Effect of Various Peening Methods on the Fatigue Properties of Titanium Alloy Ti6Al4V Manufactured by Direct Metal Laser Sintering and Electron Beam Melting

Abstract

Titanium alloy Ti6Al4V manufactured by additive manufacturing (AM) is an attractive material, but the fatigue strength of AM Ti6Al4V is remarkably weak. Thus, post-processing is very important. Shot peening can improve the fatigue strength of metallic materials, and novel peening methods, such as cavitation peening and laser peening, have been developed. In the present paper, to demonstrate an improvement of the fatigue strength of AM Ti6Al4V, Ti6Al4V manufactured by direct metal laser sintering (DMLS) and electron beam melting (EBM) was treated by cavitation peening, laser peening, and shot peening, then tested by a plane bending fatigue test. To clarify the mechanism of the improvement of the fatigue strength of AM Ti6Al4V, the surface roughness, residual stress, and surface hardness were measured, and the surfaces with and without peening were also observed using a scanning electron microscope. It was revealed that the fatigue strength at N = 107 of Ti6Al4V manufactured by DMLS was slightly better than that of Ti6Al4V manufactured by EBM, and the fatigue strength of both the DMLS and EBM specimens was improved by about two times through cavitation peening, compared with the as-built ones. An experimental formula to estimate fatigue strength from the mechanical properties of a surface was proposed.

Strength and Ductility Improvement through Thermomechanical Treatment of Wire-Feed Electron Beam Additive Manufactured Low Stacking Fault Energy (SFE) Aluminum Bronze

“…The same is true with the shot peening on an as-printed aluminum alloy AlSi10Mg [40]. These functionally flexible methods [36][37][38][39][40] were almost as effective as rolling.…”

“…Hammer peening is applied to modify the subsurface structures by severe plastic deformation with subdivision and misorientation in the previously grown grains, and eliminate the growth textures and large columnar grains [36,37]. Surface modification processes such as cavitation peening, shot peening and laser peening methods were applied on Ti-6Al-4V samples fabricated with the use of direct metal laser sintering and electron beam melting [38], achieving 70-97% improvement in fatigue strength.…”

Custom-Made Titanium Mesh Tray for Mandibular Reconstruction Using an Electron Beam Melting System

“…The alumina blasting treatment removed the metal particles, reducing Ra and Rz—that is, it was expected that the strength would increase as the stress concentration was reduced by smoothing the surface [ 21 ]. It was also thought that there could be a peeling effect due to the alumina blast treatment of the surface [ 19 , 28 ]. However, it was confirmed that oxygen and aluminum adhered to the sandblast-treated surface.…”

“…Because CAD/computer-aided manufacturing (CAD/CAM) technology has the advantage that the thickness and strength of the metal can be designed [ 12 , 16 ], it should be able to reproduce the mandibular morphology of individual patients and manufacture customized titanium mesh trays of sufficient strength [ 17 , 18 ]. However, such additive manufacturing also has a problem in that an incomplete dissolution layer is formed on the outer surface, which affects mechanical strength [ 19 ]. Regarding mechanical strength, SLM products are reported to outperform or be equivalent to EBM products [ 20 , 21 ].…”

Advanced Surface Modification for 3D-Printed Titanium Alloy Implant Interface Functionalization

“…(A) Implant surface microstructure produced by electrophoretic deposition ( Surmeneva et al, 2019 ). (B) Microstructure of implant surface produced by laser peening ( Soyama and Takeo, 2020 ). (C) Surface microstructures of implants produced by hydrogel packaging ( Mieszkowska et al, 2020 ).…”