Rail Head Research Articles

Application of Sensors for Incorrect Behavior Identification in a Transport System.

This article focuses on cranes that are moving on a fixed crane track. There are specific problems and malfunctions arising during the operation of these cranes caused mainly by the crane skewing phenomenon. Crane skewing induces undesirable additional forces as a result of force contact between the crane wheel flange and the head of the crane track rail. This negative phenomenon induces additional stress in the crane construction as well as wear of the crane components and, finally, a global reduction of the crane operational durability and reliability. There is described in this article a methodology and data processing for the experimental measurement targeted on the crane skewing, namely in the case of a bridge crane installed in a laboratory. The crane skewing phenomenon was experimentally induced by an intentional disruption of speed synchronization of the crane travel drives. The intensity of the crane skewing was measured by means of the strain gauge sensors. A suitable application of the measuring sensors, together with the utilization of the drive control algorithm, enables efficiency to eliminate crane skewing and also prevent its occurrence.

R260 Rayının Mantar, Gövde ve Taban Kısımlarının Tribolojik Özelliklerinin Araştırılması

It is important to know tribological properties of rail and wheel for predicting the service life of both components. In railway, the tribological system is open and the harsh working condition can be seen as the contact stress between rail and wheel is extremely high. The behaviour of the tribological system varies depending on the chosen rail-wheel materials and also third body (water, humidity, lubricant, debris and combination of these elements). The coefficient of friction and wear resistance are strongly dominated by chosen material and its properties. Up to now, a number of researchers focused only on the tribological properties of the head of rail material. Recent experimental study has devoted to investigate the tribological properties of head, web and foot sections of R260 rail, as the mechanical properties of rail changes from the head to the foot of rail. Different sections of R260 rail have been evaluated in terms of microstructural, hardness, tribological and wear resistance properties. According to obtained results of the ball-on-disc wear tests, the highest wear resistance belongs the head of R260 rail as expected. The coefficients of friction of the web, head and foot of R260 have been found as 0.39, 0.35 and 0.38, respectively.

Novel Characterizations of Effective SIFs and Fatigue Crack Propagation Rate of Welded Rail Steel Using DIC

The fatigue crack growth-rate test of rail head, waist, and bottom material for U71Mn welded rail was carried out. Digital image correlation (DIC) was used to capture the full-field displacement. The crack-tip position was accurately obtained based on the full-field displacement data, and an accurate crack-tip opening displacement (CTOD) measurement point was found. The CTOD values of the welded rail head under overloaded and unloaded condition were extracted, and the area size of elastic CTOD and plastic CTOD was obtained. According to COD data under different experimental conditions, the corresponding crack opening force was extracted, the crack opening function introduced based on the Elber model, and a calculation method of effective stress-intensity factors (SIFs) considering the plasticity-induced crack closure proposed. The results in this paper provide some references for accurately assessing the fatigue life of welded rail.

FORECASTING THE WORK RESOURCE OF THE RAILS IN DIFFERENT CONDITIONS OF OPERATION OF THE RAILWAY TRACK

In different operating conditions of the railway track, the service life of the rails is different. This indicates that there are external factors that have a significant impact on the process of rail wear. In the work, the analysis of influential factors was carried out and their degree of influence was determined in comparison with each other and in the statistical population.
 To study this problem, the most difficult section of the Slavsko-Lavochne-Beskid-Volovets track on the regional branch of Lviv Railway was chosen. The collection and processing of statistical data was carried out, measurements of the rail track and measurements of rail wear were carried out.
 The process of lateral wear of the rail depends on various factors, among which it is possible to single out those that are the same for the entire curve, and those that are different for different intersections of the curve. For the entire curve, the tonnage passed, the radius, the set speed, the rise of the outer rail, the longitudinal slope, the type of rails and the binding are the same. These parameters can be called global for the curve, and the wear that depends on them is global. Along the curve, there are local irregularities, that is, deviations in the plan, profile, pattern and inclination of the rail in the middle of the track. These parameters can be called local for the curve, and the wear that depends on them is local. Local wear is additional. The total side wear can be manifested to a greater or lesser extent depending on external conditions: lubrication, sanding of rails, excessive impact of wheels, which is taken into account by the coefficient of external conditions.
 The results of track measurements show that when a horizontal unevenness appears on a curved section, the bending radius increases, and in such places, there is an increase in lateral wear. When the width of the track in the curves exceeds the established norms, there is also an increase in the amount of wear. Over-inflating causes the wheelset to slide to the inner rail. At the same time, the larger rolling circle is not on the outer wheel, but on the inner one. The vertical force transmitted from the wheel to the rail is also greater along the inner thread. This leads to slipping of the wheel on the outer thread, which increases the lateral wear of the rail. As the measurements showed, when the slope of the rail increases from 1:20 to 1:10, the amount of lateral wear increases. The use of lubricators that lubricate the side surface of the rail head can increase its service life by 3 times. An increase in the surface roughness of the rail by 20 μm leads to a decrease in wear resistance by 20-25%. Based on the received empirical data, a mathematical model of lateral wear of the rail head based on 16 parameters was created.
 Based on the norms of permissible wear of the rails and the created mathematical model, the service life of the rails is determined in the work depending on the curvature of the track. Forecasting the resource of rails allows to implement resource-saving in railway transport.

Numerical Study of Rayleigh Wave Interaction with Rolling Contact Fatigue Type of Defects

ABSTRACT Rolling Contact Fatigue or Damage (RCF/RCD) presents significant maintenance challenges to railroads across the globe. Quantifying RCF/RCD crack depths and density in rails is important for all railroads to manage their grinding programs effectively and efficiently and being able to conduct ultrasonic testing (UT) of rails for reliable detection of internal fatigue damage. This work focuses on the modeling of Rayleigh waves UT approach to detect and characterize RCF type of defects which can form as: vertical, oblique or branched shaped surface breaking defects in the rail head. Specifically, the transmission coefficient (Tc) of Rayleigh waves was studied using finite element analysis (FEA). The effect of crack tip geometry on Tc values is discussed. The results suggest that for oblique, and branch cracks, characterization based purely on the Tc can be challenging due to symmetric sinusoidal fluctuations in the Tc. A real crack using a micrograph image was also modeled to validate the Tc results for oblique and branched cracks. This points to the need for additional parameters to be identified for efficient and reliable characterization of RCF/RCD type of defects in rails.

Calculation-empirical estimation of the vertical dynamic coefficient in the event of additional oscillations of the car

According to the results of derailment investigations, the ensuring of train traffic safety was found to be a paramount and urgent task. The growth of freight density and speed of movement on the railway network leads to a significant increase in the number of damaged wheels and rails and, as a result, to an increase in the level of force interaction during load transfer, which provokes the likelihood of a wagon derailment. The operation safety level of rolling stock on railways is determined mainly by the presence of a car derailment stability margin, which depends on the vertical dynamics and the coefficient kdv, which changes throughout the entire time of movement and, accordingly, on the technical condition of the car and the track as a whole. The vertical addition to each element of this “wheel-rail” system depends on many factors, therefore, the level of operational safety of the car, as a mechanical system, is determined mainly by its sprung and non-sprung car parts. The calculation schemes used to study the stability of unperturbed motion are non-linear systems. Non-linearities occur due to the gaps in axle boxes, side bearings and similar connections, non-linearity of the interaction forces of wheels with rails and, at present, also in some types of spring suspension. When moving in a curve, the cart is known to perform a complex movement. The rotation and transverse displacement of the bogie is prevented by frictional forces between the wheels and the rails. The bogie is affected by a part of the centrifugal force, unbalanced by the elevation of the outer rail and depending on the speed of movement, as well as by the guiding force from the side of the outer rail. It is known the process of a car movement results in the appearance of horizontal transverse (relative to the direction of movement) forces, which are determined by the level of interaction between the wheel flanges and the rails. The nature of the perturbed movement of the car leads to the appearance of horizontal transverse with respect to the axis of the path of movement. At relatively low speed, the forces that arise after wearing out of the gaps in the track and when the wheel flanges rest against the rail heads, at a certain level of irregularities, are not dangerous for the wheel-rail system. But with an increase in the speed of the car, these forces increase so that there is a threat to traffic safety as the likelihood of derailment increases.

Evaluation of Rail Overturning under the Influence of Lateral Forces by Mathematical Modeling

The article discusses the change in the rail canting of the railway track on the intermediate fastenings of the ZHBR-PSHR under the influence of the load from the rolling stock at different tightening values of the fasteners. To evaluate the change in the angle of inclination of the rail, a model of the superstructure of the railway track was developed in a finite element environment with full compliance with the geometric and physical characteristics. Based on this model, the calculation of the change in the rail canting at different degrees of screw tightening was made. Based on the results of the calculation, conclusions were drawn about the change in the rail canting and the stress-strain state of the rail sole. Changing the rail canting can lead to a change in the nature of contact in the "wheel-rail" system with a significant increase in equivalent stresses. The obtained values of the rail canting change were used to calculate the contact stresses in the rail head. As a result of the change in the rail canting, the contact patch shifted, as well as a sharp increase in the equivalent stresses by 65-67%, depending on the vertical force. An increase in contact stresses adversely affects the service life of the rail and can lead to the formation of defects, which adversely affects traffic safety.

Methodology for the formation of rail repair profiles by grinding

The formation of a rail transverse profile to reduce contact loading and wear from railway rolling stock wheels is one of the main tasks of rail grinding. At present, when designing a rail grinding technology, a future rail profile contour is selected from a set of repair profiles available in a database. Frequently, the profile selected from the database is less than optimal, as it does not provide the required interaction in the wheel-rail system for a particular track section, and its formation requires excessive metal removal, which reduces the rail's lifespan. The paper proposes a new methodology for designing rail repair profiles based on a fundamentally new approach, consisting in designing rail geometric parameters at the stage of preparing the technological process of its grinding. This approach to the rail grinding technology design allows specifying a geometric profile for the certain railway track operating conditions and the worn rail condition, thus bringing metal removal from a rail head to required minimum and, as a result, increasing the service life of rails and the performance of a rail grinding train. To assess the efficiency and applicability of the proposed method for different railway track operating conditions, a comparative modelling of the existing approach in selecting a rail repair profile with the proposed approach to its design was carried out. The proposed method showed the best result in all cases.

Modelling the acoustic signature and noise propagation of high speed railway vehicle

The proportion of high speed railway vehicles in the rolling stock of national carriers providing public transport services is constantly increasing. Currently, Alstom vehicles run at the highest speed on railway lines in Poland. The paper attempts to identify the acoustic signature of high speed railway vehicles. There are many works and studies aimed at identifying or defining the acoustic signature of high speed railway vehicles. However, the authors of these works carried out their research in a rather narrow scope, i.e. the measurement cross-section had only 1 or 2 measure-ment points with one microphone at each point. As part of the conducted experimental research, the location of testing grounds was determined, the measurement apparatus was selected and the methodology for carrying out measurements including the assessment of noise emission on curve and straight line were specified for electric multiple units. The object of the tests were railway vehicles of Alstom company, type ETR610, series ED250, the so-called Pendolino, moving on a selected measuring route without stops at a speed of 200 km/h. Measurements were carried out on the railway line no. 4 Grodzisk Mazowiecki – Zawiercie, section Grodzisk Mazowiecki - Idzikowice at kilometre 18+600 (curve) and 21+300 (straight section). When measuring the acoustic signals with a microphone array (4x2), 8 meas-urement microphones operating in the audible range were used. The microphones were placed at a distance of 5 m, 10 m, 20 m and 40 m from the track centre, at a height of 4 m (from the rail head) and at the rail head (approx. 0.8 m from the ground surface). In addition, an acoustic camera with 112 directional microphones was used to locate the main noise sources, which was located at a distance of approximately 20 m from the track centreline. The identification of the main noise sources for high speed railway vehicles, basig on actual acoustic measurements, made it possible to isolate the dominant noise sources, as well as to find out the amplitude-frequency characteristics in the range from 20 Hz to 20 kHz, divided into one third octave bands.

INVESTIGATION OF THE DISTRIBUTION OF RESIDUAL STRESSES IN THE ZONE OF THE WELDED SEAM OF RAILS OF THE R65 TYPE OF THE DT350 CATEGORY

Rails are the most important element of the superstructure of the railway track. To increase the smoothness of the ride, reduce dynamic loads at the junctions of the rails, contact welding of rails in a whip in stationary conditions and aluminothermic welding directly on the way are becoming more common. Despite the improvement in the quality of the joints, the zone of welded joints, due to a change in the structure due to the physical processes of welding and heat treatment, is still a place with lower mechanical characteristics compared to the metal of solid- rolled rails. The development of defects in welded butt joints is one of the main reasons for removing rails from service. An important component of ensuring the quality of rails and welded joints is the formation of a favorable diagram of residual stresses. In order to assess the effect of induction heating and hardening, a study was made of the distribution of residual stresses before and after heat treatment of the welded joint, full-profile samples of R65 type rails of the DT350 category of steel grade E76HF, the current production of EVRAZ ZSMK JSC. It has been established that compressive residual stresses predominate in the rail head both before and after heat treatment,heating reduces the overall stress level to the level of 210–264MPa, the maximum compressive stress level equal to 586 MPa is fixed at joint No. 224, after hardening heat treatment. Tensile stresses predominate in the neck of the rail, a sharp increase in stresses after hardening heat treatment was noted, the stress level increased more than three times, from 68 MPa to 254 MPa. After heating the welded joint, a slight decrease in residual stresses in this area is observed. Compressive stresses are recorded in the rail sole, with identical diagram, regardless of heat treatment. A minimum of stress is fixed in the center of the sole, with a subsequent increase towards the edge of the feather. The greatest difference was recorded after hardening heat treatment, from 57MPa to 537MPa, respectively.

NFLUENCE OF DEVIATIONS IN THE POSITION OF WHEEL PAIRS IN A FREIGHT-CAR ON THE GUIDING FORCES

The article puts forward a hypothesis according to which the violation of the nominal setting of wheel pairs in railway rolling stock carts is the main reason for the increase in guiding forces in the wheel flange contacts of the wheels of freight cars with the rails. Increased loads in wheel flange contacts are the cause of a number of other negative phenomena: increased intensity of wear (undercutting) of wheel flange, increased wear of the side surfaces of rail heads, decrease in the coefficient of stability of wagons from derailment, etc. To test this hypothesis, a study was conducted to obtain dependencies, first of all, these are the characteristics of the influence of geometric deviations of the position of the wheel pairs in the cart on the level of guiding forces in the contacts of the wheels with the rails and the wear of the wheel flanges. The relevance of this study is confirmed by data on the catastrophic wear of rails and solid-rolled wheels of wagons. An analysis of statistical data oblique setting of wheel pairs in carts in plan due to running-in of side frames was made, which shows that in 80% of wagons these angles can be up to 0,015 rad (0,85 degrees). The formula for the critical derailment ratio of the frame force to the vertical load on the wheel has been clarified, in contrast to Nadal's formula, which additionally takes into account the deflection forces in the contact of the overlapping wheel.

Simulation of the contact pair “wheel-rail” of the experimental design of the flexible rail in the lightweight tracks of the uST string transport system

Rationale: Development of string rails with low weight per meter and high-performance characteristics that determine durability, wear resistance, reliable grip of vehicle wheels to the rail rolling surface is a vital task.
 Objective: to investigate impact of the geometric parameters of the steel wheel and the flexible string rail with a polymer coating on the performance characteristics; to choose the most optimal parameters of the contact pair wheel-rail.
 Methods: The calculation was made using the ANSYS finite element analysis software package.
 Results: in order to reduce the level of contact pressures, it is more expedient to lower the load on the wheel or increase the width of the contact, rather than to increase the radius of the wheel; the most optimal is the contact pair, where the modulus of elasticity of the polymer rail head is equal to the modulus of elasticity of the wheel material, that is, materials similar in elasticity are used in the contact pair.

An inspection method of rail head surface defect via bimodal structured light sensors

An inspection method of rail head surface defect via bimodal structured light sensors

INVESTIGATION OF THE AUSTENITE DECAY KINETICS DURING CONTINUOUS COOLING OF STEEL WITH 0.84 % С, 0.44 % Si, 0.95 % Mn, 0.01 % B, 0.0006 % Са FOR RAILWAY RAILS OF THE NEW GENERATION

Purpose. Investigation of the supercooled austenite decay kinetics during continuous cooling of steel with 0.84 % C, 0.44 % Si, 0.95 % Mn, 0.01 % B, 0.0006 % Ca for railway rails of a new generation with increased operational properties to develop parameters of differential cooling. Method. The investigation of the austenite decay kinetics was carried out using differential thermal analysis. Samples were cooled at different cooling rates, temperature control was performed using chromel-aluminum thermocouples installed in the center of the sample. Microstructural investigations are performed using optical (AxioVert 200M mat) and electronic (SEM-106) microscopes. The interplate distance in pearlite is determined by the linear method, the diagonals are located perpendicular to the plate packages. Vickers hardness at a load of 10 kg. The number of structural components is recognized on microstructural images using the imageJ software complex. Results. The TKD analysis showed that at cooling rates of 0,06...5,96 °C/s, the structure of the investigated steel consists of pearlite. As the cooling rate increases, the morphology changes and the dispersion of pearlite increases: from medium pearlite to sorbitol-like. It should be noted that in the cooling rate range of 0,06...0,07°С/s, tertiary cementite is formed from ferrite. The diagram shows that at a cooling rate of 5.96 °С/s the hardness is 468 НВ (432 НВ), and the structure does not contain bainite. At a cooling rate of 1.47 °С/s, the hardness is 356 НV (345 НВ). This is slightly below the minimum allowable value (370 HV), but by interpolation it can be determined that the cooling rate must be at least 2.5 °C/s to achieve a hardness of at least 393 HV (370 HV). That is, when the rolling surface of the rail is cooled at a rate of 5.96 °C/s, the central volumes of the rail head at a rate of at least 2.5 °C/s, high-strength rails of the following categories can be manufactured: higher (DSTU (National Standard of Ukraine) 4344:2004) and R400HT (EN 13674-1:2011) from steel with 0.84 % С, 0.44 % Si, 0.95 % Mn, 0.01 % B, 0.0006 % Ca. Scientific novelty. Constructed thermokinetic diagram of steel austenite decay with 0.84 % С, 0.44 % Si, 0.95 % Mn, 0.01 % B, 0.0006 % Са. Practical value. It was established that with the use of experimental steel with 0.84 % C, 0.44 % Si, 0.95 % Mn, 0.01 % B, 0.0006 % Ca it is possible to achieve a hardness above 400NV without the formation of needle-like structures, therefore this is recommended chemical composition for the manufacture of high-strength rails of the R400NT category according to EN 13674-1-2011.

IMPROVEMENT OF THE METHOD FOR DETERMINING RELATIVE RAIL WEAR

Purpose. To evaluate the existing method of determining the relative wear of the rail in modern operating conditions of the railway track and to improve it. Methodology. An analysis of the existing method of determining the relative wear of rails was carried out to achieve the goal. 30 pieces of cross-sections of worn rails were processed. They were compared with the profile of the new rail. The actual wear area is determined digitally. Due to the measured values of vertical and lateral wear, calculations, corresponding analysis and research were carried out. Findings. The existing method of calculating the rail wear area is not relevant for modern rails and operating conditions. The inaccuracy is 60 %. A detailed analysis made it possible to establish a new mathematical dependence of the rail wear area on vertical and lateral wear. The condition of the wheels of the rolling stock is taken into account. Inaccuracy decreased to 3 %. Originality. On the basis of the conducted research, the concept of «pseudo lateral wear» was introduced for the first time. This is the vertical wear of the working face of the rail, measured as the lateral wear of the rail. Vertical wear of the rail is caused by the action of a vertical force. The mathematical dependence is given. This made it possible to clarify the value of parameter e for practical calculations and its physical meaning (e=50 mm2 with vertical wear greater than 1.5 mm, and e=20 mm2 with vertical wear equal to or less than 1.5 mm). Practical value. It is established that the relative wear of the rail is the sum of 94 % vertical wear and 30 % lateral wear for modern conditions. The physical essence of the specified percentages is the ratio of the average width and height of the vertical and lateral wear to the width of the rail head in the calculated plane. The physical meaning of relative wear is an estimate of the mass of worn metal. For every 1 mm of relative wear of the P65 rail, according to the refined methodology, there is 0.50 kg of worn metal per 1 m of the rail length.

Defect Detection inside a Rail Head by Ultrasonic Guided Waves

Early detection of defects inside a rail is of great significance to ensure the safety of rail transit. This work investigated the ability of ultrasonic guided waves (UGWs) to detect internal defects in a rail head. First, the model of UGW propagation in rail, which has an irregular cross-section, was constructed based on the semi-analytical finite element (SAFE) method. Fundamental characteristics, such as wavenumber, phase or group velocity, and wave structure inside the rail, were then calculated. Following modal and vibration energy distribution analysis, a guided wave mode that is sensitive to transverse fissure (TF) defects was selected, and its excitation method was proposed. The effectiveness of the excitation method was confirmed by simulations performed in the ABAQUS software. According to the simulation data, the dispersion curve calculated by using the two-dimensional Fourier fast transform (2D-FFT) coincided well with that of the SAFE method. After that, the sensitivity of the selected mode to internal rail defects was validated and its ability to locate defects was also demonstrated. Finally, the effects of excitation frequency, defect size, and vertical and horizontal defect depth on the reflection waveforms were investigated.

On the issue of wearing mechanism of abrasive wheels during rails grinding

Issues related to the study and theoretical description of the mechanism of wear of abrasive grains on a grinding tool used in the machining of railway rails are reviewed in the article. Abrasive wheels often do not cope with the task of removing surface defects that partially remain on the treated surface. In this case, the rail-grinding train is forced to make several passes (3 …4 passes). This leads to a decrease in the productivity of the rail grinding process. It is noted that it is possible to achieve an increase in the productivity of grinding the rails by controlling the pressing force of the wheels to the machined surface of the rail head. It is shown that the role of the destruction of the wheel grains in the grinding of the working profile, and, consequently, the profile of the rail head remains undisclosed. These unresolved issues of the mechanisms of abrasive wheels wearing during rails grinding require their own special studies. The process of formation of the individual grain wearing surface during grinding is described. It is noted that the mechanism of wearing of abrasive wheels is predictable. In this work, theoretical studies are carried out and the process of wearing of the abrasive grain is idealized, as well as mathematical simulation of the process of wearing of an individual particle is carried out on the basis of the analysis. The size of the areas of grain wearing and the intensity of its growth is the most important factor that characterizes the wearing of the tool caused by the destruction and loss of grains from the bond.

Determination of the form of loss the freight cars stability taking into account the gap in the rail track

Derailments of freight cars occur for various reasons: breakdown of equipment or individual parts; maintenance deviations in the track superstructure; incorrect order of passing and making-up trains; violation of normal dynamic conditions, which occurs due to hunting and unfavorable traffic conditions on a curved track section. In order to avoid derailments and ensure a stability coefficient, the restrictions expressed using certain indicators are set. These indicators determine the conditions for lifting the wheel above the rail head, overturning the rail and widening the railway track. One of the most widely used restrictions is the restriction expressed in terms of the ratio of the lateral force acting on the wheel to the vertical force.Rolling stock derailment when the wheel flange is rolled onto the rail head, as a rule, is facilitated by longitudinal compressive forces.The presence of longitudinal forces in the train results in unloading the wheels moving along the outer rail line, and overloading the wheels moving along the inner rail line.The stability loss of freight cars as part of a train should be divided into two stages: stability loss of the body on suspension springs and the stability loss of the wheel set, which results directly in the derailment.
 The work is aimed to study the influence of longitudinal quasi-static compressive forces arising during stationary modes of train movement on the form of freight cars’ instability. The relevance of this study relates to the need to control the longitudinal forces arising during the train movement, taking into account the increase in speeds, masses and lengths of trains, especially freight trains, by in the locomotives power increase. The use of the above methodology will improve the stability of freight rolling stock, justify the cause of derailment, as well as develop and put into practice technical measures to prevent the lift of the carriages, widening and shear of the track.

РЕПРОФИЛИРОВАНИЕ ЖЕЛЕЗНОДОРОЖНЫХ РЕЛЬСОВ НА РЕЛЬСОФРЕЗЕРНЫХ СТАНКАХ

The study objective is to increase the productivity of restoring rail profiles. The paper is devoted to the solution of the problem to determine thermal force, vibro-acoustic and energy parameters of milling machining of rail steel in various conditions. The computational and analytical method of research, express diagnostics are used. The novelty is in the proposed improved technology of rail reprofiling. The following results are obtained: it is found that the most productive and effective method of rail reprofiling in stationary conditions is milling on special rail milling machines; the main directions of increasing the machinability of rail steel are determined, which allows the development of induction heating technology for softening the surface defective metal layer of the rail head. Conclusion: the range of rational cutting modes of rail steel with thermal annealing are found.

Laser metal deposition characterization study of metal additive manufacturing repair of rail steel specimens

ABSTRACT Research on rail steel repair with Stellite 6 powder using a laser metal deposition process was investigated and reported in this study. Rail failures due to excessive wear and other rail head defects can increase the risk of operation and reliability problems in service life. This study examines the deposited material compatibility of a cobalt-based alloy, Stellite 6 with the head-hardened R350HT grade rail steel substrate. Materials characterization work includes metallurgical, wear, and shear properties testing and analysis. Microstructural analysis and hardness measurements of the cross-section from raster scan pattern deposition strategy of Stellite 6 on rail steel substrate surface showed minimal dilution and high hardness of the deposited layer with no presence of defects. Experimental testing of rail wear was conducted using a laboratory ball-on-disc tribometer setup and the wear coefficients for Stellite 6 and rail steel were derived from the wear volume analysis using Archard’s wear model. The material interface bond strength was evaluated from shear testing and analysis to measure the shear interface strength of the metallurgical bond between deposited material on a rail steel substrate.