Plasma Polishing as a New Polishing Option to Reduce the Surface Roughness of Porous Titanium Alloy for 3D Printing

Zhiwei Lin; Lincong Luo; Dongxin Lin; Yuping Deng; Yang Yang; Xuecheng Huang; Tingrui Wu; Wenhua Huang

doi:10.3791/65108

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Method Article

Plasma Polishing as a New Polishing Option to Reduce the Surface Roughness of Porous Titanium Alloy for 3D Printing

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DOI:

10.3791/65108

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April 28th, 2023

Zhiwei Lin^*¹^,² , Lincong Luo^*³ , Dongxin Lin^*⁴ , Yuping Deng⁴^,⁵ , Yang Yang⁴ , Xuecheng Huang⁶ , Tingrui Wu¹ , Wenhua Huang¹^,²^,⁴

¹Orthopedic Center, Affiliated Hospital of Guangdong Medical University, ²The School of Basic Medical Sciences, Guangdong Medical University, ³The School of Basic Medical Sciences, Fujian Medical University, ⁴Guangdong Engineering Research Center for Translation of Medical 3D Printing Application, Guangdong Provincial Key Laboratory of Digital Medicine and Biomechanics, National Key Discipline of Human Anatomy, School of Basic Medical Sciences, Southern Medical University, ⁵Integrated Hospital of Traditional Chinese Medicine, Southern Medical University, ⁶Shenzhen Hospital of Guangzhou University of Chinese Medicine (Futian)

^* These authors contributed equally

Summary

Plasma polishing is a promising surface processing technology, especially suitable for 3D printing of porous titanium alloy workpieces. It can remove semi-molten powders and ablative oxide layers, thereby effectively reducing surface roughness and improving surface quality.

Abstract

Porous titanium alloy implants with simulated trabecular bone fabricated by 3D printing technology have broad prospects. However, due to the fact that some powder adheres to the surface of the workpiece during the manufacturing process, the surface roughness in direct printing pieces is relatively high. At the same time, since the internal pores of the porous structure cannot be polished by conventional mechanical polishing, an alternative method needs to be found. As a surface technology, plasma polishing technology is especially suitable for parts with complex shapes that are difficult to polish mechanically. It can effectively remove particles and fine splash residues attached to the surface of 3D printed porous titanium alloy workpieces. Therefore, it can reduce surface roughness. Firstly, titanium alloy powder is used to print the porous structure of the simulated trabecular bone with a metal 3D printer. After printing, heat treatment, removal of the supporting structure, and ultrasonic cleaning is carried out. Then, plasma polishing is performed, consisting of adding a polishing electrolyte with the pH set to 5.7, preheating the machine to 101.6 °C, fixing the workpiece on the polishing fixture, and setting the voltage (313 V), current (59 A), and polishing time (3 min). After polishing, the surface of the porous titanium alloy workpiece is analyzed by a confocal microscope, and the surface roughness is measured. Scanning electron microscopy is used to characterize the surface condition of porous titanium. The results show that the surface roughness of the whole porous titanium alloy workpiece changed from Ra (average roughness) = 126.9 µm to Ra = 56.28 µm, and the surface roughness of the trabecular structure changed from Ra = 42.61 µm to Ra = 26.25 µm. Meanwhile, semi-molten powders and ablative oxide layers are removed, and surface quality is improved.

Introduction

Titanium and titanium alloy materials have been widely used as dental and orthopedic implant materials because of their good biocompatibility, corrosion resistance, and mechanical strength¹^,²^,³. However, due to the high elastic modulus of the compact titanium alloy produced by traditional processing methods, these plates are not suitable for bone repair, since close proximity to the bone surface for long periods can result in stress shielding and bone embrittlement⁴^,⁵ . Therefore, the porous microstructure of simulate....