Effect of surface condition on the fatigue characteristics of Ti – 6Al – 4V, titanium alloy produced by selective laser melting

The effect of various types of surface post-treatment on the fatigue characteristics of Ti – 6Al – 4V, titanium alloy samples produced by selective laser melting has been studied. The values of the low-cycle fatigue of Ti – 6Al – 4V, titanium alloy samples as built and after turning, waterjet and vibro-grinding treatment were compared. The surface roughness Ra nano-hardness after selective laser melting were 8 μm and 5.1 GPa, respectively. These samples have a low fatigue life. The surface roughness Ra after vibro-grinding treatment decreased to 3.5 μm, whereas the fatigue characteristics remained the same. After turning, the minimum roughness value 0.1 μm at the nanohardness of 5 GPa were obtained. This treatment allows a slight increase in the fatigue characteristics. However, the maximum fatigue properties were obtained on samples after waterjet treatment ( Ra attained 1 μm and the nano-hardness of the subsurface zone increased to 6.1 GPa). One of the reasons for a significant increase in the fatigue characteristics after waterjet treatment is hardening of the surface layer of the material, which becomes an effective obstacle to the occurrence and spread of microcracks. Waterjet treatment of samples produced by selective laser melting makes it possible to solve the problem of increasing fatigue characteristics and improving the surface quality of Ti – 6Al – 4V, titanium alloy products to be used in biomedicine.