Quality and Process Variability in Ti-6Al-4V Powder Bed Electron Beam Additive Manufacturing

Transcription

1 Quality and Process Variability in Ti-6Al-4V Powder Bed Electron Beam Additive Manufacturing Northrop Grumman Aerospace Systems 2015 Euromold September 25, 2015 Eric Fodran, Ph.D.

2 EBM AM In-Process Surface Finish Optimization: Program Objective Developed and executed comprehensive DOE to evaluate EBM AM process parameters and identify parameters for most refined surface finish Targeted Attributes Layer thickness Powder size\distribution Energy source\beam characteristics Qty of beams Beam size\focus beam offset Beam velocity Preheat duration Quantify surface finish with representative geometric features (pocket depth, fillet radii, etc.) 2 Quantify mechanical performance as a function of process parameters and surface condition

3 Powder Size Distribution Histogram of Powder Size Distribution Normal 40 FMW 30 TIMET 40 A metek Frequency A RC A M V irgin Pow der A RC A M O ld In Process Particle Diameter (μm) 3 Variable N Mean StDev Min Q1 Median Q3 Max FMW TIMET ARCAM Virgin Powder ARCAM Old In Process Ametek

4 Design of Experiment Development and Execution 5 Factor DOE developed with up to 3 levels within each factor Results in 38 unique sets of process parameters 12 experimental builds with 4 coupons within each build to execute all experimental combinations 4

5 Representative Results: DOE Builds 4-6 5

6 Post-AM Processing Surface Finish Enhancement Optimized process parameter static and dynamic performance assessment in work Post- AM surface finish process evaluation Improvement in overall surface finish: Legacy baseline average of μin Achieved <180 μin with DOE optimized process parameters Achiev <50 μin with post-am processing Surface Finish Evaluation Coupons Surface Finish Process As-EBM Built, Timet 50 micron layers Chemically- Assisted Aggregate Chem Mill + Chemically-Assisted Aggregate Engineered Aggregate Supplier None REM Ducommun* + REM MicroTek 6 Example Result (R a ) Min. 173 µin 191 µin 139 µin 27 µin Mean 599 µin 515 µin 271 µin 227 µin * Chem mill did not trade favorably as a stand-alone post-process

7 EBM AM Mechanical Properties Assessment: Tensile Properties Elastic Modulus (Msi) 0.2% Offset Yield Strength (ksi) Ultimate Tensile Strength (ksi) Elongation Increase (%) Reduction of Area (%) Legacy Arcam, machined Legacy Arcam, as-fabricated Optimized AM Processes, machined Optimized AM Processes, as-fabricated

8 8 EBM AM Mechanical Properties Assessment: Fatigue Properties

9 EBM AM Mechanical Properties Assessment: Fatigue Properties 9

10 Variability of Additive Manufacturing for Aerospace Structures: Program Objective Develop a model-informed probabilistic approach to quantify the variability associated with AM materials and processes Framework targeted at extracting the most information out of a series of efficient experiments utilizing prior knowledge to minimize overall test requirements Benchmark process capability of multiple AM processes spanning multiple sectors Satellite Airframe Liquid Rocket Propulsion Quantify risk of using AM for aerospace applications Material integrity, property variability, inspectability, surface finish, etc. Develop a method of analysis to identify future manufacturing practice and equipment enhancements for reduced product quality variability 10

11 Variability Assessment of Additive Manufacturing (AM) for Aerospace Applications Powder Bed Electron Beam (Ti-6Al-4V) Arcam Cross Cutting AM Technology Impact Pervasive DoD / Aerospace Impact Sources of Variability Service Provider Inter-OEM Model Itra-OEM Model Powder Recycling Maintenance Interval Layer Thickness Parts in a Build Part Feature Orientation Thick vs. Thin Features Vicinity to Build Plate Quality Metrics Surface Finish Dimensional Tolerance Mechanical Performance Porosity size/density Probabilistic Framework Multi-Stage Nested Factor DOE Adaptive Bayesian Optimal Design Iterative Updating of Prior Information Test Matrix Validation via Physics-Based Models Adaptive Test Articles TRL Process Product Fundamental AM Material and Process Development Preliminary Machine Parameters Preliminary Feed Stock Parameters Cost Trades Practical Applications / Reliability Supply Chain Management Process Development Variability Studies Efficiency, Performance, and Production Material Specifications Process Specifications NDA and In-Process Monitoring 11

12 Ti-6Al-4V EBM Test Article ID Z-Height (in) Thickness (in) Angle (deg) A A A A A A B C C C C C C

13 Post-Build Material Quality Measured via CT Multiple build sequences completed Begun to characterize anomalies throughout components Size Location Vicinity to free surface Vicinity to other defects Clustering All parts are characterized in pre-hip condition 13 CT has been identified as a limiting factor Attempting to overcome geometry limits of process

14 Conclusions and Recommendations Conclusions Ability To Significantly Impact Surface Finish Achieved Powder size distribution Powder morphology Arcam process parameters Ability to Further Refine Surface Finish via Post Additive Manufacturing Processes can also be achieved Begun quantification of effects of surface finish on mechanical properties Current Variability Assessment Program Indicates Significant Effects Of Process Variability On Component Quality Support structure Build layout\component orientation Ongoing and Further Potential Future Development: Computational Build Design Interrogation Tool Evaluates effects of part geometry and build layout on process parameters Assesses whether process parameters fall within safe operating zone Provides opportunities to modify part and/or build Post-Build Interrogation Tool Evaluates build log file for indications of potential failure Thresholds for part rejection are set by TBD industry specification 14

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