Temperature Simulations and Measurements p for Process - PowerPoint PPT Presentation

Advanced Qualification of Additive Manufacturing Materials Workshop Manufacturing Materials Workshop Temperature Simulations and Measurements p for Process Qualification in Powder-Bed Electron Beam Additive Manufacturing Electron Beam Additive Manufacturing Kevin Chou Kevin Chou Professor Mechanical Engineering Department The University of Alabama The University of Alabama Assistant Director for Technology Advanced Manufacturing National Program Office g g U.S. Department of Commerce July 20, 2015

Disclaimer and Note • The materials presented and opinions expressed in this seminar were solely from the presenter himself. They do not represent the viewpoints of The University of Alabama, nor the Advanced Manufacturing National Program Office. • The materials presented in this seminar are mainly from the following articles. Cheng, B., S. Price, J. Lydon, K. Cooper and K. Chou, " On Process Temperature in Powder ‐ Bed – El Electron Beam Additive Manufacturing: Model Development and Experimental Validation ,” Journal t B Additi M f t i M d l D l t d E i t l V lid ti ” J l of Manufacturing Science and Engineering , Vol. 136, No. 6, pp. 061018 (1 ‐ 12), 2014. – Price, S., B. Cheng, J. Lydon, K. Cooper and K. Chou, " On Process Temperature in Powder ‐ Bed Electron Beam Additive Manufacturing: Process Parameter Effects ,” Journal of Manufacturing Science and Engineering , Vol. 136, No. 6, pp. 061019 (1 ‐ 10), 2014. Science and Engineering , Vol. 136, No. 6, pp. 061019 (1 10), 2014. – Gong, X., J. Lydon, K. Cooper, and K. Chou, “ Beam Speed Effects on Ti ‐ 6Al ‐ 4V Microstructures in Electron Beam Additive Manufacturing ,” Journal of Materials Research , Vol. 29, No. 17, pp. 1951 ‐ 1959, 2014. – Gong, X., J. Lydon, K. Cooper, and K. Chou, “ Characterization of Ti ‐ 6Al ‐ 4V Powder in Electron ‐ Beam ‐ g, , y , p , , Melting Additive Manufacturing ,” International Journal of Powder Metallurgy , Vol. 51, No. 1, pp. 1 ‐ 10, 2015. Contact information: Kevin Chou, kchou@eng.ua.edu, 205 ‐ 348 ‐ 0044 2

Quality Control in AM Material and Process Material and Process ∆ 2 ∆ 2 Process Part ∆ f ∆ ∆ 1 EBAM Process Video EBAM Process Video Feedstock GE Aviation ∆ f = Fn ( ∆ 1 , ∆ 2 , etc.) 3

EBAM System Characteristics EBAM System Characteristics EBAM machine ( (example, old model) l ld d l) Build chamber High power Leaded glass 60 keV electron gun High strength glass No moving part Heat shield Sensor access limitation 4

EBAM Viewport Window EBAM Viewport Window Metal Leaded Shutter Glass Build Build Area Machine Outside Heat Sacrificial Vacuum Shield Glass Glass Machine Inside Metalized film deposit 5

EBAM Process Characteristics Speed Function (SF) 1000 18 900 16 800 14 14 Beam Speed (mm/s) Beam Current (mA) 700 12 600 10 500 8 400 6 300 B B 4 200 100 2 0 0 0 5 10 15 20 25 30 0 5 10 15 20 25 30 Build Height (mm) Build Height (mm) Beam Speed = function (SF, height) B S d f ti (SF h i ht) 1800 Vacuum (little He) y = 24.133x - 12.631 R² = 0.9996 Layer 95 1600 (6.65 mm) Pre-heating, sintering y = 20.211x - 12.612 R² = 0.9996 Layer 97 1400 y = 17.866x - 25.355 y (6.79 mm) Warm process (> ~650 ˚ C) W ( 650 ˚ C) R² = 0.9988 Layer 153 1200 Beam Speed (mm/s) y = 10.587x - 0.4949 (10.71 mm) High scanning speed R² = 0.9997 Layer 155 1000 (10.85 mm) Process parameters change 800 Layer 223 (15.61 mm) through the build g 600 Layer 225 (15.75 mm) (15 75 mm) Metalizing film 400 Layer 347 (24.29 mm) Slow post-process cooling 200 Layer 349 (24.43 mm) 0 6 0 10 20 30 40 50 60 70 Speed Function Index

EBAM Process/Material Studies EBAM Process/Material Studies Process Physics Process Physics Temperature Temperature Simulation (2) AM Part (4) Powder-Bed (1) Powder-Bed (1) Ti-6Al-4V Temperature Measurement (3) 7

(1) Feedstock Characterization (1) Feedstock Characterization   Powder-Bed Particles, Porosity √ √ - Metallography, Micro-CT √  Thermal Conductivity - Hot-Disk Thermal Analyzer Hot Disk Thermal Analyzer 8

Preheated Powder Z-plane X-plane 9

Porosity Study - Micro-CT y y  10 mm Ti-6Al-4V Cube (hollow)  Skyscan 1172 Micro CT  Skyscan 1172 Micro-CT  Size/Porosity Distribution ~ 2 μ m resolution ~ 2 μ m resolution Loose powders Sintered powders 10

Porosity and Powder Size y  Powder-Bed Porosity, ~ 50%  Particle Size Distribution  Particle Size Distribution Major: ~ 30 to 50 μ m (a) (b) 11

Powder Thermal Conductivity  TPS2500 S Thermal Analyzer (Hot Disk) - Solid and Hollow samples Hollow sample with Solid vs. Hollow 12 shell removed (1 side)

Powder Thermal Conductivity  Sintered Powder Specimens 13

(2) Temperature Simulation - Finite Element Modeling  Heat Transfer √ √ √  Heat Source  Heat Source  Material/Powder Properties √  Latent Heat of Fusion √ √ 14

Governing Equations g q Heat Transfer           ( ( c c T T ) ) ( ( c c T T ) )       p  p ( k T ) Q v s   t x T - Temperature  Q - Absorbed heat flux   x y z , , c - Specific heat capacity Latent Heat of Fusion ρ - Density λ - Thermal conductivity          v s - Constant speed of the C d f h H T cdT d L f f f moving heat source  0  T T ,  S   T T Assumptions: p f  f      T T T T T T , S   S S L L  T T   Heat Conduction L S  T T  1  L  Negligible molten flow within molten pool  Radiation considered as boundary condition Δ H f - latent heat of fusion   Uniform temperature as the part initial temperature T l - liquidus temperature T s - solidus temperature f s - solid fraction 15

Heat Source Equations Intensity distribution: a conical source:  Horizontal – Gaussian distribution  Vertical – Decaying with increasing of penetration depth η - electron beam efficiency coefficient U - voltage U voltage I b - current S - penetration depth Φ E - beam diameter Φ E beam diameter x S , y S - horizontal position of heat source center H s - Gaussian heat source, Cline and Anthony I z - penetration function, Zäh and Lutzmann p , z 16

Simulation Example p Process Simulation Animation

(3) Temperature Measurements - Near IR Thermography  Spectral Range √  B ild A  Build Area View Access √ √ Vi A  Resolutions (Spatial/Temporal) √  Emissivity √  Transmission Loss  Transmission Loss √ √ 18

EBAM Temperature Measurements Measurements Near Infrared Thermal Imager  LumaSense MCS640  Spectral Range: 780 – 1080 nm Spectral Range: 780 – 1080 nm  640 by 480 FPA (Amorphous Si based)  Temperature Range: 600 to 3000 ˚ C Temperature Range: 600 to 3000 C (3 domains)  Frame Rate: Max. 60 Hz  Lens: ~ 500 mm Focal Distance Lens: 500 mm Focal Distance  View Area: 32 mm by 24 mm  Spatial Resolution: ~ 50 µm Challenges: Emissivity and Transmission 19

Measurement Setup Emissivity (Single Setting, Estimated) Emissivity (Single Setting, Estimated) Transmission (Calibrated, 3 Ranges, with Glasses) Heat shield 20

NIR Video Examples p Build model: NIR Video 1 25. 4 mm square block High Temperature Range Medium Temperature Range NIR Video 2 21

Temperature Profile Analysis (Hatch Melt) (Hatch Melt) Single Frame (Raw Data) Average (One Video)

Transmission Loss Study Lighter side Darker side Controlled Controlled Exposure Viewing Area Sacrificial glass with two levels of metallization. Thermal image on lighter side Thermal image on darker side

Controlled Exposure Experiment p p Temperature Profiles Observed Through Different Levels of Metallization 2600 2500 2400 2250 2200 2200 y = 1 1602x y = 1.1602x - 171.85 171 85 de Temperature (C) R² = 0.9822 2000 2000 mperature (C) 1800 1750 Light Side 1600 Tem Lighter Sid D Dark Side k Sid 1400 1500 1200 1250 1000 800 1000 -8 -6 -4 -2 0 2 1000 1250 1500 1750 2000 2250 2500 Distance (mm) Darker Side Temperature (C) Average Temperature Profiles g p Relationship Between p (6.37 mm Build Height) Temperatures Observed Through Different Levels of Metallization 24

Molten State Emissivity Estimate y 1. Identify Measured Liquidus 1. Identify Measured Liquidus Temperature 2. Solve for Apparent Liquidus Temperature, (function of measured liquidus temperature, d li id t t assumed emissivity, etc.) 3. Solve for True Emissivity, (function of True Liquidus ( q Temperature, Apparent Liquidus Temperature, etc.) Estimated molten Estimate Estimate pool ε : ~0.28 Estimate ε true with T app ( ε =1), ε true value T m true T m , with T m with T m m measured d T app measured 25

Temperature Profile Compensation p p 3000 Uncompensated 2600 Compensated for Transmission Loss e (°C) Compensated for 2200 Transmission Loss and emperature Emissivity Adjustment 1800 1400 Te 1000 600 600 -7 -6 -5 -4 -3 -2 -1 0 1 2 Distance (mm) Average Temperature Profile (6 37 mm Build Height) Average Temperature Profile (6.37 mm Build Height) 26