直接レーザ焼結法で作製したチタン合金Ti6Al4Vの表面改質による疲労強度向上

抄録

Additive manufactured AM titanium alloy is attractive material for medical implants and aviation components. However, the fatigue life and strength are remarkably weak comparing with bulk titanium alloy. As a conventional way to improve fatigue properties of metallic materials is surface modification such as shot peening. Namely, one of the methods to enhance fatigue properties of AM titanium alloy is mechanical surface treatment. Recently, it was reported that the fatigue life and strength of the titanium alloy Ti6Al4V made of electron beam melting EBM was improved by cavitation peening with abrasive, as the compressive residual stress was introduced with removing surface roughness. In the present paper, in order to demonstrate the improvement of fatigue strength of AM titanium alloy by means of mechanical surface treatments, Ti6Al4V manufactured by direct metal laser sintering DMLS was treated by cavitation peening, submerged laser peening and shot peening, and then evaluated the fatigue life and strength by a displacement controlled plane bending fatigue test. Note that used Ti6Al4V was heat treated before the mechanical surface treatment to improve fatigue properties. It was concluded that the fatigue strength was improved 97 % by cavitation peening, 96 % by submerged laser peening, and 94 % by shot peening, comparing with that of non-peened specimen.