Properties of the surface layer of titanium alloy Ti-6Al-4V produced by DMLS technology after the shot peening treatment

While considerable progress has already been made in the field of additive manufacturing further development is needed.There is a huge demand in the global market for the production of high-quality components with complex geometries.The post-production surfaces after fabrication by AM technologies require finishing treatment due to the presence of defects on the surface layer.Therefore, a series of studies have been carried out to analyse the effect of shot-peening treatment on DMLS-manufactured titanium specimens.The shot peening process was carried out using three different working media: CrNi steel shot, crushed nutshells, ceramic with working pressure of 0.3 MPa.The study included examination of surface roughness, Vickers hardness, phase composition and SEM analysis of the obtained surfaces.Analysis of the surface roughness showed a decrease in roughness using CrNi steel shot and ceramic balls.The use of nutshells resulted in an increase in roughness due to the sharp shape of the grains used.An increase in the surface hardness was observed for all modified surfaces.The least strengthening effect was obtained with nutshell shots.XRD phase analysis indicates that a two-phase structure of '+ was identified in the post-production condition.There has been an increase in the share of the phase for all treated samples.The greatest increase of the phase was obtained for steel shots and ceramic balls.Changes in the percentages of the phases in the treated samples are the results of the induced phase transformations.The shot peening process also induces plastic deformation on the surface and forms a nanocrystalline layer, as demonstrated by SEM analysis.The overall results after the shot peening treatment indicates a favourable effect on the properties and the state of the surface layer of the Ti-6Al-4V titanium alloy for ceramic and steel shots.