Use of Cavitation Abrasive Surface Finishing to Improve the Fatigue Properties of Additive Manufactured Titanium Alloy Ti6Al4V 2021-01-0024

To improve the fatigue properties of additive manufactured (AM) titanium alloy Ti6Al4V, cavitation abrasive surface finishing (CASF) was proposed. With CASF, a high-speed water jet with cavitation, i.e. a cavitating jet, was injected into a water-filled chamber, to which abrasives were added. Abrasives accelerated by the jet created a smooth surface by removing un-melted particles on the surface. Simultaneously, cavitation impacts induced by the jet introduced compressive residual stress and work hardening into the surface, similar to cavitation peening. In this study, to demonstrate the improvement of the fatigue properties of AM Ti6Al4V owing to CASF, Ti6Al4V specimens manufactured through direct metal laser sintering (DMLS) and electron beam melting (EBM) were treated using CASF and cavitation peening, and tested using a plane bending fatigue test. The fatigue life of the specimen treated using CASF was found to be better than that of an as-built specimen, as CASF made the surface smooth with the introduction of compressive residual stress and work hardening at the same time. The fatigue properties of the specimen treated using cavitation peening after CASF (CASF & cavitation peening) surpassed that of the specimen treated using CASF. The fatigue strength of the AM Ti6Al4V at 10⁷ was 185 ± 9 MPa for the as-built DMLS specimen, 169 ± 14 MPa for the as-built EBM specimen, 425 ± 9 MPa for the DMLS specimen treated using CASF & cavitation peening, and 386 ± 9 MPa for the EBM specimen treated using CASF & cavitation peening.