Effects of the secondary shot in the double shot peening process on the residual compressive stress distribution of Ti–6Al–4V

Abstract

Double shot peening is the development of shot peening by shooting large media as a first shot and re-shooting again with smaller media as a second shot in order to achieve high residual compressive stress and hardness at the surface, while the in-depth effect can still be maintained. This research aims to examine the effect of media type and media size when used in the second shot of double shot peening on hardness, roughness, and residual stress to identify the suitable conditions and compare them with single shot peening, such as conventional shot peening and fine shot peening, which was used as the first shot and second shot. Ti–6Al–4V was used as the substrate material, while various diameter sizes of silica and SUS304 media were selected as the media for the second shot in the process. The results showed that in the case of the larger size of silica media in the second shot of double shot peening, the hardness and residual compressive stress on the surface clearly increased more than with the smaller media due to the higher Almen intensity, which affected impact energy. On the other hand, when shooting with SUS304 media as a second shot, the increment of residual compressive stress and hardness, including roughness reduction on the surface, showed less effect than was the case for silica media, due to the lower Almen intensity, which affected the impact energy transfer. This research found that the condition of shooting with 80 μm of silica media as the second shot could generate the highest hardness and residual compressive stress on the surface, which increased by 14% and 53%, respectively, while roughness was decreased by 20% when compared with single shot peening.

Study on the Surface Layer Properties and Fatigue Life of a Workpiece Machined by Centrifugal Shot Peening and Burnishing

“…Examples of shot-peened components are gears [ 1 ], fan blades [ 2 ] and compressor discs of aero-engine [ 3 ]. The impact of a shot peening medium (usually in the form of balls) on the treated surface causes hardening of the surface layer of a workpiece and formation of compressive residual stresses [ 4 , 5 ].…”

Investigation of surface hardness and roughness on formability of aluminum alloy sheet AA2024-T3 subjected to the shot peening process by silica shots

“…Shot peening is a cold-working technique that changes the surface properties of a material by hitting the surface with small media under compressed air [16]. Shot peening leaves dimples on the material, which serve as points for plastic deformation [18,20]. Surface and subsurface areas with these dimples have increased hardness and residual compressive stress [21][22][23].…”

“…Therefore, the higher hardness could be interpreted by plastic deformation generated from dimples on the surface after shot peening [22,23]. The hardness is also increased with the impact energy from the collision of silica media on the surface specimen due to generating more dumpers on the surface [18][19][20]24]. The plastic deformation generated by silica media collisions could be successfully accumulated if the quantity of media was increased.…”

“…This is because every parameter plays a part in the change in material properties after testing. Several researchers have dedicated their work to investigating the effects of the shot peening process on the mechanical properties and modified surface treatment as described in [4,[14][15][16][17][18][19][20].…”

Effect of Regular Shot Peening and Semi-Random Shot Peening Conditions on Selected Properties of the Surface Layer of Gray Cast Iron

“…Burnishing and shot peening are usually employed for machining elements made of materials with high ductility, such as steel [22], aluminum alloys [23], and titanium alloys [24]. However, a vast number of elements exposed to variable operational loads and tribological wear are made of cast iron.…”