The laser shock peening (LSP) process using a Q-switched pulsed laser beam for surface modification has been reviewed. The development of the LSP technique and its numerous advantages over the conventional shot peening (SP) such as better surface finish, higher depths of residual stress and uniform distribution of intensity were discussed. Similar comparison with ultrasonic impact peening (UIP)/ultrasonic shot peening (USP) was incorporated, when possible. The generation of shock waves, processing parameters, and characterization of LSP treated specimens were described. Special attention was given to the influence of LSP process parameters on residual stress profiles, material properties and structures. Based on the studies so far, more fundamental understanding is still needed when selecting optimized LSP processing parameters and substrate conditions. A summary of the parametric studies of LSP on different materials has been presented. Furthermore, enhancements in the surface micro and nanohardness, elastic modulus, tensile yield strength and refinement of microstructure which translates to increased fatigue life, fretting fatigue life, stress corrosion cracking (SCC) and corrosion resistance were addressed. However, research gaps related to the inconsistencies in the literature were identified. Current status, developments and challenges of the LSP technique were discussed.

/pdf/laser-peening-process-and-its-impact-on-materials-properties-1up080uvlh.pdf

Laser Peening Process and Its Impact on Materials Properties in Comparison with Shot Peening and Ultrasonic Impact Peening

7075 aluminum alloy weldments were processed by an intensive process known as laser shock peening (LSP), meanwhile its stress corrosion behaviors were observed by scanning electron microscopy (SEM) and slow strain rate tensile (SSRT) tests. Results showed that the effect of LSP on corrosion behavior of the joint was fairly useful and obvious. With LSP, the elongation, time of fracture and static toughness after the SSRT test were improved by 11.13%, 20% and 100%, respectively. At the same time, the location of the fracture also changed. LSP led to a transition of the fracture type from transgranular to intergranular The reasons for these enhancements of the joint on corrosion behavior were caused by microstructure, residual stress, micro-hardness, and fracture appearance.

Effects of laser shock peening on stress corrosion behavior of 7075 aluminum alloy laser welded joints

Laser shock peening (LSP) or Laser shock processing is a novel surface treatment technique for strengthening metal materials. In this work, several investigations were performed to evaluate the effect of LSP on some mechanical properties of a near-α titanium alloy Ti834. Micro-hardness measurements of the untreated and LSP treated specimens were carried out by using a Vickers indenter. The depth profiles of subsurface micro-hardness of the shocked region were determined through the electro-polishing material removal in steps of 0.1 mm. It is observed that the micro-hardness of Ti834 alloy can be improved by LSP, and repeated shocks have a very beneficial effect on surface hardening. Residual stress distribution as a function of depth was determined by X-ray diffraction (XRD) with the sin 2 ψ method. The high-cycle fatigue performance of the alloy was investigated and the fractographs of fatigue specimens were observed by SEM. Results reveal that the high-cycle fatigue life of Ti834 alloy increases after laser shock peening due to the introduction of compressive stress which can delay the initiation and growth of the fatigue crack.

Effect of laser shock peening on the mechanical properties of a near-α titanium alloy

Experimental investigation of laser peening on TiAl alloy microstructure and properties

To address the effects of laser shock peening (LSP) on surface integrity and high cycle fatigue (HCF) vibration fatigue lives of Ti17 compressor blades, LSP experiments on the 1st-order bending vibration nodal region of the blades were performed by a Neodymium-doped Yttrium Aluminum Garnet (Nd:YAG) laser system with square spots. Surface roughness, in-depth residual stresses both on the pressure and suction surfaces, local bending deformations at the leading and trailing edges, and surface microstructure were analyzed by surface profiles, X-ray diffraction (XRD), three-coordinate measurement and transmission electron microscopy (TEM), respectively. HCF vibration fatigue tests were carried out on a DC-4000 electric vibration system and fatigue fracture morphologies were analyzed by scanning electron microscope (SEM). Results showed that surface roughnesses values were not more than Ra 0.4 μm both on the pressure and suction surfaces of the blades with and without LSP. Compressive residual stresses layers with about 1 mm were generated both on the pressure and suction surfaces of the blade and the maximum values were located at the topmost surface. Two-way local bending deformations induced by LSP were convex bending deformation at the trailing edge and concave bending deformation at the leading edge. High density dislocations, twinning and nano-grains were observed on the surface microstructure. Compared with as-received blades, HCF vibration fatigue lives of the blades with LSP were increased by one order of magnitude. Fatigue strengthening mechanism was implied by establishing the relationship between fatigue fracture morphologies and effects of compressive residual stresses and refined grains.

Surface integrity and fatigue lives of Ti17 compressor blades subjected to laser shock peening with square spots

https://cyberleninka.org/article/n/1122136.pdf

Haiying Xu

Papers

Investigation of Surface Integrity on TC17 Titanium Alloy Treated by Square-spot Laser Shock Peening