Effects of LDED Scanning Strategies on Deposition Defects, Microstructures and Properties of Ti6Al4V Coatings

WU Di; LIU Gang; ZHAO Man

doi:10.16490/j.cnki.issn.1001-3660.2025.13.013

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Surface Technology ›› 2025, Vol. 54 ›› Issue (13) : 151-160. DOI: 10.16490/j.cnki.issn.1001-3660.2025.13.013

Laser Surface Modification Technology

Effects of LDED Scanning Strategies on Deposition Defects, Microstructures and Properties of Ti6Al4V Coatings

WU Di^1,2, LIU Gang^1,2*, ZHAO Man¹

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Abstract

Laser directed energy deposition (LDED) has a good application prospect in the manufacturing of large titanium alloy aviation parts due to its high deposition rate and low cost. However, the huge temperature change causes a series of complex physical phenomena such as metal melting and solidification, energy absorption and transfer, material phase change and molten pool flow in the manufacturing process, which induces deposition defects and microstructure and macroscopic performance evolution of Ti6Al4V coatings, bringing great challenges to the engineering application of laser directed energy deposition technology. In order to obtain fewer deposition defects and better material properties, the work aims to study the effect of scanning strategy on the deposition defects, micro and macro structures and performance of Ti6Al4V coatings. Ten Ti6Al4V cladding layers were prepared by LDED technology and laser deposition strategies of variable powers were proposed to optimize the temperature gradient during the deposition process. A two-level three-factor orthogonal experiment was designed based on the three important process parameters of laser power, scanning speed, and deposition direction to study the effect of scanning strategies on coating defects, and the temperature history, phase and microhardness of the coating during the manufacturing process were characterized and analyzed. It was found that the phase composition of Ti6Al4V deposits prepared by the four scanning strategies was similar. The deposits were mainly composed of needle-shaped α/α′ martensite and basket- shaped Widmanstatten phase, and the microhardness fluctuated within 373HV10-388HV10. Compared with the forged Ti6Al4V titanium alloy, the microhardness of the Ti6Al4V coating prepared by LDED process was significantly improved. The microhardness gradually increased from the substrate to the cladding layer, among which the substrate had the lowest hardness, the bottom of the cladding layer had significantly improved hardness due to rapid cooling and grain refinement and the middle and top parts had slightly lower hardness than the bottom due to grain coarsening caused by heat accumulation. The deposition strategy had a significant impact on the temperature history. When the substrate temperature was higher, the size of the α′ needle phase was smaller, the microstructure was finer, and the hardness was higher. Among the four deposition strategies, strategies B and D had lower peak temperatures of the substrate due to faster scanning speeds and cooling times, respectively, while strategy C reduced a certain amount of laser power at the initial deposition position of each layer, and the peak temperature was reduced by an average of 11.72% compared with strategy A. Strategy B and strategy D had various deposition defects such as poor bonding, pores and cracks due to insufficient energy density and large temperature fluctuations. Strategy A and strategy C had a smaller average crystal size due to greater supercooling, obtained higher microhardness, and had fewer manufacturing defects in the deposited layer. Experiments and subsequent material characterization prove that the deposition strategy is a key factor in temperature changes and will have a significant impact on the deposition quality. Variable power laser can improve the internal structure of the deposited layer by optimizing the temperature gradient, thereby obtaining fewer deposition defects and better material properties.

Key words

LDED / Ti6Al4V / deposition strategy / microstructure evolution / mechanical properties

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WU Di, LIU Gang, ZHAO Man. Effects of LDED Scanning Strategies on Deposition Defects, Microstructures and Properties of Ti6Al4V Coatings[J]. Surface Technology. 2025, 54(13): 151-160 https://doi.org/10.16490/j.cnki.issn.1001-3660.2025.13.013

References

[1] EMINE Ş, YıLDıRıM Ç V, ŞENOL Ş, et al. Comprehensive Analysis of Cutting Temperature, Tool Wear, Surface Integrity and Tribological Properties in Sustainable Milling of Ti₆Al₄V Alloy: LN2, Nanofluid and Hybrid Machining[J]. Journal of Manufacturing Processes, 2024, 131: 1360-1371.
[2] SARAF G, NIRALA C K.Experimental Investigation of Micro-Pillar Textured WC Inserts during Turning of Ti₆Al₄V under Various Cutting Fluid Strategies[J]. Journal of Manufacturing Processes, 2024, 113: 61-75.
[3] BAKHSHAN H, OÑATE E, CARBONELL J M. Microstructure Evolution Modeling of Ti₆Al₄V Alloy during Cutting Using the Particle Finite Element Method and Homogeneous Field Distributions[J]. Journal of Manufacturing Processes, 2024, 131: 73-92.
[4] YUE L S, ZHOU Q J, PAN Y, et al.Fatigue Deformation Behavior and Fracture Mechanism of High Fatigue- Resistant Laser Directed Energy Deposition Fabricated Titanium Alloy: Effect of Multi-Scale Microstructure[J]. International Journal of Fatigue, 2024, 188: 108518.
[5] SUN J F, LU H F, LIANG Y C, et al.Evolution of Microstructure and Mechanical Properties of Ti65 High- Temperature Titanium Alloy after Additive Manufacturing and Annealing[J]. Materials Science and Engineering: A, 2024, 913: 147002.
[6] WANG X L, ZHANG Z X, ZHAO Y Q, et al.Macroscopic Morphology and Properties of Cobalt-Based Laser Cladding Layers on Rail Steel Based on Pulse Shaping[J]. Optics Laser Technology, 2024, 168: 109940.
[7] PRAHARAJ A K, BONTHA S, BALLA V K, et al.Investigation on High-Temperature Tribological Performance of Laser Directed Energy Deposited Inconel 625 for Aerospace Applications[J]. Tribology International, 2025, 202: 110388.
[8] ACAR M T, O Ç, ARSLAN M E. Selective Laser Melting of Ti₆Al₄V Alloy: Effects of Graphene-TiO₂ Nanotubes Composites Corrosion and Biocompatibility[J]. Journal of Alloys and Compounds, 2024, 1008: 176710.
[9] RONG P, BAI Q S, YIN M, et al.Thermal Mechanical Modeling and Residual Stress Prediction for Laser Direct Energy Deposition of 30CrNi₂MoVA Steel Considering Solid-State Phase Transformation[J]. Journal of Materials Research and Technology, 2024, 30: 7727-7740.
[10] FAN W, PENG Y J, QI Y, et al.Partially Melted Powder in Laser Based Directed Energy Deposition: Formation Mechanism and Its Influence on Microstructure[J]. International Journal of Machine Tools and Manufacture, 2023, 192: 104072.
[11] LIU C M, DONG T, GUO C H, et al.Evolution and Elimination of Pore in Molten Pool during Directed Energy Deposition Assisted by Ultrasonic Vibration[J]. Optics & Laser Technology, 2025, 180: 111454.
[12] LIANG S Q, LI F X, LIU Y C, et al.Processing Correlations of Laser Direct Energy Deposited Inconel718 Based on Multi-Field Numerical Simulation[J]. Materials Science and Engineering: A, 2024, 913: 147075.
[13] SHRESTHA S, PANAKARAJUPALLY R P, KANNAN M, et al.Analysis of Microstructure and Mechanical Properties of Additive Repaired Ti-6Al-4V by Direct Energy Deposition[J]. Materials Science and Engineering: A, 2021, 806: 140604.
[14] OJO S A, SHRESTHA S, EL RASSI J, et al.The Use of Compact Specimens to Determine Fracture Toughness Anisotropy of Ti-6Al-4V Additively Manufactured for Repair[J]. Materials Science and Engineering: A, 2021, 823: 141779.
[15] SANDEEP K J, TEJA P J, CHOUDHARY A K, et al.Development of Correlation between Temperature, Liquid Life Span, Molten Pool, and Porosity during Wire Arc Additive Manufacturing: A Finite Element Approach[J]. CIRP Journal of Manufacturing Science and Technology, 2022, 38: 274-287.
[16] CHOI Y R, SUN S D, LIU Q C, et al.Influence of Deposition Strategy on the Microstructure and Fatigue Properties of Laser Metal Deposited Ti-6Al-4V Powder on Ti-6Al-4V Substrate[J]. International Journal of Fatigue, 2020, 130: 105236.
[17] ZHANG X, MARTINA F, DING J, et al.Fracture Toughness and Fatigue Crack Growth Rate Properties in Wire + Arc Additive Manufactured Ti-6Al-4V[J]. Fatigue & Fracture of Engineering Materials & Structures, 2017, 40(5): 790-803.
[18] BASKIN N, YUCE C.Effect of Process Parameters on the Mechanical Behavior of Ti₆Al₄V Alloys Fabricated by Laser Powder Bed Fusion Method[J]. Journal of Materials Research and Technology, 2024, 30: 7006-7019.
[19] CHEN Y, CHEN X, JIANG M, et al.Coaxial Laser Metal Wire Deposition of Ti₆Al₄V Alloy: Process, Microstructure and Mechanical Properties[J]. Journal of Materials Research and Technology, 2022, 20: 2578-2590.
[20] ZHANG K, GENG J T, LIU W J, et al.Influences of Scanning Strategy on the Quality, Accuracy, Microstructure and Performance of Inconel 625 Parts by LAM[J]. Journal of Materials Research and Technology, 2023, 26: 1962-1983.
[21] TIAN Y J, PANG M, JI F Q.Study on the Impact of Laser Power Variation on the Performance of Ti-6Al-4 V Coating by Laser Cladding on HT250[J]. Optics & Laser Technology, 2024, 175: 110809.
[22] NIE Z G, WANG G, MCGUFFIN-CAWLEY J D, et al. Experimental Study and Modeling of H13 Steel Deposition Using Laser Hot-Wire Additive Manufacturing[J]. Journal of Materials Processing Technology, 2016, 235: 171-186.
[23] LI M J, CHEN J W, LIAN Y P, et al.An Efficient and High-Fidelity Local Multi-Mesh Finite Volume Method for Heat Transfer and Fluid Flow Problems in Metal Additive Manufacturing[J]. Computer Methods in Applied Mechanics and Engineering, 2023, 404: 115828.
[24] WU D, TIAN J Y, LIAO M C, et al.Study on the Effect of Variable Laser Power on Residual Stress Distribution in Laser Directed Energy Deposition of Ti₆Al₄V[J]. CIRP Journal of Manufacturing Science and Technology, 2024, 55: 322-332.
[25] SINAN Ö, SAKLAKOĞLU N, SEVER A. Selective Laser Melting of Ti₆Al₄V Alloy: Effect of Post-Processing on Fatigue Life, Residual Stress, Microstructure, Microhardness and Surface Roughness[J]. Materials Characterization, 2023, 196: 112571.
[26] DING H H, ZHANG J, LIU J Y, et al.Effect of Volume Energy Density on Microstructure and Mechanical Properties of TC4 Alloy by Selective Laser Melting[J]. Journal of Alloys and Compounds, 2023, 968: 171769.
[27] WU W M, CHEN X Z, FANG T H, et al.Research on the Laser Quenching Performance of Ti₆Al₄V-7.3%Cu Alloys Fabricated by Wire-Powder Collaborative Arc Additive Manufacturing[J]. Journal of Alloys and Compounds, 2024, 1002: 175450.
[28] ZENG Q H, CHEN Y M, YANG Z S, et al.Effect of Grain Size and Grain Boundary Type on Intergranular Stress Corrosion Cracking of Austenitic Stainless Steel: A Phase-Field Study[J]. Corrosion Science, 2024, 241: 112557.
[29] CHONG Y, DENG G Y, GAO S, et al.Yielding Nature and Hall-Petch Relationships in Ti-6Al-4V Alloy with Fully Equiaxed and Bimodal Microstructures[J]. Scripta Materialia, 2019, 172: 77-82.
[30] RAGHAVAN N, DEHOFF R, PANNALA S, et al.Numerical Modeling of Heat-Transfer and the Influence of Process Parameters on Tailoring the Grain Morphology of IN718 in Electron Beam Additive Manufacturing[J]. Acta Materialia, 2016, 112: 303-314.
[31] 张铂洋, 李旭, 张玉娇, 等. 铝合金电弧增材制造研究现状[J]. 表面技术, 2023, 52(11): 111-127.
ZHANG B Y, LI X, ZHANG Y J, et al.Research Status of Arc Additive Manufacturing of Aluminum Alloy[J]. Surface Technology, 2023, 52(11): 111-127.