Papers by Author: Rong Lu Sun

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Authors: Wei Niu, Rong Lu Sun, Yi Wen Lei
Abstract: Self-lubricating Ni+h-BN coatings were prepared by CO2 laser cladding with powder mixtures of Ni60 and h-BN. The chemical compositions and microstructures of the coatings were analyzed using SEM and XRD. The microhardness of the coatings was measured on a microhardness tester. It was found that the morphology of CrB was changed from irregular block-like shape (in Ni60+5%h-BN coating) →short–plate structure (in Ni60+10%h-BN coating)→dendritic-plate structure(in Ni60+15%h-BN coating) with increasing the content of h-BN. The microhardness of the 5,10 and 15% h-BN coatings ranged from 650~800HV0.2, 800~1010HV0.2 and 1000~1200HV0.2, which was higher than that of Ni60 coating and substrate.
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Authors: L.P. Song, Rong Lu Sun
Abstract: We found that welding rod of the same trademark but different batch has distinct different tendency of brittleness when they are experienced step cooling embrittling treatment process.A series of 2.25Cr-1Mo-0.25V steel welds were prepared using the manual arc. The notch toughness properties were assessed in the PWHT condition and after a temper embrittlement step-cooling treatment. the J and X factors of the weld should be more rigorous than the base steel. low Mn and Si content weld metal is less susceptible to temper embrittlement. The temper embrittlement was evaluated as the shift of 54 Joule transition temperature (vTr54) by the Charpy v-notch impact tests. In the post-weld heat-treated condition (PWHT) the notch toughness requirement for weld metal is 54 J at-40°C .
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Authors: Yi Wen Lei, Cheng Qiang Gong, Rong Lu Sun
Abstract: A three-dimensional model was proposed to simulate high power laser clad TiC/NiCrBSiC composite coatings on Ti6Al4V alloys. Molten pool depth and dilution rate were obtained and compared with the experimental results. The calculated molten pool depth in the sample is about 0.76 mm and dilution rate is 21 %. The experimental data molten pool depth and dilution rate were 0.81 mm and 26%, respectively. There is a good agreement between the numerical and experimental results. A good quality laser clad TiC/NiCrBSiC coating with low dilution rate and excellent metallurgical bond can be prepared under the optimal parameters.
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Authors: Wei Niu, Rong Lu Sun, Yi Wen Lei
Abstract: Self-lubricating h-BN/Ni coating was prepared on a medium carbon steel substrate by CO2 laser cladding using a powder mixture of NiCrBSi+5%h-BN(wt.%). Microstructures and phase structure of the coating were analyzed using SEM, EDS and XRD. Wear tests were carried out using a M100 pin-on-ring wear tester. The results show that h-BN/Ni coating has much superior war resistance and noticeably lower fiction coefficient under dry sliding wear test conditions.
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