1. Jianliang Lin, Sterling Meyers, Brajendra Mishra, Sudipta Bhattacharyya, Peter Ried,, John J. Moore Advanced Coatings and Surface Engineering Laboratory (ACSEL) Colorado School of Mines Acknowledgements: NADCA/DOE Premier Tool & Die Cast, SPX Contech, GM Powertrain, H-L, Leggett and Platt, St. Clair Balzers, Hardchrome, Ion Bond, Phygen, Teer Coatings THE DEVELOPMENT OF A SURFACE ENGINEERED COATING SYSTEM FOR ALUMINUM PRESSURE DIE CASTING DIES: TOWARDS A SMART DIE COATING

2. Methodology Graded interlayer working layer H13 50 nm adhesion layer Determine the most promising working layer - Sessile drop - Soldering (DSC) - Ease of release - Tribological - In-plant trial test Design an optimal coating architecture by FEM Develop the optimized coating architecture by P-CFUBMS Field and Service testing Work done by K.Kearn, O. Salas, A. Kunrath, J.Lin Work done by S.Carrera - Multimode tester - Coating degradation - Soldering (DSC) - Ease of release J. Lin & S. Myers is working on this

3. Optimized Coating System Overall coating thickness is about 5-8 m Deposition of CrN and AlN binary phase Deposition of CrAlN Deposition of (Al,Cr) 2 O 3 working layer Deopsition of CrN/CrAlN graded layer Deposition of the overall optimized coating architecture Steps to the goal: H13 die substrate Plasma nitro- carburized Cr (60-100nm) CrN Cr x Al 1-x N Multilayer or Compositionally graded (Al,Cr) 2 O 3

4. Cr-Al-N film Deposition Using P-CFUBMS Optimize the substrate to chamber wall distance (fixed substrate position) Deposit CrAlN film with rotation system Optimize the working pressure and N 2 partial pressure Optimize the Al concentration in CrAlN films

5. Cr-Al-N films deposited at different substrate to chamber wall distances Cr Al The ion energy in the plasma is different at different substrate positions Pulsed closed field unbalanced magnetron sputtering system

6. GIXRD results All Cubic 1000W Cr-1100W Al 20 at% Al in film

7. Nano-hardness and Young s Modulus

8. Ball-on-disk test and coefficient of friction Ball on disk wear test: Micro-tribometer Counter part: 1mm WC ball Applied force: 3N Travel length: 100m

9. Photomicrographs of wear tracks after 100m travel 5 inches6 inches7 inches 8 inches9 inches

10. Wear volume and wear factor of Cr-Al-N films 3D profile of the wear track 2D profile of the wear track

11. Ion energy distribution (IED) of N(29) in plasma

12. SEM photomicrographs at cross-section of Cr-Al-N films 1000W Cr-1100W Al pulsing both 100kHz at 1 s 5 inches 6 inches 7 inches 8 inches

13. Cr-Al-N film Deposition Using P-CFUBMS Optimize the substrate to chamber wall distance (fixed substrate position) Deposit Cr-Al-N film with rotation system Optimize the working pressure and N 2 partial pressure Optimize the Al concentration in CrAlN films

14. Cr-Al-N film deposited with rotation system Deposition parameters: Total Pressure: 2mTorr; N 2 :Ar = 75:25 1000W to Cr target, 1100W to Al target -50V substrate bias Planetary rotation system with substrate to chamber wall distance ~ 4.5 inches To avoid the formation of superlattice structure, the minimum rotation linear speed is 10 cm/sec, which was calculated from the system geometry and deposition rates Rotation linear speed used: ~ 12 cm/sec Cr Al

15. Cr-Al-N film deposited with rotation system Ra=30.33nm The mechanical properties and surface roughness of Cr-Al- N film deposited with rotation system can be compared with those films deposited at fixed far positions Ra=28.67nm Ra=7.01nm

16. Cr-Al-N film Deposition Using P-CFUBMS Optimize the substrate to chamber wall distance (fixed substrate position) Deposit CrAlN film with rotation system Optimize the working pressure and N 2 partial pressure Optimize the Al concentration in CrAlN films

17. Optimized working pressure and N 2 partial pressure The optimized working pressure is 2 mtorr and N 2 partial pressure is 75%

18. Cr-Al-N Films Deposited at 2mTorr with –50V Substrate Bias p N2 =1 mTorr, 50% N 2 p N2 =1.2 mTorr, 60% N 2 P N2 =1.5 mTorr, 75% N 2 p N2 =1.6 mTorr, 80% N 2 2 m Decreased deposition rates

19. Cr-Al-N film Deposition Using P-CFUBMS Optimize the substrate to chamber wall distance (fixed substrate position) Deposit CrAlN film with rotation system Optimize the working pressure and N 2 partial pressure Optimize the Al concentration in CrAlN films

20. P-CFUBMS Deposition Matrix Cr target power (W) Al target power (W) Al/Cr target power ratio Working distance (inches) Working pressure (mtorr) N 2 :Ar Bias (V) 400 1 8 275:25-50 4006001.5 4008002 40010002.5 40012003 40014003.5 2008004 20010005 20012006 20014007 Optimized in previous work Multilayer or Compositionally graded Cr x Al 1-x N or Ti x Al 1-x N (Al,Cr) 2 O 3 Increasing Al content in the intermediate layer X=?

21. XPS of Cr-Al-N films Al:Cr target power ratioCArOAlCrNAl/(Al+Cr) 111.41.510.65.835.934.813.9 at% 3.57.11.710.018.522.340.345.3 at% 64.52.110.320.119.144.051 at% 73.82.210.421.316.745.658 at% All samples exhibit similar Cr 2p, Al 2p, N 1s high energy spectra Cr 2p photoelectron spectra Al 2p photoelectron spectraN 1s photoelectron spectra Survey spectrum results: CrN 584.8eV and 575.4eV AlN 74.2eV Al 2 O 3 75.2eV CrN/AlN 397eV

22. Optimize Al contents in Cr-Al-N films Hexagonal phase appeared Al:Cr target ratio Al/(Al+Cr) 58 51 45.3

23. Lattice parameter change

24. Nano-harness and Youngs Modulus of Cr-Al-N films Higher H/E ratio indicates good wear resistance and good toughness The highest hardness is about 36GPa hexagonal cubic cubic+ hex

25. Wear resistance and COF Ball-on-Disk wear test: Micro-tribometer Normal load: 3N Counterpart: 1mm WC ball Travel length: 100m

26. Summary of P-CFUBMS of Cr-Al-N films An Optimized coating architecture used for Al pressure die casting dies has been proposed Cr-Al-N intermediate layer with good mechanical properties and dense microstructure has been successfully deposited. Deposition of Cr-Al-N coatings with a planetary rotation system has been successfully demonstrated. The critical Al concentration in the Cr-Al-N coatings has been determined. On-going work: –Deposition of the (Al,Cr) 2 O 3 working layer –Deposition of the compositionally-graded Cr-Al-N intermediate layer

27. After each trial, half of pins: Dissolved in NaOH/Industrial Degreaser and characterized using Stereography and SEM Removing lubricant and Al from pins quite painstaking. Typical removal times at least 3 weeks in ultra-sonicator. Other half of in-plant trial pins No dissolving Cross-x cut and prepared for metallographic & SEM characterization Becoming quite difficult due to coating removal while performing metallographic prep work 2 nd In-Plant Trial Pins: Leggett & Platt Selected Core Pins 3n 2n 1n 100% of Typical pin life Shots / Cycles (n) 1 st In-Plant Trial Pins: Premier Tool & Die

28. In-Plant Trial Pins Same Pin; Lubricant Removed Conclusion: Pin after 10k shots contains no visible defects New Pins ¼ ins

29. Preliminary Results Stereographic Results CrN, CrC-TiAlN coatings show few signs of wear TiN-TiAlN, Cr/TiN- TiAlN illustrate more signs of wear FeNC surface treatment show most signs of wear and soldering SEM Results Data still not produced Edge retention of coating lost during metallography

30. One can measure the adhesion/soldering strength of the pin by separating the pin and solidified Al using a tensile testing machine with a calibrated load cell The pin must be pulled perpendicular to the solidified Al axis to assure same stress levels Ease of Release Test

31. Load/time curves – ease of release test critical load (Lc)

32. Experimental program: ease of release tests ControlACSEL G-Cr/NCrC- TiAlN ML- TiN/TiAlN Plain 333333 FeCN 333333 Ion- nitrided 333333

33. Smart die coating: experimental architecture Adhesion layer Die steel substrate Ti/Cr Surface modification of the substrate Working layer Intermediate layer Adhesion layer Die steel substrate Ti/Cr Surface modification of the substrate Working layer Intermediate layer (TiAlN) Adhesion layer Die steel substrate Ti/Cr Surface modification of the substrate Working layer Piezo. Film 1 3 2 V 3 (Sensor voltage) Thin-film Electrodes (Sputtered Ti) Stress (in-plane) Sensor module Stress (out of plane) Non piezoelectric Insulation layer (d= thickness)

34. Choice of active sensor material Requirements: Figure of MeritsPZT AlNZnO LiNbO 3 Current response: e 31,f (C m -2 )-14.7 -0.7-5.8 Voltage response: e 31,f / o 33 (GV m -1 ) -1.2-10.3 -7.2N/A Coupling Coefficient (k p,f ) 2 on Si 0.20.110.06 0.02 Curie Temperature T c ( C) ~300~1100 N/A 1210 CTE ( 10 -6 K -1 ) 7.24511 AlN appears to be the most promising of all, due to its high insulation, and good mechanical compatibility with the host structure (Ti-Al-N, Ti, and Cr). CTE: H13 11x10 -6 K -1 ; Ti 8.6x10 -6 K -1 ; Cr 4.5x10 -6 K -1 ; Pt 8. 8x10 -6 K -1 ; (LiNbO 3 also has potential with CTE match with H13)

35. Deposition details Base Pressure Operating Pressure Sputter gas PowerTime 1 X 10 -6 Torr3-30 mTorrArgon200-500 W5-10 min. Electrode deposition (Ti, Pt/Ti) (DC magnetron) Base Pressure Operating Pressure Sputter gas FrequencyPowerTime 1 X 10 -6 Torr10-50 mTorrArgon & Nitrogen 100 kHz200-300 W30 min.- 1 hr. Deposition of the piezo-layer (AlN) (Pulsed DC magnetron)

36. Methods to test the prototype sensor architecture: Dynamic testing: Indirect method (Plank method) Static testing: Direct method Substrate Electrode Aluminum nitride Electrode clamp Damping element Piezo-cantilever: cross section In-plane tensile stress ( 12 ) integrator ( 12 ) Load (Quasi-static) substrate electrodes Piezo-layer Output charge 31. 12 Apply pressure Release pressure Induced charge t (Sec.)