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Atmospheric-controlled induction-heating fine-particle peening (AIH-FPP) was applied to low-alloy, low-carbon steel AISI 4120 to achieve rapid carburizing within minutes and enhance fatigue strength. The shot particles used during AIH-FPP were specifically created by mechanically milling a mixture of steel particles and carbon powders. The specimens were analyzed using laser microscopy, optical microscopy, X-ray diffraction for residual stress measurement, a micro-Vickers hardness tester, and an electron probe micro-analyzer. Axial fatigue tests and fracture surface analyses via scanning electron microscopy and energy-dispersive X-ray spectroscopy were also conducted. AIH-FPP effectively transferred carbon to the treated surface and facilitated its diffusion in a short period, creating a martensite layer with high hardness and compressive residual stress, which resulted in increased fatigue strength. The fatigue strength of the AIH-FPP-treated specimens was influenced by the conditions of reheating and quenching, which altered the prior austenitic grain size and stress concentration at the specimen surface. Notably, specimens treated with AIH-FPP followed by reheating and water-injection quenching exhibited fatigue strength comparable to that of conventional gas-carburized specimens, owing to the formation of a carburized layer with a small prior austenite grain size.

As a fundamental component of aviation equipment, the gear has an essential effect on the service performance of the whole machine. Fine particle peening (FPP) technology is a good choice for the precision requirements of aviation gears. Therefore, a FPP model of aviation gears was constructed based on the discrete element‐finite element coupling method (DEM‐FEM) to simulate the evolution of surface roughness and residual compressive stress, and its results were verified by experiments. The effects of FPP intensity, coverage rate, and particle diameter on surface integrity were investigated. In addition, the importance degree of the intensity, coverage rate, and particle diameter of FPP on surface integrity was carried out by the random forest decision method. It demonstrates that the surface roughness Sa was mainly influenced by the FPP intensity and particle diameter. And the distribution state of the residual compressive stress was mainly affected by the particle diameter. Highlights: 1. The simulation model of FPP strengthening aviation gear based on DEM‐FEM was established. 2. The coefficient of restitution was taken into account in the damping force. 3. The importance degree of surface integrity was carried out by random forest method [ABSTRACT FROM AUTHOR]

Fine particle peening (FPP) technology offers an effective method to achieve outstanding surface integrity and fatigue performance in aviation gears. However, the lack of sufficient research on the correlation between process parameters, surface integrity parameters, and fatigue life undermines the full potential of FPP in strengthening aviation gears. Therefore, we have developed an elastic–plastic contact fatigue life model to predict the fatigue life of AISI 9310 gear steel after different strengthening processes. This model can consider surface integrity parameters such as surface micro‐topography, residual stress gradient, and hardness gradient. To validate the model, we conducted rolling contact fatigue tests and compared the results with the predictions from our model. The influence of process parameters on the rolling contact fatigue of AISI 9310 gear steel was further investigated. A process window for FPP was established, and an optimization method was proposed in order to provide guidance for selecting process parameters for FPP on high‐performance aviation gears. HIGHLIGHTS: 1. The rolling contact fatigue life of aviation gear after strengthening is predicted. 2. The simulation results are in good agreement with the rolling contact fatigue tests. 3. A process window for aviation gear steel after FPP is established. [ABSTRACT FROM AUTHOR]

To create a coating of titanium nitride, atmospheric-controlled induction-heating fine particle peening using fine particles of pure titanium was conducted for low-alloy steel in a nitrogen atmosphere, and the surface characteristics of the treated specimens were investigated. The formation of hard titanium nitride coatings with a thickness of 100–200 μmwas achieved by peening at 1373 K for 10 s and subsequent heating at 1373 K for 120 s. Titanium particles adhered to the treated surfaces during peening at the high temperature, which reacted with nitrogen in the atmosphere during the heating after peening. Ball-on-disk wear tests were conducted to examine the wear resistance of the specimens, and it was found that the created coating by AIH-FPP improved the wear resistance of low-alloy steel owing to its high hardness. The improvement was more significant at high testing temperatures because the high testing temperature and frictional heat caused oxygen in the air to react with titanium in the coating during the wear test. Immersion of the specimens into sodium chloride solution was also conducted to investigate the corrosion resistance, which revealed that the coating created improved corrosion resistance of low-alloy steel.

In this study, the surface of industrial pure iron was treated with atmospheric-controlled induction heating fine particle peening (AIH-FPP) using mechanical coating (MC) particles of carbon/steel obtained by mixing carbon powder and fine steel particles using mechanical milling. The surface modification effect and the mechanism of its effect were examined and considered by analyzing of the treated surface. Results showed that a modified layer in which carbon elements were diffused was formed near the treated surface by the AIH-FPP treatment using MC particles. In addition, by examining the influence of the treatment conditions on the formation of the modified layer by the design of experiments, the treatment temperature showed the most significant influence among the treatment temperature, peening time, and gas flow rate. The higher the treatment temperature, the deeper the carbon diffused layer. In addition, when treated at ≥1273 K, the microstructure near the surface became pearlite, and Vickers hardness increased. The time required for carbon diffusion in the AIH-FPP carburizing process using MC particles of carbon/steel was approximately the same as that of a general carburizing treatment using a reactive gas. In the AIH-FPP carburizing process, carbon is considered to be transferred from the particles to the surface, and the grain boundaries and dislocations increased by fine particle peening (FPP) are used as channels to diffuse inside the specimen. This mechanism is entirely different from the conventional carburizing methods. [ABSTRACT FROM AUTHOR]

Atmospheric‐controlled induction‐heating fine particle peening (AIH‐FPP) was performed for low‐alloy steel, and the effects of the peening temperature, the microstructure of steel, and thermal history during AIH‐FPP on the resultant microstructure of treated steel were investigated. Regardless of the prior microstructure and thermal history, the grains near the surfaces were refined by AIH‐FPP at peening temperatures from 923 K to 1023 K owing to dynamic recrystallization. To examine the effect of AIH‐FPP on the fatigue properties of steel, plane‐bending fatigue tests were performed. Compared with the steel mirror‐polished, treated with FPP at RT, or only induction‐heated, the fatigue properties of steel treated with AIH‐FPP were improved. This is because of the formation of a thick and uniform grain‐refined layer, the generation of compressive residual stress, and hardening of the surface by AIH‐FPP. Moreover, owing to the grain refinement progress, the fatigue properties of steel improved with increasing peening temperature. Highlights: AIH‐FPP can refine grains regardless of prior microstructure of steel and thermal history.AIH‐FPP can improve fatigue properties of low‐alloy steel AISI4140.The fatigue properties improved with the increasing peening temperature during AIH‐FPP.AIH‐FPP is more effective at improving the fatigue properties than FPP at RT or only IH. [ABSTRACT FROM AUTHOR]

• Peening with fine iron sulfide particles (FeS-peening) was introduced. • FeS-peening formed a layer of FeS particles without the use of aqueous Na 2 S 2 O 3. • FeS-peening increased the fatigue limit of steels by 125 MPa. • Improvement of fatigue limit (24 MPa) by residual stress was quantitatively investigated. • The fatigue limit of FeS-peened steels was 95 MPa higher than conventional processed one. Low alloy steels were subjected to peening with fine iron sulfide particles (FeS-peening) under ambient conditions to transfer a layer of such particles, which can improve seizure resistance and sliding properties, and thus enhance the fatigue characteristics of the steel. This process was performed without the use of aqueous Na 2 S 2 O 3 and the specimens were assessed using electron probe microanalysis and rotating bending fatigue tests. Treated specimens exhibited higher fatigue limits as a result of high degree of compressive residual stress generated on the steel surface. The effects of residual stress on the fatigue limit were quantitatively investigated using a modified Goodman diagram. Sample cross-sections were observed using electron backscattered diffraction, which confirmed that FeS-peening formed fine surface grains. Grain refinement was determined to be at least partly responsible for the improved fatigue properties of the steel following FeS-peening. [ABSTRACT FROM AUTHOR]

Surgery, radiation therapy, and chemical therapy have been reported as the main treatments for cancer, which is one of the deadliest reported diseases. However, because of the high invasiveness of patients, cancer hyperthermia has been studied as a non-invasive treatment. Hyperthermia uses a difference in thermal tolerance between normal and cancer cells and provides an affected part thermal stimulation to kill cancer cells selectively. To develop effective conditions for hyperthermia, an in vitro study to evaluate the thermal tolerance is required. However, because the existing cell culture vessels cannot control the culture temperature, genuine thermal tolerance of cells cannot be investigated appropriately. To reveal the critical temperature proper for hyperthermia, we developed a culture device controlling culture temperature. With the developed device, culture temperature was regulated considerably more quickly than the conventional method with the existing vessels, which enabled us to study the thermal tolerance of cells appropriately. For the control of culture temperature, the device has a titanium culture substrate, where a Peltier element is adhered. Because the biocompatibility of the device was confirmed, the difference in thermal tolerance between normal and cancer cells was investigated using the developed device as well as normal human dermal fibroblasts and Michigan Cancer Foundation-7 as model cell species. Therefore, it was confirmed that cancer cells were more sensitive to thermal stimulation than normal cells, which was qualitatively consistent with previous studies. Thus, our developed device can be used to investigate the thermal tolerance of each cell species, which will contribute to the development of cancer hyperthermia. [ABSTRACT FROM AUTHOR]

Fine particle peening (FPP) at room temperature was introduced to create finer grains at the surfaces of Fe-Cr alloys that were then treated by atmospheric controlled induction heating FPP (AIH-FPP). The effect of the proposed treatment on the grain refinement behavior of the alloys was investigated using optical microscopy and micro-Vickers hardness testing. The FPP pretreatment at room temperature increased the effectiveness of the grain refinement via dynamic recrystallization during subsequent AIH-FPP. Grain refinement at the surface of Fe-Cr alloys progressed with an increase in the cycles of the treatment. The addition of Cr in Fe-Cr alloys promotes the formation of fine grains during the treatment. Specimens with fine grains created via static recrystallization were also prepared and compared to grains formed via dynamic recrystallization by the room temperature FPP pretreatment and subsequent AIH-FPP to evaluate the effectiveness of the proposed treatment. The grains formed through dynamic recrystallization by the proposed treatment were finer than those formed through static recrystallization. These results indicate that the proposed combination of room temperature FPP and AIH-FPP is effective for the formation of fine grains at the surfaces of Fe-Cr alloys. [ABSTRACT FROM AUTHOR]

In order to fabricate a titanium alloy with superior wear resistance and fatigue strength, fine particle peening (FPP) was introduced as a post-treatment after gas blow induction heating (GBIH) nitriding. The surface characteristics of the treated alloy were examined using X-ray diffraction, scanning electron microscopy, laser microscopy and a micro-Vickers hardness tester. GBIH nitriding and post-treatment with FPP formed nitrided layers with high hardness and compressive residual stress at the surface of the alloy within a short period of time. This is due to the diffusion of nitrogen atoms during GBIH nitriding and plastic deformation of the surface layer during FPP. Reciprocating ball-on-disk wear tests were performed to investigate the wear resistance of the surface-treated alloy. The wear resistance of the titanium alloy was improved by the proposed surface treatment compared with samples that were only polished or FPP-treated. This is due to the presence of a nitrogen compound layer with high hardness at the surface. The abrasiveness toward the wear test counter material was also decreased by the combined surface treatment. [ABSTRACT FROM AUTHOR]

Fine particle peening (FPP) using hydroxyapatite (HAp) shot particles was performed to improve the fatigue strength and form a HAp transfer layer on a beta titanium alloy (Ti–22V–4Al). The surface microstructures of the FPP-treated specimen were characterized using scanning electron microscopy, micro-Vickers hardness testing, energy dispersive X-ray spectrometry, X-ray diffraction, and electron backscattered diffraction. A HAp transfer layer with a thickness of 5.5 μm was formed on the surface of the Ti–22V–4Al specimen by FPP. In addition, the surface hardness of the Ti–22V–4Al was increased, and high compressive residual stress was generated on the specimen surface by FPP. Rotating bending fatigue tests were performed at room temperature in laboratory air over a wide cycle-life region (103–109 cycles). In the long cycle-life regime, the fatigue strength at 107 cycles of the FPP-treated specimen became higher than that of the untreated specimen. This result is attributed to the formation of a work-hardened layer with high compressive residual stress by FPP. However, the fatigue strength was not improved by FPP in the short cycle-life regime, because fatigue cracks were initiated at surface defects formed during the FPP process. The fatigue fracture mode of the FPP-treated specimens shifted from surface-initiated fracture to subsurface-initiated fracture at a stress amplitude level of 600 MPa. [ABSTRACT FROM AUTHOR]

Fine particle peening (FPP) is a peening process using fine shots with an average diameter of less than 200 µm. Pairs of twin-disc specimens made of carburized and quenched 18CrNiMo7-6 gear steel were subjected to two different FPP processes and conventional shot peening (CSP) using big shots with an average diameter of 600 µm. Rolling–sliding tribology tests were carried out under oil lubrication, and comparisons of the friction coefficient were made between untreated, FPP-treated, and CSP-treated twin-disc specimens. To characterize the relationship between surface topography and friction coefficient, 3D surface parameters, including root mean square roughness (Sq), skewness (Ssk), kurtosis (Sku), core roughness depth (Sk), reduced peak height (Spk), and reduced valley depth (Svk) were measured before and after tribology tests. A linear regression method was applied to analyze the correlations between the surface parameters and the friction coefficient. It was found that FPP is effective in decreasing the friction coefficient during the lubricated rolling–sliding contact compared to untreated specimens. The friction coefficient has a higher correlation with Ssk and the ratio RSvk, which is defined as the ratio of Svk to the sum of Sk, Spk, and Svk. A lower friction coefficient was obtained when the topography had a more negative Ssk and a higher RSvk in the rolling–sliding condition. However, there was a weak linear correlation between the friction coefficient and surface parameters Sq, Sku, Sk, Spk, and Svk, and the relationship between the trend of friction coefficient and those surface parameters is not obvious. [ABSTRACT FROM AUTHOR]

Fine particle peening (FPP) using hydroxyapatite (HAp) shot particles was performed to improve the fatigue strength and form a HAp transfer layer on a beta titanium alloy (Ti–22V–4Al). The surface microstructures of the FPP-treated specimen were characterized using scanning electron microscopy, micro-Vickers hardness testing, energy dispersive X-ray spectrometry, X-ray diffraction, and electron backscattered diffraction. A HAp transfer layer with a thickness of 5.5 μm was formed on the surface of the Ti–22V–4Al specimen by FPP. In addition, the surface hardness of the Ti–22V–4Al was increased, and high compressive residual stress was generated on the specimen surface by FPP. Rotating bending fatigue tests were performed at room temperature in laboratory air over a wide cycle-life region (103–109 cycles). In the long cycle-life regime, the fatigue strength at 107 cycles of the FPP-treated specimen became higher than that of the untreated specimen. This result is attributed to the formation of a work-hardened layer with high compressive residual stress by FPP. However, the fatigue strength was not improved by FPP in the short cycle-life regime, because fatigue cracks were initiated at surface defects formed during the FPP process. The fatigue fracture mode of the FPP-treated specimens shifted from surface-initiated fracture to subsurface-initiated fracture at a stress amplitude level of 600 MPa.

Abstract In order to develop a rapid nitriding process for titanium alloy at a low temperature, fine particle peening (FPP) was performed prior to gas blow induction heating (GBIH) nitriding. The surface microstructures of a Ti-6Al-4V alloy treated by FPP and GBIH nitriding were characterized using X-ray diffraction, optical microscopy, scanning electron microscopy, laser microscopy and micro-Vickers hardness testing. The results indicate that nitrogen diffusion into titanium during GBIH nitriding was accelerated by the pre-treatment with FPP, and a nitrided layer was formed on the surface of the Ti-6Al-4V alloy at a relatively low temperature (923 K), which grain coarsening and phase transformation did not occur and a nitrided layer was not formed only by GBIH nitriding. This is because a fine-grained surface layer was generated by the pre-treatment with FPP. Reciprocating ball-on-disk wear tests were carried out to examine the wear resistance of the prepared specimens. GBIH nitriding at a low temperature improved the wear resistance of the Ti-6Al-4V alloy following the pre-treatment with FPP, due to the formation of a hard nitrogen compound layer at the surface. The results show that the proposed surface treatment process was effective at modifying the surface properties of a titanium alloy at a low temperature and within a short span of time while avoiding grain coarsening and phase transformation. Highlights • GBIH nitriding was performed on Ti-6Al-4V following fine particle peening. • Fine particle peening forms a fine-grained layer on the surface of Ti-6Al-4V. • Fine particle peening facilitates nitrogen diffusion during GBIH nitriding. • The wear resistance of Ti-6Al-4V is improved by the proposed process. • The proposed process can modify Ti-6Al-4V at a low temperature within a short time. [ABSTRACT FROM AUTHOR]

Atmospheric-controlled induction-heating fine particle peening (AIH-FPP) using Cr and Mo shot particles in a N 2 atmosphere was introduced to improve the electrochemical characteristics of AISI 316 austenitic stainless steel. The surface microstructure of the AIH-FPP-treated specimen was characterized using scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDX). AIH-FPP can be used to form transferred and diffused layers of shot particles on the surface of austenitic stainless steel. The thickness of the diffusion layers of Cr shot particles tended to increase with the heating time in the AIH-FPP process, whereas the Cr concentration at the surface tended to decrease. Electrochemical polarization tests were performed in 3 wt% NaCl + H 2 SO 4 and 20 wt% NaCl environments at 343 K using a three-electrode electrochemical cell connected to a computer driven potentiostat to examine the corrosion resistance of austenitic stainless steel treated with AIH-FPP. The pitting potential of the AIH-FPP-treated specimen was higher than that of the untreated specimen. In particular, there was clear improvement in the pitting potential of austenitic stainless steel by AIH-FPP with Cr shot particles following peening with Mo shot particles. AIH-FPP using Cr and Mo shot particles in a N 2 atmosphere is an effective method of improving the electrochemical characteristics of austenitic stainless steel. [ABSTRACT FROM AUTHOR]

To improve the high-temperature oxidation resistance of grade S45C carbon steel, we formed a Cr / Ni diffusion layer on the surface of carbon steel by atmospheric-controlled induction heating fine particle peening (AIH-FPP) treatment. Cr and Ni particles were mechanically milled in planetary ball mills and used as shot particles in the AIH-FPP treatment to create a Cr / Ni diffusion layer. High temperature oxidation tests were carried out at 900°C for 100 hours to evaluate the high-temperature oxidation resistance of the AIH-FPP treated specimen. The mechanically milled particles and specimen were analyzed using a scanning electron microscope, an energy dispersive X-ray spectrometer, and an X-ray diffractometer. Results show that the AIH-FPP treated specimen prepared using mechanically milled particles formed a Cr / Ni diffusion layer on the carbon steel. The carbon steel sample with the Cr / Ni diffusion layer exhibited improved high-temperature oxidation resistance compared to the untreated sample. This is due to the formation of Cr and Ni oxidized layers on the treated surface, which inhibited oxidation of the inner substrate. The results indicate that a Cr / Ni diffusion layer formed by AIH-FPP treatment using mechanically milled particles can improve the high-temperature oxidation resistance of grade S45C carbon steel.

The torsional fatigue strength of newly developed case hardening steel, i.e., transformation-induced plasticity-aided martensitic steel subjected to vacuum carburizing followed by fine particle peening, was investigated for the fabrication of downsized precision gears with high torque capacity and wear resistance. The surface-hardened layer properties--i.e., high Vickers hardness, high compressive residual stress, and a large amount of retained austenite--considerably increased the torsional fatigue limits of vacuum-carburized and fine particle peened TM and JIS-SNCM420 steels, although the notch-sensitivity to fatigue was increased. The relation between torsional and rotational bending fatigue limits for the smooth specimens was found to be between the maximum principal stress and the minimum shear strain energy criterions. On the other hand, this relation for the notched specimens was represented through the maximum principal stress criterion. [ABSTRACT FROM AUTHOR]

The effects of fine particle peening on the fatigue properties of a transformation-induced plasticity-aided martensitic steel with a chemical composition of 0.2% C, 1.5% Si, 1.5% Mn, 1.0% Cr, and 0.05% Nb (mass%) were investigated for applications in precision gears. When this steel was subjected to fine particle peening after heat treatment, higher fatigue limits and lower notch sensitivity were achieved compared with those of SNCM420 martensitic steel. The increased fatigue limits are principally associated with higher hardness and compressive residual stress on and just below the surface, as well as low surface roughness. Fine particle peening also increased the threshold stress intensity factor range in stage I, and decreased the crack propagation rate in stage II in this steel. The crack propagation behavior was mainly suppressed by (1) high hardness and high compressive residual stress, and (2) the strain-induced martensite transformation of retained austenite and high internal stress resulting from a difference in flow stress between the soft martensite matrix and the finely dispersed hard MA-like phase that developed during fatigue deformation. [ABSTRACT FROM AUTHOR]

Fine particle peening (FPP) using hydroxyapatite (HAp) shot particles was introduced to form the HAp surface layer and improve the fatigue properties of commercially pure (CP) titanium. The surface microstructure of the FPP-treated specimens was characterized using a micro-Vickers hardness tester, optical microscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDX), X-ray diffraction (XRD), and non-contact scanning white light interferometry. FPP could create a HAp layer on the surface of CP titanium within a relatively short time (1 s) by shot particle transfer. In addition, FPP increased the surface hardness and generated compressive residual stress at the treated surface. Four-point bending fatigue tests were performed at a stress ratio of 0.1 in air at room temperature to examine the effect of FPP using HAp shot particles on the fatigue properties of CP titanium. It was found that the fatigue limit for the FPP-treated specimen was higher than that for the unpeened specimen. The fatigue fracture mechanism for the CP titanium treated with FPP was discussed from the viewpoint of fractography. The HAp layer remained on the surface without delamination after the fatigue tests. [ABSTRACT FROM AUTHOR]

Shot peening using particles 10 μm in diameter (ultra-fine particle peening: Ultra-FPP) was introduced to improve the fatigue properties of 5056 aluminum alloy. The surface microstructures of the Ultra-FPP treated specimens were characterized using a micro-Vickers hardness tester, scanning electron microscopy (SEM), X-ray diffraction (XRD), non-contact scanning white light interferometry, and electron backscatter diffraction (EBSD). The Ultra-FPP treated specimen had higher hardness than the conventional FPP treated specimen with a short nozzle distance due to the high velocity of the ultra-fine particles. Furthermore, the surface hardness of the Ultra-FPP treated specimen tended to increase as the peening time decreased. Fatigue tests were performed in air at room temperature using a cantilever-type rotating bending fatigue testing machine. It was found that the fatigue life of the Ultra-FPP treated specimen tended to increase with decreasing peening time. Mainly, the Ultra-FPP improved the fatigue properties of 5056 aluminum alloy in the very high cycle regime of more than 10 7 cycles compared with the un-peened specimens. This is because the release of the compressive residual stress is small during fatigue tests at low stress amplitudes. [ABSTRACT FROM AUTHOR]

To fabricate novel micro-textured surfaces with valleys, dimples and plateaus as well as patterned composition as a strategy to improve surface characteristics, we combine fine particle peening (FPP) and precision surface grinding. Combined with a shallow angled FPP to form self-patterned ridge texture on aluminium surface, precision surface grinding with the specific conductive-bonded wheel removes the ridge peaks and simultaneously deposits Cu on the valleys by reducing Cu ions which are condensed in the grinding fluid. The series of those methods are the promising way to create well-processed surfaces which can be applied to tribological and biological devices. [ABSTRACT FROM AUTHOR]

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. • Considering the complex tooth geometry, the elastic-plastic model of FPP treating flexspline based on DEM-FEM is established. • The simulation results are in good agreement with the FPP experiments. • The FPP parameters for strengthening precision parts with low hardness such as flexspline are suggested. [ABSTRACT FROM AUTHOR]

Abstract: By introducing design of experiment (DOE), we examined the effect of processing parameters, such as peening pressure, particle supply rate, peening time, and heating time, on the characteristics of modified layers. The surface of structural steel was modified by AIH-FPP with Cr shot particles at 900°C in an argon atmosphere. Results showed that the peening time strongly affected the levels of oxygen concentration at the treated surface; the longer the peening time, the higher the oxygen concentration. Heating time also affected the Cr concentration at the surface; the longer the heating time, the higher the Cr concentration. Corrosion tests were performed using a three-electrode electrochemical cell connected to a computer driven potentiostat. The specimens with Cr diffused layers showed higher corrosion resistance compared to other specimens. This is because of the existence of passive films on treated surfaces. [Copyright &y& Elsevier]

In order to improve the adhesiveness of the DLC coating, Fine Particle Peening (FPP) treatment was employed as pre-treatment of the DLC coating process. FPP treatment was performed using SiC shot particles, and then AA6061-T6 aluminum alloy was DLC-coated. A SiC-rich layer was formed around the surface of the aluminum alloy by the FPP treatment because small chips of shot particles were embedded into the substrate surface. Reciprocating sliding tests were conducted to measure the friction coefficients. While the DLC coated specimen without FPP treatment showed a sudden increase in friction coefficient at the early stage of the wear cycles, the FPP/DLC hybrid treated specimen maintained a low friction coefficient value during the test period. Further investigation revealed that the tribological properties of the substrate after the DLC coating were improved with an increase in the amount of Si at the surface.

• Fine particle peening was used to improve fatigue properties of high strength bolts under transverse loading. • Surface roughness, compressive residual stress and micro-hardness was measured. • A finite element analysis combined with equivalent stress method was performed. In order to avoid the fatigue failure of high strength bolt under cyclic transverse loading, fine particle peening (FPP) treatment was conducted to the bolt using steel beads. The surface roughness, residual stress and surface hardness of the treated bolts were examined. Fatigue tests were performed for bolts with or without FPP treatment under transverse loading. The test results show that FPP treatment effectively improves the fatigue resistance of high strength bolt through reducing the surface roughness, increasing the surface hardness and introducing high compressive residual stress in the surface layer. For the FPP treated bolts, failure location changes from the bolt head fillet to thread root as loading displacement decreases to 0.3 mm. A finite element analysis was performed to analyze the failure behavior before and after FPP treatment. [ABSTRACT FROM AUTHOR]