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Manufacturability study in laser powder bed fusion of biomedical Ti alloys for orthopedic implants: an investigation of mechanical properties, process-induced porosity and surface roughness

Mudassar Rehman (Biological Additive Manufacturing University-Enterprise Joint Research Center of Shaanxi Province, Northwestern Polytechnical University, Xi’an, China and Industrial and Manufacturing Engineering Department, University of Engineering and Technology, Lahore, Pakistan)
Yanen Wang (Biological Additive Manufacturing University-Enterprise Joint Research Center of Shaanxi Province, Northwestern Polytechnical University, Xi’an, China)
Kashif Ishfaq (Industrial and Manufacturing Engineering Department,, University of Engineering and Technology, Lahore, Pakistan)
Haiou Yang (State Key Laboratory of Solidification Processing, School of Materials Science and Engineering, Northwestern Polytechnical University, Xi’an, China)
Ray Tahir Mushtaq (Biological Additive Manufacturing University-Enterprise Joint Research Center of Shaanxi Province, Northwestern Polytechnical University, Xi’an, China)
M. Saravana Kumar (Graduate Institute of Manufacturing Technology, National Taipei University of Technology, Taipei, Taiwan)
Ammar Ahmed (Biological Additive Manufacturing University-Enterprise Joint Research Center of Shaanxi Province, Northwestern Polytechnical University, Xi’an, China)

Rapid Prototyping Journal

ISSN: 1355-2546

Article publication date: 26 April 2023

Issue publication date: 2 June 2023

210

Abstract

Purpose

Since the biomedical implants with an improved compressive strength, near bone elastic modulus, controlled porosity, and sufficient surface roughness, can assist in long term implantation. Therefore, the fine process tuning plays its crucial role to develop optimal settings to achieve these desired properties. This paper aims to find applications for fine process tuning in laser powder bed fusion of biomedical Ti alloys for load-bearing implants.

Design/methodology/approach

In this work, the parametric porosity simulations were initially performed to simulate the process-induced porosity for selective laser-melted Ti6Al4V as per full factorial design. Continually, the experiments were performed to validate the simulation results and perform multiresponse optimization to fine-tune the processing parameters. Three levels of each control variable, namely, laser power – Pl (180, 190, 200) W, scanning speed – Vs (1500, 1600, 1700) mm/s and scan orientation – ϴ{1(0,0), 2(0,67°), 3(0,90°)} were used to investigate the processing performance. The measured properties from this study include compressive yield strength, elastic modulus, process-induced porosity and surface roughness. Finally, confirmatory experiments and comparisons with the already published works were also performed to validate the research results.

Findings

The results of porosity parametric simulation and experiments in selective laser melting of Ti6Al4V were found close to each other with overall porosity (less than 10%). The fine process tuning was resulted in optimal settings [Pl (200 W), Vs (1500 mm/s), ϴ (0,90°)], [Pl (200 W), Vs (1500 mm/s), ϴ (0,67°)], [Pl (200 W), Vs (1500 mm/s), ϴ (0,0)] and [Pl (200 W), Vs (1500 mm/s), ϴ (0,0)] with higher compressive strength (672.78 MPa), near cortical bone elastic modulus (12.932 GPa), process-induced porosity (0.751%) and minimum surface roughness (2.72 µm). The morphology of the selective laser melted (SLMed) surface indicated that the lack of fusion pores was prominent because of low laser energy density among the laser and powder bed. Confirmatory experimentation revealed that an overall percent improvement of around 15% was found between predicted and the experimental values.

Originality/value

Since no significant works are available on the collaborative optimization and fine process tuning in laser powder bed fusion of biomedical Ti alloys for different load bearing implants. Therefore, this work involves the comprehensive investigation and multi-objective optimization to determine optimal parametric settings for better mechanical and physical properties. Another novel aspect is the parametric porosity simulation using Ansys Additive to assist in process parameters and their levels selection. As a result, selective laser melted Ti alloys at optimal settings may help in examining the possibility for manufacturing metallic implants for load-bearing applications.

Keywords

Acknowledgements

The authors are grateful to Northwestern Polytechnical University China to provide resources during this work completion.

Funding: This research study was funded by the National key R&D plan (2022YFB3304000); the Shaanxi Province Key Research and Development Projects (2021LLRH08 and 2022GXLH-02-15); the Science and technology planning project of Xian (20KYPT0002-1); the Emerging Interdisciplinary Project of Northwestern Polytechnical University (22GH0306); and the Fundamental Research Funds for the Central Universities (3102022gxb002).

Citation

Rehman, M., Wang, Y., Ishfaq, K., Yang, H., Mushtaq, R.T., Kumar, M.S. and Ahmed, A. (2023), "Manufacturability study in laser powder bed fusion of biomedical Ti alloys for orthopedic implants: an investigation of mechanical properties, process-induced porosity and surface roughness", Rapid Prototyping Journal, Vol. 29 No. 6, pp. 1299-1323. https://doi.org/10.1108/RPJ-02-2022-0042

Publisher

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Emerald Publishing Limited

Copyright © 2023, Emerald Publishing Limited

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