Conference Publications

This community mainly contains citations, yet where permitted, the full text, of the conference papers, presentations, posters and abstracts written by ANSTO authors.

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Browsing Conference Publications by Author "Abrahams, R"

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    Effect of cladding direction on residual stress distribution in laser cladded rails
    (Zenodo, 2018-01-01) Roy, T; Paradowska, AM; Abrahams, R; Lai, Q; Law, M; Mutton, PJ; Soodi, M; Yan, W
    In this investigation, a laser cladding process with a powder feeding was used to deposit stainless steel 410L (high strength, excellent resistance to abrasion and corrosion, and great laser compatibility) onto railhead (higher strength, heat treated hypereutectoid rail grade manufactured in accordance with the requirements of European standard EN 13674 Part 1 for R400HT grade), to investigate the development and controllability of process-induced residual stress in the cladding, heat-affected zone (HAZ) and substrate and to analyse their correlation with hardness profile during two different laser cladding directions (across and along the track). Residual stresses were analysed by neutron diffraction at OPAL reactor, ANSTO. Neutron diffraction was carried out on the samples in longitudinal (parallel to the rail), transverse (perpendicular to the rail) and normal (through thickness) directions with high spatial resolution through the thickness. Due to the thick rail and thin cladding, 4 mm thick reference samples were prepared from every specimen by Electric Discharge Machining (EDM). Metallography across the laser claded sample revealed four distinct zones: The clad zone, the dilution zone, HAZ and the substrate. Compressive residual stresses were found in the clad zone and tensile residual stress in the dilution zone and HAZ. Laser cladding in longitudinally cladding induced higher tensile stress in the HAZ, whereas transversely cladding rail showed lower tensile behavior. © Creative Commons Attribution 4.0 International License
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    Evaluation of the mechanical properties of laser cladded hypereutectoid steel rails
    (Elsevier B. V., 2019-08-15) Roy, T; Abrahams, R; Paradowska, AM; Lai, Q; Mutton, PR; Soodi, M; Fasuhi, P; Yan, W
    Local material properties of the cladding layer, heat affected zone and substrate of laser cladded hypereutectoid steel rails were evaluated by uniaxial tensile tests on miniature specimens. Three laser cladding materials, i.e. 410 L, SS420 and Stellite 6, and two different heat treatment conditions were considered. To examine any possible anisotropic behaviour, specimens machined along the longitudinal and transverse laser cladding directions were tested. All the cladding layers showed similar or higher yield and ultimate tensile strengths, but lower elongation than the non-clad rail. Application of post-heat treatment significantly improved the elongation of all the cladding layer specimens. Elongation increments of 70%, 192% and 90% were respectively obtained from the 410 L, SS420 and Stellite 6 post-heat treated cladding layers. The post-heat treatment also marginally increased the yield and ultimate tensile strengths in this region. The improvement in tensile properties was associated with a more favourable microstructure, which resulted in a more dimpled morphology as depicted in the SEM images of the fractographic analysis of the tested specimens. While other properties are similar, both cladding layer and HAZ specimens showed significant different elongation values between the longitudinal and transverse directions in some cases, which indicates certain anisotropy in those materials’ ductility. © 2019 Elsevier B.V.
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    Finite element analysis of thermal cycle in laser cladding for railway repair
    (Engineers Australia, 2017-01-01) Lai, Q; Abrahams, R; Yan, W; Mutton, PJ; Qiu, C; Paradowska, AM; Soodi, M; Roy, T
    Material degradation in the forms of wear and rolling contact fatigue is one of main hindrances in the development of today's expeditious heavy-haul railway systems. Laser cladding is proposed as a promising repair technique for damaged rail tracks so as to mitigate the material degradation rates and prolong the component service life. This paper reports the influence of laser cladding directions on thermal cycle and the corresponding mircostructures and service performance of laser cladded premium hypereutectoid rails. For two separate cladding directions, thermal information of pre-, during and post-laser treatment on three dimensional 68 kg rail models was simulated via ANSYS platform. Furthermore, microstructural characteristics of the actual rails under the analogous processing conditions were assessed via optical microscopy. Potential mechanical and tribological properties were characterized by Vickers indentation. The unified correlations between the measured properties and observed microstructural features were acquired. The reasons for the formation of martensite renowned for great cracking tendency at certain regions in HAZ were unveiled, thus future prevention of forming martensite can be achieved.
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    Influence of tempering and surface grinding on the residual stress of 415SS laser clad hypereutectoid rail components
    (Australian Institute of Nuclear Science and Engineering (AINSE), 2020-11-11) Kendal, O; Abrahams, R; Paradowska, AM; Reid, M
    A growing reliance on critical transport infrastructure combined with the dependence upon railway for mining and mineral export has heightened operational requirements and lead to premature failure of rail components under severe loading conditions caused by plastic deformation, rolling contact fatigue and accelerated wear rates. Rail replacement is a costly and disruptive undertaking therefore in-situ maintenance is necessary for ongoing repairs to keep these extensive railway networks operational. Traditional maintenance techniques such as arc welding can be damaging to the rail and promote undesirable microstructural changes and softening due to the large thermal input. Laser cladding is an emerging regenerative maintenance strategy that utilises a high energy laser to metallurgically bond a deposition layer that imparts superior mechanical and tribological properties to restore the rail profile. Despite the smaller heat affected zone (HAZ) generated from the reduced thermal input, laser cladding produces a complex residual stress state due to thermal gradients, phase changes and solidification shrinkage. It is the combination of residual stress and cyclic wheel-rail contact stresses that govern the rail fatigue behaviour and susceptibility to wear and defect formation, therefore high internal stresses may increase the likelihood of failure. 415SS is a new martensitic stainless steel alloy developed to recondition hypereutectoid rail substrates and contains beneficial compressive stresses in the untempered cladding deposition, determined using neutron diffraction techniques. For in field applications, laser cladding repairs require further tempering and rail grinding procedures to prepare the surface for wheel contact by achieving the required mechanical properties and reducing surface roughness to minimise friction, wear and noise. Both thermal and machining processes alter the post cladding internal stress state which in turn impacts the fatigue behaviour. Non-destructive neutron diffraction has been undertaken on the Kowari strain scanner at ANSTO to assess the effect of post cladding tempering and surface grinding on the residual stress of 415SS clad high carbon rail. The triaxial residual stress distribution was measured after 350oC and 540oC tempering processes and surface grinding to remove 0.5 mm and 1.4 mm from the cladding surface. Strain scanning was also performed on a disc with a 0.4µm surface finish. The research outcomes from this investigation will assist in better understanding the effect of post cladding processes on the rail fatigue behaviour as accurate measurement of the internal stress state is a critical aspect in developing a viable laser cladding maintenance strategy. These findings will be used in conjunction with full microstructural and mechanical property evaluation to determine the influence of cladding repairs on rail performance and identify the most desirable parameters for post cladding procedures to optimise the operation lifetime of rail components.
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    Laser cladding for railway repair: influence of depositing materials and heat treatment on microstructural characteristics
    (American Society of Civil Engineers (ASCE), 2017) Lai, Q; Abrahams, R; Mutton, PJ; Qiu, C; Paradowska, AM; Soodi, M; Roy, T; Yan, W
    The contact between train wheels and rail tracks is known to induce material degradation in the form of wear, and rolling contact fatigue in the railhead. Laser cladding, a state of the art surface engineering technique, is a promising solution to repair damaged railheads so as to alleviate the rates of degradation and extend the component longevity. In this paper, effects of cladding material and heat treatment on microstructures of laser treated rails is presented. Laser cladding of premium hypereutectoid rail, four different depositing materials, and different heat treatments were investigated. For the preheating length of 400 mm, equal to the cladding length, the formation of martensite in heat affected zone (HAZ) was not hindered by the application of preheating to 350 °C on the rail-longitudinally deposited railhead of the four materials. Consequentially, cracking in the clad and HAZ was expected. An uncracked microstructure with excellent microstructural consistency across the entire rail-longitudinally deposited railhead and its HAZ was established using a heat treatment combination consisting of pre-heating, postheating, and slow cooling, regardless of the depositing materials. © 2018 American Society of Civil Engineers
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    Material characteristics of laser-cladded hypereutectoid rail steels
    (Railway Technical Society of Australasia (RTSA); Technical Society of Engineers Australia. , 2018-01-01) Lai, Q; Roy, T; Abrahams, R; Yan, W; Paradowska, AM; Qiu, C; Mutton, PJ; Soodi, M
    The impact of preheating conditions and carbon dilution on the microstructural and mechanical properties of laser cladded rails at various number of deposition layers has been investigated for hypereutectoid steel grades typically used under heavy hall conditions. The microstructures in the HAZ showed that formation of martensite, which has a detrimental effect on behaviour in wheel-rail contact, was successfully inhibited by increasing the length of the preheated region using a preheating temperature of 350C. Dilution of carbon from the hypereutectoid substrate was observed and its effect on the microstructures on the 410L ferritic stainless-steel deposits was investigated. The formation of the ferrite in the 410L cladding layers was attributed to the very low carbon content, and no carbide formation was observed on boundaries of the ferritic grains. The thickness of the dilution band was determined to be approximately equal to the thickness of the first cladding layer. Mechanical charaterization of the 410L deposits undertaken in terms of Vickers microhardness was correlated with the observed microstructural morphologies. © 2021 Informit
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    Neutron diffraction based non-destructive techniques for integrity studies on copper-stainless steel hybrid composites fabricated by friction stir forming
    (Engineers Australia, 2017-11-27) Ahuja, Y; Abrahams, R; Paradowska, AM
    A novel technique based on probeless tool aided friction stir forming (FSF) has enabled fabrication of bimetallic composites of copper (Cu) with immiscible metals such as tungsten (W) and stainless steel (SS). Thermomechanical bonding of Cu and the embedded SS-insert, with different interfacial geometries and with different intermediate metal powder layers, was investigated. A full 360 tomography of the Cu-SS composites was performed on the neutron imagining station DINGO, at ANSTO. Sequentially stacked neutron images were reconstructed into a 3D model of the sample to examine the existence of voids and tunnel defects. Complete encapsulation and continuous bonding of the SS-insert with thermo-mechanically conditioned Cu established the feasibility of FSF for fabricating such hybrid Cu-SS composites. Additionally, peak temperatures during the process were noted to reach up to 600C, bonding at such temperatures may lock in strain. Furthermore, on cooling significant thermal stresses might develop at the Cu-SS interface owing to the difference in the mechanical properties of two metals. Exposure to continuous heating and cooling cycle during the double pass technique might also result in residual stresses. These stresses occurring as a result of the thermomechanical bonding may affect the integrity of the composite. Owing to the architecturally intricate character of the fabricated Cu-SS hybrid composite, non-destructive neutron diffraction technique of KOWARI strain scanner at ANSTO was utilised. Through-thickness scans across the Cu-SS interfaces were performed using 2 x 2 x 2 mm3 gauge volume. The stress analysis performed in isolated spots of the Cu-SS composite showed minimal variation in the residual stress distribution in all three – longitudinal, traverse and normal directions.© 2017 Engineers Australia
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    Residual stress measurement in laser cladded rail utilizing neutron diffraction technique
    (Engineers Australia, 2017-11-27) Roy, T; Paradowska, AM; Abrahams, R; Law, M; Mutton, PJ; Soodi, M; Yan, W
    The residual stress distribution of an excellent abrasion and corrosion resistant steel was evaluated to assess the potential of using laser cladding as a repair tool for rail track components. 410L steel powder was used to clad over a head treated rail steel substrate using a 4 kW IPG fibre laser. Pre-heating the substrate before cladding was investigated. Residual stress was measured by using neutron diffraction facility at the OPAL reactor, ANSTO (Australian Nuclear Science and Technology Organisation). A new experimental method was developed to measure residual stress of a small area of interest in large thick component. Residual stress results showed a compressive residual stress at the top surface of virgin and cladded rail. Clad layer was characterised by compressive residual stress and HAZ was characterised by tensile residual stress. A beneficial compressive residual stress was found at the cladding-substrate interface. © 2017 Engineers Australia
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    Tribological behaviour of laser cladded rail under rolling contact test
    (American Society of Civil Engineers (ASCE), 2017) Roy, T; Abrahams, R; Lai, Q; Mutton, PJ; Soodi, M; Paradowska, AM; Yan, WW
    Rolling contact fatigue (RCF), a pervasive and insidious problem on all types of railway systems, dominates the cause of maintenance and replacement on heavy-haul rail lines. It also plays a significant role in economic and safety challenge for commuter and metro lines. Intensive research around the world has been taken to improve RCF by introducing different surface modification techniques. Laser cladding has attracted attention because of its advanced and more efficient repairing technique. In this present investigation, influence of laser cladding on wear and RCF of a premium hypereutectoid rail steel, currently used in Australian heavy haul railways, has been studied under a roller-on-disc test rig in laboratory conditions. Rolling test was carried out using a roller made of heat treated harden steel with laser cladded and un-cladded rail steel discs. Micro-hardness of the roller was 820-850 HV5 to minimize plastic deformation and wear of the roller. Considering the real scenario of rail-wheel contacts, tests were run under partial sliding and rolling motion. The maximum contact pressure was similar to that experienced in rail due to rail-wheel contact. Wear resistance of laser cladded specimen was found to be significantly improved compared to non-cladded rail steel. © 1996–2021, American Society of Civil Engineers