Conventional Shot Peening Research Articles

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.

Correlation between shot peening coverage and surface microstructural evolution in AISI 9310 steel: An EBSD and surface morphology analysis

In this study, martensitic high-strength steel serves as the subject of investigation, with both conventional and severe shot peening experiments being conducted. The coverage levels for conventional shot peening (CSP) are set at 100 % and 200 %, while severe shot peening (SSP) sees levels of 800 % and 1200 %. For the first time, the use of kernel average misorientation (KAM) enables the calculation of geometrically necessary dislocation (GND) density after peening, facilitating the study of GND density distribution across different coverage and offering a method for the visual assessment of peening degree. Results reveal that, under CSP, the gradient distribution of grain size is relatively uniform, whereas SSP leads to a pronounced gradient in grain size distribution. Taking into account the heterogeneous distribution of the initial material microstructure, a gradient in grain size from the surface to the interior of the material will appear after the coverage reaches a certain value, which is 400 % for AISI 9310 steel. Compared with CSP, SSP will further reduce the surface roughness Sa and improve the surface quality. The research presented further understands the relationship between shot peening process parameters and martensitic steel microstructure, providing an important reference for revealing the strengthening mechanism and selecting reasonable process parameters.

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.

Comparison of the effects of induction heating composite shot peening and conventional shot peening on residual stress, microhardness, and microstructure of 20CrMnTi gear steel

As a commonly used surface strengthening technology, shot peening, which can significantly improve the fatigue strength of mechanical parts, is widely used in the fields of vehicles and aviation. To obtain a larger residual compressive stress and further refine the grain size under normal shot peening intensity and coverage, this study proposes an induction heating composite shot peening (IHCSP) surface strengthening method, aiming to utilize the coupling effect of temperature and stress fields to promote the shot peening strengthening effect. An IHCSP test plan was designed and an IHCSP test bench was created to achieve simultaneous induction heating and shot peening. This study compares the surface integrity parameters and microstructures under three processes: un-peened, conventional shot peening, and IHCSP. The results show that the maximum axial and radial compressive residual stresses increase by 72.41 and 75.4 MPa respectively; the depth of the hardened layer increases by 0.3 mm, the martensitic transformation more complete, the grain size decreases by 483 nm, the dislocation density increases significantly, and nanocrystals are obtained on the surface of the material. These results verify the superiority of IHCSP surface strengthening.

Comparison of conventional and severe shot peening effects on the microstructure, texture, roughness, hardness, and electrochemical behavior of austenitic stainless steel

In the present research, microstructure, texture, roughness, hardness, and electrochemical behavior of AISI 316L austenitic stainless steel before and after shot peening were studied to elucidate the effect of conventional and severe shot peening (CSP and SSP) processes. After the shot peening, the fraction of strain-induced martensite (SIM) and mechanical twins (MTs) in the sub-surface layer was increased. The fraction of SIM and MTs in the SSP sample was higher than in the CSP sample. The XRD patterns indicated that the SSP sample had a higher peak broadening compared to the CSP sample. In the CSP and SSP samples, a gradient microstructure was formed along the depth direction. The microstructure of the topmost layer of the CSP and SSP samples exhibited numerous ultrafine grains. The grain refining during severe shot peening was faster because of the accumulation of more strain. The CSP and SSP samples revealed a gradient distribution of elements. After the SSP, the intensity of ⟨110⟩‖ED fiber texture decreased from 12.7 to 11.6 × R and the average intensity of ⟨100⟩‖ED fiber texture increased from 1.7 to 2.0 × R, respectively, compared to the CSP sample. The surface roughness of the SSP sample (Rq = 73.6 nm and Ra = 45.2 nm) was lower than that of the CSP sample which represented the roughness decreased with surface coverage increasing from 100 % to 1500 %. Also, the wettability increased after the conventional and severe shot peening processes. In addition, the microhardness of the CSP and SSP samples showed a gradient distribution. The CSP sample had the lowest corrosion current density (0.13 μA/cm2) whereas the NP (non-peened) sample exhibited the highest current density (0.65 μA/cm2). The presence of ⟨100⟩-oriented grains in both CSP and SSP samples led to the higher corrosion resistance of shot-peened steels compared to the NP sample. The presence of favorable texture with higher intensity in the CSP sample was responsible for the higher corrosion resistance of the CSP sample compared to the SSP sample. Finally, the gradient distribution of elements along the depth direction in the CSP and SSP steels improved the corrosion resistance of the surface.

Microstructural Features Intimated in Automotive Grade IF Steel Subjected to Conventional and Severe Shot Peening

Microstructural Features Intimated in Automotive Grade IF Steel Subjected to Conventional and Severe Shot Peening

A comprehensive study on the effects of surface post-processing on fatigue performance of additively manufactured AlSi10Mg: An augmented machine learning perspective on experimental observations

In this study, the efficacy of 21 distinct surface post-processing methods on the fatigue behavior of an additively manufactured (AM) material was investigated. Various treatments, encompassing single-step processes like sand blasting (SB), conventional shot peening (CSP), severe shot peening (SSP), gradient severe shot peening (GSSP), ultrasonic shot peening (USP), severe vibratory peening (SVP), ultrasonic nanocrystal surface modification (UNSM), laser shock peening (LSP), laser polishing (LP), tumble finishing (TF), chemical polishing (CP), electro-chemical polishing (ECP), and machining (M), as well as hybrid treatments, were systematically investigated for their impact on the fatigue behavior of hourglass laser powder based fused (LB-PBF) AlSi10Mg specimens. A comprehensive series of experimental tests were carried out, covering surface texture analyses, microstructural characterizations, porosity measurements, hardness, residual stresses (RS), monotonic tensile tests, and rotating bending fatigue tests at four stress levels. Following the experimental investigations, the acquired data were leveraged to develop a machine learning (ML)-based model to correlate the fatigue life with the influencing factors and conduct parametric and sensitivity analyses. The model utilized a deep learning approach to predict the fatigue response of LB-PBF AlSi10Mg, incorporating various artificial neural networks (ANNs) and considering input parameters such as yield strength, ultimate tensile strength, elongation to fracture, porosity, depth of pore closure, surface hardness, depth of hardness variation, surface RS, maximum compressive residual stresses (CRS), depth of the CRS field, top surface grain size, surface layer mean grain size, surface roughness, and stress amplitude. Depending on the life regime, the factors influencing fatigue behavior can vary significantly. In higher stresses, dominated by plastic strains, surface residual stress emerges as the primary factor. Conversely, in lower stresses, dominated by elastic strains, the significance of surface roughness becomes more pronounced, followed by surface residual stress, surface hardness and other factors. These findings underscore the contextual importance of different influencing factors for enhancing fatigue resistance based on varying loading conditions.

Low cycle fatigue behavior and life prediction of a directionally solidified alloy

Low cycle fatigue behavior and life prediction of a directionally solidified alloy

Enhancement of fatigue properties of selective laser melting fabricated TC4 alloy by multiple shot peening treatments

This study investigated the impact of multiple shot peening (SP) treatments on the surface morphology, microstructure, residual stress and fatigue performance of TC4 alloy manufactured by selective laser melting (SLM). The multiple SP treatments were conducted sequentially using cast steel beads, ceramic beads and glass beads at different peening intensities. In comparison to the conventional single SP process, multiple SP treatments reduced surface roughness and stress concentration coefficient while further increasing the residual compressive stress on the alloy surface. SP significantly enhanced the fatigue life of the alloy by 6.4 to 9.6 times, with a more pronounced improvement observed with multiple SP. Fatigue fracture analysis revealed that the untreated alloy showed multiple fatigue sources which all located on the surface, with surface printing defects acting as potential sites for crack initiation. After SP treatments, all fatigue cracks were initiated beneath the surface. The improved fatigue performance of SLM-formed TC4 alloy could be mainly attributed to the SP-induced surface microstructure refinement and residual compressive stresses. Furthermore, results indicated that, for subsurface crack initiation, the initial cracks primarily stemmed from the fracture of α/α' martensite in the primary β columnar grains.

Conventional shot peening treatment effects on thermal fatigue crack growth and failure mechanisms of a solid solution alloy

This study presents the effects of conventional shot peening as a surface post-treatment method on the fatigue crack growth behavior and failure mechanism of a solid solution alloy used in the flat seal component under thermal fatigue conditions. The study employs a combination of experimental tests and finite element simulations to evaluate the effect of shot peening on thermal fatigue crack growth behavior. The corrected J-integral and Paris model are used to calculate the stress intensity factor and predict the thermal fatigue crack growth behavior, respectively. Additionally, the ZENCRACK method is employed to predict thermal fatigue life. The results indicate that shot peening induces compressive residual stress, leading to a decreased distribution of thermal stress, particularly along the crack propagation path. The simulated fatigue life curve obtained by ZENCRACK demonstrated a good agreement between the simulated and experimental crack growth results. The incorporation of shot peening caused a significant reduction in the rate of thermal fatigue crack growth, and the simulated stress intensity factor analysis revealed an increase during the heating stage. Consequently, the thermal fatigue crack propagated during the heating-up process. SEM evaluation reveals that the shot peening post-treatment impacts both thermal fatigue crack initiation and propagation. Furthermore, the failure mode of shot-peened specimens involves inter- and trans-granular cracking, while non-shot-peened specimens exhibit trans-granular cracking.

Surface Conditions after LASER Shock Peening of Steel and Aluminum Alloys Using Ultrafast Laser Pulses.

Laser shock peening (LSP) is a mechanical surface treatment process to modify near-surface material properties. Compared to conventional shot peening (SP) the process parameters can be finely adjusted with greater precision and a higher penetration depth of compressive residual stresses could be reached. However, high process times of LSP leads to high production costs. In this study, ultrafast LSP (U-LSP) with an ultrafast laser source (pulse time in the picosecond range) was applied on specimens made of X5CrNiCu15-5 and AlZnMgCu1.5. The surface characteristics (surface roughness) and surface-near properties (microstructure, residual stresses, and phase composition) were compared to the as-delivered condition, to conventional laser shock peening (C-LSP), and to SP, whereas metallographic analyses and X-ray and synchrotron radiation techniques were used. The process time was significantly lower via U-LSP compared to C-LSP. For X5CrNiCu15-5, no significant compressive residual stresses were induced via U-LSP. However, for AlZnMgCu1.5, similar compressive residual stresses were reached via C-LSP and U-LSP; however, with a lower penetration depth. A change in the phase portions in the surface layer of X5CrNiCu15-5 after C-LSP compared to SP were determined.

Ultrasonic pulsed waterjet peening of commercially-pure titanium

Commercially-pure titanium (CP-Ti) has proven indispensable in critical industries such as aerospace and automotive. To meet the ever-increasing demands of titanium applications, ultrasonic pulsed waterjet peening (UPWJ) has been evaluated for the first time on CP-Ti, as a novel method to optimise compressive surface residual stress. UPWJ offers the potential for an environmentally benign, non-contaminating peening process, paving the way for sustainable surface modification methods. UPWJ treatment involved directing a waterjet at a pressure of 69 MPa onto CP-Ti coupons, maintaining a stand-off distance of 25.4 mm and adjusting traverse speeds from 200 to 1000 mm/s. The effects of stand-off distance were also evaluated (varied from 25.4 to 44.4 mm), at a constant traverse speed of 1000 mm/s. Conventional shot peening was also applied on the same CP-Ti alloy as a baseline. The experimental results revealed relationships between the applied traverse speed and stand-off distance, and the measured surface roughness and residual stress. Furthermore, it was shown that UPWJ improves the surface mechanical behaviour, in terms of both the Rockwell hardness (HRB) and the scratch hardness. A higher stand-off distance and faster traverse speed contributed to increasing the induced compressive residual stress (to a maximum of −391 MPa), while keeping the surface roughness at moderate levels (i.e., Ra <3 μm). Comparing UPWJ with shot peening, this study highlights the potential of UPWJ for CP-Ti alloy surface modification, while removing the potential for surface contamination, which can be detrimental in many applications. Comparison of UWPJ used for peening Ti-6Al-4V (Grade 5) is also briefly discussed.

Influence of Conventional Shot Peening Treatment on the Service Life Improvement of Bridge Steel Piles Subjected to Sea Wave Impact

The first goal of the current study is to estimate the fatigue life of the middle steel piles of an integrated bridge installed in water and subject to the impact of sea waves. In the following, the authors have tried to improve the service life of this critical part of the bridge, which is also the main purpose of the study. To this end, conventional shot peening, as one of the most well-known surface treatments, was used. Axial fatigue tests were performed on samples fabricated from IPE-220 steel piles in two states without and with shot peening surface treatment. Next, the modified S-N curve was entered into the finite element software to define the effect of shot peening treatment. Different analysis, including thermal, thermal-structural coupled, and transient dynamic, were performed and various outputs were extracted for the entire structure. In all these analyses, changes in air temperature have been neglected. The most important achievement of this research is the discovery that motionless water cannot cause serious damage to steel piles. Moreover, application of conventional shot peening can increase the fatigue life of steel piles, or in other words the service life of the bridge, subjected to the impact of sea waves by about 22%.

Comparative study of the effects of conventional shot peening and ultrasonic shot peening on very high cycle fatigue properties of GH4169 superalloy

This study investigates the effects of two different shot peening techniques, conventional shot peening (CSP) and ultrasonic shot peening (USP), on the very high cycle fatigue (VHCF) properties of the GH4169 superalloy. The study evaluates and compares surface roughness, X-ray diffraction patterns, microhardness, and residual stress in specimens treated with CSP and USP. The VHCF tests reveal that both CSP and USP treatments improve the VHCF properties of the GH4169 superalloy. However, while the USP-treated specimens have deeper work hardening and compress residual stress layers, their VHCF lives are significantly shorter than those of the CSP-treated specimens. Additionally, the study finds that the stress triaxiality, which inhibits dislocations at the crack tip, is higher closer to the center of the specimen. The transmission electron microscopy (TEM) results further confirm that the reduced dislocation density and increased stress concentration in the plastic zone of the high stress triaxiality region promote fatigue short crack propagation and reduce the fatigue properties of the material.

The synergistic effect of texture and surface roughness on electrophoretic deposited bioactive glass coating

AbstractTo improve the biocompatibility of AISI 316L, bioactive glass (BG) coating of SiO2–CaO–P2O5 which helps bonding with bone implants was used by an electrophoretic deposition method. Before coating deposition, the samples were treated by shot peening, known as an efficient process for metal grain refinement and fatigue properties. The stainless steel 316L was investigated in terms of microstructure, texture, and roughness. This research covers the effects of chosen shot peening parameter on the BG‐coating properties on the obtained results. Shot peening was carried using two different sets of parameters as conventional shot peening, and severe shot peening. Wettability, roughness, microstructure, coating thickness, and corrosion behavior of coated sample were investigated in terms of potentiodynamic polarization and electrochemical impedance spectroscopy in simulated body fluid (SBF) solutions at 37°C. The results indicated that the coating thickness decreased from 35.5 ± 10 µm for coated not peened (CNP) to 20 ± 5 and 17 ± 2 µm for coated conventionally shot‐peened (CCSP) and coated severely shot‐peened (CSSP), respectively. As well as, the water contact angle of CSSP sample was equal to 15.71° which is much lower than CNP (20.7°). The protection ability of the tested samples in the SBF was improved in the following order: CCSP &lt; CNP &lt; CSSP.

Adapting Shot Peening for Surface Texturing Using Customized Additive Manufactured Shots

Surface textures in engineering materials not only affect the reflective properties and aesthetics but if properly designed can modulate surface‐related properties such as wettability, fatigue, wear, corrosion, and scratch resistance. Herein, a new surface texturing method is introduced based on the conventional shot peening process. Custom shots are designed, and their surface texturing capability is investigated on acrylonitrile butadiene styrene (ABS) polymer substrates. A finite‐element model is developed to bombard the substrate using AISI 316 stainless steel customized shots. The generated unique textures are compared qualitatively by visual examination and quantitatively using the standard surface roughness parameters. As a proof of concept, preliminary experiments are performed using a candidate custom shot and a spherical shot to treat the ABS sheets. The results highlight the high potential of the shot peening technique paired with additive manufacturing for customizing the peening media to be used for surface texturing polymeric materials.

Effect of shot peening on electrophoretic deposition of bioactive glass coating on AISI 316L stainless steel

Bioactive glass coating of SiO2–CaO–P2O5 was synthesized and deposited on shot peened stainless steel AISI 316L substrates through electrophoretic deposition. Shot peening is known to enhance the fatigue properties of the substrate material; however, the present study aims to investigate how this prior shot peening can affect on the electrophoretic coating properties and performance. Shot peening was carried using two different sets of parameters as conventional shot peening (Almen intensity: 15A and coverage:100%), and severe shot peening (Almen intensity: 7C and coverage:1500%). The coated samples were studied regarding deposition thickness, microstructure, macrotexture and surface roughness, as well as wettability with contact angle tests. Corrosion behavior was also investigated using potentiodynamic polarization and electrochemical impedance spectroscopy in simulated body fluid solutions at 37 °C. The results confirmed that the coating thickness decreased from 55.3 μm for CNP to 27 μm and 9.5 μm for CCSP and CSSP respectively. Shot peening applied before electrophoretic deposition modulated the wettability and corrosion resistance of the coated samples through variation of roughness and the extent of grain refinement. As well as, the water contact angle of CSSP sample was equal to 15.64° which is much lower than CNP (55.3°). Also, the amount of coated samples’ corrosion rate changed by this order CCSP (1.91 × 10−2)>CNP (1.31 × 10−2)>CSSP (1.07 × 10−2). The high surface energy on shot peened samples caused the smaller BG grain size deposited on surfaces. The amount of BG grain size of each sample is as follow CNP 2.12 ± 1.6 μm, CCSP 1.34 ± 0.8 μm and CSSP 0.81 ± 0.3 μm.

Anti-fatigue strengthening mechanism of conventional shot peening and micro-shot peening on bare and micro-arc oxidation coated 6082-T6 aluminum alloy

Conventional shot peening (CSP) and micro-shot peening (MSP) are used to enhance the fatigue property of bare and micro-arc oxidation (MAO) coated 6082-T6 aluminum. The difference in the anti-fatigue strengthening mechanism of CSP and MSP on bare and MAO coated 6082-T6 aluminum alloy is revealed. Results show that MSP provides a more significant improvement in fatigue properties of bare specimens than CSP since the intensely inhibiting effect on crack initiation. Nevertheless, MAO coating impairs the surface integrity of MSP specimens, thus reducing the crack initiating life. In comparison, the effect of deeper affected layer induced by CSP on the improvement of crack propagating life is mostly retained after the MAO process. Hence, for the MAO coated specimen, the CSP prior-treatment is more effective in improving its fatigue property.

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.

Study on the Measurement Method of Shot Velocity and Mechanical Properties Based on Conventional Shot Peening.

Shot velocity is a crucial control parameter that is closely related to the shot peening effect. However, the traditional measurement method of shot velocity corresponding to air pressure is complicated and cannot reflect shot peening parameters (impingement angle, etc.). This study proposes a robust method to measure shot velocity by coupling simulations and experiments. By developing the measurement method presented in this paper, we can quickly and easily derive the linear shot velocity formulas corresponding to a series of impingement angles. The validity is verified and characterized by the arc height, surface roughness, residual stresses, and existing literature. The measured shot velocity can be applied to predict the effect of shot peening by the simulation method in aerospace and automotive industries. In addition, optimization of process parameters in terms of microstructure, microhardness, and mechanical properties is discussed in the context of experiments. This study shows that shot velocity is linearly related to shot peening pressure and is affected by impingement angles. The air pressure and exposure time should not be too large, and no microcracks should be created. The ultimate strength reaches the maximum, and the yield strength is significantly improved.