Browsing by Author "Yang, Che-Hua"

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    Investigation of high temperature wear performance on laser processed nodular iron using optimization technique
    (Elsevier B.V., 2019-08-16) Jeyaprakash, N; Yang, Che-Hua; Duraiselvam, Muthukannan; Prabu, G; Tseng, Sheng-Po; Raj Kumar, D
    Nodular cast iron (NCI) are used in nuclear energy and transportation industries. Also, NCI are used in gear boxes, camshaft, crank shaft, rolling mill rolls and machine tool beds. The reliability of the NCI under heavy loading condition is affected through several tribological aspects. In the present study, NCI surface has been melted by using an Ytterbium-doped fiber laser. The wear resistances of the substrate and melted surface have been analyzed by using a tribometer. Sliding speed, load and working temperatures have been considered as input parameters to tribometer. From the optimization trials, the applied load was identified as the most significant parameter followed by sliding speed and ambience temperature. The responses of the optimized tribological parameters attained by GRA was confirmed through experimental and agreed closely to the predicted value. Further, the surface of the substrate and laser melted samples were analyzed. The melted surfaces were free from surface deformities and exhibited a noticeable improvement in the wear resistance compared to the substrate.
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    Microstructure and tribological evolution during laser alloying WC-12%Co and Cr3C2−25%NiCr powders on nodular iron surface
    (Elsevier B.V., 2019-01-30) Jeyaprakash,N; Yang, Che-Hua; Duraiselvam, Muthukannan; Prabu, G
    The laser surface alloying has emerged as an important tool to form wear resistant layer. In this work, the characteristics of laser alloyed WC-12%Co and Cr3C2-25%NiCr powders over nodular cast iron and their effects on microstructure, microhardness and wear resistance properties has been investigated. Results shows that the laser alloyed layers are crack free with a very fine structure, improved homogeneity and good metallurgical bonding with the substrate. Microhardness of the alloyed layer has been remarkably increased from 220 HV0.3 to 1199 HV0.3 and 905 HV0.3. The results shown that the wear resistance of the laser alloyed layer was improved by 97.77% and 89.77% for WC-12%Co and Cr3C2−25%NiCr, respectively, compared to that of the substrate nodular cast iron. The enhancement in wear resistance was due to the combined results of the solution strengthening effect, grain refining and good bonding between the hard phases and the matrix.
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    Surface alloying of FeCoCrNiMn particles on Inconel-718 using plasma-transferred arc technique: microstructure and wear characteristics
    (Royal Society of Chemistry, 2021-07-17) Jeyaprakash, N; Yang, Che-Hua; Prabu, G; Balamurugan, K. Ganesa.
    Inconel-718 (IN-718) is a commonly used nickel-based superalloy in various fields, such as gas turbine and power generation applications. However, the lower wear and oxidation resistance hinder their wide usage. In this work, FeCoCrNiMn particles were mechanically ball-milled and preplaced on the IN-718 substrate. Then, the preplaced FeCoCrNiMn particles were scanned by heat source using plasma-transferred arc (PTA) technique. The effect of PTA alloying on the phase changes, microstructure, nanohardness and wear resistance has been investigated. The result showed that the PTA region contained different phases, such as FCC, BCC and intermetallic. No cracks were observed in the PTA alloyed region. Moreover, the porous free structure was viewed in the alloyed region, which revealed that the PTA alloying process was effectively used to perform the alloying process. More hard phases, such as NiFe, CoMn, Cr9Mn25Ni21, MnNi, FeCo, FeMn and MnCo, were formed on the PTA-alloyed region. The obtained wear rate of the substrate specimen at 30 N applied load is 2.45 × 10−3mm3m−1and 1.79 × 10−3mm3m−1for the PTA specimen. Similarly, the wear rate of the substrate specimen at 50 N is 5.38 × 10−3mm3m−1and for the PTA sample, it is 2.29 × 10−3mm3m−1. The PTA specimen showed lower CoF than the substrate specimen due to increased surface hardness and minimum deformation of asperities. The primary wear type was mildly abrasive, accompanied by slight oxidative wear. Oxygen reacted with the surface alloying elements and formed different oxides, such as CoO, Cr2O3, MnO2, Mn2O3, Mn3O4, FeO and Fe2O3. These dense oxidation films covered the working surface and enhanced the wear resistance. The worn-out PTA surface showed that the wear scar depths were shallow and lower than the substrate, and reduced the roughness.