Effect Of Peening Research Articles

Effect of Laser Shock Peening on Surface Morphology of Cold-Sprayed Pure Aluminum Coating

Effect of Laser Shock Peening on Surface Morphology of Cold-Sprayed Pure Aluminum Coating

Optimize Multiple Peening Effects on Surface Integrity and Microhardness of Aluminum Alloy Induced by LSP

Laser shock peening is a modernized surface enhancement performed methodically to improve fatigue life, enhance the hardness of the material and make coarse grains flat under the superficial layer. In this current study, the effect of varying optimized multiple laser shock peening (LSP) is studied on the surface integrity, microhardness, and mechanical properties. The results show that the LSP-treated specimens have visible signs of valleys, wavy and varying height distribution as well as dimples. However, the presence of non-uniformity and sharp protrusions was detected from the superficiality of the as-received specimen and this was so because of the SiC abrasive material used to polish the superficial layer of the specimen before the test experiment. Prior to LSP, the surface roughness was 2 μm, however, after LSP the roughness increased to 4 μm, 6 μm and 17 μm for 1, 2, and 4 impacts, respectively. High-density dislocation can also be observed close to the grain boundary because the grain boundary prevents the migration of dislocation which could lead to dislocation walls and dislocation tangles. The increase in impacts decrease the average grain size, nevertheless, the micro-strain increased after multiple impacts. Furthermore, coarse grains after LSP were transformed into finer grains. The increase in the number of impacts increases the micro-strain likewise the full-width half maximum (FWHM). Finally, the increase in microhardness increases as the LSP impacts increase.

Effects of Micro-Shot Peening on the Stress Corrosion Cracking of Austenitic Stainless Steel Welds

Micro-shot peening on AISI 304 and 316 stainless steel (SS) laser welds was performed to evaluate its effect on the susceptibility to stress corrosion cracking (SCC) in a salt spray containing 10% NaCl at 80 °C. The cracking susceptibility of the welds was disclosed by testing U-bend specimens in a salt spray. Micro-shot peening caused an intense but narrow deformed layer with a nanocrystal structure and residual compressive stress. Austenite to martensite transformation occurred heavily on the top surface of the micro-shot peened welds. SCC microcracks were more likely to be initiated at the fusion boundary (FB) of the non-peened welds. However, fine pits were formed more easily on the micro-shot peened 304 fusion zone (FZ), which was attributed to the extensive formation of strain-induced martensite. The nanograined structure and induced residual compressive stress in the micro-shot peened layer suppressed microcrack initiation in the 304 and 316 welds in a salt spray. Compared with the other zones in the welds in a salt spray, the high local strain at the FB was the cause of the high cracking susceptibility and could be mitigated by the micro-shot peening treatment.

Fatigue Limit Improvement and Rendering Surface Defects Harmless by Shot Peening for Carburized Steel

Remanufacturing has become popular as a system for reducing CO2 emissions caused by the life cycle of products. Therefore, producing more components via remanufacturing is important. Shot peening can be used to render surface defects harmless owing to the compressive residual stress effects. This study investigated the effects of shot peening as a means of remanufacturing gears. In this study, carburized steel specimens containing artificial defects were used to investigate the effects of shot peening on the fatigue strength; the defect size was rendered harmless by shot peening. Shot peening was conducted after inducing semicircular slits with depths of a = 0.15, 0.20, and 0.30 mm. Subsequently, plane bending fatigue tests were carried out. A maximum compressive residual stress of 1400 MPa was induced after shot peening. The fatigue limit of the smooth specimen increased by approximately 31% after shot peening. A semicircular slit of at least 0.20 mm deep could be rendered harmless by shot peening (SP). The defect size reduced by SP was evaluated on the basis of fracture mechanics. The estimated results are consistent with the experimental results. On the basis of the results, the feasibility of shot peening as a remanufacturing method for gears is discussed.

Erosion-corrosion behaviour of shot peening treated nickel-aluminium bronze in simulated sand-containing seawater

The effect of shot peening on the erosion-corrosion property of nickel-aluminium bronze was investigated. The results show that erosion-corrosion has a shot peening-like effect and thus increases the hardness and compressive residual stress. Shot peening alters the erosion-corrosion mechanism. With peening intensity increasing, the predominant reason for causing materials removal shifts progressively from ductile deformation coupled with selective phase corrosion to brittle cleavage-like fracture, highlighting the overriding role of strain-hardening capacity over hardness, compressive residual stress, and surface roughness in erosion-corrosion performance. However, the mass loss rate can be reduced by up to 30% by implementing appropriate peening intensity.

Effect of shot peening on surface characterization and cavitation resistance of nickel aluminum bronze

Nickel aluminum bronze is subjected to cavitation corrosion as propellers working in the seawater. The cavitation corrosion is dominated by the synergistic effect of corrosion and mechanical attack. Previous studies have demonstrated that shot peening (SP) could enhance surface mechanical strength through residual stress and refined grains. In this work, shot peening with Almen intensities from 30 A to 40 A is performed on the nickel aluminum bronze to investigate the effect on the corrosion and cavitation performance. After shot peening with the rough surface, the samples exhibit higher corrosion current densities due to the increased corrosion area and galvanic cells compared to the as-treated samples. Meanwhile, the samples treated by 40 A show the lowest mass loss during the cavitation test and the highest surface micro-hardness. The enhancement of the cavitation resistance is dominated by the coupling mechanism of the surface corrosion aggravation and strain strengthening. Meanwhile, the higher current intensity, the more pronounced surface strengthening enhancement due to the grain refinement's synergistic mechanism and dislocation density.

Effect of surface shot peening on the microstructure and mechanical properties of fuel cladding 1515-Ti austenitic steel

Lead-bismuth fast reactor is considered to be the most promising solution to meet the enormous energy demand in the future. The 15-15Ti austenitic stainless steel with outstanding corrosion and irradiation resistance has been proposed as main cladding candidate material for lead-bismuth fast reactor. However, the mechanical properties of 15-15Ti are weakly influenced by LBE. Shot peening as one of surface strengthening technique can efficiently improve metal mechanical properties. In this paper, shot peening (SP) treatment was applied on 15-15Ti. The microstructures and compositions were investigated using Optical Microscope, Scanning Electron Microscope and X-Ray Diffraction. It concludes that the material hardness is improved, and the residual stress induced by SP did not cause martensitic phase transformation on the sample surface. The presence of slip bands and other obstacles in the reinforcement layer improved the yielding and tensibility of the material.

Effect of Ultrasonic Peening on Mechanical Properties of Low Carbon Steel AISI 1020 TIG Welding Joints Process

In this paper, the effect of ultrasonic peening surface treatment on the mechanical properties of TIG butt weld joints of low-carbon steel (AISI 1020) was studied. A single V-angle (<i>45</i>°) was made on sheets of metal used then welded at constant parameters, namely: current, voltage. Wire filler ER70S-3 with argon was used to obtain many butt welding joints. Some of them were subjected to ultrasonic peening at one, two and three passes. The micro-hardness, microstructure, tensile and bending were tested. The results show increases in the tensile strength after the welding process. The test results showed improvements in the tensile strength of the weldments in comparison to the base metal. On the other hand, the tensile strength decreased with the ultrasonic process. Nevertheless, the tensile strength increased at a high number of ultrasonic passes. On the contrary, the ultrasonic process enhanced the bending strength compared to the base metal, whereas the weldments ability to bend deteriorated.

In-situ laser shock peening for improved surface quality and mechanical properties of laser-directed energy-deposited AlSi10Mg alloy

In the recent decades, the laser-directed energy deposition (L-DED) of aluminium alloy has encountered significant challenges owing to the defects and tensile residual stress. In this study, the in-situ laser shock peening method is employed for the first time to improve the surface quality and mechanical properties of L-DED-fabricated AlSi10Mg alloy. The physical mechanism of the compressive pressure on the pore defects is accounted for using the finite element method. The numerical results indicate that severe plastic deformation driven by the shock wave contributes to defect healing, and the maximum pressure plays a crucial role. The effects of surface laser shock peening (SLSP) and layer-by-layer laser shock peening (LLSP) on the densification, surface quality, including the roughness and residual stress, microstructure, and mechanical properties of the samples are experimentally studied. After the LLSP treatment, the surface quality and mechanical properties of the samples exceed those of common aluminium alloys fabricated by laser powder bed fusion (L-PBF). After the SLSP treatment, a compressive residual stress with a maximum value of 30 ± 14 MPa is formed on the upper surface, and the LLSP treatment overcome the depth limitation of the affected zone. Furthermore, the LLSP treatment addresses the strength–ductility trade-off, and realizes an excellent combination of strength and ductility through grain refinement, dislocation strengthening, and compressive residual stress. Therefore, this work establishes the viability of in-situ laser shock peening for the rapid additive manufacturing of large-size aluminium alloys. The data used to support the findings of this study are available from the corresponding author upon request.

Effect of water jet cavitation peening on electrochemical corrosion behavior of nickel-based alloy 600 in NaCl solution

Surface roughness, residual stress, grain boundary microstructure of the surface layer, the electrochemical corrosion behavior and the surface chemical state after the electrochemical test in alloy 600 in 3.5 wt% NaCl medium was investigated. After the WJP treatment, the surface roughness was increased and residual compressive stress was introduced. A low angle grain boundary layer and a lamellae-shaped layer were formed on the surface. A passivation film with higher Cr content was formed on the WJP treated surface after the electrochemical test. After the WJP treatment, the electrochemical corrosion potential changed from −151 ± 4.6 mV to −133 ± 3.1 mV, the corrosion current density changed from 0.298 ± 0.003 μA/cm2 to 0.052 ± 0.001 μA/cm2, the pitting potential increased from 258 ± 13 mV to 350 ± 8 mV, and the film resistance increased from 4283 ± 158 Ω/cm2 to 124,850 ± 187 Ω/cm2. The superior corrosion resistance was attributed to the change in stress state and microstructure of the surface layer.

Effect of shot peening on high cycle and very high cycle fatigue properties of Ni-based superalloys

In this work, the GH4169 superalloy specimens were shot-peened at two different intensities (0.15 mmA and 0.3 mmA) to improve the fatigue properties, and the fatigue behavior of the shot-peen-treated specimens was investigated in the high cycle fatigue (HCF) and very high cycle fatigue (VHCF) regime. The results of the HCF and VHCF tests indicated that shot peening improved the fatigue properties of the material. In addition, it has shown that the tensile residual stresses introduced by excessive shot peening intensity reduce the benefits of shot peening in terms of improving fatigue properties.

Laser shock wave-induced enhanced thermal corrosion resistance of Ti6Al4V alloy fabricated by laser powder bed fusion

In this study, the effect of laser shock peening (LSP) on the microstructural evolution and thermal corrosion behaviors of laser powder bed fusion processed (LPBFed) Ti6Al4V samples was characterised in Na2SO4 + NaCl mixed solutions at 500 °C, 600 °C and 700 °C. Thermal corrosion resistance was evaluated using thermo-kinetic curves, thermal corrosion products, and corrosion morphology. The results indicated that the thermal corrosion layer of the LSPed samples was thinner and denser than that of the LPBFed samples, and the mass gain of the LSPed samples was significantly reduced, suggesting a better thermal corrosion resistance. This is attributed to the refined grains, high-density dislocations, and nano-twins. Finally, the improvement mechanism of LSP on the thermal corrosion resistance of the LPBF-treated Ti6Al4V titanium alloy was revealed.

Surface smoothening and strengthening combined effect of mechanical hammer peening on inconel 718 superalloy

ABSTRACT In this study, the surface strengthening and smoothening combined effect of the mechanical hammer peening (MHP) treatment is demonstrated. On a IN718 nickel-based superalloy workpiece surface, the MHP treatment introduced a subsurface residual stress field featured with a maximum stress around −1.4 GPa and a penetration depth exceeding 1 mm, and an increase of the micro-hardness from 286.43 HV to 426.27 HV. Simultaneously, it produced a significantly smoothened surface (Ra 27 nm) compared with the untreated sample (Ra 555 nm). Moreover, applying an electric pulse of 100 A would further reduce the surface roughness, without deteriorating the surface strengthening effect. The surface strengthening effect of MHP treatment mainly originates from the increase of dislocation density, grain misorientation and refinement, which are caused by impacts of the punching head; while the surface smoothening effect is the result of precisely controlled and regularly aligned punching indents. Utilizing MHP in the manufacturing process chain of aircraft parts could combine the surface strengthening and smoothening processes into one single process, which substantially improves both the production efficiency and enhances the surface finish. Especially, the working principle of MHP makes it suitable for arbitrary or complicated surfaces, that is, aeroengine blades.

Improving effects of cavitation peening, using a pulsed laser or a cavitating jet, and shot peening on the fatigue properties of additively manufactured titanium alloy Ti6Al4V

To demonstrate and compare the improving effects of cavitation peening and shot peening on the fatigue properties of additively manufactured metals, titanium alloy Ti6Al4V specimens prepared by direct metal laser sintering were treated by cavitation peening, using a pulsed laser or a submerged high-speed cavitating water jet, and shot peening and, subsequently, subjected to torsion fatigue tests. It was revealed that cavitation peening using a laser, shot peening, and cavitation peening using a cavitating jet prolong the fatigue life of AM Ti6Al4V at τa (applied stress) = 450 MPa by factors of 3.5, 3.2, and 1.4, respectively.

Microstructural response and surface mechanical properties of TC6 titanium alloy subjected to laser peening with different laser energy

In this paper, the main purpose was to investigate the effects of laser peening (LP) on the microstructural evolution and frictional wear resistance of TC6 titanium alloy. The surface topographic features, microhardness and residual stress distribution in the depth direction of differently treated specimens were measured using three-dimensional topography instrument, digital microhardness tester and residual stress instrument. The frictional wear test was carried out using a multifunctional friction wear tester. Meanwhile, X-ray diffraction (XRD), optical microscope (OM) and transmission electron microscopy (TEM) were utilized to investigate the effects of LP on the microstructural response of TC6 titanium alloy. The results indicated that the micro-pits induced by LP increased the surface roughness to a maximum of 6.94 μm. LP technique effectively improved the microhardness and frictional wear resistance of TC6 titanium alloy, and the wear form changed from abrasive wear, adhesive wear and fatigue spalling wear to abrasive wear at the laser energy of 8 J. Compared to the untreated specimens, the surface microhardness of the specimens treated by LP with 8 J increased from 356 HV to 442 HV, and the affected layer depth was approximately 500 μm. Moreover, the friction coefficient decreased from 1.2 to 0.5, the abrasion depth of the abrasion track was reduced by approximately 32 % compared to the untreated specimen. Additionally, the surface compressive residual stress induced by LP with 8 J reached about −510 MPa. The microstructural evolution of the specimens processed by LP was dominated by twin formation and dislocation slip, while the intercalation between multidirectional twins and the formation of sub-grain boundaries promoted grain refinement of TC6 titanium alloy. Refined grains, high density of dislocations, mechanical twins and the implantation of compressive residual stresses effectively improved the friction and wear resistance of TC6 titanium alloy.

Effect of surface stress concentration control and surface material strengthening on the fatigue performance of shot-peened single-crystal superalloy

This study analyzes the effect of shot peening on the surface integrity of nickel-based single crystal superalloys (SX) and the evolution of stress concentration factors caused by surface finishing and casting micropores near the surface before and after shot peening by numerical simulation. On one hand, SX forms a surface gradient plastic deformation structure after shot peening. The surface yield strength is 82% higher than that of the matrix by nanoindentation fitting. The deformation of the surrounding materials of the near-surface casting micropores is significantly greater than that of the materials at the same depth by EBSD. On the other hand, the series parameters of surface roughness after shot peening are higher than those of grinding. However, the stress concentration Kt1.32 at the bottom of the smooth crater is significantly lower than that of grinding "furrow" Kt1.94. The surface gradient deformation caused by shot peening flattens the surface casting micropores so that the stress concentration at the upper end of the micropores is significantly smaller than that in the grinding state. Based on the above two effects, the rotary bending fatigue limit of the single crystal alloy after shot peening at 650 °C is increased by 13.0% compared with the ground state. The peened sample no longer originates from the casting micropores.

Improved fatigue strength of Cr-electroplated 7075-T6 Al alloy by micro-shot peening

The effects of micro-shot peening (MSP) on the rotating bending fatigue resistance of Cr-electroplated AA 7075-T6 Al alloy were investigated. Fe-based amorphous particles with sizes of 50–80 μm were used as the shot balls and peened under 100 % surface coverage. The shot-peen intensity, determined by the height of the N-type Almen specimen, was 0.110 mm. The Cr-electroplated layer consisted of a network of microcracks in the as-plated condition. Without the necessity of micro-crack initiation, the Cr-electroplated substrate had the shortest fatigue life and lowest fatigue strength among the tested samples. MSP significantly increased the fatigue strength/life of 7075-T6 Al alloy with or without Cr-plating. The introduction of high residual compressive stress combined with the formation of a nanograined structure in the MSP zone was responsible for the high resistance to fatigue crack growth of the MSP sample.

A Study on Effect of Multiple Laser Shock Peening on Microstructure, Residual Stress, and Mechanical Strength of 2.5 Ni-Cr-Mo (EN25) Low-Alloy Steel

A Study on Effect of Multiple Laser Shock Peening on Microstructure, Residual Stress, and Mechanical Strength of 2.5 Ni-Cr-Mo (EN25) Low-Alloy Steel

The effects of laser peening treatment on the very high cycle fatigue properties for AA2024-T351 alloy using a crystal plasticity framework

The effects of laser shot peening (LSP) on very high cycle fatigue (VHCF) properties of AA2024-T351 alloy were investigated using the combination of experiment and modified crystal plasticity finite element (CPFE) method. The experimental observation found a contradictable result that the fatigue life decreased after laser peening with relatively high pulse energy in this work. The fatigue fracture observation shows that there are obvious facets and refined grains on the shot peening surface, which are not uniform and their aspect ratio is obviously larger than that of the matrix material. In particular, the fracture surface of the sample treated with 20 J pulse energy shows a highly distorted zig-zag crack propagation path. In order to further understand the ultra-high cycle fatigue failure mechanism of aluminum alloy treated with laser shot peening, a modified crystal plasticity (CP) model was applied to find a possible explanation for the contradictable experimental results. In this model, the critical resolved shear stress (CRSS) evolution of the deformation systems in the CP model was variable due to the refined average grain size after different laser peening conditions using the Hall-Petch type relationship. Additionally, the effects of grain morphology characterized by aspect ratio were considered after LSP of AA2024-T351. The fatigue indicator parameters (FIPs) were calculated based on the modified CPFE model under cyclic low stress amplitudes to estimate the fatigue driving force for fatigue crack initiation and microstructural small crack propagation. It is found that the LSP treatment has a beneficial effect on the fatigue properties only considering the refined influence of grain size. However, LSP has a detrimental effect on VHCF properties when considering the combined influences of grain refinement and the changing of grain aspect ratio due to the laser peening surface treatment with relative high pulse energy in this work.

Fatigue crack growth rate of AISI 4140 low alloy steel treated via shot peening and plasma nitriding

In this study, the effects of conventional shot peening (CSP), severe shot peening (SSP), and plasma nitriding (PN) on the fatigue crack growth (FCGR) of AISI 4140 low alloy steel were investigated. FCGR tests were performed on axial fatigue equipment, associated with slow-motion camera and COD gauge. As a result of the experiments, an improvement of 8% in CSP, 15% in SSP, and 5,5% in the PN operations were observed on the number of cycles of all specimens at 30 mm crack length. Particularly for SSP treatments, hardness, compressive stresses, and the creation of nano-crystallization on the surface provide the most effective improvement in FCGR behavior. Additionally, for PN, formation of nitrogen diffusion and effective hardness improvement showed positive results in FCGR behavior. CSP and SSP (particularly SSP) behaved dominant on the improvement of FCGR performance compared to PN treatment. The formation of two-phase brittle structural white layer on the surface prevented the effective FCGR improvement.