Shot Peening Treatment Research Articles

Effect of ultrasonic shot peening duration on the microstructure and mechanical properties of CrMnFeCoNi high-entropy alloy

In this work, ultrasonic shot peening (USP) was performed for a CrMnFeCoNi high-entropy alloy with an equal atomic ratio to improve the mechanical performance at room temperature. The microstructure evolution and mechanical properties of the CrMnFeCoNi high-entropy alloy under different USP durations were studied. The effects of USP-induced grain refinement, phase transformation, strengthening, and fracture morphologies were analyzed. The results indicated that a certain thickness of compressive residual stress layer with nanocrystalline was formed on the surface of the alloy. After USP, the phase was transformed from the FCC phase to the mixed dual phases FCC+BCC. The alloy exhibited a strength-ductility balance, with hardness and strength enhanced significantly, while elongation to failure remained at around 30%. Additionally, the sample before USP exhibited a typical ductile fracture, while after USP, it was transformed into a mixed fracture of dimple and quasi-cleavage or cleavage. The crack initiated from the sub-surface rather than the initial surface, and then propagated to the interior structure after coming into contact with the surface strengthening layer, effectively delaying the failure of the material. It was demonstrated that the ultrasonic shot peening treatment is a general and efficient physical strengthening method for high-entropy alloy at room temperature.

Thermal stability of nanostructured uranium within a surface layer processed using shot peening

A nanostructured α‑uranium surface layer with an average subgrain/grain size of 140 nm was obtained by using shot peening treatment (SPT). While, the nanostructures might be unstable in thermal condition due to dense lattice defects, high density of dislocations and ultrafine grains induced by severe plastic deformation. In this work, the thermal stability of the nanostructured surface layer was investigated using quasi-in situ electron backscatter diffraction (EBSD) after annealing treatments at temperatures ranging from 400 °C to 500 °C. Results show that the nanostructured surface layer has reasonably good thermal stability below 400 °C. Recrystallization and subsequent growth occurred when the temperature increased to 450 °C. The recrystallization nuclei are rooted in the initial nanostructured sites in the top surface layer and from dense dislocation walls in the subsurface consisting of high density of twin boundaries. At 450 °C, the exponent of recrystallization subsequent growth is determined to be 2.86, and the apparent activation energy value is 112.24 kJ/mol. Recrystallization occurs predominantly in a continuous manner. Furthermore, the evolution of dislocation density and grain size accounts for the decaying of surface mechanical properties.

An investigation of the wettability and chemical stability of superhydrophobic coatings on titanium

This study employs a two-step process to fabricate a superhydrophobic surface on the titanium substrate with outstanding corrosion resistance and chemical stability. Initially, a shot-peening treatment was carried out on the titanium surface, followed by chemical etching. Once the etching process was complete, the surface was modified with Methyltrichlorosilane (MTCS) to lower its surface energy. The impact of shot peening on wettability, corrosion resistance, and long-term chemical stability of the produced superhydrophobic surfaces was then investigated. Scanning electron microscopy images demonstrated the formation of fibrous network structure in the nanoscale, and Fourier transform infrared spectroscopy analysis confirmed the existence of chemical bonds between the functional groups of MTCS and the titanium surface. Furthermore, the corrosion resistance of the superhydrophobic surface was evaluated using immersion, potentiodynamic polarization, and an electrochemical impedance spectroscopy test in a 3.5 wt% NaCl solution. The long-term stability of the fabricated coating was tested by immersing samples in a 3.5 wt% NaCl solution for various immersion times. Based on the obtained results, the pre-shot peened samples exhibited a maximum water contact angle of 159° after MTCS modification. Furthermore, they also demonstrated excellent corrosion resistance and stability.

Ultra-high fatigue property and fracture mechanism of modified 20CrMoH steel by gas carburizing technology combined with shot peening treatment

Carburizing combined with shot peening (SP) were applied on the 20CrMoH steel, and the rotary bending fatigue (RBF) mechanisms of the modified (Carburizing, SP, Carburizing + SP) 20CrMoH were systematically analyzed. Results indicated the combined treated specimen obtained the microhardness of 1020 HV0.2, the residual compressive stress (RCS) value of −1429 MPa and the RBF strength of 1.05 GPa. The prolonged life of the combined treated specimen is attributed to the dislocation strengthening, stress strengthening and surface integrity improvement. The RBF modes of the combined treated specimen are S-mode and II-mode, and its modes mainly depend on the residual stresses.

Tribological Behavior of a Shot-Peened Nickel-Based Single Crystal Superalloy at High Temperature

The tribological behavior of a nickel-based single crystal superalloy treated by shot-peening has been investigated. Friction tests under three normal loads and three temperatures were carried out based on the ball-on-disk configuration. The results showed that coefficient of friction (COF) and wear rate of the shot-peened nickel-based single crystal superalloy (SP-NBSC) at room temperature were nearly 2 times and 4 times that at 600 ℃, respectively. However, there were no significant differences in COF and wear rate between the SP-NBSC superalloy and the as-received NBSC superalloy, which was ascribed to the competing effects between the increased hardness and roughness of the SP-NBSC superalloy. High-temperature friction promoted the formation of a glaze-layer on the substrate, which was derived from the sintering and compacting of the wear debris. The formed glaze-layer prevented the direct contact of the friction pair and contributed to the reduced COF and wear rate. The wear mechanism of the SP-NBSC superalloy at high temperature including oxidation, adhesion, and abrasion. With the decreasing normal load and increasing temperature, the adhesive wear weakened. This work provided insights into the effects of shot-peening treatment on the tribological properties of the NBSC superalloy.Graphical Abstract

Rotating Bending Fatigue Properties of Age Hardening Treated Additive Manufactured Maraging Steel and their Improvement with Additional Treatments

Rotating bending fatigue tests were conducted to investigate the fatigue property of age hardening treated maraging steel made by direct metal laser sintering process which was one of additive manufacturing processes. In this study, fatigue properties were evaluated firstly using the as-additive manufactured specimen with the surface shape remaining in the additive manufacturing process. After that, the effects of additional treatments such as mechanical polishing, hot isostatic press (HIP) treatment and shot peening (SP) treatment on fatigue properties were investigated. The main results obtained are as follows. The effect of surface roughness produced during manufacturing process on fatigue strength is significant, and is greater than the effect of initial defects. If HIP treatment is performed with the surface shape remaining, the fatigue life will be shortened. On the other hand, the fatigue strength of the maraging material which was made by additive manufacturing process can be dramatically improved by SP treatment and fatigue fracture from surface can be suppressed. The fatigue fracture mode shifts by SP treatment from surface origin type where fatigue cracks initiate from dents on the surface to the internal origin type where fatigue cracks initiate from cleavage crack of martensite block or initial defect. To further improve fatigue property, it is necessary to suppress the occurrence of cleavage crack.

Investigation of wet shot peening on microstructural evolution and tensile-tensile fatigue properties of Ti-6Al-4V alloy

Ti–6Al–4V (TC4) alloy was treated by wet shot peening (WP) using ceramic beads compared with dry shot peening (SP). The effects of shot peening on surface integrity, microstructural evolution, fatigue crack initiation behavior and tensile-tensile fatigue performance were investigated applying multiple characterization techniques. The result exhibited that the surface plastic deformation caused by WP and SP treatment resulted in microstructure changes near the surface. Surface morphology was distinctly changed by shot peening treatment. The roughness value increased from 0.596 μm (Ra) to 1.594 μm (Ra). Microhardness gradients and compressive residual stress (CRS) distributions along the depth were induced by shot peening. The maximum hardness reached 373.5 HV, 407.8 HV and 445.3 HV. The maximum value of CRS reached 884 MPa, 1038 MPa and 1207 MPa with the corresponding depth at 21 μm, 25 μm and 40 μm. The fatigue life was significantly improved by shot peening treatment. Cracks tended to initiate at the subsurface layer instead of the treated surface after shot peening. The reason for crack initiation position altering was tentatively explained by the CRS stable zone. The competition mechanism between the surface stress concentration and local strengthening factors were discussed based on the analysis of stress concentration factor, Kt.

Influence of Shot Peening on the Wear Behaviour of Medium Carbon Steel

Abstract Influence of shot peening on the wear behaviour of medium carbon, C55 steel was experimentally verified. Experimental work included determination of the chemical composition, heat treatment, microstructure evaluation, mechanical properties measurement, shot peening treatment, the magnitude of the compressive residual stresses was evaluated, roughness profiles measurement and finally the friction tests. The results evidence the significant role played by the applied shot peening on wear behaviour of medium carbon steel. An important effect of surface roughness has been demonstrated. The coefficient of friction after shot peening compared to ground surface increased, 1.44 – 1.85 times.

Long crack propagation and closure in DC(T) specimens of Ni-based superalloy Inconel 718 and stainless steel AISI 301 after shot peening

In this study, the effects of severe shot peening on ambient temperature long crack growth, threshold and closure behavior in Nickel-based superalloy Inconel 718 and stainless steel AISI 301 were investigated. To assess the relationship between shot peening, crack tip shielding and crack growth, pre-cracked disk-shaped compact tension (DC(T)) specimens were treated at distinct locations around and ahead of the crack front. A beneficial influence of shot peening on crack propagation and closure was only identified in Inconel 718, albeit limited to shot peening of the entire area around the crack front. In contrast, the applied shot peening treatments had detrimental effects on crack growth properties in AISI 301. While the effective threshold of Inconel 718 was not affected by shot peening, AISI 301 featured a decreased intrinsic resistance against the onset of crack propagation. Strain-induced near-surface α′-martensite formed due to shot peening of AISI 301 was found to promote martensite formation during crack growth, giving rise to embrittlement of the material.

Fatigue improvement and residual stress relaxation of shot-peened alloy steel DIN 34CrNiMo6 under axial loading

Shot-peening treatment was applied to a quenched and tempered DIN 34CrNiMo6 steel to improve its high-cycle R: −1 axial fatigue strength. Compared with the machined condition, the increase in the fatigue limit was 21.8%. S-N curves for shot-peened and the as machined condition were presented and compared with those obtained in previous research for rotating bending fatigue, including curves for mirror-polished specimens.The applied shot-peening treatment in this work (Isp: 8A and 200% coverage) for quenched and tempered (Q + T) DIN 34CrNiMo6 steel introduced a compressive residual stress field and an increase in surface roughness, as well as minor variations in microstructure, hardness and the FWHM (full width of the diffraction peak at half maximum intensity) parameter.The introduced compressive residual stress field tended to reduce when an external stress is applied. This was due to the onset of plastic strain. In this paper, two types of quasi-static tests were conducted by applying an axial stress with six different magnitudes and in the two directions (compressive or tensile). This was in order to assess their influence on the relaxation of surface residual stresses. Due to the introduced compressive residual stresses, if the applied stress was compressive, the onset of plastic deformations was achieved with a lower stress magnitude.In addition, surface residual stress relaxation under cyclic applied stress was evaluated at four different stress magnitudes. Due to the cyclic-softening behaviour of this Q + T steel, its cyclic mechanical properties must be considered to assess the onset of plastic strains. With the experimental data, a logarithmic model to predict the evolution of surface residual stresses with the number of cycles for different applied stress magnitudes was presented.

Effect of Shot Peening and Heat Treatment on Fatigue Strength and Microstructure of Stir Casted Al7075-SiC Composites

Effect of Shot Peening and Heat Treatment on Fatigue Strength and Microstructure of Stir Casted Al7075-SiC Composites

Improving the high-cycle fatigue life of a high-strength spring steel for automobiles by suitable shot peening and heat treatment

Shot peening (SP) treatment is a common and useful method that can affect the fatigue life of metallic components. In this work, the high-cycle fatigue (HCF) lives of 50CrMnMoVNb spring steels with different SP intensities and conditions were investigated. Meanwhile, the differences in the microstructures and crack initiation sites were compared. The fatigue life of the investigated steels is greatly improved via suitable heat treatment. Furthermore, SP treatment is beneficial to the improvement of the fatigue life of heat-treated specimens with higher strength, and the optimal SP intensity is 0.15 ∼ 0.25 mmA. However, SP deteriorates the HCF life of the as-received specimens with lower strength. This study can enrich the fundamental knowledge on how to improve the HCF life of spring steels and provide new ideas about the influence of different SP intensities on the surface layer and fatigue properties.

Effects of Shot Peening and Cavitation Peening on Properties of Surface Layer of Metallic Materials-A Short Review.

Shot peening is a dynamically developing surface treatment used to improve the surface properties modified by tool, impact, microblasting, or shot action. This paper reviews the basic information regarding shot peening methods. The peening processes and effects of the shot peening and cavitation peening treatments on the surface layer properties of metallic components are analysed. Moreover, the effects of peening on the operational performance of metallic materials are summarized. Shot peening is generally applied to reduce the surface roughness, increase the hardness, and densify the surface layer microstructure, which leads to work hardening effects. In addition, the residual compressive stresses introduced into the material have a beneficial effect on the performance of the surface layer. Therefore, peening can be beneficial for metallic structures prone to fatigue, corrosion, and wear. Recently, cavitation peening has been increasingly developed. This review paper suggests that most research on cavitation peening omits the treatment of additively manufactured metallic materials. Furthermore, no published studies combine shot peening and cavitation peening in one hybrid process, which could synthesize the benefits of both peening processes. Moreover, there is a need to investigate the effects of peening, especially cavitation peening and hybrid peening, on the anti-wear and corrosion performance of additively manufactured metallic materials. Therefore, the literature gap leading to the scope of future work is also included.

Influence of gas pressure on the low-temperature plasma nitriding of surface-nanocrystallined TC4 titanium alloy

The influence of gas pressure on plasma nitriding of surface nanocrystalline TC4 titanium alloy prepared by shot peening (SP) was investigated. SP treatment under 0.3 MPa-25 min (Almen intensity is 0.32 mm) before plasma nitriding effectively refined the surface grain size of TC4 alloy to about 42 nm, which helped to sufficiently lower the nitriding temperature of TC4 to 500 °C. After nitriding treated under different gas pressures from 50 Pa to 300 Pa, nitriding gas pressure was found to has an optimal value at 200 Pa with which a thickest nitriding layer of 1.34 μm and highest hardness of 1569 HV was achieved at 500 °C for 20 h. Furthermore, the influence of gas pressure on the formation and migration of active nitride particles was revealed to be related with their energy and efficiency. Higher nitriding pressure would produce more active nitride particles but consume more energy during collision which made active nitride particles difficult to transit through the nitriding environment to land on the specimen. Balanced between these two aspects, 200 Pa was found to form more active nitride particles as well as maintain a high level energy. Meanwhile, SPed specimen presented a thicker nitriding layer than coarse-grained specimen. So in this study, we combine the promotion effect of surface nanocrystalline and the optimization of nitriding pressure to comprehensively improve the plasma nitriding efficiency.

Effect of shot-peening on corrosion behavior of austenitic steel in supercritical carbon dioxide at 700 °C

The contribution of shot-peening treatment on the corrosion resistance of Sanicro 25 exposed to supercritical carbon dioxide (S-CO2) at 700 °C and 15 MPa was investigated. Complex corrosion layers formed on shot-peened Sanicro 25 were approximately ten times thicker than those formed on non-peened Sanicro 25. Rapid diffusion paths induced by shot-peening treatment accelerated inward diffusion of C, resulting in the formation of subsurface carbide-containing core/shell structure precipitates. Increased voids in shot-peened Sanicro 25 and the stress concentration promoted scale spallation after exposure. In summary, shot-peened Sanicro 25 exhibited worse corrosion resistance compared to non-peened Sanicro 25 in 1000 h.

Investigations on the adhesion and fatigue characteristics of hybrid surface-treated titanium alloy

This study is critical for aiding the development of a hybrid treatment consisting of a tungsten-doped diamond-like carbon coating (WC/C) deposited atop shot-peened Ti-6Al-4V surfaces. Residual stresses, considered a key indicator of fatigue performance, were measured by X-ray diffraction (XRD). Rotating bending fatigue tests were carried out while microscopy allowed for fractographic analysis of resultant surfaces. Results show that despite the pronounced surface roughness produced by the shot peening treatment, the high residual compressive stresses, together with the refined and cold-worked microstructure were capable of marginally improving the fatigue performance of the shot peened Ti-6Al-4V compared to the untreated alloy. Conversely, following fatigue testing, the WC/C coating displayed extensive cracking which propagated prematurely into the substrate and yielded a reduction in fatigue limit. On the other hand, despite some annealing of the compressive residual stresses during the coating deposition treatment, the hybrid treatment yielded a reasonable improvement in the fatigue limit over the untreated condition. This result, coupled with the high coating hardness and adhesion, confirm this hybrid treatment's capability in retaining both the adhesive and fatigue performance of the Ti-6Al-4V alloy.

Corrosion Protection on AISI 304 by Shot Peening Treatment with Variation of Particle Size and Shooting Pressure

AISI 304 is widely used as biomedical material due to its lower cost and availability, but low corrosion resistance. The shot peening method can increase the mechanical characteristics and corrosion resistance of a surface. The purpose of this study was to determine the effect of shot peening surface treatment with a combination of steel ball diameter variations and pressure on corrosion resistance of AISI 304 material. Shot peening treatment was carried out using variations of 0.2, 0.5, and 0.8 mm steel ball diameters with a hardness of around 40-50 HRC. Shot peening pressure varies from 7, 8, and 9 bar. Corrosion rate testing was carried out using bovine serum media. The results showed that the best increase in corrosion resistance was 0.117 mpy for a steel ball diameter of 0.5 mm with a pressure of 9 bar, 3 times lower than that of non-treated specimens, which was 0.378 mpy.

Microstructure change and corrosion resistance of selective laser melted Ti-6Al-4V alloy subjected to pneumatic shot peening and ultrasonic shot peening

Titanium alloys fabricated by selective laser melting (SLM) are typically subjected to post-treatments, such as shot peening, to improve the mechanical properties. However, the same Almen intensity may correspond to various combinations of peening parameters, which will generate different microstructures and comprehensive properties. Herein, the SLMed Ti64 alloy was treated by pneumatic shot peening (SP) and ultrasonic shot peening (USP) under the same Almen intensity of 0.2 mmA, investigating the changes of the microstructure and corrosion resistance. The average surface roughness (Ra) of the SPed sample was 1.806 μm, which was significantly higher than those of the USPed samples (0.942 μm and 0.999 μm). The USP and SP treatments led to the surface plastic deformation and grain refinement, while the SP produced a smaller crystallite size. The SP treatment led to the biggest surface and max compressive residual stress, which were −654.0 MPa and −805.5 MPa, but the USP resulted in thicker compressive residual stress layers. The USPed sample reached the highest microhardness (443.2 HV0.025) and the thickest hardened layer (247.8 μm). The USP and SP samples offered superior corrosion resistance, but the USPed samples showed higher corrosion potentials and lower corrosion current densities.

Evaluation of the influencing factors of combined surface modification on the rolling contact fatigue performance and crack growth of AISI 52100 steel

In this study, the combined treatment technology of shot peening (SP) and ultrasonic surface rolling (USR) were applied to the surface modification of AISI 52100 steel. The results revealed that SP, USR and combined treatment effectively improved the microhardness and residual stress of the alloy; however, SP and combined treatment were often accompanied by increased surface roughness. A nanocrystalline structure layer was prepared on the surface of the material through combined treatment, and the reason for the formation of the nanocrystalline structure layer was explained in detail. Compared with ceramic beads, the combined treatment of SP with steel beads was beneficial. The surface hardness and residual stress were improved while the minimum surface roughness was obtained. Under this process, the RCF life was significantly increased. Studies have shown that with the increased of RCF life, crack initiation transferred from the surface to the subsurface, and the crack depth increased significantly.

Load capacity of single-lap adhesive joints made of 2024-T3 aluminium alloy sheets after shot peening

The goal of the work reported was to determine the influence of selected shot peening parameters on the deflection of the Almen strip and the load capacity of single-lap adhesive joints made of 2-mm-thick aluminium alloy EN AW-2024-T3. Moreover, the research was aimed at checking the possibility of using the Almen strip deflection indicator to predict the load capacity of adhesive joints after shot peening. The analysis was carried out according to Hartley’s PS/DS-P:Ha3 plan. The input factors were the shot peening parameters: treatment time t (60–180 s), ball diameter dk (0.5–1.5 mm) and compressed air pressure p (0.3–0.5 MPa). It has been proved in this work that shot peening treatment of the outer surface of single-lap adhesive joints can be used to strengthen the joint. The maximum increase in the load capacity of the shot peened joints was 33.4%. It was observed that the load capacity of the joints decreases with an increase in the deflection of the Almen strip (in the assumed area of variability of technological parameters). Moreover, the results obtained indicate that the adoption of too intensive treatment, manifested in high values of deflection of the Almen strip, may weaken single-lap adhesive joints.