Roll Surface Research Articles

Effect of laser shock peening on the retention ability of surface roughness in forged Cr5 steel

The roughness retention ability of the work roll surface during the cold rolling process is of great significance, especially in the production of the high-quality rolling section. Laser shock peening (LSP) is an advanced and effective surface treatment technique to improve the fatigue life, wear resistance, and other mechanical characteristics of metal components. Current studies commonly examined the reinforcement effect of single and multiple LSP treatments on Cr5 steel samples through XRD analysis, hardness testing, and residual stress measurements of different parameters. In addition, the abrasion test is widely conducted to determine the wear resistance. Compared to unprocessed samples, LSP could promote grain refinement and thus significantly increase the hardness and residual stress. Furthermore, the slight decrease in surface roughness shows that LSP treatment is an effective approach to slowing down the roughness decline rate and prolonging the roller service life. It is also found that multiple LSP impacts could remarkably improve the surface roughness retention of Cr5 steel, in which the optimal laser power density was around 23 GW/cm2.

Synergistic effects of heat-assisted ultrasonic rolling textures and self-lubricating coatings on the friction and wear properties of AISI 52100 steel

Wear is an important factor in limiting the service life of AISI 52100 steel components. In order to improve the tribological properties of AISI 52100 steel, we investigated the synergy between polyphenylene sulfide-silicon dioxide/polytetrafluoroethylene (PPS-SiO2/PTFE) self-lubricating coatings and surface textures fabricated by heat-assisted ultrasonic surface rolling process (USRP). The influences of different heat-assisted temperatures (20, 80, 140, and 200 ℃) on the surface characteristics of the textures such as morphology, hardness, and residual stress were investigated. The synergistic effects of self-lubricating coatings and textures at different heat-assisted temperatures were investigated by dry friction and wear tests. The results showed that the synergistic effect of the coating with the texture at 200 °C had a performance improvement than the individual effect, but the synergistic effects with textures at other heat-assisted temperatures had a negative influence. The heat-assisted temperature influenced the synergistic effect by affecting the texture shape and strengthening effect, and the influence of texture shape was stronger. The texture with an appropriate shape not only had a strengthening effect to increase the load-bearing capacity of the coating-substrate system, but also stored the coating material to improve the wear resistance.

Improving the fatigue resistance of plasma electrolytic oxidation coated titanium alloy by ultrasonic surface rolling pretreatment

Plasma electrolytic oxidation (PEO) damages fatigue strength of titanium alloy, ultrasonic surface rolling process (USRP) pretreatment is used to mitigate this adverse effect. The microstructure, stress distribution and fatigue performance of Ti6Al4V alloy with different treatment are tested by FESEM, TEM, X-ray stress tester and rotating-bending fatigue tests, and anti-fatigue mechanism of co-strengthened sample is discussed. USRP treatment refines surface grains and introduces a compressive stress field of above 560 μm, which helps to improve the compactness and reduce surface roughness of PEO coating, and significantly increase fatigue resistance of PEO coated samples. Under covering the coating of 20 μm, the fatigue life of co-strengthened sample is about 14 times higher than that of simple PEO sample at 600 MPa, and fatigue crack source also changes from multi-source to single-source and transfers to the subsurface. PEO consumes part of surface nanocrystalline layer and releases some compressive stress for ultrasonic-rolled sample, but the effective compressive stress field with a thickness of 180 μm is still present, and the grains at coating/substrate interface also remain at the nanoscale (∼81 nm), which are the key reasons for USRP to improve fatigue resistance of titanium alloy treated by PEO.

The effect of the track plan on the damage to rails by contact fatigue crambling

An analysis of foreign and domestic experience in improving traffic safety while extending the service life of rails and improving their interaction with the wheels of rolling stock shows that the working conditions of rails are much more difficult in curved sections of the track, especially in the outer thread, due to the intense impact of the ridges of the wheels of rolling stock on the lateral working One of the reasons for the formation of contact fatigue stains on the lateral working surface of the rail head is the presence of tangential stresses that occur in the absence of perpendicular pressure of the wheel on the rail head. In addition, the movement of the wheels on the rails is accompanied by slippage, which appears due to the taper of the wheels and the occurrence of the wheel crest on the rail head. A typical case of the wheel crest running over the rail head is the movement of the crew along curved sections of the track. In this case, the guide axle runs over one of the wheels on the rail head. As a result, there is a transverse slip of the wheel on the rolling surface and friction forces between the wheel and the rail are appropriately oriented to the axes. These processes, enhanced by an increase in dynamic action, cause more intense damage to the rail heads by defects 11 in the curves, while defects mostly appear on the outer rail thread.

Study on the effect of the application of metallic alloys on continuous casting machine segment drive roller surface

Study on the effect of the application of metallic alloys on continuous casting machine segment drive roller surface

Low strain hardening enables improved water droplet erosion performance through deep rolling

The present work investigates the role of deep rolling surface treatment on the water droplet erosion behavior of 17–4 PH stainless steel. Standard heat treatments were first applied to samples of 17–4 PH stainless steel to achieve three states, solution treated and two different aging conditions. The mechanical properties of these conditions were determined using hardness and tensile tests. Then, deep rolling surface treatments were applied to the various conditions of the 17–4 PH. Water droplet erosion tests were subsequently performed at impact velocities of 250 m/s and 300 m/s, and the erosion performance in terms of incubation period and maximum erosion rate before and after the deep rolling treatment is compared. It was found that deep rolled samples exhibited considerably longer incubation periods compared to only heat-treated samples. The improvement in erosion resistance of the 17–4 PH stainless steel is attributed to its lower strain hardening exponent values, which reduces embrittlement that is usually associated with the work hardening due to deep rolling. Hence, it is concluded that low strain hardening exponent is essential to the effectiveness and success of mechanical surface treatments to combat water droplet erosion.

Image segmentation method of rail head defects and area measurement of selected segments

The operation safety of railway transport, which is the most important economic and social factor, is largely determined by the technical condition of the rail track and measures to maintain the quality of its track management system. One of the system elements for ensuring the accident-free operation of the track is the technical diagnosis of rails using a method complex of non-destructive control of rails, such as acoustic (ultrasonic), magnetic, combined, etc., and monitoring of the track using methods of measuring the geometry of the rail track and its disturbances. When the wheel interacts with the rail, especially on high-speed and load-stressed sections, defects and damage inevitably occur in the rails. A rather large share of such defects are on the rolling surface of the rail head. Formed defects develop rapidly, which seriously complicates the safety of train traffic. Therefore, accurate and quick detection of defects on the rolling surface of the rail head is very important. However, it is quite difficult to detect defects on the rolling surface of the rail by the acoustic (ultrasound) method due to the violation of tight contact between the rolling surface of the rail head and the piezoelectric transducer. In this case, it is quite convenient to detect surface defects of the rail head using video control. The article provides a comparative analysis of segmentation methods. There has been presented the method of image segmentation of main rail defects based on general contour preparation and parallel-hierarchical (PH) transformation using their classification. The parallel-hierarchical transformation method allows to increase the segmentation accuracy of individual areas in the original image compared to similar ones. The algorithm of pyramidal generalized-contour preparation and the criterion system allows, by calculating the threshold for each level of the gray scale, to present the study of the image with the corresponding contour preparations at the segmentation level. Modeling of recursive generalized-contour preparation and PH transformation method for image segmentation problem of rail head defects shows that, compared to the segmentation method based on the increase of areas, the accuracy of image segmentation is better. A modified method of calculating the image contour area based on the coding of lines forming the boundaries of the black and white areas of the two-gradation image has been given.

Determination of cutting modes when turning railway wheelsets used in heavy traffic

Increasing the durability of the cutting tool when restoring the profile of the rolling surface of railway wheels by controlling the vibrations of the machine-tool-part system. Vibrations arising during the turning of the rolling surface of wagon wheels under various cutting modes were studied. To do this, a matrix of experimental planning was built using the Box-Wilson method, according to which all factors change in turn (cutting depth, cutting speed, feed). After the experiment, a mathematical model is selected and the numerical values of the coefficients of this equation are estimated. In accordance with the power dependences accepted in the theory of cutting, a mathematical model was constructed for the experiments in the form of a logarithmic polynomial of the first degree series. Mathematical processing of measurement results using fractal dimension was carried out. The fractal dimension was determined by the normalized span method. A correspondence has been established between the durability of the he cutter and the intensity of its vibrations when turning railway wheels. A mathematical dependence of the fractal dimension on the cutting modes is obtained, which makes it possible to adjust the cutting speed or feed during the restoration of the rolling surface of the wheel in the presence of defects. Optimal cutting modes, which allow to achieve a given quality of the rolling surface of the wheel in the shortest possible time, give the highest value of fractal dimension. Defects in railway wheels such as sliders, bumps, and gouges lead to a decrease in fractal dimension. The determination of the fractal dimension in the process of turning wheelsets makes it possible to automatically adjust the cutting modes to ensure a given quality of the rolling surface of the wheel and the required durability of the cutting tool.

Analysis of the influence of brake pad material on the formation of defects on the rolling surface of railway wheels

The results of research and production experience in the field of identifying the causes and mechanisms of defects on the rolling surface of wheels of railway rolling stock are analysed. The article presents different views on the mechanism of influence of brake pad material on the occurrence of wheel surface defects caused by their frictional interaction with pads made of cast iron or composite material in the form of a composite rubber compound. It has been clearly shown that brake pads made of composite rubber compound damage the rolling surface of wheels to a greater extent and more often. This leads to the need to grind wheel sets and reduces their service life. The main cause of defects on the working surface of the wheels is the thermal load on the friction zone between the pad and the wheel during train braking. The temperature in this zone changes periodically and can reach 900 °C, while the self-ignition temperature of the rubber compound used to make the friction element of composite pads is 350-500 °C. The unacceptably high temperature in the friction zone between the composite pad and the wheel surface, which occurs during train braking, is due to the relatively low thermal conductivity of the composite rubber compound compared to the thermal conductivity of cast iron. Equipping the friction element of composite pads with cast iron inserts does not save the situation with regard to the low thermal conductivity of such pads in general and their tendency to damage the rolling surface of the wheels of vehicles. Recommendations have been proposed to improve the technical and economic performance of railway transport by improving the quality of brake pads for vehicles.

Effect of contact stress and slip amplitude on fretting fatigue behaviour of ultrasonic surface nanocrystallized TC11 titanium alloy

In this paper, combined experimental and numerical methods are applied to investigate the effect of different contact stress and slip amplitude on the fretting fatigue (FF) behaviour of TC11 titanium alloy with gradient nanostructure introduced by ultrasonic surface rolling process (USRP). The properties of gradient nanostructure are characterized using scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray residual stress tester, microhardness tester. As evidenced by the FF experimental results, USRP can significantly improve the FF life of TC11 by introducing large compressive residual stress and work hardening layer. The dominant parameters in improving the FF resistance under different loading conditions are investigated. In addition, the simulated results from Abaqus show that contact stress plays a more important role in influencing FF life compared to fretting bridge span, which is attributed to the change in slip amplitude and stress concentration. Fretting fatigue life initially increases and then decreases with contact stress and there is a contact stress threshold that leads to minimum lifetime. This threshold of USRP specimens is greater than that of untreated specimens. The transition of fretting mode along with contact stress is observed and discussed.

Surface integrity, corrosion resistance, and low-temperature impact property of FH36 marine steel subjected to ultrasonic surface rolling process

Surface integrity, corrosion resistance, and low-temperature impact property of FH36 marine steel subjected to ultrasonic surface rolling process

Experimental Investigation of the Effect of Alternative Sandblasting Processes on the Surface Roughness Data of Smooth Rolls

The process of sandblasting is a method applied to remove oil, dirt, rust, and corrosion from metal surfaces, aiming to extend the metal's service life due to the gradual development of rust and corrosion over time. This procedure involves using various abrasive substances, specially manufactured under the name "grit." Sandblasting, similar to sandpaper, not only eliminates visible or micron-sized rust and corrosion on the metal surface but also aims to achieve a specific level of surface roughness. An essential criterion in this process is to texture the surface with appropriate abrasives.
 The sandblasting machine used in this study is designed to achieve the desired average surface roughness level, denoted by the R a value, on the smooth rolls in flour mill rolls and flaking rolls. The machine features a sand recycling system, a filtered vacuum suction line, and employs a blower system to provide a dust-free environment. The majority of the abrasive material sprayed by the nozzle is conveyed to the rear sand tank through vacuuming, allowing dust and abrasive material to accumulate in a closed tank without extensively mixing with the air. 
 
 Consequently, the operator can achieve abrasive material recovery through the blower method without being adversely affected by the sandblasting process. 
 The abrasive particles with a brown aluminium oxide property and a size of 24 mesh aim to create a homogeneous roughness on the surface of smooth rolls using a PLC system. In this study, the rotation of the roll bearings at a constant speed around their axis and the comparison of different surface roughness values with the variable linear velocity h of the nozzle positioned at different angles to this movement are investigated.

Wear performance of GGG60 ductile iron rollers coated with WC-Co by electro spark deposition

Nodular cast irons are used in many industrial applications such as machine frames and body, rollers and engine blocks due to their higher strengths and ductility with good machinability comparable to grey cast irons. In this study, the outer surface of nodular cast irons (GGG-60) was coated with WC/Co using electro spark deposition (ESD). The aim of the study is to improve both the surface quality and wear behaviour with the coatings formed on the surface of the plastic deformation rollers, whose wear resistance decreases over the time due to high stress working conditions. Heat treatment at 950 ºC for 2 h was applied to the GGG60 specimen rollers and half of the rollers were uncoated and the other half was coated with WC-Co electrodes. The wear behaviour of the heat treated and coated surfaces was measured by ball-on-disc wear method using Al2O3 ball bearing with a diameter of 6 mm for a sliding distance of 250 m at a sliding rate of 6.5 m·s-1 under a dry condition, and using a load of 40 N. WC/Co coatings were successfully applied to rollers. In the SEM/EDS images, the presence of W, Fe, C, Co and Al elements in the coated part of the rollers and Fe, C and Al elements in the uncoated region were detected. It was concluded that Coating and heat treatment increased the wear resistance by nearly 5 times and decreased the friction coefficient by 2.13 times.

Tribological Properties and Lubrication Mechanisms of Water-Based Nanolubricants Containing TiO2 Nanoparticles during Micro Rolling of Titanium Foils.

The tribological behavior of traditional oil-in-water (O/W) lubricants (1.0 wt.%) and nano-TiO2 additive lubricants (1.0-9.0 wt.%) during micro rolling of titanium foils were analyzed. In this study, the surface morphologies of titanium foils under various lubrication conditions were assessed, and the corresponding lubrication mechanisms were revealed. The tribological behavior of nano-TiO2 additive lubricants during micro rolling of titanium foils was also explored through a series of characterization methods. The utilization of nano-TiO2 additive lubricants in micro rolling reduces the surface roughness of titanium foils. Moreover, it effectively inhibits the generation of indentations and cracks during rolling processes, enhancing the surface quality of rolled specimens. Additionally, owing to the synergism of rolling, tribo-film, mending and polishing effects of the nanoparticles, both the rolling force and surface roughness were minimized by using lubricants containing 3.0 wt.% TiO2 nanoparticles. Overall, an optimal concentration (3.0 wt.%) of TiO2 nanoparticles in water-based nanolubricants was obtained with enhanced tribological properties and lubrication performance during micro rolling of titanium foils.

Strategy and mechanism to improve the fatigue properties of Ti6Al4V ELI alloy by microstructure modulation combined with surface strengthening process

The hot isostatic pressing (HIP) technique allows obtaining powder metallurgy Ti6Al4V parts with high densities, but its microstructure is not ideal, resulting in a lower fatigue life than expected. In this work, the ideal microstructure was obtained by heat treatment, but this process produces thermally induced porosity (TIP). After heat treatment, the fatigue strength of the bimodal Ti6Al4V alloy reached 680 MPa at 107 cycles, whereas the HIP Ti6Al4V alloy with a fully equiaxed microstructure was lower than 590 MPa. This is because the bimodal Ti6Al4V alloy has better resistance to fatigue crack initiation. This result confirmed that TIPs do not have a significant negative impact on fatigue properties. To further improve the fatigue performance, this study induced gradient nanostructured (GNS) in Ti6Al4V alloy by ultrasonic surface rolling process (USRP), and the fatigue strength of the USRP-treated specimen reached 750 MPa at 107 cycles. Combining microstructure observations and theoretical analysis, the surface hardening mechanism of the USRP-treated Ti6Al4V alloy was quantitatively described. The results showed that the plastic deformation layer is approximately 130 μm, but grain boundary strengthening maintained its effect to a depth of about 200 μm whilst dislocation strengthening maintained its effect to a depth of approximately 350 μm. Under the comprehensive effect of surface hardening and compressive residual stress field, the fatigue crack initiation period of the USRP specimen was significantly extended. This may be the primary reason behind the enhanced fatigue performance obtained through USRP treatment.

Effect of two strengthening processes on the fretting wear mechanism of CoCrMo alloy

To alleviate fretting damage of the artificial joint CoCrMo alloy, the substrate was treated by ultrasonic surface rolling process (USRP) and solid solution treatment (SST) respectively. Meanwhile, the fretting wear behavior and failure mechanism of the treated-samples were quantitatively analyzed via experimental study. Compared with the substrate, the wear rates of USRP and SST samples are reduced by about 8.895 and 13.463 µm3/mJ in slip regime. In addition, the wear resistance of USRP samples is improved due to grain refinement, but the expanded grain boundary channels aggravate the oxidative wear degree (8.13% higher than substrate). The intergranular carbides are dispersed in grains and constructed into stacking faults through SST, hence, the fretting wear resistance of the alloy is greatly improved.

Effect of ultrasonic rolled material layer on the corrosion fatigue resistance of railway axle EA4T alloy steel

Surface treatment has been validated to improve the fatigue crack resistance of engineering components, while the coupling effect of corrosive atmosphere and external loading is relatively less reported with detailed experimental studies. In this study, gradient structure (GS) axle EA4T alloy steel specimens were prefabricated by using the ultrasonic surface rolling process (USRP), and their corrosion fatigue resistances were investigated. First, the optimal USRP parameters were determined via orthogonal tests. After the USRP treatment, the microstructure, surface topography, surface roughness, residual stress, and electrochemical corrosion behavior were measured to characterize the surface under various conditions. The electrochemical tests results indicated that the compressive residual stress (CRS) is an important factor in improving the corrosion resistance of axle steel. Rotating bending fatigue tests in both air atmosphere and corrosion liquid showed that the fatigue and corrosion fatigue performances could be significantly improved with the strengthened layer obtained via the USRP. Factor separation analyses substantiated that the remarkable enhancement of fatigue and corrosion fatigue strengths can be mainly attributed to the CRS introduced by the surface strengthening treatment. Simultaneously, the GS layer and hardened layer exhibited a synergistic effect.

Определение оптимальных режимов резания при обточке железнодорожных колес

Purpose: Increasing the durability of the cutting tool when reprofiling the tread of the railway wheels by controlling the vibrations of the “machine-tool-workpiece” system. Methods: Vibrations arising in the process of turning the tread of car wheels under various cutting modes have been investigated. To do this, a matrix of experiment planning has been built using the Box-Wilson method, according to which all factors change in turn (cutting depth, cutting speed, feed). Based on the results of each series of the experiment, a mathematical model is selected and the numerical values of the coefficients of this equation are estimated. In accordance with the power dependences accepted in the theory of cutting, a mathematical model in the form of a logarithmic polynomial of a series of the first degree has been postulated for the experiments carried out. Mathematical processing of measurement results has been carried out using fractal dimension. The fractal dimension has been determined by the standardized range method. Results: A correspondence has been established between the durability of the cutting tool and the intensity of its vibrations when turning railway wheels. The mathematical dependence of the fractal dimension on the cutting modes is obtained, which allows to adjust the cutting speed or feed during the reprofiling the tread of the wheel when there are defects. Optimal cutting modes, which allow to achieve a given quality of the rolling surface of the wheel in the shortest time, give the highest value of the fractal dimension. The presence of such defects of the wheel tread, such as slid flat, buildups, shellings, leads to a decrease in the fractal dimension. Practical significance: The determination of the fractal dimension in the process of turning wheel pairs makes it possible to automatically adjust the cutting modes to ensure a given quality of the wheel tread and the required durability of the cutting tool.

Root cause analysis of indentation mark defect on Zn coated steel sheet in continuous galvanizing line

The coated steel industry is growing as demand of corrosion resistant steels are ever increasing in automotive, construction, appliances, and general engineering segments. The surface requirement of the coated steel is becoming more stringent that demands coated surfaces within specified roughness, waviness, reflectance and free from surface defects. The continuous galvanising line number 2 of Tata Steel Limited, Jamshedpur suffers from a chronic surface defect that appears like a scratch mark in the coated steel. The present study deals with the root cause analysis of the defect focussing on the rolls within annealing furnace in CGL#2, Jamshedpur. The roll profile, roll and strip slippage, roll surface compositions (using profilometer, XRF) are studied in detail. Similarly, the steel strip collected from inside the furnace was also studied for the defect orientation, surface composition (using SEM & EDS), trapped particles etc. The mathematical calculation of slippage along with the characterization evidence confirm the formation of defect through a complex mechanism of particle formation due to non-uniform roll profile, followed by particle coagulation and finally formation of the defect on the strip under tension by those particles. Possible operational strategies to eliminate the defect is also outlined.

Study on microstructure of 42CrMo steel by ultrasonic surface rolling process

To explore the microstructure formation mechanism of 42CrMo steel under the strengthening of ultrasonic surface rolling process (USRP), the combination of theoretical analysis and experiment was used to conduct in-depth research on USRP. Firstly, according to contact mechanics and Hertz contact theory, the calculation model of contact stress distribution and elastoplastic strain between the rolling ball and the part during USRP is obtained. Secondly, the USRP processing test was carried out by single-factor experimental design method, and the microstructure of 42CrMo steel after USRP was analyzed by LEXT OLS5100 3D laser surface topography instrument and VEGA3 tungsten filament scanning electron microscopy, which found that with an increase in static pressure, residual stress and plastic strain gradually increase, the hardness firstly increases and then decreases, while surface roughness exhibits an initial decrease followed by an increase. The results show that USRP produces violent plastic deformation inside the material under the superposition of high-frequency impact and static pressure, at the same time, it refines the grains, so as to improve the surface performance of the part and improve its fatigue resistance.