Shot Peening Research Articles

How to Improve Fatigue Life and Residual Stress in Compressor Reeds through Shot Peening

Abstract: Numerous industrial areas involve the utilization of shot peening as a well-known surface enhancement method for increasing the fatigue life and residual stress of cyclically loaded crucial parts. This study examines the effects of shot peening on compressor reeds that can lengthen their life cycle with an accelerated rate of residual stress thereby improving reliability and performance of entire compressor system. The paper explains the principles behind shot peening, its influence on materials, and some specific advantages that it gives to thin reed compressors. Materials selection, parameters for shot peening and testing methods are described as experimental methods. Results from residual stress analysis show how much more efficient shot peening makes compressor reeds tough and reliable. Moreover, this paper provides insight into practical aspects, difficulties faced in practice and directions for further research when applying shot peeing to compressor’s reed components.

Microstructure evolution and surface strengthening behavior of 300 M ultrahigh strength steel under engineered surface treatments

In this work, the most efficient and common engineered surface treatments identified as shot peening (SP), laser shock peening (LSP) and ultrasonic surface rolling process (USRP) were utilized to impact the 300 M ultrahigh strength steel. The microstructure evolution and surface strengthening behavior were carefully characterized and compared for the 300 M steel with various treatments. Besides, the underlying mechanisms for difference in grain refinement and surface mechanical properties by the arranged surface modification are revealed. The results indicate that a gradient structure with nano-grains at the top surface appears on the SP, LSP and USRP treated samples. The process of repeated impacts of SP in different directions leads to activation of multiple slip systems, which thus causes severe refined grains and dense dislocation activities associated with dislocation tangles, dislocation walls and blocking. A great variety of strikes per unit area by USRP results in higher plastic deformation compared to SP where numerous dislocation cells and deformation bands were generated. In contrast to SP and USRP, fewer slip systems are activated in LSP due to the short duration time which thus leads to the thinnest refined grain layer and more planar dislocation structures. The combination of low plastic work and lack of refined grains leads to lowest full width at half maximum (FWHM) in case of LSP samples whereas high FWHM comes from both fine grain size and dislocations in SP. The grain refinement and plastic work contributes to an increase of microhardness and compressive residual stress for the SP, LSP and USRP samples. To be clear, SP leads to a higher magnitude of hardness and compressive residual stress on the topmost surface while LSP causes a larger depth due to that shock wave in LSP influences material to much greater depth. Besides, the decomposition and redistribution of carbides are also noticed on the surface layer after the surface treatments with very high strain rate where numerous dislocations accumulate at the border of the carbides and slip trace is also observed within the carbides.

Shot peening coverage effect on laser powder bed fused steel

Developing effective strategies for enhancing the damage tolerance of laser powder bed fusion (LPBF) components remains a formidable challenge in the disruptive additive manufacturing field. The typical shot-peening (SP) is a promising and efficient post-treatment procedure owing to its capability to introduce compressive residual stress, enhance the surface integrity, shrinkage the subsurface lack-of-fusion (LoF) defects of LPBF components. However, there is still a significant gap in understanding the appropriate utilization of the SP procedure to enhance fatigue performance, hindering its full potential in practical applications. This study systematically investigated the influence of surface coverage (150 %, 300 %, and 450 %) on surface characteristics, subsurface characteristics, and mechanical properties of LPBF 304L austenitic steel. Though evaluating the feasibility of severe shot peening and observing post-deformed microstructures, the process-microstructure-performance relationship of shot-peened LPBF austenitic steel was preliminarily established for the first time. The results indicated that increasing surface coverage up to a threshold (300 % in this work) could effectively enhance the strength and fatigue performance without significantly sacrificing ductility, primarily attributed to the increased gradient strain generated by the gradient deformation structures as well as the shrinkage of detrimental near-the-surface defects. The excessive surface coverage may be detrimental to ductility and fatigue performance, as it directly increases the severe plastic deformation and near-saturated micro-defects in the gradient deformation layer, substantially weakening the strain gradient's capability to accommodate dislocation flow during deformation. The findings suggested careful selection of shot peening coverage to balance enhanced mechanical properties and minimal introduction of detrimental defects.

Micro-mechanical properties characterization of shot peening strengthened layer with nanoindentation

In this work, the influences of shot peening (SP) on ultra-high strength steel were investigated. For the characterization of the strengthened layer, an inclined specimen was proposed for X-ray diffraction and nanoindentation, the micro-mechanical properties in the strengthened layer were studied with both experimental and crystal plasticity finite element (CPFE) analysis. It's noted that SP introduced grain refinement and compressive residual stress were highly concentrated in the surface layer due to the high strength and hardness, and the maximum depth influenced was only 0.1 mm. Based on simulation results, it's found that the differences in nanoindentation loading curves were introduced by the work done by residual stresses. To estimate the residual stress in the strengthened layer, a modified model was proposed with nanoindentation. The newly proposed model gives improved estimation accuracy compared with Wang's model, and it could give more precise results in contrast to the X-ray diffraction method for strengthened layers.

Surface integrity of consecutive shot-peened additively manufactured 316L stainless steel

ABSTRACT The shot peening procedure enhances the mechanical characteristics with the transformation of compressive residual stresses which helps in the increment of operational lifespan of the product. The study comprehensively analyzed the effect of consecutive shot peening procedures up to four peening passes with the coverage increases 100% on each peening pass up to 400% on the laser powder bed fused austenitic stainless steel and compared with the as-built condition focusing on surface characteristics, mechanical characteristics, and corrosion potential. Surface damage of the peened samples was found very minimal with the absence of visible scan tracks and unmelted powder particles due to the controlled peening parameters. The inducement of compressive residual stresses (−625 MPa) was observed to be higher at the fourth consecutive peening passes without strain-induced martensite, with an increment of hardness proportion of 29.12% with a depth of 1 mm, and increment of corrosion resistance across each peening pass.

Regulating material wettability through surface plastic deformation post-processing via friction modification

The wettability of engineering materials significantly influences their cleaning and antifreeze properties, making it a key consideration in aerospace applications. Methods for controlling surface plastic deformation can alter the wettability of materials and contribute to a certain level of strengthening effect, thereby presenting significant application potential. This study aimed to modify the wetting characteristics of aviation titanium alloys in harsh environments through adjustments in surface roughness via peening treatments (such as laser shock peening with coating and mechanical shot peening). The impact of various peening processes on wetting characteristics was investigated through comprehensive surface energy, macro, and nano morphology analyses. Static contact angle measurements were quantified, followed by evaluating other properties, such as surface free energy. Through adjustments in post-treatment processes and control of surface roughness, tailored acquisition of wetting characteristics was achieved. This study elucidates the beneficial effect of surface plastic deformation post-processing on controlling material wettability and introducing strengthening effects. Additionally, the study indicates the importance of accurately determining the sampling range for precise characterization of material wettability.

Depth-resolved mechanical behaviour of shot peened 7050-T7451 aluminium surfaces using in-situ synchrotron X-ray diffraction

We have assessed the elasto-plastic (sub)surface behaviour of 7050-T7451 aluminium alloy treated by shot peening using S110 steel shots of 300 μm in diameter and two different intensities, namely Almen intensity (A) of 3.4 (low-intensity) and 10.9 (high-intensity). Shot peening (SP) is a cold work process applied in the aerospace industry to enhance the fatigue tolerance of structural components after machining. The local mechanical response within the SP-induced layer was depth profiled at room temperature by performing an X-ray micro-diffraction experiment in transmission geometry at a synchrotron source, during tensile loading of the specimen to rupture. The presence of a SP-induced layer in the specimen is evidenced by compressive longitudinal lattice strains (∼-540 με for low-intensity and ∼-4200 με for high-intensity at 0.1 mm from the surface for the 311 reflection), parallel with respect to the applied load, i.e. perpendicular to the direction of impact of the steel shots, and also by higher values of the Full-Width-at-Half-Maximum (FWHM) of the diffraction peaks than those measured in the bulk material, due to the local plastic deformation induced by shot peening. High-intensity shot peening produced a higher surface roughness (Sa ∼13 μm), and also two times thicker deformed surface layer (∼0.4 mm), than low-intensity shot peening (Sa ∼2 μm and ∼0.2 mm thick deformed layer). For both shot peening conditions, the local yield stress of the surface layer and bulk material were similar, however the severely affected layers exhibit a non-linear elastic behaviour when applying loads lower than the yield stress of the material. Beyond yielding, the presence of SP-induced layers is mainly evidenced by the relatively higher value of the FWHM near-surface compared to the bulk (∼20 % higher for low-intensity and ∼40 % for high-intensity), due to the initial plastic deformation accumulated during shot peening and additional plasticity during loading of the specimen.

Investigating the Impact of Shot Materials on Surface Roughness in Ti6Al4V Alloy-Based Bone Implants treated by Shot Peening Process

This study explores the impact of different shot materials on the surface roughness of Ti6Al4V alloy-based bone implants treated with shot peening. Shot peening is a prevalent surface treatment method in the biomedical field used to enhance implant osseointegration. The choice of shot material can significantly influence surface morphology and, consequently, biological responses. This research examines the effects of various shot materials, including mild steel, stainless steel, glass beads, and alumina, on the surface roughness of Ti6Al4V alloy-based bone implants subjected to shot peening. Surface roughness measurements reveal distinct outcomes: glass beads result in the lowest roughness at 1.45 µm, while stainless steel leads to a higher roughness of 6.27 µm. These findings highlight the critical role of shot material selection in modulating surface characteristics essential for implant integration and performance. Understanding these variations provides valuable insights for optimizing implant design and enhancing biomedical applications. Key Words: shot peening, shot materials, surface roughness, Ti6Al4V alloy

Strengthening a non-equiatomic quaternary high-entropy alloy via concurrent gradient structures of nanotwin and dislocation cell

One main drawback of FCC high-entropy alloys (HEAs) is their insufficient room temperature yield strength. In this work, concurrent gradient structures of nanotwins and dislocation cells have been introduced into a non-equiatomic quaternary Fe40Ni20Co20Cr20 (at. %) high-entropy alloy by ultrasonic shot peening to meet this challenge. The gradient alloy exhibits a significantly enhanced yield strength, i.e., from the original 204 MPa to 559 MPa, combining with a well-retained ductility of 29 % and a good work hardening ability. Strengthening mechanisms at different depths (5, 30, 200, 400 μm) are also carefully discussed. The current work presents a strategy for hardening FCC HEAs significantly while maintaining the single solid solution microstructure.

Enhanced properties of alumina coating produced by combining plasma electrolytic oxidation and ultrasonic shot peening

A short-duration ultrasonic shot peening (USP) is used as a post-treatment to plasma electrolytic oxidation (PEO) coatings produced on a 2017 aluminium alloy under various sparking regimes (arc or soft) and time durations. USP is detrimental on PEO layers produced for short durations and under the arc regime because the typical pancake structure at the topmost surface is partially blasted. In contrast, PEO layers grown under the soft regime not only keep their structural integrity after short duration USP but also experienced a densification of their internal sublayer and a resurfacing of the sponge structure at the external sublayer. Under the specific PEO soft regime, the proposed duplex surface treatment makes the coating harder with a higher fracture toughness compared to the as-produced PEO coating.

Effect of induction heating composite shot peening on surface integrity parameters of 20CrMnTi gear steel

Effect of induction heating composite shot peening on surface integrity parameters of 20CrMnTi gear steel

Numerical simulation study of combined shot peening and laser shock peening on surface integrity of Ti-6Al-4V titanium alloy

Combined shot peening and laser shock peening (CSP) can introduce high surface compressive residual stress (CRS) and deep CRS layer, and reduce the high surface roughness caused by shot peening. The relationship between CSP sequences and surface integrity, including CRS and surface roughness, is far from satisfying the actual demand. In this paper, we construct a finite element model considering initial surface profile features. The experimental results agree with the simulated results. Based on the simulation results, axial and longitudinal stress wave transfer effects on surface CRS and depth CRS are investigated. Compared with shot peening (SP) and laser shock peening (LSP) alone, CSP treatment can increase CRS depth and CRS magnitude by 1060 μm and 50 ∼ 80Mpa, respectively. In addition, the roughness following CSP treatment is lower than that observed after SP treatment alone, and the roughness varies depending on the sequence of CSP treatment. Specifically, the roughness values for SP, SP + LSP, and LSP + SP are 0.938 ± 0.031 μm, 0.982 ± 0.11 μm, and 1.168 ± 0.093 μm, respectively. The surface morphology, hardness, and simulation results are combined to reveal the reasons for the reduction of surface roughness after CSP treatment. The changes of peaks and valleys after CSP treatment compared with single SP treatment were studied, and the variation trend of surface roughness was further explained.

Effect of deformation twinning on the early oxidation behaviour of 316L steel exposed to liquid lead-bismuth eutectic

Twins were introduced into 316L austenitic stainless steel by shot peening treatments. The twinned 316L was then exposed along with pristine 316L to oxygen-saturated liquid lead-bismuth eutectic at 550 °C for 120 h. We observed that the inner oxide layer on the pristine 316L consisted of Fe–Cr spinel and reticulated nickel-rich phases, whereas that on the twinned 316L consisted of Fe–Cr spinel and Cr2O3 without the nickel-rich phases. The factor contributing to the different microstructure and composition of the oxide layer on pristine and twinned 316L is that the twin boundaries provide additional channels for Cr diffusion into the oxide front, allowing the formation of Cr2O3 and high Cr dense Fe–Cr spinel. As a result, the Ni rich phases do not have sufficient space to exist and are pushed back into the Cr poor steel matrix.

Исследования соединений AA7075, сваренных трением с перемешиванием и ультразвуковым воздействием: механические свойства и анализ разрушения

Introduction. Joint efficiency and strength, particularly in aluminum alloys, are crucial in aerospace, defense, and industrial applications. Post-welding treatments like shot peening and laser shock peening significantly improve joint efficiency and strength, enhancing fatigue life, grain structure, and tensile strength. The purpose of the work. The literature reviewed shows that the ultrasonic vibration-assisted friction stir welding (UVaFSW) and post-weld treatment improved the mechanical properties and material flow. However, limited studies have been observed on the UVaFSW joints of AA7075-T651, considering the consequence of welding speed, tool rotation, and post-weld shot peeing treatment. The methods of investigation. The study investigates the ultrasonic vibration-assisted friction stir welded (UVaFSwed) AA7075-T651 joint's tensile strength, microhardness, microstructure, and fracture behavior, considering the impact of tool rotation, welding speed, and post-weld shot peening treatment. Results and Discussion. The post-weld treated shot-peened UVaFSWed joints demonstrated the maximum tensile strength of 373.43 MPa, the microhardness of 161 HV, and the lowest surface roughness of 15.16 µm at 40 mm/min welding speed when compared to the friction stir-welded (FSWed) joints. These results indicate that shot peening improved the mechanical properties and surface quality of the UVaFSWed joints. The high tensile strength and low surface roughness make these joints suitable for applications requiring strength and aesthetics. The fracture for the shot peened UVaFSWed joints mainly occurred in the heat-affected zone (HAZ) during the tensile test. It could be attributed to the higher temperature experienced during welding, which resulted in grain growth and decreased material strength in the HAZ. The shot-peened UVaFSWed joint has a more uniform grain distribution than the FSWed one, which contributed to the joint's higher tensile strength. The fractured surface of the shot peened UVaFSWed joints showed larger, equiaxed, and shallow dimples, resulting in higher ultimate tensile strength (UTS) and microhardness compared to the conventional FSWed joints. The mechanical properties and microstructure observed in the welding zones of shot peened UVaFSWed joints are superior to those of conventional FSW joints. However, further investigation is required to determine the specific factors contributing to this localized failure at HAZ, considering the effects of shot peening parameters. This study also suggests the potential for optimizing shot peened UVaFSWed joints of AA7075-T651.

Fluid-particle-structure interaction in single shot peening

Shot peening is a widely used cold-working process. Physical phenomena of shot peening are analyzed using the developed fluid-particle-structure coupled solver. The influences of the flow field and shot peening parameters such as the shot impact velocity and shot size are investigated in the case of the falling, impacting, and rebounding single particle. The weakly coupled solver applies the immersed boundary method which enables direct evaluation of the interactions between the unsteady flow field and moving/deforming objects. The elastoplastic object of AISI4340 during the collision of rigid steel shot is analyzed dynamically using the finite element method. Consequently, it is clarified that the flow field of the post-collision between the shot and structure can be characterized by the relative Reynolds number, which is based on the shot diameter and relative velocity between the uniform flow and rebounding shot velocities. As the relative Reynolds number increases, the complex flow field and vortex structures are generated at the collision location. These fluid structures affect the collision phenomena resulting in the random behavior of the shot and the asymmetric indentation in the structure.

Effect of Shot Peening Duration on Microstructure and Mechanical Properties of GH4169 Alloy Prepared by 3D Printing

Effect of Shot Peening Duration on Microstructure and Mechanical Properties of GH4169 Alloy Prepared by 3D Printing

Effect of Ultrasonic Shot Peening on Microstructure and Corrosion Properties of GTA-Welded 304L Stainless Steel

Austenitic stainless steels used in structural applications suffer from stress corrosion cracking due to residual stresses during welding. Much research is being conducted to prevent the stress corrosion cracking of austenitic steels by inducing compressive residual stresses. One method is ultrasonic shot peening (USP), which is used to apply compressive stress by modifying the mechanical properties of the material’s surface. In this study, 304L stainless steel was butt-welded by gas tungsten arc welding (GTAW) and subsequently subjected to compressive residual stress to a depth of 1 mm from the surface by a USP treatment. The influence of USP on microstructural changes in the base metal, the HAZ and weldment, and the corrosion properties was analyzed. A microstructural analysis was conducted using SEM-EDS, XRD, and EBSD methods alongside residual stress measurements. The surface and cross-sectional corrosion behavior was evaluated and analyzed using a potentiodynamic polarization test, electrochemical impedance spectroscopy (EIS) measurements, a double-loop electrochemical potentiokinetic reactivation (DL-EPR) test, and an ASTM A262 Pr. C test. The surface was deformed and roughened by the USP. The deformed areas formed crevices, and the inside of the crevices contained some cracks. The crevices and internal cracks caused pitting, which reduced the resistance of the passivation film. The cross-section was subjected to compressive residual stress to a depth of 1 mm from the surface, and the outermost area of the cross-section had fine grain refinement, forming a solid passivation film that improved the corrosion resistance.

Hydrogen charging can relax compressive residual stresses caused by shot peening

Surface engineering to generate compressive stresses via processes such as shot peening is commonly employed to mitigate fracture or fatigue failures in metallic systems. Localized plastic deformation is used to generate the generally biaxial compressive elastic stresses. This study examined the residual stress conditions and local mechanical performance of medium carbon steel in a quenched and tempered state. Electrolytic hydrogen charging of peened samples led to a permanent reduction in the compressive surface stress while concurrently hardening the surface. Slight changes in elastic modulus when solute hydrogen was present could not explain the resulting change in the measured residual stress; a reduction in X-ray peak breadth suggests that the combined effects of elastic stresses and solute hydrogen caused local dislocation annihilation and re-organization of the dislocation structure in the severe plastically deformed layer, leading to a lower magnitude and shallower depth of compressive residual stress on the peened surface after hydrogen charging.

Research on corrosion resistant of shot peening to micro-arc oxidation coating on ZL101A

The corrosion of ZL101A in a 3.5% NaCl solution was studied using the polarization curve method. The effect of the composite treatment of shot peening and micro-arc oxidation on the corrosion resistance was investigated compared with the single treatment of micro-arc oxidation. The results showed that compared with the single treatment of micro-arc oxidation, the composite treatment can significantly reduce the depth of intergranular corrosion and self-corrosion current density of ZL101A, exhibiting minimal effect on the self-corrosion potential. The shot peening treatment was beneficial in reducing the corrosion sensitivity of ZL101A.

The structure evolution of austenite stainless steel with pre-shot peening during plasma nitriding

Abstract Austenitic stainless steel is a very promising metal bipolar plate for proton exchange membrane fuel cells (PEMFC), which has advantages such as high mechanical strength, easy processing, and low cost. However, it is prone to corrosion in the acidic environment of PEMFC, which can have adverse effects on its lifespan and conductivity. By adopting a composite modification method to generate a dense nitride structure on the surface of 304 stainless steel bipolar plates, the corrosion resistance of the bipolar plate substrate can be improved. In this paper, shot peening pretreatment and plasma nitriding hybrid modification methods were employed to improve nitriding efficiency and reduce nitriding critical temperature, which generated a modified layer with good corrosion resistance on the surface of 304 austenitic stainless steel.