Effect Of Laser Shock Peening Research Articles

Study on Effect of Laser Shock Peening as a Pre-Treatment on Fatigue Performance of Hard-Chorme Plated 15–5 PH Stainless Steel

Study on Effect of Laser Shock Peening as a Pre-Treatment on Fatigue Performance of Hard-Chorme Plated 15–5 PH Stainless Steel

Recovery of fatigue life using laser peening on 2024‐T351 aluminium sheet containing scratch damage: The role of residual stress

AbstractThe aim of the current work was to study the effect of laser shock peening (LSP) when applied to 2‐mm thick 2024‐T351 aluminium samples containing scratch‐like defects in the form of V‐shaped scribes 50 to 150 μm deep. The scribes decreased fatigue life to 5% of that of the pristine material. The effect of laser peening on fatigue life was dependent on the specifics of the peen treatment, ranging from further reductions in life to restoration of the fatigue life to 61% of pristine material. Fatigue life was markedly sensitive to near‐surface tensile residual stress, even if a compressive residual stress field was present at greater depth. Fatigue life after peening was also dependent on sample distortion generated during the peening process. Sample distortion modified local stresses generated by externally applied loads, producing additional life changes. Models based on residual stress intensity and crack closure concepts were successfully applied to predict fatigue life recovery.

Investigation on the effect of microstructure and mechanical properties of laser cladded TC17 titanium alloy following laser shock peening

This paper aims to determine the effects of microstructure and mechanical properties of laser cladding TC17 titanium alloy post laser shock peening (LSP) In this work, A 3J, 20ns, 1064nm wavelength, Nd:YAG laser was employed on laser cladded TC17 titanium alloy samples with multiple impacts. Micro-hardness, residual stress were measured. The microstructure of LSPned sample was mapped by Electron Backscattered Diffraction (EBSD). The residual stress results showed that a stable compressive residual stress has been formed on the cladded coating surface with a value of 190MPa due to LSP modification. Additionally, LSP also improves the surface microhardness of cladded TC17 samples with an increase rate of 13.1%. Vibration fatigue tests were designed and carried out to examine the effects of LSP on the fatigue strength of cladded TC17 specimens. Results show that the fatigue strength of unpeened cladded sample is 290MPa while of peened claded sample is 300MPa. This work will contribute to prolong the service life of repaired TC17 components in aero-engines thereby economizing the repairing costs.

Selective modal control of blade vibrations by local laser shock peening

The main purpose of this study is to explore the selective modal control of blade vibrations using laser shock peening (LSP) for the mode shapes with stretching of the mid-plane, which are commonly encountered in some local zones of the higher-order mode shapes. The zones with stretching of the mid-plane are selected for LSP, which leads to residual stresses and grain refinement, in order to control the corresponding mode. A kind of diamond-shaped specimen is chosen as the object of the study to simulate the actual blade. First, theoretical measurements and the finite element method are used to analyze the mechanism of selective modal control. The effects of LSP in different selected zones on modal stiffness and damping are compared, and the selective modal control is simulated. Then, an excitation test was conducted; the experimental results are in good agreement with the simulation, which effectively proves the correctness of the analysis. As the amplitude of the excitation increases, the vibration shows a significant nonlinearity. At this time, the blades treated by LSP show an unusual jump phenomenon, which limits the vibration amplitude in a smaller range. A further experimental analysis is performed for the interpretation of this phenomenon. Based on the above results, it is proved that the local LSP can effectively control the vibration of a certain mode, which provides a more flexible method for blade design, especially for improved design of the blade after styling.

Effect of Laser Shock Peening on Surface Residual Stress and Plastically Affected Depth of TC11 Titanium Alloy

The confined laser shock peening (LSP) is an innovative surface treatment technique designed to improve the fatigue performance of materials by imparting compressive residual stresses into materials. A 3D finite element model was developed to predict the surface residual stress and plastically affected depth of the TC11 titanium alloy after LSP. The modeling procedure consists of two successive explicit analysis steps. The performance of finite element model was verified by comparing simulated results with the experimental data. With the validated finite element model, the influence of the process parameters (LSP path, thickness of the sample, number of impacts) was investigated on the surface residual stress and plastically affected depth of the TC11 titanium alloy after LSP. Some simulated results can be used to mentor the optimization of the process parameters of LSP.

激光冲击处理对GH3039高温合金疲劳寿命的影响

激光冲击处理对GH3039高温合金疲劳寿命的影响

Effects of laser shock peening on the corrosion behavior and biocompatibility of a nickel–titanium alloy

Nickel-titanium (NiTi) alloy is an attractive material for biomedical implant applications. In this study, the effects of laser shock peening (LSP) on the biocompatibility, corrosion resistance, ion release rate and hardness of NiTi were characterized. The cell culture study indicated that the LSP-treated NiTi samples had lower cytotoxicity and higher cell survival rate than the untreated samples. Specifically, the cell survival rate increased from 88 ± 1.3% to 93 ± 1.1% due to LSP treatment. LSP treatment was shown to significantly decrease the initial Ni ion release rate compared with that of the untreated samples. Electrochemical tests indicated that LSP improved the corrosion resistance of the NiTi alloy in simulated body fluid, with a decrease in the corrosion current density from 1.41 ± 0.20 μA/cm2 to 0.67 ± 0.24 μA/cm2 . Immersion tests showed that calcium deposition was significantly enhanced by LSP. In addition, the hardness of NiTi alloy increased from 226 ± 3 HV before LSP to 261 ± 3 HV after LSP. These results demonstrated that LSP is a promising surface modification method that can be used to improve the mechanical properties, corrosion resistance and biocompatibility of NiTi alloy for biomedical applications. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1854-1863, 2019.

Effects of laser shock peening on microstructures and properties of 2195 Al-Li alloy

The effects of laser shock peening (LSP) on microstructures and properties of 2195 Al-Li alloy were studied in this paper. The top surface microstructure of this alloy after LSP was observed using transmission electron microscopy (TEM). The change of stress corrosion resistance after LSP was studied by slow strain rate tensile (SSRT) test. Moreover the effect of LSP on the mechanical properties was characterized by the microhardness and the residual stress test. The microstructure observation results suggested that the surface grain of this alloy was refined to the nanometer with size of 93 nm after single LSP and it can be further refined to 70 nm by 3 times LSP, the grain refinement during LSP should be considered as a dislocation evolution process based on the mechanism of rotating dynamic recrystallization (RDR). The results of mechanical properties test showed that LSP could improve the hardness and introduce the residual compressive stress in the surface of target alloy, and the 3 times LSP can further improve the properties on the base of single LSP. Furthermore, the experimental results of SSRT indicated that LSP was an effective method to improve the resistance to stress corrosion of 2195 Al-Li alloy, because the residual compressive stress and refined grains in the surface can prevent the initiation and growth of cracks, while retard the stress corrosion cracking.

Effects of laser shock peening on corrosion fatigue behavior of 2Cr13 stainless steel

Effects of laser shock peening (LSP) with different coverage layers on corrosion fatigue (CF) resistance of 2Cr13 stainless steel were investigated by residual stress measuring, corrosion fatigue testing and fatigue fracture morphology observing. The results show that LSP can induce high compressive residual stress on the surface of 2Cr13 stainless steel, and the value of surface compressive residual stress increases with the increase of LSP coverage layer. The CF life of LSP specimens is much larger than that of as-machined specimens, and it increases with the increase of LSP coverage layers; the CF crack growth rate of LSP specimens decrease compared with that of as-machined specimens, and it decreases with the increase of LSP coverage layers. After the analysis, we can conclude that the fatigue fracture surface of as-machined specimens is flat and contains few secondary cracks. However, for LSP specimens, due to high surface compressive residual stress induced by LSP, the growth of corrosion fatigue crack is effectively restrained, resulting in a river pattern morphology.

Effect of Laser Shock Peening on Fatigue life of Austenitic stainless steels

.Laser shock peening (LSP) is an innovative surface treatment technique for strengthening metallic materials. The treatment improves fatigue performance and is achieved by introducing compressive residual stresses into the material surface layer. The compressive stresses are created over a significant surface area by means of high pressure shock waves, which are generated by confining the laser-induced plasma. In the present study, the LSP effect on fatigue life of austenitic stainless steels was investigated by changing the laser parameters. The tested material was austenitic stainless steel 08CH18N10T. The influence of LSP treatment on the fatigue life was examined through the three-point bend fatigue test.

Study on the effect of multiple laser shock peening on residual stress and microstructural changes in modified 9Cr-1Mo (P91) steel

This paper presents an experimental study on the effect of laser shock peening (LSP) parameters on resultant surface residual stress and microstructural evolution in P91 steel. P91 steel samples were subjected to single and multiple LSP treatments. Single LSP treatment was performed with laser power density (LPD) in the range of 3.9–5.5 GW cm−2 while multiple LSP treatment was carried out a fixed LPD of 3.9 GW cm−2. The surface of laser shock peened samples was investigated with respect to residual stress, microstructure and micro-hardness through X-ray diffraction (XRD), scanning and transmission electron microscopy and micro-hardness measurements. Single LSP treatment produced significant increase in the magnitude of compressive residual surface stress (−570 to −610 MPa) with respect to unpeened sample with compressive surface stress of around ±85 MPa. However with increasing the LPD beyond 3.9 GW cm−2, the compressive residual surface stress has marginally increased. On the other hand, in case of multiple LSP treated samples, the magnitude of compressive residual surface stress has been observed at increased depth of 975 μm (double LSP) and ~1200 μm (triple LSP) compared to single LSP impact (~750 μm). Further, microstructural analysis carried out using electron microscopy of laser peened samples demonstrated that in the near surface region, martensite lath structure under gone severe refinement with respect to the unpeened sample having average lath width ~1.2 μm. It has also been noticed that grain refinement is found be more prominent in the case of multiple LSP treated samples. The grain refinement in LSP treated samples was also confirmed by XRD peak broadening which progressively increases with an increase in laser impacts. Electron microscopic characterization revealed that in triple LSP treated P91 samples, well-defined polygonal subgrains of average size ~115 ± 10 nm have been observed at near surface (20 μm depth from top).

Improvement of friction characteristics of cast aluminum-silicon alloy by laser shock peening

Piston friction is the primary cause of power loss in automotive engines and thus reducing the friction on piston surface is crucial for the improvement of engine performance. In this work, the effects of laser shock peening on friction characteristics of JIS-AC8A aluminum-silicon alloy, a piston material for automotive engines, were investigated experimentally. Laser shock peening was carried out using a Nd:YAG laser (wavelength = 532 nm, pulse width = 8 ns) at the conditions of laser intensity 4 GW/cm2, overlapping ratio 50% and spot diameter 2.06 mm with no protective coating. When laser shock peening was applied, surface hardness increased by 22% and significant enhancement of compressive residual stress was achieved. Friction coefficients of the laser peened surface decreased by 19%, 41% and 45% from those of unpeened surface at the 50, 100 and 150 N normal load conditions, respectively, demonstrating the effectiveness of laser shock peening in reducing surface friction. Also, the mass loss by wear decreased by 94%.

Effect of laser shock peening on the microstructure and corrosion resistance in the surface of weld nugget zone and heat-affected zone of FSW joints of 7050 Al alloy

Laser shock peening (LSP) was used to strengthen the surface properties of friction stir welding (FSW) joint for 7050-T7451 aluminium alloys. The microstructure, precipitates, dislocations and electrochemical corrosion properties in the surface of weld nugget zone (WNZ) and heat-affected zone (HAZ) of FSW joints were analyzed. The microstructure experienced an obvious change in the cross-section region close to the upper surface of WNZ and HAZ after LSP. The number of precipitates near the grain boundary increased obviously after the LSP. The dislocation in the shock region mainly shows the dislocation line, dislocation tangle, dislocation walls and sub-grain structure (Grain size 2–3 μm). The surface of as-received shows the highest corrosion potential (−0.835 V) in a 3.5% NaCl solution, and the corrosion potential in the surface of WNZ (−0.898 V) and HAZ (−0.932 V) after LSP is higher than the one before LSP. Grain refinement, precipitates and high density dislocation could play an important role to improve the corrosion resistance in the surface of WNZ and HAZ after LSP.

Laser shock peening of welded joints

The effect of laser shock peening (LSP) process on the mechanical characteristics of aluminum and titanium welding joints was investigated. Since LSP requires special ablative and transparent coatings, efficiency of different coatings was analyzed. It was shown that highest LSP effect was obtained by using aluminum foil attached with adhesive tape as an ablative layer and water as a transparent overlay. Several laser peening conditions with different intensities, durations, and number of shots were tested to determine the applicability of the method for an aluminum and titanium alloys. Surface microhardness of observed materials was increased up to 70 %. It was shown LSP of welded joints of Al-6Mg aluminum alloy allows to change tensile residual stresses in the weld zone, on compressive stresses.

Surface modification technique to enhance metallurgical and mechanical properties of alloy C-276 weldment by laser shock peening without coating

Microsegregation of alloying elements is prone to hot cracking in the weldment of alloy C-276. The formation of topologically close packed phases P and µ is largely responsible for the hot cracking. The present study articulates the effect of laser shock peening (LSP) to improve the metallurgical and mechanical properties of the weld joint. The weld joint was fabricated by pulsed current gas tungsten arc welding (PCGTAW) using an ERNiCrMo-3 filler wire. LSP without coating was carried out on the cap surface of the weldment. Microstructural studies were carried out to compare the as-welded and laser-peened microstructure on the fusion zone. The results show that a fine equiaxed dendritic structure was observed in both conditions. EDS analysis was carried out to evaluate the microsegregation of alloying elements. EDS analysis indicates that there are no secondary intermetallic phases. X-ray diffraction analysis was carried out to evaluate the phase change and crystallite size in the as-welded and laser shock peened fusion zone. The result shows 48.99% reduction in crystallite size after LSP. Hardness and tensile strength results indicate there is a consequential increase in laser shock peened specimen compared with as-welded specimen.

Effects of Laser Shock Peening over Minimally Detectable Partial Through-Thickness Surface Cracks

Abstract Laser shock peening (LSP) has evolved as a viable alternative to other surface treatments (shot peening, burnishing, etc.) that induce beneficial residual stress in structural components. While fatigue life improvements have been recognized by the aerospace industry, in-service components may have surface flaws with sizes below current inspection limits. A concern is that the application of LSP over an existing crack may cause unintended detrimental consequences. To address this concern, two different LSP processes were applied over a 0.25 in. (6.35 mm) partial through-thickness surface fatigue crack in 7075-T651 aluminum. The resulting residual stresses were measured using combinations of included X-ray diffraction with layer removal, incremental center-hole drilling, and neutron diffraction. Both LSP processes resulted in a through-thickness residual stress profile in which compressive stresses at either surface were balanced by tensile stresses in a band centered in the mid-thickness of the specimen. Peened and unpeened (baseline) specimens were then tested under constant-amplitude cyclic loading to assess the fatigue response. The average fatigue life of the baseline specimens was about 49,000 cycles. The peened specimens (both treatments) survived to runout, exhibiting no crack growth when examined with an optical microscope even when the crack tip was either very close to or inside the region of tensile residual stress.

Effects of laser shock peening with different coverage layers on fatigue behaviour and fractural morphology of Fe-Cr alloy in NaCl solution

Effects of massive laser shock peening (LSP) treatment as a function of coverage layer on surface residual stress, microstructure, and corrosion fatigue (CF) resistance of Fe-Cr alloy were studied by X-ray diffraction technique, scanning electron microscope observations, and corrosion fatigue crack growth (CFCG) testing. Special attention was paid to the details of compressive residual stress and fracture morphology, and the influence mechanism of coverage layer on CF behaviour was also determined. Results indicated that LSP generated deeper compressive residual stress and effectively decreased the CFCG rate, and increased coverage layers further improved the corrosion fatigue life of notched specimens.

Investigation of multiple laser shock peening on the mechanical property and corrosion resistance of shipbuilding 5083Al alloy under a simulated seawater environment: publisher's note.

This publisher's note corrects the labeling of Figs.10-13 in Appl. Opt.57, 6300 (2018)APOPAI0003-693510.1364/AO.57.006300.

Effect of Laser Shock Peening on Residual Stress, Microstructure and Hot Corrosion Behavior of Damage-Tolerant TC21 Titanium Alloy

The effect of laser shock peening (LSP) on the residual stress, microstructure and hot corrosion behavior of damage-tolerant TC21 alloy was investigated. The equilateral scanning pattern was adopted to obtain a large overlapping area for LSP. The hot corrosion experiments in a salt mixture composed of 75 wt.% Na2SO4 + 25 wt.% NaCl at 700 and 800 °C for a total exposure of 25 h were conducted. The results demonstrated that LSP caused a high compressive residual stress with a significant increase in micro-hardness and microstructural changes in the form of crystal defects, i.e., high density dislocations. The crystal defects promoted the outward diffusion of Al, Cr and Ti to form protective mixed oxides (Al, Cr, Ti)O2. These oxides improved the adhesion of outer oxide layer and hindered the inward diffusion of O, S and Cl, which was beneficial to improve hot corrosion resistance. The mass gains of LSP-treated specimens after hot corrosion at 700 and 800 °C were, respectively, 3.72 and 4.78 mg/cm2, which were much lower than those of untreated specimens (5.65 and 6.81 mg/cm2). Therefore, LSP leads to an improvement in resistance to hot corrosion of TC21 alloy.

Effect of laser shock peening on wear behaviors of TC11 alloy at elevated temperature

Titanium alloy is regarded as a high performance material which has wide application prospect in aerospace and medical field. However, their poor wear properties may lead to failures in early service stages. In this paper, the microstructure, micro-hardness and residual stress of TC11 alloy treated by laser shock peening (LSP) are investigated. The sliding wear experiments are performed to study the influence of various temperature and applied load on the wear behaviors of TC11 alloy with and without LSP. The results indicate that the LSPed specimen has a superior wear properties to that of as-received specimen under the same wear test conditions. The tribological properties are greatly dependent on wear testing temperature and applied load. For the specimens tested under 15 N, the variation trend of friction coefficient and wear rate reduces first (25–500 °C) and then increases (500–600 °C) with increasing the test temperature. When the sliding wear test conducted at 400 °C, the larger the applied load, the more the friction coefficient and wear rate. The prominent tribological performances of LSPed TC11 alloy is ascribed to the high compressive residual stress and grain refinement induced by LSP.