Effect of Fine Particle Peening Using Hydroxyapatite Particles on Rotating Bending Fatigue Properties of β-Type Titanium Alloy

Fine particle peening (FPP) using hydroxyapatite (HAp) shot particles was performed to improve the fatigue strength and form a HAp transfer layer on beta titanium alloy (Ti–22V–4Al). The surface microstructures of FPP-treated specimen were characterized scanning electron microscopy, micro-Vickers hardness testing, energy dispersive X-ray spectrometry, diffraction, backscattered diffraction. A with thickness 5.5 μm formed Ti–22V–4Al by FPP. In addition, increased, high compressive residual stress generated Rotating bending tests at room temperature in laboratory air over wide cycle-life region (103–109 cycles). long regime, 107 cycles became higher than that untreated specimen. This result is attributed formation work-hardened However, not improved FPP short because cracks initiated defects during process. fracture mode specimens shifted from surface-initiated subsurface-initiated amplitude level 600 MPa.