Effect of shot peening on surface mechanical properties of selective laser melting TC4 titanium alloy

Selective laser melting TC4 titanium alloy samples were strengthened with ϕ2.3 mm and ϕ4.0 mm ceramic projectiles respectively. The surface morphology, surface roughness, surface friction coefficient, surface wear morphology and surface microhardness of the sample were observed and analyzed by laser confocal microscope, comprehensive surface property tester, scanning electron microscope and Vickers microhardness tester. The results show that after shot peening, the surface roughness of the sample decreases by 80.2%～86.3%. For the sample treated with ϕ2.3 mm shot, the surface roughness increases gradually with the increase of shot peening time. The surface roughness of the sample treated with ϕ4.0 mm projectile decreases with the increase of peening time. Peening diameter, peening time and load all have effects on the friction coefficient of the sample. When the load is 10 N, the friction coefficient of the sample treated with ϕ2.3 mm projectile changes obviously, while the friction coefficient of the sample treated with ϕ4.0mm projectile changes little. When the load increases to 20 N, the average friction coefficient of the samples treated with ϕ2.3 mm projectile slows down, while the friction coefficient of the samples treated with ϕ4.0 mm projectile has little change. The surface of selected laser melted TC4 alloy after shot peening has obvious wear marks and plastic deformation, and the wear mechanism is mainly abrasive wear. The friction and wear properties of the surface of the material are improved by the reasonable matching of the diameter of the projectile and the strengthening time of the shot peening, and the deformation of the material is effectively inhibited during the friction process.