Influence of laser peening on microstructure and fatigue lives of Ti–6Al–4V

Laser shock peening: a promising tool for enhancing the aeroengine materials’ surface properties

“…For all the applied stress conditions, the number of cycles to failure increased for laser-peened samples compared to unpeened samples. In another case, Kumar et al [150] showed the shift in the S-N curve on LSPed Ti-6Al-4V alloy (Figure 18c). Another study by Cuellar et al [151] also revealed increased fatigue life after the laser peening process (Figure 18d).…”

“…Ganesh et al [159] studied the effect of laser peening on spring steel SAE9260 coated with black paint of 30-40 μm, which induces CRS of −500 MPa on the surface and a maximum of −625 MPa at 50 µm depth, in addition, LSP induces lower roughness on the surface of about half to shot peening. Hence prominent CRS with lower surface roughness leads to an increase in fatigue cycle (applied stress of 1500 MPa at R = 0.3) LSP samples (104 × 10 5 [152], (c) [150] and (d) [151].…”

“…For instance, Zhang et al [100] studied the effect of laser peening on Ti–6Al–4V alloy subjected to one and two peening passes and observed the increase in fatigue life with an increase in peening passes, as illustrated in Figure 17.

Figure 17 S–N curve of Ti–6Al–4V (reprinted with permission [100]).

Figure 18 The fatigue life of titanium alloys after laser peening process (a) [29], (b) [152], (c) [150] and (d) [151].

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Experimental investigation of laser peening on Ti17 titanium alloy for rotor blade applications

“…It shows that the laser energy and impact times have an influence on the roughness and residual stress value, which is easy to explain: the higher the energy delivered to the material, the larger the roughness and compressive residual stress value. Accordingly, when the laser power density reaches a level of several GW/cm 2 , high-amplitude shock waves, through rapid expansion of high-temperature (around 1000 ℃) plasma of a pressure of about several GPa, can be generated in ablative medium layer 29 . As the high pressure plasma is trapped between the materials and confining medium layers, the high peak pressure stress shock waves are generated (The law of peak plasma pressure (P) can be expressed as Eq.…”

“…Laser peening has become the state-of-the-art to generate deeper than 1mm of compressive stresses into the treated components 18 , without adversely affecting surface roughness of the components 19 . It involves irradiation of the thin opaque coating layer with high-energy short-width laser pulses causing instantaneous vaporization of the surface layer into high-temperature high-pressure plasma 20 .…”