Shot Peened Surface Research Articles

Hot salt corrosion behavior of Ti–6Al–4V alloy treated with different surface deformation strengthening processes

In this study, the effects of shot peening (SP) and ultrasonic surface rolling process (USRP) on the high-temperature oxidation and hot salt corrosion (HSC) behavior of the Ti–6Al–4V alloy were systematically investigated. The results showed that the high-temperature oxidation resistance of this titanium alloy can be significantly improved by the above two treatments. However, the hot salt corrosion resistance of Ti–6Al–4V alloy cannot be improved by SP due to surface roughness increasement, the surface defects and the complete relaxation of compressive residual stress (CRS) at high temperature. On the contrary, the hot salt corrosion resistance of USRP treated specimen was remarkably improved because USRP treatment significantly reduced the surface roughness and introduced deep CRS field with good thermal stability. In addition, the refined surface microstructure promoted the formation of a protective oxide film, which was also beneficial for inhibiting hot salt corrosion.

Influence of Conventional Shot Peening Treatment on the Service Life Improvement of Bridge Steel Piles Subjected to Sea Wave Impact

The first goal of the current study is to estimate the fatigue life of the middle steel piles of an integrated bridge installed in water and subject to the impact of sea waves. In the following, the authors have tried to improve the service life of this critical part of the bridge, which is also the main purpose of the study. To this end, conventional shot peening, as one of the most well-known surface treatments, was used. Axial fatigue tests were performed on samples fabricated from IPE-220 steel piles in two states without and with shot peening surface treatment. Next, the modified S-N curve was entered into the finite element software to define the effect of shot peening treatment. Different analysis, including thermal, thermal-structural coupled, and transient dynamic, were performed and various outputs were extracted for the entire structure. In all these analyses, changes in air temperature have been neglected. The most important achievement of this research is the discovery that motionless water cannot cause serious damage to steel piles. Moreover, application of conventional shot peening can increase the fatigue life of steel piles, or in other words the service life of the bridge, subjected to the impact of sea waves by about 22%.

Effect of ultrasonic surface shot peening on the microstructure and properties of Cu-8Cr alloy

Surface nanocrystalline layers were prepared on Cu-8Cr alloy using ultrasonic shot peening (USSP) technique by controlling the pellet size and shot peening time. The tissue morphology, microstructure, surface hardness, surface strength and corrosion resistance of the generated surface nanolayers were systematically characterized using x-ray diffractometer (XRD), scanning electron microscope (SEM), and the corresponding test methods. The results showed that the USSP treatment did not change the surface phase of Cu-8Cr alloy, but only refined the surface grains into nanocrystals. The pellet size and shot peening time had a large effect on the surface properties of Cu-8Cr alloy. The best overall surface properties were obtained with a shot size of 2 mm and a shot time of 30 min The average grain size of the nano-layer is about 66 nm, the surface hardness is increased to 126.69 HV0.05, the tensile strength reached 417 MPa, and the corrosion resistance of the alloy is significantly enhanced. The USSP treatment provides a new method for the preparation of CuCr alloys with excellent surface properties.

Impact of Surface Roughness on the Impingement of Urea–Water Solution Droplets

The understanding of impingement processes is crucial for optimizing automotive selective catalytic reduction (SCR) systems. An accurate description of this behavior helps design exhaust systems and increases the validity of modeling approaches. A component test bench was set up, featuring a droplet chain generator for producing droplet sizes typically found in the urea–water solution sprays of SCR systems. A heatable impingement plate with an interchangeable surface enabled investigation of the influence of surface roughness. Data were acquired using a high-speed camera and image postprocessing. The droplet–wall interaction could be described using different regimes. An approach to characterizing impingement behavior based on weighted-regime superposition enabled gradual transitions between regimes, instead of step-like changes. It was observed that the surface roughness increased the droplet–solid contact area and generated thermal-induced secondary droplets at lower temperatures. A region of enhanced mechanical disintegration of the droplet was found, caused by peaks of the surface shearing off parts of the droplet. The probability of a droplet rebounding from the wall was reduced on a rough surface, due to the interference of the surface spikes with the droplet’s spreading and contracting motion. Additionally, the influence of surface topography was investigated using a shot-peened surface. Caused by this surface’s reduced root mean square slope, the aforementioned enhancement of mechanical disintegration was not observed.

A tribological study of shot peening process on stainless steel

The goal of this study is to figure out how to use the microstructure, friction, and wear parameters of a shot-peened stainless steel 316L surface to study tribology. Tribology is the study of how moving parts rub against each other, wear out, and are oiled. Tribology looks at all of these things from a mechanical point of view. Improves the surface and frictional properties of materials, making them less likely to break and giving them a longer life. Because of this, it can make materials smoother and less likely to stick together. This is possible because it can improve the properties of many different materials. Shot peening is a type of cold working technique that can change the mechanical properties of materials like metals and composites. Because shot peening is a part of the peening process, this improvement is possible. Also, as a direct result of the result, a layer of compressive residual stress will form in the material. Before the process can be finished, the surface of the SS316L needs to be honed with abrasive sheets and a double-disc polishing machine. Next, a Vickers hardness test is done on the material, and then a pin-on-disc tribometer is used to study how the material wears. At the end of the process, a trinocular microscope is used to look at the structure of the substance being studied on a small scale.

An optimization method of rough surface adapted small rectangular LD laser source based on combination of Powell prism and cylindrical lenses

A combination optimization method was proposed to design a small-size rectangular laser spot and decrease the measurement error caused by the uneven intensity distribution of LD laser source. First, the intensity distribution of LD was analyzed and the combination lens structure of Powell prism and cylindrical lenses was proposed. The equations were established to calculate the profile parameters of lenses. And an illuminance loss model δΔED±R was built to determine the values of laser spot size, working reference and range. Secondly, the specific design process of our method was given, the 3D model was established and simulated in ZEMAX to further improve the imaging uniformity. Finally, the collimation, uniformity and location deviation of the spot were discussed. The average uniformity was 95.626%, and the difference of location deviation on shot peened surfaces was 0.004 μm in x direction and 0.121 μm in y direction when compared with the white ceramic surface.

A combined computer vision and image processing method for surface coverage measurement of shot peen forming

Coverage is an essential monitored parameter during the shot peen forming process. However, the conventional manual visual inspection methods suffer from low efficiency and poor accuracy. In this paper, a combined computer vision and image processing method is applied to realize the automatic measurement of shot peening surface coverage, and the critical issues involved, such as shot peening image pre-processing, indentation light spots recognition, shot-peened area segmentation, etc., are systematically investigated. The results indicate that the influence of machining streaks on the subsequent image processing is effectively reduced by adjusting the illumination conditions and adopting the median filtering algorithm. The number and location of indentations in the shot peening surface image are easily obtained by treating the central light spot as an identifier for the indentation. The features of the shot-peened area can be extracted effectively by segmenting the image reconstructed based on the light spots. The effectiveness of the coverage measurement method is verified by shot peen forming experiments, and the accuracy of the measurement results can be over 97 %. The influence of coverage on shot peening deformation is further examined using the results of algorithm processing, which is reflected in that the radius of curvature decreases with the coverage.

Columnar and nanocrystalline combined microstructure of the nitrided layer by active screen plasma nitriding on surface-nanocrystalline titanium alloy

The microstructure and formation mechanism of the nitrided layer by active screen plasma nitriding on surface-nanocrystalline TA17 titanium alloy were studied by TEM. The nitrided layer of both the original and shot-peened TA17 samples was composed of two sublayers: the outer TiN layer formed by deposition of titanium nitride particles and the inner Ti2N layer formed by nitrogen diffusion into the titanium substrate. The Ti2N layer was found to be an Al-depleted zone, which was a proof for its formation mode of nitrogen diffusion. Compared with the TiN layer of the original sample filled with columnar grains, the TiN layer of the shot-peened sample was composed of mainly equiaxed nanograins and a small amount of columnar grains. The large number of high-energy grain boundaries on the shot-peened surface provided numerous nucleation sites, resulting in the formation of equiaxed nanocrystalline TiN. During long term nitriding, most of the nano-scale TiN grains were maintained due to their high thermal stability, while the nano grains of the shot-peened substrate surface grew into microscale due to their low thermal stability. With the thickening of the nitrided layer, some equiaxed TiN nanograins grew into columns perpendicular to the substrate surface due to competitive growth.

Effect of coating on the oxidation behavior of turbine rotor material in supercritical water

AbstractHigh‐temperature oxidation behavior of IBN‐1 alloy, Ni–Cr thermally sprayed coating, Ni–Cr thermally sprayed coating with surface shot peening and grinding treatment in supercritical water have been investigated at 650°C under 25 MPa. The oxidation kinetics of IBN‐1 steel follows the parabolic law. Compared with substrate metals, the oxidation resistance of IBN‐1 steel with the three kinds of Ni–Cr coating treatment has been greatly improved due to the formation of Cr‐rich oxide and the oxidation kinetics deviated from the parabolic behavior seriously. The deviation may be attributed to differences in the oxide phase with an increase in oxidation time. Furthermore, the difference in oxidation rate among different Ni–Cr coating surface treatment processes can be observed. The related mechanism has been discussed.

Effect of Peening Parameters on the Ultrasonic Shot-Peened Surfaces of Electro-co-deposited Ni/Ni-TiO2 Coatings

Effect of Peening Parameters on the Ultrasonic Shot-Peened Surfaces of Electro-co-deposited Ni/Ni-TiO2 Coatings

Surface and Tribological Properties of Powder Metallurgical Cp-Ti Titanium Alloy Modified by Shot Peening

The present study reveals for the first time the dry sliding wear behavior of a powder metallurgical pure titanium alloy (Cp-Ti) modified by shot peening. Cp-Ti samples were manufactured via powder metallurgy, and then their surface and subsurface features were modified using a custom-made, fully automated shot-peening system. The texture isotropy rate and the highest orientation angle of the shot-peened samples were 71.5% and 36°, respectively. The Abbott curves of the shot-peened surfaces revealed that the most common areal roughness value was 5.177 μm, with a frequency of 8.1%. Shot-peened surfaces exhibited an ~20% lower wear rate than unpeened surfaces under dry sliding wear, whereas the coefficient of friction was the same for both surfaces. Micro-ploughing, micro-cutting, oxidation, and three-body abrasion wear mechanisms were observed on the shot-peened and unpeened surfaces. High resolution 3D surface topographies of worn unpeened and shot-peened surfaces revealed micro-scratches and inhomogeneities along wear tracks, which are indicative of three-body abrasion mechanisms during contact. In addition, vertical and horizontal microcracks were visible just beneath the wear track, suggesting a clear indication of plastic deformation during contact. The cross-sectional hardness maps of shot-peened samples revealed the formation of a work-hardened surface layer with shot peening, which improved the wear resistance. These findings support that shot peening can be a useful tool to modify the surface and tribological properties of powder metallurgical Cp-Ti alloys.

РАСЧЁТНОЕ ПРОГНОЗИРОВАНИЕ ТЕХНОЛОГИЧЕСКИХ ОСТАТОЧНЫХ ДЕФОРМАЦИЙ ПРИ ИЗГОТОВЛЕНИИ ДЕТАЛЕЙ, ПОДВЕРГАЕМЫХ УПРОЧНЕНИЮ ПОВЕРХНОСТНЫМ ПЛАСТИЧЕСКИМ ДЕФОРМИРОВАНИЕМ

Ensuring the geometric accuracy of critical parts is an actual problem for aviation industry enterprises. The blades of gas turbine engines are particularly critical and technologically complex parts. In most cases, the interlocks of the blades, as well as the blade, are subjected to surface shot peening. Residual stresses are the first cause of the appearance of technological residual deformations. It is the residual deformations caused by the action of residual stresses that in most cases are the cause of critical defects of parts. Thus, the development of scientifically based approaches to modeling residual stresses and calculating technological residual deformations is an actual task. The paper presents an approach that allows at the stage of machining to take into account the deformations that can be obtained at the final stages of manufacturing parts after shot peening strengthening. The approach is based on preliminary computational prediction of technological residual deformations from the action of residual stresses based on analytical and finite element methods. The implementation of the approach is shown on the example of a compressor blade of a gas turbine engine, subjected to hardening by shot peening over the entire surface of the part.

Effect of ultrasonic shot peening surface alloying on recrystallisation of a single crystal superalloy

Shot peening can greatly enhance the fatigue resistance of single crystal (SX) superalloy, but plastic deformation facilitates the formation of recrystallisation, which will damage the mechanical properties of SX components. In this study, we provide a novel strategy for the surface strengthening without losing or relatively maintaining the integrity of SX by ultrasonic shot peening (USP) surface alloying. An aluminum layer with 10 μm thickness is fabricated on SX substrate compound with surface strengthening treatment. After annealing at 1250 °C, surface recrystallisation is completely inhibited and cellular recrystallisation is significantly reduced in sample processed by USP surface alloying as compared to the sample only subjected to USP. The inhibition effect is attributed to the outstanding oxidation resistance and supplement of Al to the interior by alloying layer, which could enhance the stability of cubic γʹ.

Effect of surface shot peening on the microstructure and mechanical properties of fuel cladding 1515-Ti austenitic steel

Lead-bismuth fast reactor is considered to be the most promising solution to meet the enormous energy demand in the future. The 15-15Ti austenitic stainless steel with outstanding corrosion and irradiation resistance has been proposed as main cladding candidate material for lead-bismuth fast reactor. However, the mechanical properties of 15-15Ti are weakly influenced by LBE. Shot peening as one of surface strengthening technique can efficiently improve metal mechanical properties. In this paper, shot peening (SP) treatment was applied on 15-15Ti. The microstructures and compositions were investigated using Optical Microscope, Scanning Electron Microscope and X-Ray Diffraction. It concludes that the material hardness is improved, and the residual stress induced by SP did not cause martensitic phase transformation on the sample surface. The presence of slip bands and other obstacles in the reinforcement layer improved the yielding and tensibility of the material.

Elastic Contact Analysis of Shot-Peened Rough Surfaces

Shot peening can effectively improve the mechanical performance of metal components, and thus has been widely employed in the engineering field. During the processing, the surface roughness of treated components will be completely changed, which could strongly affect their tribological behavior. However, few of the existing contact models are directed toward the rough surfaces generated by shot peening. In this study, the normal contact response between a shot-peened surface and a rigid plane is investigated based on the finite element method and the recently developed incremental contact model. The elastic contacts of the rough surfaces experimentally measured on three different shot-peened specimens are considered. Contrary to the conventional rough contact models, it is found that the dependence of the external load on the real contact area for the shot-peened surfaces is not at all linear, even for light loads. The slope of the area–load curve significantly varies at two transition points, which are intrinsically linked to the special structure of shot-peened surfaces.

An Investigation on Laser shot peened surfaces

The present work is focused on the influence of zinc trivalent plating on laser shot peened AISI 304 stainless steel samples to improve the corrosion resistance of the steel surface. AISI 304 steel samples were heat treated by annealing and polished to perform Laser Shot Peening (LSP) process using Nd-YAG laser functioning at a pulse interval of 10ns with different energies of 200 mJ, 300 mJ and 400 mJ on each sample. The highest magnitude of compressive residual stresses is induced using the pulse density of 2500 pulses/cm2. The laser treated sample was characterized by surface hardness using Vickers micro hardness test and surface morphology using an optical microscope and SEM analysis. The surface hardness of the sample is increased by increasing laser energy. The prepared zinc trivalent is plated using electro deposition on the laser treated surface by maintaining current between 1.5 to 4 amps/Dm2, and temperature between 20 to 40 deg C. MAHR’s roughness tests were performed to find the surface roughness of the sample. The surface roughness has drastically increased on zinc coated samples compared to samples without coating. The Vickers micro hardness test conducted on zinc trivalent plated sample revealed the increase in hardness value of 200mJ by 24% compared with 200mJ sample without coating. SEM and EDAX were carried out to know the changes occurred in the chemical composition of the samples before and after coating.

A new method of layered superposition reconstruction modeling on grinding-shot peening surfaces

Shot peening for semi-finished or finished parts is a high-performance precision manufacturing process, and the final micro-surface morphology has layered superposition features, that is, the original surface features and shot peening features coexist on the part surface. The existing layered superposition theory is based on the idea that the surface is superimposed under different baselines, but it cannot characterize the two-process surface where the characteristic baseline cannot be separated after shot peening. To solve this problem, a new layered surface superposition modeling method is proposed in this paper with the grinding-shot peening surface as the research object. In this method, the main texture features of the grinding surface are extracted by B-spline surface fitting, and the spatial distribution of craters in the shot peening surface is adjusted by this texture feature. The initial profile of the grinding-shot peening surface is constructed according to the Pawlus superposition theory, and its height parameters are adjusted by the time-frequency iteration method. In this paper, the modeling method is verified by the measured grinding-shot peening surfaces with a coverage of 100% and 200%. The results show that this method can not only ensure the uniformity of crater texture on the reconstructed surface, but also ensure that the maximum error of spatial parameters is less than 2%. Moreover, the symmetrical autocorrelation functions of the reconstructed surface are consistent with the characteristics of the measured surface.

The effects of laser peening treatment on the very high cycle fatigue properties for AA2024-T351 alloy using a crystal plasticity framework

The effects of laser shot peening (LSP) on very high cycle fatigue (VHCF) properties of AA2024-T351 alloy were investigated using the combination of experiment and modified crystal plasticity finite element (CPFE) method. The experimental observation found a contradictable result that the fatigue life decreased after laser peening with relatively high pulse energy in this work. The fatigue fracture observation shows that there are obvious facets and refined grains on the shot peening surface, which are not uniform and their aspect ratio is obviously larger than that of the matrix material. In particular, the fracture surface of the sample treated with 20 J pulse energy shows a highly distorted zig-zag crack propagation path. In order to further understand the ultra-high cycle fatigue failure mechanism of aluminum alloy treated with laser shot peening, a modified crystal plasticity (CP) model was applied to find a possible explanation for the contradictable experimental results. In this model, the critical resolved shear stress (CRSS) evolution of the deformation systems in the CP model was variable due to the refined average grain size after different laser peening conditions using the Hall-Petch type relationship. Additionally, the effects of grain morphology characterized by aspect ratio were considered after LSP of AA2024-T351. The fatigue indicator parameters (FIPs) were calculated based on the modified CPFE model under cyclic low stress amplitudes to estimate the fatigue driving force for fatigue crack initiation and microstructural small crack propagation. It is found that the LSP treatment has a beneficial effect on the fatigue properties only considering the refined influence of grain size. However, LSP has a detrimental effect on VHCF properties when considering the combined influences of grain refinement and the changing of grain aspect ratio due to the laser peening surface treatment with relative high pulse energy in this work.

Influence of surface treatment on the metal dusting behavior of alloy 699 XA

AbstractMetal dusting attack is a serious problem in processing industries using carbonaceous gases and high temperatures. Ni‐based alloy 699 XA was recently developed as an alloy for these types of environments with high resistance against metal dusting. In this study, different surface treatments of this chromium‐ and aluminum‐rich alloy are shown to have an important influence on the metal dusting onset behavior. It was found that surface treatments that are traditionally considered to be helpful for fatigue performance, for example, shot peening, and pickling were detrimental to the metal dusting performance of alloy 699 XA. Additionally, the shot peening surface treatment promoted Fe surface contamination, resulting in a negative impact on the metal dusting pitting resistance of the alloy. Deformation accompanied by apparent BCC α‐Cr precipitation in the bulk microstructure, but a comparison with cold‐rolled materials shows that the surface treatment dominates the metal dusting resistance.

Mechanical characterisation of water-jet shot peened H13 tool steel surface

A wear-resistant surface is achievable via the surface treatment of various sources such as laser, water-jet, ion beam, and plasma. This paper investigates the parameters of water-jet shot-peened H13 tool steel for minimum surface roughness and maximum hardness properties. Water jet processing parameters are significant in determining the surface roughness as well as hardness properties. Water-jet shot-peened (WJSP) was used in this experiment to improve the surface properties of H13 tool steel. The parameters are pressure and feed rate of 172 MPa to 310 MPa and 2600 mm/min to 10000 mm/min. The shot-peened samples were characterised for surface topography, surface roughness, and hardness properties. A laser confocal microscope was used to determine the dimension of the modified surface from shot peening and average surface roughness. Hardness properties were measured using the Vickers scale. From topography analysis, the surface roughness reading on the shot-peened surface was measured as much as 6.88 µm to 14.06 µm. Minimum surface roughness measured was 6.88 µm on sample processed at pressure and feed rate 172 MPa and 2600 mm/min. The hardness properties of the shot-peened subsurface were between 196 HV and 227 HV. The resulted hardness properties were due to plastic deformation from abrasive particle bombardment during shot peening. The findings are important to designing enhanced surface properties for mould and die applications.