Papers by Keyword: Shot Peening

Abstract: The color of water atomized steel shots changes upon processing and heat treatments due to the compound formation on the steel shot surface. In this study, color change is studied at each step of the water atomized steel shots and for size variation using various microscopic techniques such as OM, SEM, TEM and spectroscopic techniques such as AES and XPS. The results show that the color of the shot balls changes due to the formation of FeOOH, Fe_xO_y, etc. depending on the heat treatment and natural oxidation upon exposure to the environment, whose thicknesses also depend on the severity of processing and heat treatment for the compound formation.

Abstract: Shot peening mechanical treatment surface, commonly used to improve material surface mechanical properties, as fatigue and wear resistance increase, induces deformations in the material crystal lattice, characterized by the presence of stress. Additionally, plasma nitriding, another surface treatment used to minimize failures in austenitic stainless steels, can produce resistant surface layers, composed of the interstitial nitrogen atoms accommodated in austenitic structure, increasing the layer hardness. Thus, the present work aims to study the residual stress and layer formation on austenitic stainless steel F138 surface, after different treatment conditions. Plasma nitriding treatment after shot peening differences were analyzed. Residual stress was investigated by X-ray diffraction, using sin²ψ method. Samples of surface morphology and formed layer were analyzed by scanning electron microscopy (SEM) and X-ray diffraction. Previous shot peening treatment to plasma nitriding promotes the formation of a less homogeneous layer, with microcracks and induced residual stress increase. It was observed the formation of iron nitrides and expanded austenite after plasma nitriding treatment. Surface residual stress induction after shot peening and plasma nitriding treatments can be efficient methods to improve material mechanical properties.

Abstract: Ti-6Al-4V, renowned for its high strength and corrosion resistance, is a preferred material in aerospace and marine applications for lightweight structures due to its durability in challenging environments. Typically, GTAW welding is used for it’s fabrication. The residual tensile stresses produced after welding are known to worsen the corrosion and mechanical properties of welds. However, these properties can be improved by introducing near surface residual compressive stress by shot peening. When compared to the traditional shot peening treatment, the surface roughness that results from multiple shot peening with varying ball sizes and intensities can be significantly reduced. In the present work, Ti-6Al-4V plates were welded using conventional GTAW technique. Six different combinations of multiple shot peening treatments were applied to the welded specimens. Surface morphology and surface roughness were analysed. Surface residual stresses measurement were performed using by X-ray stress analyzer. Domain size and microstrain were measured using X-ray diffraction technique. Micro-hardness measurements were made along the weld thickness. Corrosion studies were carried out using potentiodynamic polarization test in 3.5% NaCl solution. The SP4 parameter comes out to have the best combination among all the multiple shot peened samples. It results in lowered surface roughness, higher compressive residual stress, better grain refinement, increased surface hardness, and enhanced corrosion resistance.

Abstract: Recently, researchers have developed the method as a harmless the crack by the surface modification. For the purpose of contributing to reliability improvement of the A6061-T6 structure by harmless method, the following research was carried out: The tensile residual stress of friction stir welding was added by shot peening, resulting in a more significant compressive residual stress than that of the base metal. The effect of the surface crack aspect ratio on the maximum harmless crack depth (a_hml) of A6061-T6 was evaluated for residual stress distribution. The detectable depth was evaluated in the relationship between a_hml and the maximum detectable crack depth (a_NDI) by non-destructive inspection (NDI).

Abstract: Additive manufacturing (AM), notably Laser Powder Bed Fusion (PBF-LB), has transformed metal component production, including the widely used AlSi10Mg alloy. However, optimizing surface properties for longevity remains challenging. Shot peening enhances mechanical properties, while silver shell-copper core (SSCC) coatings provide corrosion resistance and conductivity. This study investigates their combined effects on AlSi10Mg specimens, analyzing various shot media types' impact on surface roughness, coating thickness, and fatigue strength. Insights gleaned contribute to advancing surface treatment methodologies for AM components.

Abstract: The fatigue strength of maraging steel, which is an ultra-high-strength steel, is relatively low, compared to that of conventional high-strength steel. The fatigue life of a structure is highly dependent on the surface conditions, because fatigue cracks generally start at the surface of the material. In particular, surface cracks considerably degrade the fatigue limit. To expand the application range of maraging steel, it is necessary to improve the fatigue limit, and render the surface cracks harmless. This study aims to investigate the effect of shot peening (SP) on the fatigue strength of maraging steel with surface cracks. The SP application introduced a compressive residual stress from the specimen surface to a depth of 170 μm, and increased the fatigue limit by 77 %. The estimated crack size that can be rendered harmless, based on fracture mechanics, is (0.170 − 0.202) μm in the range As = (1.0 − 0.1). The intersections of the harmless crack sizes were determined at depth. A semicircular surface crack below this value is harmless in terms of fatigue limit. The usefulness of non-destructive inspection (NDI) and non-damaging technology was evaluated in relation to a_hml, a_NDI, a_25,50, and As. Thus, the SP process can improve the reliability of the maraging steel. Compressive residual stress is the dominant factor to improve fatigue strength and render the surface crack harmless.

Abstract: The present work was aimed at increasing the fatigue life of laser powder bed fusion manufactured maraging steel (MS) using surface modification. Samples were manufactured to investigatethe mechanical properties of the material with two types of heat treatment routes that were both subjected to severe shot peening (SSP). In addition, bending fatigue testing was utilized to reveal theeffect of shot peening (SP) and SSP on fatigue resistance of the MS. Microhardness profiles weremeasured near the surface and electron backscatter diffraction analysis was used for microstructuralanalysis. A thin layer of austenite was noted on the surface making it a softer section, which SP orSSP was able to transform. The fatigue life of the MS was notably icreased by the SP processing andeven greater improvement was achieved with the SSP, which raised the fatigue limit of the materialfrom 200 MPa to nearly 500 MPa.

Abstract: S45C carbon steel is widely used as a raw material for tools and automotive components. In machine components, a material that has hard and ductile properties is also needed, with this problem, of course, it is necessary to have material engineering to improve the mechanical properties of steel in order to obtain good quality. The heat treatment process on the material has the advantage of improving mechanical properties. The purpose of this study was to determine the effect of heat treatment and shot peening on the mechanical properties and microstructure of the S45C carbon steel surface. S45C carbon steel was heat-treated at 900 oC and held for 15 minutes, then quenched using oil media. Next, the shot peening process was carried out with pressure variations of 4, 5, 6, and 7 bar for 20 minutes. Hardness testing was carried out using micro Vickers with a load of 0.49 N for 10 seconds. The results of the heat treatment on S45C material experienced an increase in hardness of 251.56 VHN compared to non-treatment, namely 187.38 VHN. Specimens that have been heated treated and shot peening with pressure variations of 4, 5, 6, and 7 bar experienced an increase in hardness of 286.18, 289.22, 357.24, and 450.22 VHN. The microstructure of the heat treatment material is formed by the phases of ferrite, pearlite, and martensite. The pearlite structure is denser and denser, showing increased hardness compared to non-treated S45C. Furthermore, the cross-sectional microstructure shows the depth of the shot peening effect as far as 130 μm. The surface of the specimen has a denser structure than the raw material.

Abstract: 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.

Abstract: The effects of the peening conditions on the surface characteristics and fatigue strength of stainless steel were investigated by microshot peening (MSP). In recent years, MSP technology has attracted attention. The use of MSP technology with minute media has become more widespread in consideration of the reduction of the notch effect in the material surface. However, the effect of MSP technology on stainless steel has not been much studied. In the present study, an air-type machine was used. The media used was high-carbon cast steel (490 HV) and Fe-Cr-B alloy (1130 HV), with an average diameter of 0.1 mm. The peening time was in the range of 0 - 100 s. Four types of stainless steels, SUS304, SUS304L, SUS316, and SUS316L, were tested. The workpieces were annealed at 1100 K for 1.2 ks in air. In the measurement of fatigue strength, the workpieces were machined in hour-glass shape. As the results, surface roughness of the workpieces treated by MSP was small. Work hardening was evident to the depth of approximately 0.2 mm from the surface. This depth was about twice the diameter of shot media. However, the effect of the peening time on the hardness distribution was not large. The compressive residual stress was added in the surface vicinity. It is assumed that the fatigue limit had increased because the work hardened layer was formed near the workpiece surface.