ICME Design of Ni Superalloys and Optimization for Additive Manufacturing

Transcription

1 ICME Design of Ni Superalloys and Optimization for Additive Manufacturing 31st Annual Meeting Jiadong Gong, PhD Senior Materials Design Engineer QuesTek Innovations Mar 24, 2014 p. 1

2 Outline ICME Background Case Study: Single Crystal Ni Design and Modeling Prototype and Characterization Additive Manufacturing of Ni Alloys Conclusion and Future p. 2

3 The ICME methodologies ICME: a paradigm change from the traditional empirical methodologies methods Traditional Empirical Methods ( trial and error ) ICME Methodologies (Materials by Design ) Empirical approach Genotypic mechanistic-based approach p. 3

4 Computational Materials Design Overview p. 4

5 QuesTek s ICME based Materials by Design Combines rigorous stage gate materials design process with proprietary: Thermodynamic & kinetic elemental databases Materials-specific software Mechanistic models (input chemistry and processing) for prediction p. 5

6 QuesTek ICME Architecture p. 6

7 ICME/MGI framework for Materials by Design p. 7

8 Case Study: Single Crystal Ni Superalloy for IGT SX castings High Temperature Performance Desirable from a creep standpoint no grain boundaries IGT blade castings are large > 8 inches Slower solidification / cooling rates exacerbate processing issues (below) Primary casting (processing) constraints: Freckle formation Formation of high angle boundaries (HAB) and low-angle boundaries (LAB) Hot-tearing Shrinkage porosity 3 rd generation blade alloys are especially difficult to cast as SX due to their high refractory content Increased tendency for hot tearing Increased tendency for freckle formation QuesTek s proposed approach: ICME-based design of a new processable, highperformance single crystal alloy for IGT applications p. 8

9 Systems design chart for SX castings p. 9

10 Modeling and design tasks Thermodynamic and kinetic database Freckling model Processing design (HT windows, incipient melting) γ + γ Including γ coarsening model TCP, HAB and LAB Models used in Phase I design Creep modeling (intermediate temperature) Calculation of Reed-D for existing alloys (climb-controlled creep) Develop explicit vacancy diffusivity model Oxidation/alumina formation Indirect consideration during Phase I design (for further expansion in potential Phase II) Alloy design Alloy design in Phase I p. 10

11 List of benchmark alloys ID Re Al Co Cr Hf Mo Ta Ti W other PWA PWA C GTD C CMSX CMSX PWA CMSX Rene N Y CMSX Nb TMS Ru Re-free alloys Recentlydeveloped 2 nd Gen alloys High-Re alloys QuesTek s Phase I design ( QT-SX ) contained these same elemental constituents, but with 1% Re p. 11

12 liquid density, g/cm3 Modeling of liquid density during solidification Freckle-resistance is related to the modeling of the liquid density during solidification base on a critical Rayleigh number: ReneN5 Liquid density vs. T liquidus % Actual modeling output is a combined use of various databases and software % ,320 1,330 1,340 1,350 1,360 1,370 1,380 1,390 1,400 1,410 1,420 Temperature, C p. 12

13 Coarsen rate and liquid density difference comparisons (lower is better) 1.40E E E E E E E E+00 (a): Coarsening Rate Constant for different alloys (b): Liquid density difference at 20% solidification Comparable coarsening rate to CMSX-8 (1.5% Re) alloy Reduced buoyancy differences (less than non-re CMSX-7) p. 13

14 1 st round of casting results Simulation of chosen casting scenario with N5: (a) R contour (b) G contour (c) location designations One tree (four castings) produced by PCC from both N5 and QT-SX (left) Setup of the small scale test slab cluster (right) Picture of actual casting with N5 showing a bi-grain formation, p. 14

15 As-cast microstructures Along growth direction Transverse QT-SX ReneN5 p. 15

16 Modeling freckling behavior in N5 and QT-SX castings Target this range (>B, <A) p. 16

17 2 nd round of casting results p. 17

18 2 nd round of casting results p. 18

19 Single Crystal Microstructure of fully heat treated alloys after double-step aging Characterization and microstructure analysis confirm the achievement of the design goal of γ phase fraction and lattice misfit (no evidence of TCP phases were found during all heat treatments) p. 19

20 Atom-probe (LEAP) analysis of the QT-SX nanostructure γ' γ γ' γ γ' γ' γ' γ' Excellent agreement with predicted compositions (γ comparisons below) Ion, at.% Cr % Ni % Co % Al % Hf % Mo % Re % Ta % Ti % W % LEAP LEAP Prediction < p. 20

21 Evolution of microstructures during long-term exposure at elevated temperature p. 21

22 Oxidation modeling progress Continuous Al 2 O 3 and Cr 2 O 3 formation Wahl applied Wagner s model to multicomponent systems y 0 0 M y MC1 = πg 2ν N D O V Alloy o D M V MO 1/2 Oxygen concentration computed at FCC/Oxide* boundary assumed to be the content in FCC when the spinel forms Both Al 2 O 3 and Cr 2 O 3 expected to form at high T Internal Al 2 O 3 expected to form below 850 C Model agrees well with experimental data for benchmark alloys p. 22

23 Oxide characterization QTSX oxidized in air for 100h at 900 C, 1000 C and 1100 C EDS mapping of continuous oxide in QTSX alloy heat treated for 100h at 1000 C. Continuous Al-rich oxide observed in all samples p. 23

24 QuesTek Creep Modeling Gamma Coarsening Rate Constant Reed creep merit index: Assumes that the diffusivity at the γ/γ interface controls the climb process = rate controlling mechanism during creep Alloy Creep merit index (m -2 s *10 15 ) Coarsen K MP *10 20 CMSX PWA CMSX TMS QTSX René N TMS PWA Re free 1 wt.% Re 3 wt.% Re 5 wt.% Re QTSX is predicted to have creep behavior similar to alloys containing higher amount of Re, like the 2 nd generation alloys p. 24

25 Oxidation-Creep merit Summary 1000 C parameters should be maximized for improved behavior QTSX is predicted to have creep behavior and oxidation behavior similar to benchmark alloys, and is not necessarily sensitive to compositional variations p. 25

26 Experimental creep data Resistance to creep: Maximize Larson-Miller parameter (LMP) Time to rupture at given temperature and stress QTSX is measured to have creep behavior similar to the 2 nd generation alloys, confirming the design prediction. p. 26

27 Summary: Single Crystal Ni Superalloy for IGT A demonstration of successful computational Materials by Design methodologies A final round of full IGT-size casting will be performed to serve as the final validation of the highly processable design Further characterization and testing is on-going for accelerated qualification and insertion p. 27

28 Additive Manufacturing of Ni Superalloys QuesTek is participating the DARPA Open Manufacturing Program on the additive manufacturing of 718Plus Ni-Superalloy, collaborating with Honeywell Aerospace. Acknowledge: DARPA contract number HR C p. 28

29 Yield Strength Prediction for Additive QuesTek predicted Yield Strength based on actual production heat treat parameters and microstructure: Cooling rate from solution temperature DMLS Grain size and evoluation Stress Relief HIP Solution Age DMLS IN718PLUS RT yield strengths are better than Cast IN718PLUS but significantly lower than Forged IN718PLUS Acknowledge: DARPA contract number HR C Based on initial Uncertainty Quantification findings, QuesTek calibrated YS model using APB energy and following the probabilistic methodology developed under the DARPA AIM program. Use or disclosure of information contained on this page is subject to the restrictions on the cover.

30 Additive Manufacturing of Ni Superalloys Other Additive Fronts at QuesTek: Solid Solution Ni-base Superalloy: The microstructure and property modeling for the additive processing of a Ni-Cr-W-Mo alloy that combines excellent high-temperature strength and oxidation resistance with superior long term stability and good fabricability. High fraction Ni-base Superalloy: The composition and process optimization of a Ni-base superalloy commonly used for blade rings and high pressure turbine blades. It is traditionally a polycrystalline cast alloy with exceptional high temperature strength (high precipitate fraction), corrosion and oxidation resistance. p. 30

31 Conclusions and Future Directions Thermodynamic and process modeling tools have been developed/applied to the design of highly processable high creep strength Ni-base single crystal superalloys CALPHAD calculations and PrecipiCalc simulations optimized the design and the heat treatment process The predictions are in good agreement with the experimental observations of the microstructures and the compositions validated via SEM and LEAP Prototypes has been produced and the testing results show excellent properties and high potential for market success The ICME tools and databases are also playing a critical role in the composition and process optimization of the additive manufacturing process of Ni-base alloys Future research and development will help accelerate scale-up, manufacturing optimization, qualification and insertion of the materials p. 31

32 Thank you! You are welcome to contact us for licensing, producing, application inquiries or further development cooperation! Questions? p. 32

33 Back up p. 33

34 Oxidation merit calculations using Ni7 database 1000 C Oxidation prone Oxidation merit index : combine ΔG and Val eff into one parameter, for easy ranking of alloys distance from point to line Re free 1 wt.% Re 3 wt.% Re 5 wt.% Re Oxidation resistant Alloy Oxidation merit index PWA CMSX TMS-138A QTSX CMSX René N TMS CMSX PWA CMSX TMS p. 34