On the surface integrity resulting from laser powder bed fusion of Ti6Al4V: Improvements by cavitation abrasive surface finishing

As the manufacturing readiness level of laser powder bed fusion (L-PBF) advances, post-processing has become increasingly important for achieving net-shape components and to enhance surface texture and integrity. Apart from surface roughness, one concern is the unique morphology of printed surfaces with vertical, upskin, and downskin inclinations. In this study, we characterized the surface texture and integrity of L-PBF Ti6Al4V with respect to build orientation. In the as-built condition, the downskin surfaces possessed the highest roughness, the largest effective surface stress concentration(),Ktand the greatest presence of partially melted powder particles fused to the surface. Cavitation abrasive surface finishing (CASF) was adopted to improve surface quality, with consideration of the build orientation. The results indicated that CASF reduced roughness, lowered Kt posed by the surface texture, and introduced compressive residual stress regardless of the build orientation. Downskin surfaces were the most challenging to treat; they exhibited substantially greater Ktthan the other orientations after treatment (>2×) and lower compressive residual stress (50%). More extensive powder coverage of the downskin surfaces appears to shield the underlying substrate from abrasive attack and direct implosion of cavitation bubbles, which are central to the CASF treatment mechanism. The importance of orientation to the effectiveness of CASF treatment is discussed, as well as strategies to overcome this challenge. Overall, downskin surfaces require greater surface treatment intensity or duration to obtain the same degree of improvement.

- Diegel O, Nordin A, Motte D. A practical guide to design for additive manufacturing. Springer Series in Advanced Manufacturing. Berlin: Springer; 2019. doi: 10.1007/978-981-13-8281-9_2
- Galati M, Calignano F, Viccica M, Iuliano L. Additive manufacturing redesigning of metallic parts for high precision machines. Crystals (Basel). 2020;10(3):161. doi: 10.3390/cryst10030161
- Zegard T, Paulino GH. Bridging topology optimization and additive manufacturing. Struct Multidiscipl Optim. 2016;53(1):175-192. doi: 10.1007/s00158-015-1274-4
- Allen J. An Investigation into the Comparative Costs of Additive Manufacture vs. Machine from Solid for Aero Engine Parts. In: Cost Effective Manufacture via Net-Shape Processing. France: Neuilly-sur-Seine; 2006.
- Cabanettes F, Joubert A, Chardon G, et al. Topography of as built surfaces generated in metal additive manufacturing: A multi scale analysis from form to roughness. Precis Eng. 2018;52:249-265. doi: 10.1016/j.precisioneng.2018.01.002
- Elambasseril J, Rogers J, Wallbrink C, Munk D, Leary M, Qian M. Laser powder bed fusion additive manufacturing (LPBF-AM): The influence of design features and LPBF variables on surface topography and effect on fatigue properties. Crit Rev Solid State Mater Sci. 2023;48(1):132-168. doi: 10.1080/10408436.2022.2041396
- Gomez-Gallegos A, Mandal P, Gonzalez D, Zuelli N, Blackwell P. Studies on titanium alloys for aerospace application. Defect Diffus Forum. 2018;385:419-423. doi: 10.4028/www.scientific.net/DDF.385.419
- Williams JC, Boyer RR. Opportunities and issues in the application of titanium alloys for aerospace components. Metals (Basel). 2020;10(6):705. doi: 10.3390/met10060705
- Boyer RR. An overview on the use of titanium in the aerospace industry. Mater Sci Eng A. 1996;213(1):103-114. doi: 10.1016/0921-5093(96)10233-1
- Singh P, Pungotra H, Kalsi NS. On the characteristics of titanium alloys for the aircraft applications. In: Mater Today: Proceedings. Vol. 4. Netherlands: Elsevier Ltd.; 2017. p. 8971-8982. doi: 10.1016/j.matpr.2017.07.249
- Bache MR. Processing titanium alloys for optimum fatigue performance. Int J Fatigue. 1999;21:S105-S111. doi: 10.1016/S0142-1123(99)00061-4
- Hosseini S. Fatigue of Ti-6Al-4V. London: IntechOpen; 2012. doi: 10.5772/45753
- Novovic D, Dewes RC, Aspinwall DK, Voice W, Bowen P. The effect of machined topography and integrity on fatigue life. Int J Machine Tools Manuf. 2004;44(2):125-134. doi: 10.1016/j.ijmachtools.2003.10.018
- Javidi A, Rieger U, Eichlseder W. The effect of machining on the surface integrity and fatigue life. Int J Fatigue. 2008;30(10):2050-2055. doi: 10.1016/j.ijfatigue.2008.01.005
- Arola D, Williams CL. Estimating the fatigue stress concentration factor of machined surfaces. Int J Fatigue. 2002;24(9):923-930. doi: 10.1016/S0142-1123(02)00012-9
- Arola D, Ramulu M. An Examination of the effects from surface texture on the strength of fiber reinforced plastics. J Compos Mater. 1999;33(2):102-123. doi: 10.1177/002199839903300201
- Persson BNJ. Surface roughness-induced stress concentration. Tribol Lett. 2023;71(2):66. doi: 10.1007/s11249-023-01741-4
- Ye C, Zhang C, Zhao J, Dong Y. Effects of post-processing on the surface finish, porosity, residual stresses, and fatigue performance of additive manufactured metals: A review. J Mater Eng Perform. 2021;30(9):6407-6425. doi: 10.1007/s11665-021-06021-7
- Pegues J, Roach M, Scott Williamson R, Shamsaei N. Surface roughness effects on the fatigue strength of additively manufactured Ti-6Al-4V. Int J Fatigue. 2018;116:543-552. doi: 10.1016/j.ijfatigue.2018.07.013
- Vayssette B, Saintier N, Brugger C, Elmay M, Pessard E. Surface roughness of Ti-6Al-4V parts obtained by SLM and EBM: Effect on the high cycle fatigue life. Procedia Eng. 2018;213:89-97. doi: 10.1016/j.proeng.2018.02.010
- Singh K, Sadeghi F, Correns M, Blass T. A microstructure based approach to model effects of surface roughness on tensile fatigue. Int J Fatigue. 2019;129:105229. doi: 10.1016/j.ijfatigue.2019.105229
- Snyder JC, Thole KA. Understanding laser powder bed fusion surface roughness. J Manuf Sci Eng. 2020;142(7):1-37. doi: 10.1115/1.4046504
- Whip B, Sheridan L, Gockel J. The effect of primary processing parameters on surface roughness in laser powder bed additive manufacturing. Int J Adv Manuf Technol. 2019;103(9-12):4411-4422. doi: 10.1007/s00170-019-03716-z
- Obilanade D, Dordlofva C, Törlind P. Surface roughness considerations in design for additive manufacturing - a literature review. In: Proceedings of the Design Society. Vol. 1. Cambridge University Press; 2021. p. 2841-2850. doi: 10.1017/pds.2021.545
- Khan HM, Karabulut Y, Kitay O, Kaynak Y, Jawahir IS. Influence of the post-processing operations on surface integrity of metal components produced by laser powder bed fusion additive manufacturing: A review. Mach Sci Technol. 2020;25(1):118-176. doi: 10.1080/10910344.2020.1855649
- Lu D, Liu Z, Wei X, Chen C, Wang D. Effect of post-processing methods on the surface quality of Ti6Al4V fabricated by laser powder bed fusion. Front Mater. 2023;10:1126749. doi: 10.3389/fmats.2023.1126749
- Makhetha WMI, Becker TH, Sacks N. Post-processing framework for as-built LPBF Ti-6Al-4V parts towards meeting industry functional requirements. JOM (1989). 2022;74(3):764-776. doi: 10.1007/s11837-021-05078-y
- Triantaphyllou A, Giusca CL, Macaulay GD, et al. Surface texture measurement for additive manufacturing. Surf Topogr Metrol Prop. 2015;3(2):24002. doi: 10.1088/2051-672X/3/2/024002
- Covarrubias EE, Eshraghi M. Effect of build angle on surface properties of nickel superalloys processed by selective laser melting. JOM (1989). 2018;70(3):336-342. doi: 10.1007/s11837-017-2706-y
- Leach RK, Bourell D, Carmignato S, Donmez A, Senin N, Dewulf W. Geometrical metrology for metal additive manufacturing. CIRP Ann. 2019;68(2):677-700. doi: 10.1016/j.cirp.2019.05.004
- Rott S, Ladewig A, Friedberger K, Casper J, Full M, Schleifenbaum JH. Surface roughness in laser powder bed fusion - Interdependency of surface orientation and laser incidence. Add Manuf. 2020;36:101437. doi: 10.1016/j.addma.2020.101437
- Shange M, Yadroitsava I, Pityana S, Yadroitsev I, Bester D. Surface morphology characterisation for parts produced by the high speed selective laser melting. IOP Conf Ser Mater Sci Eng. 2019;655(1):12045. doi: 10.1088/1757-899X/655/1/012045
- Lizzul L, Bertolini R, Ghiotti A, Bruschi S. Effect of AM-induced anisotropy on the surface integrity of laser powder bed fused Ti6Al4V machined parts. Proc Manuf. 2020;47:505-510. doi: 10.1016/j.promfg.2020.04.149
- Metelkova J, Vanmunster L, Haitjema H, Van Hooreweder B. Texture of inclined up-facing surfaces in laser powder bed fusion of metals. Add Manuf. 2021;42:101970. doi: 10.1016/j.addma.2021.101970
- Calignano F. Investigation of the accuracy and roughness in the laser powder bed fusion process. Virtual Phys Prototyp. 2018;13(2):97-104. doi: 10.1080/17452759.2018.1426368
- Jurg M, Medvedev AE, Yan W, Molotnikov A. Surface improvement of laser powder bed fusion processed Ti6Al4V for fatigue applications. Add Manuf Lett. 2022;3:100070. doi: 10.1016/j.addlet.2022.100070
- Soe AN, Sombatmai A, Promoppatum P, Srimaneepong V, Trachoo V, Pandee P. Effect of post-processing treatments on surface roughness and mechanical properties of laser powder bed fusion of Ti-6Al-4V Effect of post-processing treatments on surface roughness and mechanical properties of laser powder bed fusion of Ti-6Al-4V. J Mater Res Technol. 2024;32:3788-3803.
- Risposi T, Rusnati L, Patriarca L, Hardaker A, Luczyniec D, Beretta S. Fatigue of Ti6Al4V manufactured by PBF-LB: A comparison of failure mechanisms between net-shape and electro-chemically milled surface conditions. Eng Failure Anal. 2025;172:109403. doi: 10.1016/j.engfailanal.2025.109403
- Bertolini JC. Hydrofluoric acid: A review of toxicity. J Emerg Med. 1992;10(2):163-168. doi: 10.1016/0736-4679(92)90211-B
- Kahlin M, Ansell H, Basu D, et al. Improved fatigue strength of additively manufactured Ti6Al4V by surface post processing. Int J Fatigue. 2020;134:105497. doi: 10.1016/j.ijfatigue.2020.105497
- Maleki E, Bagherifard S, Bandini M, Guagliano M. Surface post-treatments for metal additive manufacturing: Progress, challenges, and opportunities. Add Manuf 2021;37:101619. doi: 10.1016/j.addma.2020.101619
- Grover HJ. Factors by Which Shot Peening Influences the Fatigue Strength of Parts. SAE Technical Paper 540138; 1954. doi: 10.4271/540138
- Huang L, Kinnell P, Shipway PH. Removal of heat-formed coating from a titanium alloy using high pressure waterjet: Influence of machining parameters on surface texture and residual stress. J Mater Process Technol. 2015;223:129-138. doi: 10.1016/j.jmatprotec.2015.03.053
- Arola DD, McCain ML. Abrasive waterjet peening: A new method of surface preparation for metal orthopedic implants. J Biomed Mater Res. 2000;53(5):536-546. doi: 10.1002/1097-4636(200009)53:5<536:AID-JBM13>3.0.CO;2-V
- Arola D, Alade AE, Weber W. Improving fatigue strength of metals using abrasive waterjet peening. Mach Sci Technol. 2006;10(2):197-218. doi: 10.1080/10910340600710105
- Yao SL, Wang GY, Yu H, et al. Influence of submerged micro-abrasive waterjet peening on surface integrity and fatigue performance of TA19 titanium alloy. Int J Fatigue. 2022;164:107076. doi: 10.1016/j.ijfatigue.2022.107076
- Soyama H. Cavitation peening: A review. Metals (Basel). 2020;10(2):270. doi: 10.3390/met10020270
- Soyama H, Korsunsky AM. A critical comparative review of cavitation peening and other surface peening methods. J Mater Process Technol. 2022;305:117586. doi: 10.1016/j.jmatprotec.2022.117586
- Soyama H, Kuji C. Improving effects of cavitation peening, using a pulsed laser or a cavitating jet, and shot peening on the fatigue properties of additively manufactured titanium alloy Ti6Al4V. Surf Coat Technol. 2022;451:129047. doi: 10.1016/j.surfcoat.2022.129047
- Soyama H, Iga Y. Laser cavitation peening: A review. Appl Sci. 2023;13(11):6702. doi: 10.3390/app13116702
- Sato M, Takakuwa O, Nakai M, Niinomi M, Takeo F, Soyama H. Using cavitation peening to improve the fatigue life of titanium alloy Ti-6Al-4V manufactured by electron beam melting. Mater Sci Appl. 2016;7(4):181-191. doi: 10.4236/msa.2016.74018
- Petram R, Wisdom C, Montelione A, et al. Removing alpha case from laser powder bed fusion components by cavitation abrasive surface finishing. Materials. 2025;18(9):1977. doi: 10.3390/ma18091977
- ASTM International. F2924-14: Standard Specification for Additive Manufacturing Titanium-6 Aluminum-4 Vanadium with Powder Bed Fusion. Vol. 1. United States: ASTM International; 2021.
- Standard Terminology for Additive Manufacturing Coordinate Systems and Test Methodologies ASTM Standard: ISO/ASTM 52921-13 (Reapproved 2019), ASTM International, United States.
- International Organization for Standardization, ISO 4288:1998. Geometrical Product Specifications (GPS) - Surface Texture: Profile Method - Rules and Procedures for the Assessment of Surface Texture, Geometrical Product Specifications (GPS). Vol. 1998. United Kingdom: International Organization for Standardization; 1998.
- Noyan IC, Cohen JB. Residual Stress: Measurement by Diffraction and Interpretation. Berlin: Springer-Verlag; 1987.
- He BB. Two-Dimensional x-Ray Diffraction. 2nd ed. United States: John Wiley & Sons, Inc.; 2018. p. 249-325.
- ASTM E407-07. Designation: E407- 07 (Reapproved 2015) Standard Practice for Microetching Metals and Alloys. United States: ASTM International; 2015.
- Soyama H, Okura Y. The use of various peening methods to improve the fatigue strength of titanium alloy Ti6Al4V manufactured by electron beam melting. AIMS Mater Sci. 2018;5(5):1000-1015. doi: 10.3934/matersci.2018.5.1000
- Du Plessis A, Beretta S. Killer notches: The effect of as-built surface roughness on fatigue failure in AlSi10Mg produced by laser powder bed fusion. Add Manuf. 2020;35:101424. doi: 10.1016/j.addma.2020.101424
- Vilardell AM, Krakhmalev P, Fredriksson G, et al. Influence of surface topography on fatigue behavior of Ti6Al4V alloy by laser powder bed fusion. In: Procedia CIRP. Vol. 74. Elsevier B.V; 2018. p. 49-52. doi: 10.1016/j.procir.2018.08.028
- Barricelli L, Patriarca L, du Plessis A, Beretta S. A comparison of fatigue analysis methods for L-PBF net-shape surfaces in Ti6Al4V parts. Theor Appl Fracture Mech. 2023;128:104143. doi: 10.1016/j.tafmec.2023.104143
- Nicoletto G. Influence of rough as-built surfaces on smooth and notched fatigue behavior of L-PBF AlSi10Mg. Add Manuf. 2020;34:101251. doi: 10.1016/j.addma.2020.101251
- Simson D, Subbu SK. Effect of process parameters on surface integrity of LPBF Ti6Al4V. Proceedia CIRP. 2022;108: 716-721. doi: 10.1016/j.procir.2022.03.111
- Wang N, Zhu J, Liu B, Zhang X, Zhang J, Tu S. Influence of ultrasonic surface rolling process and shot peening on fretting fatigue performance of Ti-6Al-4V. Chin J Mech Eng. 2021;34(1):1-13. doi: 10.1186/s10033-021-00611-1
- Li K, Fu XS, Li RD, et al. Fretting fatigue characteristic of Ti–6Al–4V strengthened by wet peening. Int J Fatigue. 2016;85:65-69. doi: 10.1016/j.ijfatigue.2015.12.013
- Mancisidor AM, García-Blanco MB, Quintana I, et al. Effect of post-processing treatment on fatigue performance of Ti6Al4V alloy manufactured by laser powder bed fusion. J Manuf Mater Process. 2023;7(4):119. doi: 10.3390/jmmp7040119
- Rigon D, Coppola F, Meneghetti G. Fracture mechanics-based analysis of the fatigue limit of Ti6Al4V alloy specimens manufactured by SLM in as-built surface conditions by means of areal measurements. Eng Fracture Mech. 2024;295:109720. doi: 10.1016/j.engfracmech.2023.109720
- Meneghetti G, Rigon D, Gennari C. An analysis of defects influence on axial fatigue strength of maraging steel specimens produced by additive manufacturing. Int J Fatigue. 2019;118:54-64. doi: 10.1016/j.ijfatigue.2018.08.034
- Lee S, Rasoolian B, Silva DF, Pegues JW, Shamsaei N. Surface roughness parameter and modeling for fatigue behavior of additive manufactured parts: A non-destructive data-driven approach. Addit Manuf. 2021;46:102094. doi: 10.1016/j.addma.2021.102094