Laser Shock Peening Research Articles

Effect of Combined Laser Thermal and Shock Wave Effects on the Mechanical and Tribological Properties of Steels

Herein, we present the results of an experimental study on the mechanical properties of Fe-C alloys with different carbon contents (0.2, 0.45, and 0.8%) in a wide range of deformation rates (10−3–103 s−1) and abrasive wear resistance, which underwent combined laser thermal (laser surface hardening—LSH) and laser shock wave (Laser Shock Peening—LSP) processing. The combined treatment modes included a different sequence of exposure to laser thermal and laser-induced shock pulses on the material. The amplitude and duration of laser-induced shock waves were measured using a laser Michelson interferometer. The mechanical properties of steel samples were studied under conditions of uniaxial tension under static loads on a standard universal testing machine, the LR5KPlus, and under dynamic loading, tests were carried out on a specialized experimental complex according to the H. Kolsky method using a split Hopkinson rod. The abrasive wear resistance of hardened surfaces was studied using the Brinell–Haworth method. Studies have shown that the use of a combination of LSH and LSP treatments leads to an increase in both the mechanical properties of steels and abrasive wear resistance compared to traditional laser hardening. It has been established that in the combinations considered, the most effective is laser treatment, in which LSP treatment is applied twice: before and after LSH. Thus, after processing steels using this mode, an increase in the depth of the hardened layer was recorded—by 1.53 times for steel 20, by 1.41 times for steel 45, and by 1.29 times for steel U8—as well as a maximum increase in microhardness values by 22% for steel 20, by 27% for steel 45, and by 13% for U8 steel. The use of this mode made it possible to obtain the maximum strength properties of the studied materials under static and dynamic loading, which is associated with an increase in the volume fraction of the strengthened metal and high microhardness values of the strengthened layer of traditional LSH. The dependences of abrasive wear of the studied steels after various combinations of LSP and LSH impacts were established. It is shown that the greatest wear resistance of the studied steels is observed in the case when the LSH pulse is located between two LSP pulses. In this case, abrasive wear resistance increases by 1.5–2 times compared to traditional LSH.

Thermal Stability of Nanocrystals in SLM-printed Ti64 Alloy Treated by Laser Shock Peening and Plasma Nitriding

Thermal Stability of Nanocrystals in SLM-printed Ti64 Alloy Treated by Laser Shock Peening and Plasma Nitriding

Artificial neural network and ANFIS approaches for mechanical properties prediction and optimization of a turbine blade treated by laser shock peening

This research article covers a comprehensive investigation on the prediction and optimization of residual stresses, plastic deformations and damage induced by laser shock peening (LSP) on a thin Ti-6Al-4 V leading edge sample of a turbine blade. The study is based on a two-part approach: the first part involves a numerical simulation of the LSP process and the characterization of its effects on the material. The finite element analysis (FEA) is used to simulate the complex interactions between laser parameters, material properties and mechanical response. This numerical analysis generates valuable insights into the residual stress distribution, the plastic deformation and the potential damage within the sample being treated. Based on the numerical results, the second part highlights the novel application of the artificial neural network (ANN) and the adaptive neuro-fuzzy inference system (ANFIS) methods. By taking advantage of the strength of ANN and ANFIS, the models are able to learn accurately from all the data generated by numerical simulations, allowing them to precisely predict and optimize the effects induced by LSP: residual stresses, plastic strains and damage. This paper provides a significant contribution to the field of materials science and engineering, by offering an in-depth comprehension of the LSP process impact on Ti-6Al-4 V leading-edge turbine blade specimens. The combined utilization of numerical analysis and artificial intelligence AI-driven techniques offers a comprehensive approach to optimize the LSP process, leading to the fatigue resistance improvement and service life extension of turbine blades and other critical aerospace components. The proven capability of ANN and ANFIS enables innovative solutions in aerospace engineering and surface treatment technologies, promoting the AI implementation in materials processing and design.

Evaluation of 3D Printing Orientation on Volume Parameters and Mechanical Properties of As-Build TI64ELI

The discovery of the utility of various titanium alloys as implant biomaterials has resulted in these materials becoming far more popular than other metals in the medical world. However, the production of these materials using additive manufacturing has its own challenges some of those being the surface finish that can be used as an implantology material. As such, the purpose of this study is to evaluate the influence of 3D-printed Ti64ELI on the as-built samples printed at 60°, 90°, and 180° orientations. Such studies are very limited, specifically in the development of the laser shock peening surface modification of dental implants. The study showed that each mechanical test that was performed contributes differently to the printing orientation, e.g., some tests yielded better properties when 180° printing orientation was used, and others had poorer properties when a 180° printing orientation was used. It was observed that 60° testing yielded a micro-hardness value of 349.6, and this value was increased by 0.37% when 90° orientation was measured. The lowest HV value was observed under a 180° orientation with 342.2 HV. The core material volume (Vmc) was 0.05266 mm3/mm2 at a 60° orientation, which increased by 11.48% for the 90° orientation. Furthermore, it was observed that the surface roughness (Sa) at 60° orientation was 43.68 μm. This was further increased by 6% when using the 90° orientation.

Chloride-induced stress corrosion cracking in Austenitic steels for SNF storage canisters - Recent understanding and advances in mitigation and repair

Chloride-induced stress corrosion cracking (CISCC) is a critical threat to stainless steel (SS) spent nuclear fuel (SNF) and radioactive materials storage canisters currently in service worldwide. In the past decade, extensive research has been conducted to understand fundamental mechanisms of CISCC, as well as to develop effective repair and mitigation methods to prevent catastrophic failure of the SNF canisters from CISCC. This review article aims to: (1) summarize recent progress from fundamental studies of CISCC in SS, and (2) present state-of-the-art developments in CISCC mitigation and repair techniques that may be especially well-suited for SNF storage applications, including cold spray (CS), friction stir welding (FSW), friction surfacing (FS), laser shock peening (LSP), and ultrasonic nanocrystal surface modification (UNSM). Knowledge gaps in current understanding of CISCC and roadmaps for deployment of the repair techniques are also discussed.

The impact of successive laser shock peening on surface integrity and residual stress distribution of laser powder-bed fused stainless steel 316L

Abstract The utilization of laser shock peening (LSP) in laser powder bed fused (LPBF) stainless steel (SS) 316L components enhances the mechanical characteristics and operational lifespan of the product quality through a significant reduction of residual stress and a noticeable increase in roughness parameters. The key objective of the study is to analyze the influence of consecutive laser shock peening (LSP) without ablative coating and low pulse energy on the surface properties, residual stress distribution, and microhardness of samples produced by LPBF with SS316L material. The surface quality of the sample subjected to consecutive laser shock peening shows a slight deterioration in its condition. This can be attributed to the combined impact of ablative surface and surface damage resulting from the production of high-energy plasma. However, the implementation of successive LSP results in a distinctive enhancement of compressive residual stresses (CRS) that are evenly distributed throughout the central axis and sharp edges. In contrast, the as-built condition exhibits non-uniform stress magnitudes. CRS observed in each LSP iteration exhibits a notable increase, reaching a maximum magnitude of −389 MPa compared to the initial stress level of 165 MPa in the as-built sample. This enhancement can be attributed to the repetitive impact of shock waves on the surface, leading to the formation of plastic deformation. The refinement of surface grains and the presence of favorable residual stresses were proven by the utilization of x-ray diffraction (XRD) studies and the Cos α plot. The XRD investigation also indicated the absence of any newly formed phases or secondary phases. A significant enhancement in microhardness was observed, with an increase of 58.3% achieved after the third consecutive peening process. The successive LSP samples displayed a gradual improvement in electrochemical behavior. Though the amplitude parameters increased after LSP, the increase in wear rate was observed.

Improving mechanical property and corrosion resistance of high electrical conductivity Al-Ce-Sc-Y and Al-Mg-Si-Ce-Sc-Y alloys by laser shock peening

The high electrical conductivity Al-Ce-Sc-Y and Al-Mg-Si-Ce-Sc-Y alloys were used to study the effects of laser shock peening on their mechanical property, pitting and intergranular corrosion resistance. The strength and elongation of the alloys were improved simultaneously at the expense of very low electrical conductivity after laser shock peening due to the gradient structure and residual compressive stress. After two side laser shock peening, the strength and elongation of Al-Ce-Sc-Y and Al-Mg-Si-Ce-Sc-Y alloys increased to 231 ± 3 MPa/16.2 ± 0.2 % and 359 ± 3 MPa/17.1 ± 0.3 %, respectively. The samples with two surface states were used to study the corrosion behaviors. The number and depth of corrosion pits can be significantly reduced by laser shock peening and the crystallographic corrosion morphology exists in the corrosion pits. After two side laser shock peening with polished surface, the intergranular corrosion depth of Al-Mg-Si-Ce-Sc-Y alloy can reach the minimum and the intergranular corrosion cracks are much finer at the same depth. The Al-Ce-Sc-Y alloy had no tendency of intergranular corrosion, but the unpolished surface was prone to form the deep corrosion pits rather than occurred uniform corrosion. According to the microstructure analysis, the corrosion mechanism of pitting and intergranular corrosion was revealed.

The effect of laser shock peening on the rotating bending fatigue resistance of S51740 stainless steel

The effect of laser shock peening on the rotating bending fatigue resistance of S51740 stainless steel

Laser shock peening of laser melting deposited TiAl alloy for enhancing its corrosion resistance

Laser shock peening (LSP), as a post-treatment process, was employed to improve the corrosion resistance of Ti45Al8Nb alloy fabricated via laser melting deposition (LMD). Microstructure analysis indicated that nanograins and nanotwins structures were formed on the surface layer of LSP-treated Ti45Al8Nb alloy, accompanied by high-density dislocations and stacking faults. Electrochemical results showed that LSP improves the corrosion resistance of Ti45Al8Nb alloy. The formation of nanograins, nanotwins and compressive residual stress during LSP was conductive to dense oxidation films, thus improving the corrosion resistance of the as-deposited Ti45Al8Nb alloy.

Effect of laser shock peening on stress corrosion cracking of TC4/2A14 dissimilar metal friction stir welding joints

Stress corrosion cracking (SCC) of welded joints is a significant issue that affects the widespread application of multimetal welded structures in aerospace, transportation, and other fields. This paper investigates the effect of laser shock peening (LSP) on the SCC of TC4/2A14 friction stir welded (FSW) joints with dissimilar metals. The microstructural evolution, mechanical properties, and corrosion behavior with and without LSP treatment were investigated using optical microscopy, transmission electron microscopy, X-ray analysis, electrochemical testing, and slow strain rate tensile testing (SSRT). The results showed that the LSP significantly refined the grains and induced work-hardening on the near-surface of the material. After LSP, the compressive residual stresses on the surface of the titanium and aluminium sides were −817.6 MPa and −153.6 MPa for the joint, respectively. Corrosion resistance was also improved, with the self-corrosion current density on the Al side of the joints reduced by 77% and the SCC susceptibility index (Issrt) reduced from 0.140 to 0.121. The enhanced SCC resistance of the LSP-treated TC4/2A14 dissimilar metal FSW joints is primarily due to grain refinement, work-hardening effect, and high-level compressive residual stress. These factors not only enhance the material strength and improve the pitting resistance of the joints but also prevent the initiation and propagation of SCC.

Microstructural evolution and mechanical properties of 7050 aluminum alloy modified via laser shock peening at different heat-treated states

In this study, a combination of laser shock peening (LSP) and solid solution treatment (ST) was employed to modulate the microstructures of 7050 aluminum alloy, aiming to optimize mechanical properties and fatigue life. Microstructure observations showed that after LSP, the material experienced significant plastic deformation, introducing numerous dislocations, thereby enhancing the mechanical and fatigue properties of 7050Al. In comparison to a single LSP process, the process of ST prior to LSP is more advantageous for promoting the accumulation of dislocations and the transmission of shock waves, leading to the successful introduction of a deeper hardened layer exceeding 1 mm in depth. The migration and movement of dislocations result in the formation of subgrains, consequently initiating a mechanism for fine-grain strengthening. The surface hardness demonstrates a 30% increase, accompanied by a rise in residual compressive stress by 167 MPa. The yield strength and ultimate tensile strength exhibit notable increments of 23% and 17%, respectively, which attributed to the synergistic interplay of grain boundary strengthening, precipitation strengthening, and dislocation strengthening. Moreover, the fatigue life shows a substantial enhancement of 5.3 times.

Effects of low-power laser hardening on the mechanical and metallurgical properties of biocompatible SAE 420 steel

The present experimental work is carried out on SAE 420 steel to optimize process parameters of low-power laser hardening to improve surface micro-hardness and wear resistance for dry sliding for bio-medical applications. Laser power is the most significant factor for micro-hardening and wear resistance. Rank two for scanning speed and three for standoff distance, respectively. The experiments show that the surface micro-hardness of treated samples varies from 711 to 833 Vickers Pyramid Number by optimized process parameters such as laser beam power of 300 W, laser scan speed of 1.0 mm/s, and standoff distance of 225 mm. In comparison, the base material micro-hardness is 208 Vickers Pyramid Number as the predictive equation generated for finding micro-hardness value for the above three laser hardening process parameters. The dry sliding wear test is conducted on all laser-treated samples and a comparison is made with the untreated sample. A significant improvement in wear resistance was observed for treated as compared to untreated samples. The wear of laser hardened sample of SAE 420 steel was 3.67 x10-9 g/cm compared to untreated base metal wear rate of 139.00 x 10-9 g/cm at an applied load of 30 N and sliding speed of 300 revolutions per minute. The scanning electron microscopy analysis of wear samples (untreated, treated maximum, and minimum hardness) is observed for investigating material removal patterns.

Enhancing strength-ductility balance in AZ31 Mg alloy through single-shot laser shock peening and subsequent annealing

This research demonstrates that single-shot laser shock peening followed by annealing significantly improves the strength−ductility balance of the AZ31 alloy. This is achieved by creating a heterostructure that reduces the dislocation density and enhances work hardening, thereby presenting a viable method for developing magnesium alloys with superior mechanical properties.

Effect of laser shock peening without coating on fretting wear behavior of GH4169 superalloy at high-temperature

Improving the high-temperature wear resistance of aero-engine components is critical. Laser shock peening without coating (LSPwC) seems to have more potential because of lower morphology changes and simpler processing compared with conventional laser shock peening (LSP) techniques. The influence of LSPwC process and test temperature on the fretting wear behavior of GH4169 superalloy for 2 × 105 cycles was investigated. The results indicate that a molten layer and a hardened layer are formed sequentially below the periodic dimple structure under the combination of shock wave and thermal effect. The formation of hardened layer enhances the difficulty of abrasive ploughing and the increase in test temperature promotes the generation of a glaze layer. Therefore, both LSPwC process and high temperature cause a reduction in wear volume. However, the main wear mechanism is similar before and after LSPwC. Besides, the protective mechanism of glaze layer under the gross slip regime may be ascribed to the frictional sintering process.

Analysis of the effect of deep-profile compressive residual stress induced by laser peening on fatigue strength of 7075 aluminum alloy

The effect of laser peening-induced compressive residual stress on the fatigue strength improvement of A7075 specimens was investigated. Rotary bending fatigue tests and residual stress distribution measurements using the sequential polishing method were conducted on untreated, shot-peened, and laser-peened specimens. The results revealed that laser peening provides a deeper compressive stress and a deeper fracture origin, resulting in higher fatigue strength. Furthermore, controlling the laser parameters could extend the depth of the compressive stress layer by approximately 5 mm, indicating the possibility of applying laser peening to thicker materials to improve the fatigue strength.

Effect of laser shock peening on wear resistance of M50 steel

The effects of laser shock peening (LSP) on the surface state and wear resistance of M50 steel are studied by microstructure observation, hardness, and residual stress detection. Results show that after LSP, the carbides on the surface of steel are broken and micro-pits appear. After removing the surface carbide damage by electrolytic polishing, the number of sub-surface carbides increases, and the maximum content is 26.1%. After LSP, the wear resistance of the steel is improved because LSP causes a large residual compressive stress on the surface. The wear performance of the sample after removing the surface damage becomes better, which is related to the elimination of many crack sources and the larger residual compressive stress.

Laser shock peening as a post-processing technique for Inconel 718 components manufactured by laser powder bed fusion

Laser shock peening as a post-processing technique for Inconel 718 components manufactured by laser powder bed fusion

Experimental research on mechanical, material, and metallurgical properties of Inconel 600: Application in elevated temperature environment

Du to high strength and toughness, high oxidation resistance, and high ductility, the Inconel 600 alloy is an ideal choice for the components used in combined heat and power turbines. Therefore, in this paper, the authors conducted experimental tests to better underestand the mechanical behavior of superalloys Inconel 600. The experiments included tensile, fatigue, and creep tests. The material deformation and stress-strain behavior were measured. In addition the yield strength, ultimate tensile strength, elongation, and modulus of elasticity were captured. By illustrating the engineering and true stress-strain curves the Ramberg-Osgood relation were extracted. As a result of fatigue test, the relationship between strain amplitude and the number of cycles to failure for specimens were obtained. The creep tests were conducted at a constant temperature of 650℃. 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Laser peening without coating fabricated superhydrophobic aluminum alloy with favorable mechanical properties

This study prepared 2024-T351 aluminum alloy surfaces with excellent hydrophobic properties by laser peening without coating(LPwC) and post-treatment process (silane solution immersion modification treatment). The surface morphology, microhardness, roughness and residual stress of the specimens before and after LPwC were characterized. Besides, the surface composition and droplet contact angle of the specimens before and after LPwC were measured to investigate the mechanism of enhancing the hydrophobic properties by LPwC. The results showed that after LPwC treatment, the surface of the specimen was uniformly distributed with a large number of micro-nano porous structures and the surface roughness was significantly increased. After the modification treatment with fluorosilane solution, the F element on the surface of the specimen significantly increased, the surface energy decreased, the droplet contact angle rose to above 150°, and the sliding angle dropped to below 10°, which imparted the superhydrophobicity on the surface. After LPwC treatment, the grain size of the specimen near-surface layer was reduced, and high magnitude residual compressive stress was generated inside the matrix, which increased the microhardness of material. The as-prepared superhydrophobic surface exhibits excellent water flow repellency and favorable mechanical properties, which promoted the application of superhydrophobic preparation process in the aerospace field.

Femtosecond laser shock peening Cu-Zn welds: Experiments and multi-scale modeling investigation

Laser shock peening of the weld surface is a cutting-edge treatment technology following welding. However, the conventional nanosecond pulsed lasers used for this process can unintentionally damage the weld surface quality due to secondary melting, which can reduce the comprehensive mechanical properties of the material. Here, we applied femtosecond laser shock peening (FLSP) to Cu-Zn welds as a paradigm. Experimental results show that FLSP cause the finer grain size on the surface of welds, with the maximum increases of approximately 17.6 % in surface hardness of the welds. The residual stress on the surface was transformed from tensile residual stress to compressive residual stress. Crucially, to provide a more precise depiction of the FLSP process, we developed a comprehensive multi-scale modeling approach that involves integrating the inputs and outputs among models with different scales. This multi-scale modeling approach provides an enhanced understanding of the FLSP process compared to traditional single scale models. The high-density electron pressure evolution process, the shock compression fragmentation process of the weld dislocation network during FLSP and the depth of compressive residual stress could be investigated by this model. These findings provide electronic-level and atomic-level insights and imply promising applications of FLSP on various welds surface.