Peening Pressure Research Articles

Enhancing Tribological Properties of Pump Shafts through Shot Peening: A Study of Surface Roughness, Hardness and Performance Comparison with Heat Treatment

Abstract This research employed Shot Peening (SP) to enhance the tribological behavior of the En-31 pump shaft material. The study compared the effects of varying peening pressures (2.5, 3, 3.5, and 5 bar) and shot sizes (S110 and S230) on surface roughness, hardness, and tribological behavior. The results shown highest hardness of 12.5% was achieved at a pressure of 4 bar with the S230 shot material, while the surface roughness increased by over 75% under the same conditions. The 3.5 bar peening process produced the most significant improvements based on fractographic analysis.

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 shot peening pressure on fretting wear properties of 42CrMoA steel

Effect of shot peening pressure on fretting wear properties of 42CrMoA steel

Effects of Shot Peening on Mechanical Properties and Microstructural Evolution of AMS 6265 Steel Surface Treated for Critical Aircraft Components

Considering its very good mechanical properties, especially the high strength and toughness, and also its well-known case-hardening ability, the AMS 6265 (9310 VAR) low alloy steel is widely used in the aeronautical industry for manufacturing heavy-duty products and parts, like pinions, shafts, gears, piston pins, and other critical aircraft components. In this study, a surface modification treatment via shot peening method was applied to an initially case-hardened (quenched and carburized) AMS 6265 aircraft steel. In shot peening, the mechanical properties of the surface layer are improved, by generating plastically deformed micro-areas when exposing the metal surface to a stream of steel, glass, or ceramic shots. The initial case-hardened AMS 6265 alloy steel and all surface treated samples were structurally investigated by means of OM (optical microscopy), SEM-BSE (scanning electron microscopy – backscattered electrons imaging), and XRD (X-Ray diffraction) analysis, being also mechanically tested in tensile and microhardness tests. The influence of different shot peening parameters (shot size, peening pressure, and exposure time) on mechanical properties evolution and microstructural features, for the analyzed AMS 6265 alloy steel, was established in this present research.

Study on the Influence of Surface Integrity on Hydrogen Permeation Resistance of Hydrogen Production Reactor Materials

Hydrogen permeation reduces a material’s properties and increases the risk of brittle fracture, which causes a potential safety hazard. A workpiece’s hydrogen permeation resistance could be improved by improving its surface integrity through surface processing. This paper studies low-alloy steel’s surface integrity and its hydrogen permeation resistance in a hydrogen production reactor, using the electrochemical cathodic hydrogen-charging method to carry out electrochemical hydrogen-charging experiments. After the specimens were pretreated using different surface-grinding methods and shot peening pressure strengthening, they were hydrogen-charged on a self-designed and built electrolytic hydrogen charging platform. Before and after hydrogen charging, the specimens’ section hardness and tensile strength were tested, and the fracture morphology of the specimens was observed. The influence laws of surface roughness and surface residual compressive stress on the distribution of material hardness along the depth, the variation in material hardness, the fracture morphology, and the decline in the tensile properties of the low-alloy steel specimens after 5 h of hydrogen charging were analyzed. The reasons for the influence of surface integrity indexes on the hydrogen permeation resistance of the specimens were also analyzed. Based on the experimental results, a series of mechanical processing parameters were proposed to improve the material’s permeation resistance, which provides a theoretical and practical basis for the processing of materials with high surface integrity and hydrogen permeation resistance. Through the experiments, it was found that the hydrogen permeation resistance of the Ra 0.17 μm surface roughness specimen was the best of all specimens with different surface roughness values, and its hydrogen embrittlement sensitivity index was 20.96%. The specimen had the best hydrogen permeation resistance under 336 MPa surface residual compress stress, and its hydrogen embrittlement sensitivity index was 16.45%.

Effects of Shot Peening Pressure on Friction and Wear of High Pressure Cold Sprayed Ti-6Al-4V Coatings Under Dry and Lubrication Conditions

Effects of Shot Peening Pressure on Friction and Wear of High Pressure Cold Sprayed Ti-6Al-4V Coatings Under Dry and Lubrication Conditions

Atypical phase transformation behavior of Fe-33%Ni alloys induced by shot peening

The phase transformation behaviors of two Fe-33 mass%Ni alloy specimens subjected to shot peening (SP) were investigated. The first sample consisted solely of an austenite (γ) phase while the second also contained a high proportion of a martensite (α′) phase. When the specimen containing only the γ phase was subjected to SP, a stress-induced martensitic transformation occurred. In contrast, the second sample underwent the reverse transformation from the α′ to γ phase. Moreover, the volume fraction of the γ phase in the vicinity of the peened surface of each specimen was found to plateau as the SP treatment was prolonged. The final volume fraction of the γ phase was the same in both specimens regardless of their initial microstructure prior to the SP process. In addition, the volume fraction of the γ phase was found to increase with increasing peening pressure, meaning that the reverse transformation was promoted by SP at higher pressures. Calculations of the deformation heat generated during SP indicated that this heat was not primarily responsible for the reverse transformation induced by SP. Estimation of the change in the phase transformation temperature resulting from the residual compressive stress imparted by SP showed that this treatment changed the value of T0 (the arithmetic mean of the martensitic transformation start temperature and the reverse transformation start temperature) for the Fe-33 mass%Ni alloy from 328.5 K to 287.8 K. Because T0 after SP was lower than the temperature to which the specimens were raised during SP, this process could have caused stress-induced reverse transformation. Therefore, the decrease in the phase transformation temperature stemming from residual compressive stress is believed to explain the reverse phase transformation observed during SP of this alloy.

Assessment of Corrosion Resistance and Hardness of Shot Peened X5CrNi18-10 Steel.

Although the application of shot peening facilitates increasing hardness and corrosion resistance of stainless steel, the inappropriate peening parameters result in overestimated hardening and exaggerated surface roughness, which deteriorate the surface morphology and negatively affect the corrosive behavior of treated steel. Therefore it is crucial to select the peening parameters that allow obtaining both high hardness and elevated corrosion resistance. This study aims to determine the effect of X5CrNi18-10 stainless steel samples shot peening on the surface morphology, hardness, and corrosion resistance. Samples were shot peened with a CrNi steel shot, applying 0.3 MPa and 0.4 MPa peening pressures and treatment times of 60 s and 120 s. Roughness analysis and microscopic and SEM-EDS examination were employed to state the effect of peening parameters on the sample's corrosive behavior in a 3.5% NaCl solution. The most promising shot peening parameters for Vickers hardness and electrochemical corrosion resistance were selected. It is revealed that the surface roughness increase has a detrimental effect on the corrosion behavior. Overall, high corrosion resistance and the high hardness of stainless steel samples were noted for the peening pressure of 0.4 MPa and time treatment of 60 s.

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.

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.

Effect of fine particle peening on surface integrity of flexspline in harmonic drive

High-performance precision gear drives such as harmonic gear have high requirements on tooth profile accuracy, surface quality, fatigue life and other service performance characteristics, which urgently needs an effective surface strengthening method. This work aims to examine the feasibility and effectiveness of fine particle peening (FPP) treatment on surface integrity of flexspline in harmonic drive precision transmission. To this end, FPP process experiments were carried out, and this process was simulated based on a coupling method of discrete element method and finite element method (DEM-FEM) considering the kinematic hardening behavior of the material. The simulation results were in good agreement with the test results. Effects of shot peening pressure, injection velocity, material properties and tooth profile on surface roughness and induced residual stress of the target flexspline were analyzed. The results reveal that after FPP, the amplitude of residual compressive stress of the flexspline can reach 470 MPa, and the surface roughness Sa becomes approximately 0.5 μm. For precision gears with low hardness such as flexspline in harmonic drive, it is suggested to adopt FPP with low air pressure to achieve both saturated residual compressive stress and lower surface roughness, thus benefitting enhanced fatigue life.

Modification of Surface and Subsurface Properties of AA1050 Alloy by Shot Peening.

AA1050 Al alloy samples were shot-peened using stainless-steel shots at shot peening (SP) pressures of 0.1 and 0.5 MPa and surface cover rates of 100% and 1000% using a custom-designed SP system. The hardness of shot-peened samples was around twice that of unpeened samples. Hardness increased with peening pressure, whereas the higher cover rate did not lead to hardness improvement. Micro-crack formation and embedment of shots occurred by SP, while average surface roughness increased up to 9 µm at the higher peening pressure and cover rate, indicating surface deterioration. The areal coverage of the embedded shots ranged from 1% to 5% depending on the peening parameters, and the number and the mean size of the embedded shots increased at the higher SP pressure and cover rate. As evidenced and discussed through the surface and cross-sectional SEM images, the main deformation mechanisms during SP were schematically described as crater formation, folding, micro-crack formation, and material removal. Overall, shot-peened samples demonstrated improved mechanical properties, whereas sample surface integrity only deteriorated notably during SP at the higher pressure, suggesting that selecting optimal peening parameters is key to the safe use of SP. The implemented methodology can be used to modify similar soft alloys within confined compromises in surface features.

Influence of post-processing techniques on the microstructure, properties and surface integrity of Al Si Mg alloy processed by laser powder bed fusion technique

The present work investigates the influence of post-processing techniques such as heat treatments (T5 and T6 conditions) and the shot peening (SP) under peening pressures such as 3 bar (SP-3) and 6 bar (SP-6) on the LPBF processed AlSi10Mg alloy. The microstructures of as-printed and heat-treated samples revealed a density of greater than 99.9%. The micro-hardness, yield and tensile strength properties were similar in both as-printed and heat-treated (T5) conditions. However, the samples of the heat-treated (T6) showed lower micro-hardness, yield and tensile strength properties than as-printed and heat-treated (T5) samples. There was a significant decrease in surface roughness and a notable improvement in surface hardness for shot-peened samples compared to the as-printed samples. SP process decreased the surface roughness parameter values by more than about ~50% compared to the as-printed samples. The SP-3 condition induced a smoother surface (~12%) than the SP-6 condition on the LPBF processed AlSi10Mg samples. Overall, the employed post-processing techniques such as heat treatment and shot peening on the LPBF processed AlSi10Mg alloy exhibit improved isotropic mechanical properties and surface integrity. • Post-processing techniques such as heat treatments and the shot peening on the LPBF processed AlSi10Mg alloy is studied. • The micro-hardness and tensile properties of T5 were higher than T6 conditions. • SP process decreased the surface roughness by more than about ~50% compared to the as-printed samples. • The SP-3 condition induced a smoother surface (~12%) than the SP-6 condition.

Effect of shot peening on the surface properties, corrosion and wear performance of 17-4PH steel produced by DMLS additive manufacturing

Components produced by additive manufacturing (AM) via direct metal laser sintering (DMLS) have typical as-fabricated surface defects. As a result, surface properties of AM products should be modified to increase their strength, anti-wear behaviour, and at the same time to ensure their high corrosion resistance. Surface modification via shot peening is considered suitable for additive manufacturing of medical devices made of 17-4PH stainless steel. The objective of this study was to determine the effect of shot peening pressures (0.3 MPa and 0.6 MPa) and three types of blasting media (CrNi steel shot, nutshell granules and ceramic beads) on the tribological characteristics and corrosion resistance of specimens of DMLS 17-4PH stainless steel. Results demonstrated that shot peening caused steel microstructure refinement and—except for the nutshell shot-peened specimens—induced both martensite (α) formation and retained austenite (γ) reduction. 17-4PH specimens peened with steel and ceramic shots showed the highest increase in surface hardening by approx. ~ 119% (from 247 to 542 HV), which significantly improved their wear resistance. The highest mechanical properties (hardness and wear resistance) and corrosion resistance were obtained for the surfaces modified using the following media: ceramic beads > CrNi steel shot > nutshell granules. Adhesive and fatigue wear were two predominant mechanisms of tribological deterioration. Results demonstrated that the application of shot peening using ceramic beads led to grain size refinement from 22.0 to 14.6 nm and surface roughness reduction, which in turn resulted in higher corrosion resistance of the material. DMLS 17-4PH specimens modified by shot peening using ceramic beads and a pressure of 0.6 MPa exhibited the optimum surface morphology, hardness and microstructure, and thus improved wear and corrosion performance.

Effect of shot peening on microstructure and contact fatigue crack growth mechanism of shaft steel

In this study, C53 steel was shot peened with different process parameters. The effects of shot peening pressure, coverage and shot diameter on surface hardness, roughness and residual stress of C53 steel were discussed. The effect of different shot peening parameters on the rolling contact fatigue property of C53 steel was analyzed. The results show that the coarse grains are refined into nanocrystals by shot peening, and a large number of dislocation tangles are formed. With the increase of shot peening strength, the surface hardness of C53 steel increases to 712.8 HV0.2, with an average increase of 18.3%. The maximum residual compressive stress is −677 MPa, which is 5.7 times of the original sample. And the surface roughness increases obviously. Due to dislocation tangles and nanocrystalline strengthening, the rolling contact fatigue life of C53 steel increases obviously after shot peening, but the fatigue life decreases with the increase of shot peening strength. It is found that there are two modes of rolling contact fatigue crack propagation: intergranular growth and lamellar.

Mechanical behavior study of asymmetric deformation in double-sided symmetrical sequential shot peening process

Shot peening is widely used in the aeronautical industry to enhance the fatigue life of the parts and form large, thin, and complex components, such as wing and fuselage skins. Previous research on peen forming simulation has rarely considered the influence of the shot peening sequence on the resulting deformed shape. In particular, the study on the mechanics mechanism of asymmetry in double-sided sequential (un-simultaneous) shot peening is not enough. In this study, therefore, experiments based on symmetrical plane strips (Almen-sized Al7075 strip and Almen strip) show that the final deformation is often asymmetrical with the same shot peening parameters in sequence. As the symmetrical surfaces are peened in sequence, the final bending direction is always consistent with the later shot peening effect. To explain this interesting phenomenon, the double-sided symmetrical sequential shot peening process was simulated by finite element method (FEM). The simulation and experiment results verified the universality of asymmetric deformation in double-sided symmetrical sequential shot peening process. A theory analytical model of the stiffness reduction proposed in this paper was used to explain the asymmetric deformation mechanism, and it is verified by three-point bending tests. Some new results obtained by the experiment and simulation are presented. The influences of the strip thicknesses and shot peening pressures on the asymmetric deformation are discussed in double-sided symmetrical sequential shot peening.

Study on hardness and wear resistance of shot peened AA7075-T6 aluminum alloy

AA7075-T6 aluminum alloy samples were shot peened at various shot peening pressures in the range of 10–70 psi to study their mechanical and tribological properties under dry and mineral oil lubrication conditions. The surface roughness of the shot peened AA7075-T6 samples apparently increased with increased shot peening pressure. The best bearing surface was obtained when the shot peening process was carried out at the highest shot peening pressure of 70 psi. It was found that the increased shot peening pressure increased the hardness and decreased the wear of the shot peened samples. The shot peened samples tested under the mineral oil lubrication condition also had lower wear for higher shot peening pressures due to the combined effects of their higher surface wear resistance and better bearing surfaces. The results clearly showed that using the mineral oil lubricant during sliding apparently decreased the wear of the shot peened samples as a result of the lubricating effect of the lubricant. It could be deduced that the tribological properties of the shot peened AA7075-T6 samples under the dry and lubrication conditions were affected by the shot peening pressure.

WITHDRAWN: Optimization of shot peening process parameters using PSO algorithm to maximise the fatigue strength, flexural strength and surface hardness of AA2024-T3 alloy

Shot peening (SP) process is performed on AA2024-T3 alloy to improve its fatigue strength, flexural strength and surface hardness. Response surface method (RSM) is used for designing the experiments. Experiments are conducted and the regression equations are framed using the Design Expert software. RSM based second order regression equations are used as input to Particle swarm optimisation (PSO) algorithm. PSO algorithm is used to find the best combination of shot peening process parameters, namely, peening pressure and peening distance for maximizing the responses. Validation of the solutions obtained from PSO is done by performing shot peening process with nickel balls. The results of mechanical properties of AA2024-T3 are found close to the predicted values obtained from PSO algorithm.

Surface Characteristic Function of Al Alloy after Shot Peening

The work aims to study the change rule of the surface properties of aluminum (Al) alloy after shot peening (SP), and obtain the corresponding relationship between the surface material characteristics and SP parameters. Firstly, the Finite Element Model (FEM) of multi-projectile impact Al alloy specimen was established by ANSYS/LS-DYNA (Version: Ansys15.0). Box-Benhnken design method (BBD) was used to design 3-level and 3-factor shot peening experiment with shot peening pressure. Projectile size, jet distance, the surface residual stress, as well as deformation were taken as responses. The surface stress and the deformation at the crater were obtained according to the experiments. Then, Design-Expert software was adopted to fit the values to attain the multiple regression quadratic equations, and the response surface methodology (RSM) was applied to analyse the interaction between the various factors. The degree of model-fitting was simultaneously identified in accordance with an analysis of variance of the function models. Finally, the shot peening test was carried out using 7075-T651 Al alloy as the specimen. Combined with the X-ray diffraction (XRD) stress test and the optical microscopic observation of the crater section, the value of stress and deformation value could be determined to verify the accuracy of the model. The adjusted R2 of the stress function model and the deformation function model were 94.85% and 95.08%, respectively. The deviation between calculated stress value and the experimental value was less than 5.5%. The deformation of the section showed that the deformed layer of the specimen was approximately the same as calculation value. The result indicated the function model had high accuracy. The analysis suggested that the function model could quickly and precisely deduce the parameter combination of the SP from the surface stress or deformation of the material, which provided a diversity reference for the surface stress and hardness strengthening of SP.

Analysis of surface finish and residual stresses with shot peening on cylindrical specimens

Abstract Machining of cylindrical metal pieces effects the surface parameters due totool and type of contact. Due to the surface contact of the tool with the work material, the surface texture may deteriorate depending on the machining parameters applied. In order obtain good surface finish, the tool and machining parameter are the major considerations. In this paper shot peening was considered to determine good surface finishing. Cylindrical rods of different materials were considered for obtaining good surface finishing using the shot peening process. The nozzle was turned to an angle of 10 degrees from the principal axis. The blast pressure was controlled to obtain required surface finish. The surface hardness obtained after shot peening was measured. The residual stresses induced from the depth of the surface are determined and compared for various peening pressures.