Browsing by Author "Qiu, C"

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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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    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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    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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    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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    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