Improved surface integrity of Ti6Al4V fabricated by selective electron beam melting using ultrasonic surface rolling processing

Abstract

• Surface integrity of samples with SEBM-built surface is greatly improved using USRP. • Surface wettability of USRP treated sample changes from hydrophobicity to hydrophily. • USRP is a promising post-processing technique of additive manufacturing parts. This paper investigates the effect of ultrasonic surface rolling processing (USRP) on the surface integrity, microstructure, hardness, and residual stress of selective electron beam melted (SEBMed) Ti6Al4V with as-built surface. Results show that the semi-melted powder and melting pool ridges are flattened due to the ultrasonic impact and static load, as well as surface defects, such as ‘stairs’ and holes, are eliminated. The surface integrity of the sample is significantly improved. The surface roughness Ra and Rz of the USRP treated sample with 800 N is reduced by ∼95 % and ∼90 %, the surface hardness is increased by ∼16.2 % compared with the as-built surface. A gradient microstructure and hardened layer exceeded 110 μm is obtained. What’s more, the surface wettability changes from hydrophobicity to hydrophily.