Material Characterization, Thermal Analysis, and Mechanical Performance of a Laser-Polished Ti Alloy Prepared by Selective Laser Melting

Yu-Hang Li,Zhi-Hao Fang,Bing Wang,Shou-Feng Yang,Cheng-Peng Ma,Long-Fei Chen,Ying-Chun Guan

doi:10.3390/met9020112

Abstract

The laser polishing technique offers an adaptable, accurate, and environmentally friendly solution to enhance the surface quality of additive manufactured metallic components. Recent work has shown that the surface roughness of laser additive manufactured metallic alloys can be significantly reduced via the laser polishing method. This paper examines the mechanical performances of a laser polished surface fabricated by selective laser melting (SLM). Compared with the original SLM surface, systematic measurements revealed that the surface roughness of the laser polished surface can be effectively reduced from 6.53 μm to 0.32 μm, while the microhardness and wear resistance increased by 25% and 39%, respectively. Through a thermal history analysis of the laser polishing process using the finite element model, new martensitic phase formation in the laser polished layer is carefully explained, which reveals significant effects on residual stress, strength, and fatigue. These findings establish foundational data to predict the mechanical performance of laser polished metallic components fabricated by additive manufacturing methods, and pave the way for functional surface design with practical application via the laser process.

Highlights

The Ti-6A-4V alloy has been widely employed in the aerospace and medical device industry due to its high specific strength, corrosion resistance, and biocompatibility [1]
Metals 2019, 9, 112 the surface quality of the SLMed surface was poor due to the uneven distribution of powders at the surface caused by the waviness of laser scan tracks and the layered geometries [4,5,6], and rough surfaces generally limit the practical applications of the entire component
Surface roughness Ra of initial selective laser melting (SLM) specimens was reduced from 6.53 μm to 0.32 μm after laser polishing

Summary

Introduction

The Ti-6A-4V alloy has been widely employed in the aerospace and medical device industry due to its high specific strength, corrosion resistance, and biocompatibility [1]. Selective laser melting (SLM) has attracted much attention as a promising method to fabricate complex geometries, as well as new microstructures with novel properties, including an excellent mechanical performance in terms of yield, tensile strength, and ductility [2,3]. Metals 2019, 9, 112 the surface quality of the SLMed surface was poor due to the uneven distribution of powders at the surface caused by the waviness of laser scan tracks and the layered geometries [4,5,6], and rough surfaces generally limit the practical applications of the entire component. Among the most desirable properties of SLM components, a high surface finish and good surface performance are crucial for the direct mechanical application of SLM components in the future. Difficult to machine materials, geometrical flexibility, environmental pollution, a low processing efficiency, and being incompatible with the automation of these methods limit their application and development [7]

Methods

Results

Conclusion