Friction surfacing-based additive manufacturing of Ti–6Al–4V: process parameters, coating geometry, surface analysis, mechanical properties and corrosion behavior

Abstract In the present work, the solid state deposition of Ti–6Al–4V on grade 2 titanium substrates by friction surfacing was investigated. After initial parameter optimization to select adequate horizontal and vertical forward speeds, tests were conducted with rotational speeds of 4000, 5000, 6000, 7000 and 8000 rpm. The deposited material was subsequently characterized in terms of its overall geometry and surface texture, mechanical properties, microstructure and electrochemical corrosion resistance in Hank’s Balanced Salt Solution (HBSS). Except for the coating obtained with 4000 rpm rotational speed, in all remaining cases deposits were relatively uniform and all coatings exhibited excellent bond strength—superior to the shear strength of the titanium substrate. The coatings exhibited elevated average hardness values ( $$\approx $$ 350 HV) and their microstructure was found to be composed mostly of needle-shaped $$\alpha $$ located at previous $$\beta $$ grain boundaries, with minor quantities of equiaxed $$\alpha $$ grains located near the substrate interface. No significant differences were noticed regarding the electrochemical behavior of the tested coatings, which exhibited similar corrosion resistance compared to the original base material, an indication of the reliability of the friction surfacing process for producing corrosion resistant coatings.