Effect Of Peening Research Articles

Effects of Surface Peening on Residual Stress and Microstructure of Nickel-base Alloy 182 and 52 M Welds

Effects of Surface Peening on Residual Stress and Microstructure of Nickel-base Alloy 182 and 52 M Welds

Effect of ultrasonic shot peening on microstructure and properties of Cu-Ti alloy

Abstract Modified surface layers with refined grain size and high hardness characteristics were prepared on a Cu-Ti alloy using ultrasonic shot peening (USP) by controlling the shot diameter. The phase structure and organization morphology of the modified layer were analyzed using X-ray diffraction (XRD), optical microscopy (OM) and scanning electron microscope (SEM). The hardness, wear resistance and corrosion resistance of the modified layer were systematically characterized. The results showed that the comprehensive surface properties of the sample was optimized at a shot diameter of 3.0 mm. The average grain size was refined to 12.4 nm under the high-frequency impact of steel balls. Owing to the grain refinement and work hardening, the surface hardness, wear resistance and corrosion resistance of the sample was significantly improved. Among these, the surface hardness of the sample was enhanced from 257.68 HV0.1 to 313.51 HV0.1, the volume wear rate was decreased from 0.3305 um2/N to 0.1707 um2/N, and the self-corrosion current density was also decreased from 1.658×e-5 mA/μm2 to 4.053×e-6 mA/μm2. It was shown that USP is one of the effective methods for preparing Cu-Ti alloys with excellent surface properties.

Study on the effects of laser shock peening on the microstructure and properties of 17-7PH stainless steel

To investigate the surface integrity of 17-7PH stainless steel welded structural components used in aviation, laser shock peening (LSP) with different power densities was applied to stainless steel welded joints. The microstructural morphology, structural features, full-width at half-maximum, microhardness, and surface roughness of the stainless steel welded joint specimens before and after LSP were characterized and measured using SEM, TEM, XRD, a microhardness tester, and a high-resolution confocal microscope. The effects of different laser power densities on the microstructure and properties of the stainless steel welded joints were explored. Results indicate that the stainless steel welded joints exhibit a typical BCC phase. Laser shock peening promotes grain refinement in the welded joints, leading to the phase transformation of residual austenite into martensite. The surface roughness of the specimen is positively correlated with laser power density. At a power density of 5.17 GW/cm2, the surface roughness increased to 1.919 μm, which is 117.08% higher than that of the non-peened specimen. The microhardness of the specimens shows a decreasing trend with increasing power density. When the power density is 2.79 GW/cm2, the microhardness of the specimen significantly increases to 462.94 HV0.5, which is 22.26% higher than that of the non-peened specimen.

Effect of Dual Shot Peening on Microstructure and Wear Performance of CNT/Al-Cu-Mg Composites.

This work systematically investigated the effect of dual shot peening (DSP) and conventional shot peening (CSP) on the microstructure, residual stress and wear performance of the CNT/Al-Cu-Mg composites. The results indicated that compared with CSP, DSP effectively reduced surface roughness (Rz) from 31.30 to 12.04 μm. In parallel, DSP introduced a smaller domain size (33.1 nm) and more dislocations, higher levels compressive residual stress and a stiffer deformation layer with deeper affected zones. Moreover, DSP effectively improved the uniformity of the surface layer's microstructure and residual stress distribution. The improvement is mainly due to secondary impact deformation by microshots and fine grain strengthening. In addition, the transformation of the hard second phases such as Al4C3 and CNT and its effects on improving the surface strength and deformation uniformity were discussed. Significantly, DSP improved the wear resistance by 31.8% under the load of 6 N, which is attributed to the synergistic influence of factors including hardness, compressive residual stress, surface roughness, and grain size. In summary, it can be concluded that DSP is an effective strategy to promote the surface layer characteristics for CNT/Al-Cu-Mg composites.

Effect of laser shock peening on the surface integrity and fretting fatigue properties of high-strength titanium alloy TC21

High-strength titanium alloy TC21 is often used to make aircraft load-bearing components in the aviation field. However, due to vibration, load-bearing components often suffer from fretting fatigue (FF), which greatly reduces their actual service life. Nowadays, laser shock peening (LSP) is being recognized as an effective strengthening process for many materials. Therefore, in this study, the effectiveness of LSP on the strengthening of high-strength titanium alloy TC21 is studied, in terms of surface integrity and FF properties. TC21 fretting specimens and tests are designed. Before fretting tests, the specimens are processed by LSP with varying laser pulse energies, number of shocks and overlap rate, and their surface integrity and FF properties are analyzed. It is found that the greater the laser pulse energy and number of shocks, the higher the surface hardness and compressive residual stress, the more the grain refinement, the greater the improvement in FF life. Under 32J-50%-T1, the FF life is improved by 191.3% compared with BM. But the overlap rate has little effect on surface integrity and FF life. Meanwhile, there forms amorphous structures, which tended to be transformed into nanograins during fretting process. This transformation is helpful for prolonging FF life due to its action of energy absorption. This study reveals the strengthening mechanism of LSP on TC21 and its effect on the FF properties of TC21 specimens.

Influence of shot-peening on the self-heating behavior and fatigue properties of 300M steel

Shot peening is an established cold working process used to introduce residual compressive stresses on a surface and is extensively studied using conventional fatigue tests. However, it has not been widely studied using the self-heating method. Specifically, the heterogeneity of the dissipation field has not been estimated, with only an average approach being used. Previous investigations in the case of 300M steel demonstrated that the effect of shot peening on the high cycle fatigue properties can be either beneficial or detrimental. This study proposes to apply the self-heating method on polished 300M and to investigate the effect of mean stress and shot peening on the dissipation behavior. A modified self-heating model is proposed and calibrated for 300M steel. Combined with residual stress profiles, a method to compute and determine the shot peening effect on self-heating behavior through single point surface measurements is proposed. Application on 300M steel shows excellent results, the over-dissipation being mainly due to the sub-surface compressive residual stresses. The self-heating method has proven useful to quickly estimate fatigue properties of polished 300M steel. Based on the understanding of the self-heating curve of shot peened 300M steel, a quantification of shot-peening effect on fatigue limit is discussed.

Effects of ultrasonic shot peening followed by surface mechanical rolling on mechanical properties and fatigue performance of 2024 aluminum alloy

Aiming to improve the mechanical properties and fatigue performance of 2024 aluminum alloy, the experimental investigations on composite treatment consisting of ultrasonic shot peening (USP) followed by surface mechanical rolling (SMR) were carried out. The experimental results were compared with the specimens only treated by USP or SMR in terms of surface roughness, microhardness gradient and microstructure observation. The uniaxial tension test and low cycle fatigue test were conducted on the as-received specimen and the ones treated by USP, SMR and USP/SMR composite treatment, respectively. The tensile mechanical properties were effectively improved by USP. The introduction of SMR following USP can significantly increase the number of cycles to failure. Combining fracture morphology analysis and DEM-FEM coupling simulation of USP/SMR composite treatment, it was concluded that the improvement of tensile mechanical properties is mainly attributed to the synergistic effect of the compressive residual stresses and gradient-structured layer produced by USP, and the decrease in surface roughness resulting from SMR is the main reason for the significant improvement of fatigue performance. This work could provide an insight into the surface strengthening mechanism for USP/SMR composite treatment of materials with respect to the improvement of mechanical properties and fatigue performance.

Subsurface hardening of Al irradiated with ultrafast infrared laser

The effect of femtosecond laser shock peening on a model Al-0.3Mn alloy was investigated experimentally and numerically by molecular dynamics. Micro-diffraction experiments performed at synchrotron source revealed the depth profiles of the residual stress and the stored energy of dislocations, a measure of local plasticity. The depth of the maximum compressive stress did not coincide with that of the maximum dislocation energy, which was found at the surface. The interaction between the laser and the metal was simulated with LAMMPS using a two-temperature molecular dynamics package. The model accurately described the equation of state of aluminum and showed nearly equal resolved shear stresses on all slip systems at the wavefront. The dislocation density at a depth of 1 μm, predicted by the Meyers' model [1], was higher than the experimental data, suggesting possible recovery due to the increased temperature of the sample after repeated shock loading.

Enhancing corrosion resistance of lightweight metal alloys through laser shock peening

In this study, we investigated the effects of laser shock peening (LSP) on the corrosion resistance of lightweight metal alloys, specifically AA6061 and AZ31. LSP was performed underwater, using a nanosecond pulse laser and without using a protective coating or layer on the workpiece. The corrosion behaviors of these alloys were analyzed through electrochemical tests, including open circuit potential, electrochemical impedance spectroscopy, and potentiodynamic polarization measurements. The results demonstrated that LSP significantly improved the polarization resistance, and higher laser power intensities led to increased corrosion resistance and reduced corrosion rates. This enhancement in anti-corrosion performance is attributed to the formation of a protective oxide layer on the surface, acting as a barrier against corrosion. The findings underscore the potential of laser surface treatment as a viable technique for enhancing the corrosion resistance of lightweight metal alloys.

Tribological behavior and surface characteristics of severe surface plastic deformed as-cast and 3D-printed SS316L using LSP

The effect of laser shock peening (LSP) on as-cast and three-dimensional (3D)-printed SS316L alloys was studied. The LSP process was found more dominant than the 3D-printing technique over as-cast alloy steel for enhancing the properties. The process of laser shock peening results in microlevel changes in the structure of the material. This, in turn, leads to grain refinement and the increase of compressive residual stresses. After LSP treatment, the surface microhardness value increased by 33% in both as-cast and 3D-printed SS316L alloys with the hardness gradient from surface to subsurfaces. The wear rate of as-cast specimens and 3D-printed specimens were reduced to 1.28 10−6 and 1.14 10−6 g/m, respectively, and tensile value increased up to 22% after LSP treatment. The scanning electron microscopy images on the wear track confirm the vulnerability of the untreated SS316L alloys with adhesion wear and surface delamination. This difference was because the wear rate of the 3D-printed specimens was lesser than the as-cast SS316L alloys due to their layer-by-layer high-temperature finishing. The samples were characterized by optical microstructure to identify the surface refinement, and confirmed by the transmission electron microscope images along with specified area electron diffraction pattern for the accumulation of dislocation and grain refinement after LSP treatment. The accumulated residual stress was measured by X-ray diffraction technique and it found the highest compressive residual stress after LSP treatment was accrued by 3D-printed SS316L alloy with 310 MPa.

Comparative assessment of Ti‐6Al‐4 V titanium alloy fatigue life improvement by vibratory peening, shot peening, and vibratory finishing

AbstractThe effects of vibratory peening (VP), shot peening (SP), and SP followed by vibratory finishing (SPVF) on the surface and fatigue properties of Ti‐6Al‐4 V were compared to conventional low‐stress grinding (LSG). VP processing produced seven times smoother surface finish than SP and 66% deeper compressive residual stresses (CRS) but with 12% lower magnitudes. SPVF produced optimal surface properties with a perfectly flat surface and CRS‐like SP. All three mechanical surface treatments generated similar fatigue life improvements (108–122%) over LSG when the cyclic stress was below the yield stress. Above the yield stress, most of the CRS relaxed during the first cycle in VP specimens, resulting in up to 97% fatigue life improvement over LSG. The CRS relaxed more gradually in SP specimens leading to larger (up to 239%) fatigue life improvement. This shows the need to amplify CRS magnitudes produced in VP to maximize fatigue life improvement.

Wet shot peening effects on surface integrity and very high cycle fatigue of TC17 titanium alloy

With the increasing reliability requirements of aerospace equipment, very high cycle fatigue of TC17 titanium alloy has gained significant attention. This study investigates the effects of different wet shot peening treatments on the surface integrity and very high cycle fatigue performance of TC17 titanium alloy, elucidating the underlying mechanisms. Experimental results show that wet shot peening exacerbates surface defects, increases roughness, creates a plastic deformation layer, and induces compressive residual stress and work hardening. The combined effect of these factors reduces the fatigue performance. However, post-peening polishing significantly enhances the very high cycle fatigue performance by reducing stress concentration from surface defects while retaining the beneficial effects of compressive residual stress. Therefore, polishing after wet shot peening is concluded to be the most effective method for improving the very high cycle fatigue performance of TC17 titanium alloy.

Effects of laser shock peening on silicon nitride ceramic with varying sintering additive ratios

Silicon nitride ceramic (Si3N4) for industrial applications is conventionally manufactured with sintering additives, and the properties of Si3N4 change significantly based on the contents of these additives. In this study, we investigate the effects of laser shock peening (LSP) on Si3N4 sintered with varying ratios of sintering additives.The Si3N4 samples were sintered with a mixture of Y2O3, MgO, and SiO2 sintering additives at 5, 7, 9, and 11 wt%. A Nd:YAG laser (wavelength = 532 nm, maximum pulse energy = 1.4 J, repetition rate = 10 Hz, pulse duration = 8 ns, beam diameter = 11 mm, top-hat profile) was used to irradiate the Si3N4 samples. The samples were coated with a protective layer (100 μm thick aluminum foil) and a water layer to confine plasma. LSP of Si3N4 with 5% sintering additives resulted in a slight change in surface hardness but a 77% decrease in surface compressive residual stress. In contrast, LSP of Si3N4 with 11% sintering additives led to a simultaneous increase in surface hardness (7.3%) and surface compressive residual stress (67%), indicating a significant difference in the effectiveness of LSP depending on the ratio of sintering additives. Additionally, the surface of Si3N4 with 11% sintering additives showed evidence of grain refinement after LSP. It was demonstrated that the bending strength of Si3N4 with 11% sintering additives increased by 15.2%, and the depth of the fracture origin was significantly deepened.

Shot peening effects on Cr-Mo-V steel: a comprehensive study of microstructure, surface roughness, residual stress, and mechanical behavior

This study presents a comprehensive study of the microstructure, mechanical characteristics, and surface roughness of Cr-Mo-V low alloy steels and a detailed investigation of the overall impact of shot peening (SP). The microstructure was examined using the optical and scanning electron microscope, showing a significant grain size decrease after shot peening. Evaluations of mechanical characteristics, such as microhardness and tensile strength, showed a noteworthy rise, suggesting enhanced material strength. Studies using fragmentography shed more light on changed fracture tendencies. X-ray diffraction technique (XRD) was used to measure residual stress distribution, and the outcomes displayed an increase after SP, which suggests that internal stresses were created. Surface roughness measurements also showed a noticeable decline, indicating better surface quality. The transformational effects of shot peening on Cr-Mo-V low alloy steels were highlighted by comparative investigations with base metals, providing insights into enhancing material performance for various engineering applications.

Effects of laser non-uniform shock peening on the microstructure and fatigue performance of SUS 304 stainless steel welded joints

Residual tensile stresses and microstructural heterogeneity in welded joints are primary factors that degrade fatigue performance. As an effective post-weld strengthening method, Laser Shock Peening (LSP) can address these issues. Given the personalized demands of different regions, this paper proposes a Laser Non-Uniform Shock Peening (LNUSP) technique. This approach involves applying high pulse energy to the weld zone (WZ) and heat-affected zone (HAZ), and low pulse energy to the base material (BM) to achieve a more uniform residual compressive stress distribution and refined microstructure, thereby improving overall performance and service life. Results indicate that LSP transforms residual tensile stresses on the weld surface into compressive stresses. Compared to original samples, uniformly LSP-treated samples, and locally LSP-treated samples, LNUSP-treated samples exhibit more uniform residual stress and hardness distribution. LSP significantly increases surface hardness, with LNUSP-treated samples achieving a maximum hardness of 308.3 HV. Additionally, LSP induces martensitic transformation in the BM and WZ areas, alters grain orientation, and promotes dislocation movement, resulting in dislocation tangling, dislocation networks, and twin structures, which refine grain size. Consequently, LSP markedly improves joint fatigue performance, delaying fatigue crack propagation. The fatigue life of LNUSP-treated samples is increased by 25.41 % compared to original samples, reaching levels comparable to high-energy large-area impacts. This enhancement is attributed to the uniform residual stress and refined grain structure.

Effect of laser shock peening on tribological properties of 55SiMoVA bearing steel

Wear is an important factor limiting the service life of 55SiMoVA bearing steel. In this work, laser shock peening (LSP) technology is used to improve the tribological properties of 55SiMoVA bearing steel, and the corresponding underlying mechanism is systematically discussed. After LSP, the kurtosis (Sku) of surface roughness asperities reduced from 10.355 to 5.488, and no new phase was generated. Electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) analysis suggested LSP induced the generation of dislocation structures and deformation twins, leading to a decrease in the average grain size and an increase in the fraction of high-angle grain boundaries. Due to the work-hardening and fine-grain strengthening, the microhardness increased by 16.6 %, the maximum residual compressive stress amounted to −793.1 MPa, and the coefficient of friction (COF) and wear volume were significantly reduced. Scanning electron microscopy (SEM) results indicated that the wear mechanism of 55SiMoVA bearing steel before and after LSP was not transformed. However, the abrasive wear and delamination wear of the LSPed specimens were significantly improved, which was mainly attributed to grain refinement, increasing microhardness and constructing a residual compressive stress layer in the subsurface layer of 55SiMoVA bearing steel. During the sliding process, the increase in microhardness limits micro-plowing on the wear surface, and the residual compressive stress inhibits the crack formation and expansion, improving the wear resistance of 55SiMoVA bearing steel.

Tailoring surface properties and corrosion resistance of laser shock peened Ti6Al4V alloy by low-temperature annealing

The present study examined the effects of laser shock peening (LSP) and low-temperature annealing after LSP (LSPA) on the corrosion resistance of the Ti6Al4V alloy. The high density of dislocations in the LSP samples contributes to the rapid formation of a TiO₂ passive film during the electrochemical corrosion process. In this study, low temperature annealing was employed to further improve the corrosion resistance. The results indicated that the corrosion resistance of the LSPA samples was significantly improved compared to that of the LSP-treated samples. The LSPA treatment facilitated the pre-generation of a dense TiO2 passive film on the alloy surface via oxidation, reduced corrosion rate, inhibited the penetration of dissolved oxygen and ions present in the sodium chloride solution into the alloy surface. Meanwhile, low-temperature annealing could rearrange and annihilate dislocations, creating subgrains and relaxing non-equilibrium grain boundaries induced by deformation. This process reduced active sites and grain boundary energy, ultimately improving the corrosion resistance of the Ti6Al4V alloy.

Effect of the conventional shot peening and multiple shot peening on microstructure and residual stress of TC17 titanium alloy

This study examines the residual stress, microstructure, and stress-induced phase transformation of TC17 titanium alloy after different shot peening processes. A comprehensive analysis of the unique impact of shot peening on α-Ti and β-Ti was performed. The results indicate a substantial reduction in the grain size of the deformed layer and the creation of a high density of dislocations. Additionally, increased peening intensity results in decreased grain size, and multiple shot peening promotes further reduction in grain size. Compressive residual stresses were detected in the deformed layer, and multiple shot peening significantly augmented the residual stresses in the surface and near-surface regions. In particular, the highest compressive residual stresses after triple shot peening treatments were measured at −1079 MPa (at a depth of 10 μm for α-Ti) and −792 MPa (at a depth of 50 μm for β-Ti). In addition, multiple shot peening can significantly reduce surface roughness and enhance surface nanocrystallization when approximate surface residual stresses are obtained. Remarkably, the use of single shot peening revealed parallel stacking faults in certain α-Ti samples. However, under multiple shot peening, these stacking faults evolved into face-centered cubic Ti (FCC-Ti) with broader widths and a greater number. The stress-induced phase transition orientation relation was determined to be (0001)HCP//(11¯1)FCC and [21¯1¯0]HCP//[011]FCC, with α-Ti grains being interspersed with FCC-Ti, thus promoting additional grain refinement.

Effects of Shot Peening Pressure, Time, and Material on the Properties of Carburized Steel Shafts.

Carburized steel shafts are commonly used in industry due to their good wear resistance and fatigue life. If the surface of carburized shafts exhibits an undesired tensile stress, shot peening treatment may be required to alter the stress condition on the surface. In the present study, the effects of shot peening pressure (3-5 kg/cm2), time (32-64 s), and material (stainless steel, carbon steel, and glass) on the residual stress, retained austenite, microhardness, and surface roughness of the carburized shafts were investigated. The experimental results showed that the surface residual tensile stress was changed into compressive stress after the shot peening treatment. The shot peening effects increased with the increasing peening pressure and time. In addition, a significant decrease in the amount of retained austenite in the subsurface region was observed. Peening with different materials can affect the peening effect. Using glass pellets exhibited the best shot peening effect but suffered massive pellet fracture during processing. In overall consideration, the optimal peening parameters for carburized steel shafts for practical industrial applications involved using the stainless-steel pellets with a peening pressure of 5 kg/cm2 and a peening time of 64 s. The maximum residual stress was -779 MPa at a depth of 0.02 mm, while the highest surface microhardness was 827 HV0.1.

Effect of scanning strategy and laser peening on microstructure and fatigue properties of laser-directed energy deposition-built 15-5 PH stainless steel

PurposeThe aim of this paper is to study the effect of laser shock peening (LSP) on mechanical behaviour of the laser-directed energy deposition (LDED)-based printed 15-5 PH stainless steel with U and V notches. The study specifically concentrates on the evaluation of effect of scan strategy, machining and LSP processing on microstructural, texture evolution and fatigue behaviour of LDED-printed 15-5 PH steel.Design/methodology/approachFor LSP treatment, 15-5 PH steel was printed using LDED process with bidirectional scanning strategy (XX [θ = 0°) and XY [θ = 90°]) at optimised laser power of 600 W with a scanning speed of 300 mm/min and a powder feed rate of 3 g/min. Furthermore, LSP treatment was conducted on the V- and U-notched fatigue specimens extracted from LDED-built samples at laser energy of 3.5 J with a pulse width of 10 ns using laser spot diameter of 3 mm. Post to the LSP treatment, the surface roughness, fatigue life assessment and microstructural evolution analysis is performed. For this, different advanced characterisation techniques are used, such as scanning electron microscopy attached with electron backscatter diffraction for microstructure and texture, X-ray diffraction for residual stress (RS) and structure information, Vicker’s hardness tester for microhardness and universal testing machine for low-cycle fatigue.FindingsIt is observed that both scanning strategies during the LDED printing of 15-5 PH steel and laser peening have played significant role in fatigue life. Specimens with the XY printing strategy shows higher fatigue life as compared to XX with both U- and V-notched conditions. Furthermore, machining and LSP treatment led to a significant improvement of fatigue life for both scanning strategies with U and V notches. The extent of increase in fatigue life for both XX and XY scanning strategy with V notch is found to be higher than U notch after LSP treatment, though without LSP samples with U notch have a higher fatigue life. As fabricated sample is found to have the lowest fatigue life as compared to machines and laser peened with both scan strategies.Originality/valueThis study presents an innovative method to improve the fatigue life of 15-5 PH stainless steel by changing the microstructure, texture and RS with the adoption of a suitable scanning strategy, machining and LSP treatment as post-processing. The combination of preferred microstructure and compressive RS in LDED-printed 15-5 PH stainless steel achieved with a synergy between microstructure and RS, which is responsible to improve the fatigue life. This can be adopted for the futuristic application of LDED-printed 15-5 PH stainless steel for different applications in aerospace and other industries.Graphical abstract