コールドスプレー法により純Tiを被覆したTi-6Al-4V合金の腐食疲労挙動

抄録

The purpose of present study was to examine the corrosion fatigue strength and fracture mechanism of Ti-6Al-4V alloy coated with cold-sprayed pure titanium. Both grit blasting and electrolytic polishing were used as the treatments of substrate surface before coating. Rod Specimens of Ti-6Al-4V alloy were coated with cold-splayed pure titanium after the surface treatment. Then, hydroxyapatite was coated using plasma spraying as top coating. Adhesive strength of coating was 27.2MPa for the specimen coated with pure titanium after grit blasting (GBC) and 20.2MPa for that after electrolytic polishing (EPC), respectively. The corrosion fatigue tests were conducted using rotating bending fatigue machine at a frequency of 10 Hz in a physiological saline solution at 310K. The fatigue life of the coated specimens decreased in comparison with the electrolytic polished substrate (EP). The reduction in fatigue strength at 10⁷ cycles was 18% for GBC and 15% for EPC in comparison with EP. The corrosion damage was not found in titanium coating and substrate. In addition, the residual stress measured by X-ray diffraction method was compressive mode in titanium coating and substrate subsurface for both GBC and EPC. From SEM examination, it was revealed that the reduction in fatigue strength was due to the stress concentration at dents formed by grit blasting in GBC and at non-bonded regions of titanium coating in EPC.