Electron Beam Wire-fed Deposition of Titanium Alloys for Repair Applications
Bibliographic record
Abstract
AM has revolutionized manufacturing with its advantages and applicability in various sectors. In aerospace, components are fabricated from high-strength materials, such as titanium alloys. Hence, application of AM to fabricate and repair Ti6Al4V alloy has been of research interest. However, during service, the components are subjected to wear and fatigue stresses. Though part replacement may be the only option in the case of extensive damage, considering the cost and sustainability challenges, the repair is beneficial. Therefore, reliable repair procedures are required.A fully coupled 3D transient thermo-mechanical finite element model was developed to simulate the EBWF process. The model has been validated using multiple EBWF Ti6Al4V coupons. Wall geometry wrought plates were used as substrates. Thermocouple measurements were recorded to validate the simulated thermal cycles. Model was proven to be reliable in terms of predicted temperatures, residual stresses, and distortion. The average error in the model was 3.7% in terms of thermal predictions. Mechanical validation measurements showed that the maximum deviations in the model were 100 MPa in residual stresses and 0.05 mm in distortion. Tensile residual stresses were observed in the deposit and the heat-affected zone, while compressive stresses were observed in the substrate.The effect of initial residual stresses on the repair integrity is critical. Hence, the effect of the initial substrate microstructure and residual stress on the final deposit properties was investigated. Three types of substrates were studied: wrought, LPBF, and EBWF plates. The results revealed that the EBWF additive repair for Ti6Al4V <350 μm yielded distortion and <150 MPa residual stresses. On the substrate stress relaxation was more dominant than residual stress development during EBWF. This showed initial residual stress of the substrate had no effect on the final residual stresses. Similar mechanical properties were observed for all substrate conditions. Deposited test specimens had YS and UTS values ranging between 800-830 MPa and 860–880 MPa, respectively. All tested specimens deformed and ruptured from deposited material above the interface. The similar mechanical properties of the interface were correlated with the microstructural features such as layer bands and α colonies.This study also focused on the microstructural evolution and local properties of the Ti6Al4V EBWF deposits. The investigation focused on extending the understanding related to the microstructural zones of transient and steady-state as well as banding phenomenon in EBWF deposited Ti6Al4V. Mechanical properties of these zones were evaluated through microhardness and miniature tensile testing. Although microstructure observed in these zones were different in terms of morphology and scale, their tensile properties were similar. The measured properties of the miniature specimens were comparable with E8 standard sized specimens, higher than the ASTM F1108 cast and lower than the AMS 4911P wrought Ti6Al4V standards.Finally, the expertise gained in previous studies was combined to perform a post-service Ti8Al1Mo1V compressor blade tip repair using Ti6Al4V wire and EBWF deposition technology. Residual stresses on the compressor blade after repair were lower than initial residual stresses due to the stress relaxation. The highest distortion after the repair was below 100 μm. Previously utilized miniature tensile testing has been adopted to investigate interface strength of the repair. The YS, UTS and elongation at break of the tested miniature specimens ranged between 869-906 MPa, 925-956 MPa, and 10-11%, respectively. Tensile properties of the interface met the minimum requirement of AMS 4911P wrought specifications. Fractography analysis showed that failure occurred in the additively deposited repair section. This work demonstrated that EB-WF deposition technology can be successfully utilized for repair applications
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".