.88 Displacement-sd Opto Probe 7.87-10 7.86 0 500 1000 1500 2000 2500 3000 3500 4000 Time (s) 7.9 Optical Probe Output (V) 24
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 25
Overall Friction Trend, 2010 Results Moist Air Friction Coefficient 0.12 0.10 0.08 0.06 0.04 0.02 0 5 10 15 20 25 Cycles Most Graphitic Balinit C* Balinit A Balinit DLC Alchrona TiAlN Friction behaviour is very similar with diamond probes for all coatings tested Compare with macro tests where TiN is ~0.6 DLC is ~0.1 Why? Friction controlled by diamond probes not samples Water present at interface Contact size effect 26
Different Material Probes Macro vs Micro 200 μm diamond probe, 100 mn 2 mm steel probe, 100 mn 10 mm steel probe, 10 N, pin-on-disc Friction Coefficient Moist Air 0.30 0.25 0.20 0.15 0.10 0.05 0.00 0 5 10 15 20 25 Pass Number Balinit C* Balinit DLC* Teer Graphitic Teer MOST TecVac TiAlN Y Axis Title 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 Balinit C* Balinit DLC* Teer Graphitic Teer MOST TecVac TiAlN 0 5 10 15 20 25 X Axis Title Friction Coefficient 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 Balinit C* Balinit DLC* Graphitic MOST TiAlN 0.0 0 2000 4000 6000 8000 10000 Time, s Dry N 2 Friction Coefficient 0.30 0.25 0.20 0.15 0.10 0.05 Balinit C* Balinit DLC* Teer Graphitic Teer MOST TecVac TiAlN 0.00 0 5 10 15 20 25 Pass Number Friction Coefficient 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 Balinit C* Balinit DLC* Teer MOST TecVac TiAlN 0.0 0 5 10 15 20 25 Pass Number Friction Coefficient 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 Balinit C* Balinit DLC* Graphitic MOST TiAlN 0.0 0 2000 4000 6000 8000 10000 Time, s 27
AFM Images TiAlN, air 10 μm indenter 1 pass 50 mn load 1 μm indenter 20 pass 100 mn load TiAlN sample Good resolution Note polishing scratches crossing main scratch (arrowed) Shows major mechanism is deformation 28 10 μm indenter 1 pass 50 mn load
TiAlN Scratch Profiles (AFM) Height, nm 50 0-50 -100-150 -200-10000 -5000 0 5000 10000 Distance, nm 1 pass 2 pass 10 pass 20 pass 50 pass 50 mn 1 μm indenter 50 mn 10 μm indenter Height, nm 20 15 10 5 0-5 -10-15 -20-25 -30-35 -40-45 -10000-5000 0 5000 10000 Distance, nm 2 pass 10 pass 20 pass 50 pass Height, nm 50 0-50 -100-150 -10000-5000 0 5000 10000 Distance, nm 1 μm 10 μm Used SPIP to obtain average profiles from scratches (average of 50) Shows uplift at edge of scratch (particularly for 1 μm) Width of scratch is same for 1 μm and 10 μm 29
Help Available? IOM3 Technology Hub on IOM3 Surface Engineering Division Board web site being developed to give guidance and access to literature Academic centres across UK 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 30
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 31