Laser Shock Peening Research Articles

Computational analysis of multivariant physical and mechanical experiments on laser hardening of gin disc saws

The article describes an original method for computational analysis of multivariate physical and mechanical experiments on laser hardening of gin saw blades. The laser processing method is one of the most effective physical and mechanical methods for improving the properties of resistance to fatigue, long-term strength, and corrosion cracking of circular saw blades that operate under conditions of elevated temperatures and cyclic loads. The stages of the analysis of multivariate experiments on hardening the teeth of a circular saw with laser radiation during grinding are described in detail. Based on theoretical studies three main factors have been selected that significantly affect the hardening of saw teeth. Considering these factors the developed technique makes it possible to increase the thinness of the teeth of circular saw blades significantly due to laser hardening, while maintaining their high hardness in thickness. It has been experimentally confirmed that the service life of gin saws has doubled.

Wear resistance enhancement of QT700-2 ductile iron crankshaft processed by laser hardening

Wear resistance enhancement of QT700-2 ductile iron crankshaft processed by laser hardening

Effects of pulsed laser hardening of cylindrical surfaces on fatigue behavior

The issues of the of laser hardening of the plain bearing effects on the fatigue strength of the crankshaft neck journal are discussed in this article. The crankshaft destruction of the crankshaft leads to catastrophic consequences, especially for heavy diesel engines. The article substantiates the assertion of a decrease in the fatigue strength of steels after pulsed laser hardening treatment of the friction surface to increase the wear resistance of a plain bearing. The process of formation of a surface hard layer of steel and the formation of dimple-shaped stress concentrators on it after interaction with a laser pulse is studied. Factors affecting the fatigue behavior of materials are analyzed. Particular attention is paid to the formation of a residual stress state in the surface layer and the role of surface defects on the fatigue behavior of steel. The assumption about the possibility of reducing the decrease in fatigue strength by optimizing the technological parameters of laser processing is substantiated. On the basis of the study, it is proposed to limit the energy of the laser pulse, preventing the surface from melting.

Effect of multiple laser shock peening without coating on residual stress distribution and high temperature dry sliding wear behaviour of Ti-6Al-4 V alloy

Effect of multiple laser shock peening without coating on residual stress distribution and high temperature dry sliding wear behaviour of Ti-6Al-4 V alloy

Modeling of Time Pressure Profile on Sample Surface during Laser Hardening of Material

Modeling of Time Pressure Profile on Sample Surface during Laser Hardening of Material

Effect of Laser Shock Peening on the Fatigue Life of 1Cr12Ni3Mo2VN Steel for Steam Turbine Blades

In the present study, laser shock peening (LSP) was employed to enhance the rotating bending fatigue life of 1Cr12Ni3Mo2VN martensitic stainless steel used in steam turbine blades, addressing the issue of insufficient fatigue performance in these components. The aim of this study was to investigate the effect of LSP on the microhardness, residual stress, and rotating bending fatigue life of 1Cr12Ni3Mo2VN steel samples. The microhardness of LSP-treated samples was increased by 10.5% (LSP-3J sample) and 15.3% (LSP-4J sample), respectively, compared to high-frequency hardening samples. The residual compressive stress of the LSP-4J sample was the largest, reaching −689 MPa, and the affected layer depth was about 800 μm. Fatigue tests showed that the number of cycles at the fracture point for the LSP-3J and LSP-4J samples increased by 163% and 233%, respectively. The fatigue fracture morphology of the four samples showed that the microhardness and residual compressive stress distribution introduced by LSP could effectively inhibit the initiation of surface cracks, slow down the crack growth rate, and improve the rotating bending fatigue life of 1Cr12Ni3Mo2VN.

Post-processing of Wire Arc Additive Manufactured Stainless Steel 308L to Enhance Compression and Corrosion Behavior using Laser Shock Peening Process

Post-processing of Wire Arc Additive Manufactured Stainless Steel 308L to Enhance Compression and Corrosion Behavior using Laser Shock Peening Process

Dual protection against electrochemical corrosion for AA5083 Al alloys: Synergistic action of superhydrophobicity and strain-strengthening

A new laser compound process, namely, laser shock peening of the surface to obtain the strain-strengthening layer (under the ultrahigh strain rates of >107 s−1), followed by laser surface texturing to achieve the superhydrophobicity on the strengthened surface, is proposed to provide dual protection against electrochemical corrosion for AA5083 Al alloys. The surface morphology, microstructure, residual stress and surface wettability of AA5083 Al alloy after laser compound processing were investigated. The corrosion experiments were performed by an electrochemical station. Results indicate that LSP-induced strain-strengthening layer with grain refinement and high-density dislocations accompanied by compressive residual stress on the surface. Subsequent LST produced surface superhydrophobic structures with an SCA of 155.95°. The electrochemical corrosion experiments displayed that the superhydrophobic surface works as the first protection to prevent the corrosive medium from adsorbing. With the failure of the defense function of superhydrophobic structures, the following refined grains and high-density dislocations in the strain-strengthening layer are preferred to generate protective passive films. Besides, compressive residual stress retards the permeation of Cl− anions, greatly delaying the breakdown of passive films. For the Al alloy immersed in 3.5 % NaCl solution for 48 h, the LSP-LST specimen exhibited the lowest Icorr and the highest Ecorr and Epit, with the value of −1.304 V, −0.662 V, and 50.71 μA/cm2, which exhibited the greatest corrosion properties.

Introducing both chemical and structural gradients in AISI 321 stainless steel via aluminizing and laser shock peening for superior properties

Aluminizing is a diffusion based chemical surface treatment on materials to provide excellent protection against high temperature oxidation and corrosion, but is likely to be accompanied by a degradation in mechanical properties. Laser shock peening (LSP) is a superior laser based surface strengthening technique for enhanced mechanical properties. In this study, we focus on combining these two methods on the AISI 321 stainless steel to introduce both chemical and structural gradients for superior properties. Comparative investigation on both the microstructure and mechanical properties of the as received 321 steel, aluminized 321 steel and the aluminizing + LSP processed steel indicated that: (1) A three-layer protective coating was introduced on the surface of the aluminized steel and the concentration of Al decreased gradually from the outermost layer to a certain depth, forming B2-FeAl(Cr) solid solution and Al2O3 in Layer-I, B2-FeAl and DO3-Fe3Al phases in Layer-II and BCC-Fe(Cr,Al) solid solution phase in Layer-III, with B2-NiAl precipitates distributed in Layer-II and Layer-III. (2) After LSP treatment, a dislocation density gradient from the surface to the matrix, dislocation-precipitate interactions and a significant compressive stress were introduced. (3) Though the aluminized steel exhibited a decrease in the high temperature tensile properties compared to that of the as received 321 steel, the aluminizing + LSP processed steel achieved a striking enhancement. The formation of three-layer coating, dislocation density gradient, dislocation-precipitate interactions and the residual stress contribute jointly to gain the yield strength, ultimate strength and fracture elongation up to 265 MPa, 430 MPa and 37.5 % at 620 °C, respectively.

A comparative assessment of the effects of laser shock peening and ultrasonic shot peening on surface integrity and ratcheting fatigue performance of HSLA steel

In this work, a comparative assessment of the effects of laser shock peening (LSP) and ultrasonic shot peening (USP) on surface integrity and ratcheting fatigue performance of ASTM A588 Grade D high strength low alloy steel was done. Surface roughness, microhardness, microstructure, residual stress, and micro-texture analyses were used to describe the unpeened and peened surfaces. Three sets of tension-compression asymmetric cyclic loading tests were carried out at room temperature on unpeened and peened specimens to evaluate the effects of the applied treatment on strain accumulation and fatigue life. The quantitative dislocation densities of selected specimens were calculated in order to examine the mechanism underlying the softening behavior of USP-treated specimens during fatigue testing. The results are presented in light of the substantial surface roughness, lower compressive residual stress, and weakening of texture intensity revealing an unexpectedly large drop in fatigue strength following USP treatment compared to the unpeened and laser-peened specimens.

Anti-Wear Property of Laser Textured 42CrMo Steel Surface

In this work, laser processing technology was utilized to fabricate micro-textures on the surface of 42CrMo steel to improve its wear resistance under high load conditions and provide an effective method to solve the wear of tooth plates in oil drilling wellhead machinery. Firstly, the friction process of the textured components was conducted by finite element analysis. Additionally, various forms of textures were compared and measured by this method to optimize the shape and parameters of the patterns. Secondly, three types of texture shapes, such as micro-dimples, micro-grooves, and reticular grooves, were created on the surface of 42CrMo steel. Lastly, the tribological characteristics of the micro-textures were analyzed in the dry friction experiments. Compared with the untextured surface, the wear resistance of the textured 42CrMo steel has been improved, and the anti-wear property of the micro-dimples was better than micro-grooves and reticular grooves. Along the direction of friction sliding, the wear of the front end is more worn than the rear end. Micro-dimples with a diameter of 0.8 mm, a spacing of 1.2 mm, and an area occupancy of 34.8% were fabricated at an output power of 200 W and a frequency of 5 Hz. The wear of the textured surface has been reduced by more than 80% in the process of ring-block dry friction with a load of 50 N, a rotation speed of 35 r/min, and a time of 15 min. The wear mechanism is mainly abrasive wear. The results showed that the hardness of the surface could be improved by laser hardening. In addition, micro-dimples on 42CrMo steel can store abrasive particles, mitigate the formation of furrows and reduce the abrasive wear of tooth plates.

Influence of Laser Shock Peening and Ultrasonic Nanocrystal Surface Modification on Residual Stress, Microstructure, and Corrosion–Fatigue Behavior of Aluminum 7075-T6

Influence of Laser Shock Peening and Ultrasonic Nanocrystal Surface Modification on Residual Stress, Microstructure, and Corrosion–Fatigue Behavior of Aluminum 7075-T6

Numerical Simulation and Process Study on Laser Shock Peening of 1Cr18Ni9Ti Material

This article mainly studies the improvement of the properties of the 1Cr18Ni9Ti material after laser shock peening. The 1Cr18Ni9Ti material is the main material used to make aviation ducts, and improving the fatigue life of aviation ducts can significantly improve the safety performance of aviation engines. The article combines simulation and experiment to study the improvement effect of laser shock peening on the material’s properties. The main results are as follows: The fatigue test showed that, under the same stress load, laser shock peening can greatly extend the fatigue life of the specimen, with the 3J process having the best effect. EBSD analysis showed that the 3J process has the best grain refinement effect. The X-ray diffraction method proved that the measurement results of residual compressive stress under the 3J process are optimal. Overall, it is shown that the properties of the 1Cr18Ni9Ti material can be greatly improved under the 3J process.

Numerical Simulation and Surface Properties of 42CrMo Steel Treated by Plasma Nitriding and Laser Quenching

In this study, we investigated the nitriding and laser quenching composite modified layers of 42CrMo steel. MATLAB was used to fit the nitrogen concentration distribution during nitriding, and the laser temperature field was fitted using ABAQUS finite element simulation software. Two groups of simulation results were integrated to fit the modified layer depth under different processes, and the nitriding and laser quenching experimental results were compared with the simulation results, which indicated that the simulation results agreed well with the experimental results. The depth of the nitriding–laser quenching composite layer greatly improved compared with the nitriding or laser hardening layers. The austenitizing temperature of the 42CrMo steel was reduced to 577 °C by nitriding. Therefore, the depth of the austenitized layer of the 42CrMo steel heated with the same laser power significantly increased. Under the same laser process conditions, more austenitic phase transformation was observed in the nitriding layer than in the non-nitriding layer, so martensitic phase transformation was more likely to occur in the subsequent cooling process. After plasma nitriding at 460 °C for 16 h and laser quenching, the modified layer depth of the 42CrMo steel reached 990 μm, and the average surface hardness of the 42CrMo steel reached 625 HV0.1. The friction coefficient of the modified layer was the lowest, with a value of 0.433, and the minimum wear value was 1.024 mm3. Double hardness and thickness of the modified layer could be obtained by nitriding and laser quenching composite processes.

Enhancing the forming quality of Al2024-T351 sheets in laser peen forming through a novel energy sequence arrangement strategy

Laser peen forming (LPF) employs laser-induced shock waves for shaping and modifying bent structures, exhibiting high flexibility and non-contact advantages. This study investigated the impact of different laser energies, laser peening sequences, and energy sequences on the bending deformation, surface quality, and stress distribution of 4 mm thick sheets, using both experiments and simulations. Increasing laser energy and peening sequences were found to enhance the degree of sheet deformation, while adjusting the energy sequence had an insignificant effect on deformation. Higher laser energy resulted in increased surface roughness in the peened area, whereas increasing the peening sequence reduced surface roughness. The optimal approach for reducing surface roughness in forming sheets was found to be utilizing low-energy peening after high-energy peening (high-then-low). Moreover, compared to single low-energy peening, employing the high-then-low-energy peening strategy decreased the attenuation rate of the compressive stress wave, which led to a 23.5 % increase in the magnitude and 25 % increase in the depth of the final compressive stress. The compressive residual stress (CRS) in the length and width direction of the sheet's surface layer was higher with the high-then-low energy peening strategy compared to other treatment strategies.

Laser Shock Peening Improves the Corrosion Resistance of an E690 High-Strength Steel Cladding Layer.

To investigate the effect of laser shock peening parameters on the corrosion resistance of an E690 high-strength steel cladding layer, NVE690 high-strength steel powder was selected for testing at various power densities of pulse lasers. The surface roughness and residual stress of the treated samples were measured, and the microstructure morphology of the sample surface was observed. The electrochemical corrosion tests were conducted with an electrochemical workstation to measure the electrometer polarization, obtain the impedance curve, and observe the electrochemical corrosion. As the laser power density increased, the surface grains of the E690 high-strength steel cladding layer continued to refine until nanocrystals formed, and the residual compressive stress on the surface increased. The residual compressive stress on the surface rendered the passivation film stable and dense; furthermore, the refinement of surface grains inhibited the initiation and propagation of microcracks. The positive shift of the corrosion potential increased from -1.004 to -0.771 V, the corrosion current density decreased from 114.5 to 5.41 μA/cm2, the radius of the impedance spectrum curve increased, and the peeling pits, as well as corrosion micropores on the surface, gradually became no longer evident after electrochemical corrosion. After laser shock treatment, the corrosion resistance of the cladding layer sample was substantially improved.

The effect of laser shock peening on very high cycle fatigue properties of laser welded 2A60 aluminum alloy joints

Laser shock peening (LSP) technology has the advantages of deep residual compressive stress field, low degree of cold hardening and controllable hardening area. The surface modification of welded structures has broad prospects. To predict the very high cycle fatigue (VHCF) life of an aero engine impeller, it is of great engineering significance to study the VHCF performance of 2A60 aluminum alloy. The effects of LSP on VHCF properties of laser welded joints were investigated from the S-N curve, fracture morphology, residual stress, hardness, and roughness. The results show that the S-N curves of the 2A60 aluminum alloy matrix under the condition of ethanol cooling belong to the infinite life type. The S-N curves of welded and LSP samples belong to the continuous decline type. In the process of LSP, the fatigue crack source is transferred from the surface of the sample to the second surface of the sample, which not only counteracts the residual tensile stress introduced on the surface of the sample during welding but also introduces considerable residual compressive stress on the surface of the sample. The roughness is reduced, thus improving the fatigue stsample's fatigue strength and life. The strengthening mechanism of LSP is discussed from two aspects of dislocation strengthening and residual stress. The LSP results in many dislocation proliferation within the grain, and the dislocation entanglement and dislocation wall are formed among the dislocations. The original coarse crystal is divided into multiple subgrains to achieve the effect of grain refinement. Grain refinement and high-density dislocation increase the hardness of the material.

Gradient structured high-entropy alloy with high hardness and corrosion resistance after laser shock peening

In the effort to improve the surface properties of FeCoCrNiMn HEA, gradient structure was prepared by laser shock peening (LSP), a versatile and efficient method to achieve distinct surface properties. The underlying mechanism of the LSP strengthening effect was discussed based on microstructure analysis, mechanical properties, and corrosion test. Our results suggested that ultra-fined grains and high density of defects were produced after LSP treatment which accounts for the significant enhancement of hardness, coefficient of friction (CoF), and corrosion resistance. The strengthened mechanical properties owed to the large amount of grain boundaries and high density of defects that significantly attenuate the movement of dislocations. Meanwhile, attributed to the compressive residual stress induced by LSP, the penetration of corrosive solution was effectively impeded and the passivation process was accelerated. Finally, the different mechanisms of LSP strengthening effect have been discussed. This study presented a promising approach to address the challenge of surface modification of FeCoCrNiMn HEA and provided a novel strategy for regulating the microstructure of HEA and achieving outstanding properties.

Improvement of Stress Corrosion Cracking Resistance of Shear Cut 304L Stainless Steel through Laser Shock Peening

Improvement of Stress Corrosion Cracking Resistance of Shear Cut 304L Stainless Steel through Laser Shock Peening

Preparation of 2024-T351 aluminum alloy superhydrophobic surface by laser peening without absorption layer and without confinement layer

The purpose of this study was to investigate the preparation of superhydrophobic surfaces on 2024-T351 aluminum alloy by laser peening without absorption layer and without confinement layer (LPwAC). The wettability, residual stress and microhardness of the treated specimens were measured. The surface morphology of the specimen was characterized by scanning electron microscopy, and the surface elements and crystal orientation were analyzed. The experimental results showed that the micro-nanoporous structure appeared on specimen surface after LPwAC treatment. The superhydrophobic state was observed after chemical modification reduced the surface energy. Additionally, the crystallinity of the surface was increased, the hardness was improved, and residual compressive stress was generated inside the material. LPwAC is an effective process for the preparation of stable 2024-T351 aluminum alloy superhydrophobic surfaces.