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Browsing Journal Articles by Author "Abrahams, R"

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    Corrigendum to “Effects of preheating and carbon dilution on material characteristics of laser-cladded hypereutectoid rail steels” [Mater. Sci. Eng. A 712 (2018) 548–563]
    (Elsevier, 2019-01-10) Lai, Q; Abrahams, R; Yan, W; Qiu, C; Mutton, PJ; Paradowska, AM; Fang, X; Soodi, M; Wu, X
    The authors regret that the scale bar was missing from Figure 7. This has now been corrected. Fig. 7. Unaffected rail substrate and corresponding HAZ of a typical rail-transverse sections at (a) left gauge corner, (b) middle section, (c) right gauge corner and (d) representative of the longitudinal sections for (i) Group 1-1L, (ii) Group 1-2L, (iii) Group 2-1L & (iv) Group 2-2L. Martensitic morphology (M=martensite) with white etching colour were detected in (c) and (d) of the (i) Group 1-1L and (ii) Group 1-2L. Copyright © 2021 Elsevier B.V.
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    Effect of deposition material and heat treatment on wear and rolling contact fatigue of laser cladded rails
    (Elsevier, 2018-10-15) Roy, T; Lai, Q; Abrahams, R; Mutton, PJ; Paradowska, AM; Soodi, M; Yan, W
    To develop a laser cladding technique for repairing rail surface damages due to rolling contact, wear and rolling contact fatigue characteristics of a set of laser cladded rails were investigated using a roller-on-disc test machine. Three deposition materials 410L, SS420 and Stellite 6, were chosen to clad a premium hypereutectoid steel rail under two different heat treatment processes. In the first heat treatment, only preheating at 350 °C was conducted and in the second heat treatment, preheating at 350 °C, post-heating at 350 °C (1 h) then slow-cooling to room temperature was conducted. Preheating the substrate was insufficient to prevent martensite formation resulting from the rapid cooling rate, whereas post heat treatment was beneficial for refining the lamellar spacing and eliminating martensite formation in the clad layer and heat affected zone. Following the roller-on-disc tests, wear loss was calculated from wear track profiles using a laser optical profilometer. The level of surface degradation, surface cracking and spalling was investigated using an optical microscope. Experimental results revealed that SS420 cladding had the highest wear resistant behaviour but severe surface cracks and spalling were found in the worn area. Stellite 6 cladding showed similar wear resistance as the parent substrate rail and the best fatigue resistance behaviour among the three cladded rail samples. Based on this research, Stellite 6 is the most promising deposition material for repairing rails by laser cladding. © 2018 Elsevier B.V.
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    Effects of preheating and carbon dilution on material characteristics of laser-cladded hypereutectoid rail steels
    (Elsevier, 2018-01-17) Lai, Q; Abrahams, R; Yan, W; Qiu, C; Mutton, PJ; Paradowska, AM; Fang, X; Soodi, M; Wu, X
    The impacts of preheating conditions and carbon dilution on the microstructural and mechanical properties of laser cladded rails using single and double cladding layers have been investigated for a hypereutectoid steel grades typically used under heavy haul 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 350 °C. Dilution of carbon from the hypereutectoid substrate was observed and its effect on the microstructures of the 410L ferritic stainless-steel deposits was investigated. The formation of 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 dilution band was determined to be approximately equal to the thickness of the first cladding layer. Texture measurement obtained by EBSD showed a random trend owing to the formation of martensite in diluted bands. Strong solidification fibre texture was developed for double deposition, particularly in the second deposit. Mechanical characterization of the 410L deposits undertaken in terms of Vickers microhardness, shear and tensile yield strengths, and ultimate tensile and shear strengths were correlated with the observed microstructural morphologies. © 2017 Elsevier B.V.
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    Influences of depositing materials, processing parameters and heating conditions on material characteristics of laser-cladded hypereutectoid rails
    (Elsevier, 2019-01-01) Lai, Q; Abrahams, R; Yan, W; Qiu, C; Mutton, PJ; Paradowska, AM; Soodi, M; Wu, X
    The effects of different cladding materials, processing parameters and heating regimes on the underlying microstructural features and mechanical properties of laser-cladded premium rails were investigated by using a hypereutectoid rail grade as a substrate, which is extensively used in heavy-haul rail systems. Cladding materials of 410L, 420SS, Stellite 6 and Stellite 21 with single and double depositions were considered for the comparative study of different cladding materials and processing parameters. To ensure the constant thickness of the claddings for comparison purposes, transverse speed and powder feed rate were modified concurrently in the ranges of 1000–1200 mm/min and 3–4 RPM, respectively. Two heating conditions, i.e. preheating only (HTA) and a combination (HTB) of preheating and post weld heat treatment (PWHT) were applied after the preferable parameters for each cladding material were obtained. The most suitable cladding material for rail-wheel contact was established by assessing all crucial aspects, i.e. surface defects, hardness, microstructural and mechanical properties. Process parameters for each considered cladding material were determined to achieve no surface defects. For cladding layers, application of HTA was not able to significantly modify the microstructures of the deposits, whereas HTB was observed to cause severe cracks in Co-base alloys, i.e. Stellite 6 and Stellite 21. In the heat affected zones (HAZs), irrespective of the cladding materials, the formation of untempered martensite was not avoided by the application of preheating at 350 °C. Consequentially, cracking in the HAZ was observed. An uncracked and desirable microstructure in the HAZs was established using HTB, regardless of the depositing materials. The addition of a second layer did not change the thickness of the HAZs but refined the HAZ’s microstructures. Shear punch testing (SPT) and Vickers hardness testing were utilized to characterize mechanical properties for the considered cladding materials and good correlations with the obtained microstructural morphologies were shown. © 2018 Elsevier B.V.
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    Investigation of a novel functionally graded material for the repair of premium hypereutectoid rails using laser cladding technology
    (Elsevier, 2017-12-01) Lai, Q; Abrahams, R; Yan, W; Qiu, C; Mutton, PJ; Paradowska, AM; Soodi, M
    In this study, the effects of cladding direction, preheating and post heat treatment on microstructural and mechanical properties of laser cladded rail repairs are presented. Laser cladding of a premium hypereutectoid rails grade with 410L stainless steel powder were conducted using a fibre laser gun with a powder feeder. Two different cladding directions and different heat treatment regimes were investigated. An excellent microstructural consistency was established across the railhead and its heat affected zone (HAZ) by changing cladding direction and using a heat treatment consisting of pre-heating and post-heating. The microstructure of the cladding layer and HAZ were characterized by optical microscopy and SEM. Phase identification and distribution were investigated by using XRD, EDS, and EBSD. Indications of the mechanical and tribological performance of the cladding layer in wheel-rail contact were obtained via shear punch tests and Vickers indentation, which demonstrated great correlation with the obtained microstructure. © 2017 Published by Elsevier Ltd.
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    Residual stress in laser cladded heavy-haul rails investigated by neutron diffraction
    (Elsevier, 2020-04-01) Roy, T; Paradowska, AM; Abrahams, R; Law, M; Mutton, PJ; Soodi, M; Yan, W
    Residual stress is one of the critical parameters affecting the fatigue behaviour of tribological components, which can be introduced by a thermo-mechanical process such as laser cladding. In this study, the residual stress distribution of laser cladded rails was evaluated using a neutron diffraction technique. The substrate rail for the laser cladding was hypereutectoid rail steel used in Australian heavy-haul railway track, and the cladding materials were 410L (a low carbon content stainless steel alloy) and Stellite 6 (a Co-based alloy). The cladding materials were selected based on their high wear, corrosion and fatigue resistance properties. This study measured the residual stress in full-scale laser cladded rails where the residual stresses were measured in the cladding layer, heat affected zone (HAZ) and substrate zone of the railhead. A new sample preparation strategy was developed to quantify the residual stresses in the full-scale rails with high spatial resolution. Higher compressive residual stress was found in the cladding layer, which may have resulted from the martensitic transformation occurred in that region. Tensile stresses occurred in the HAZ to a depth of 4 mm, which might be mainly caused by thermal contraction and volumetric change in the microstructure. The addition of a second cladding layer did not significantly affect the magnitude of the residual stresses, but the peak tensile residual stress shifted to a deeper location from the surface, which is beneficial in resisting wear. Post-cladding heat treatment significantly reduced the undesirable high residual stress from the cladding layer and HAZ. © 2019 Elsevier B.V.