Browsing by Author "Subramaniyan, S."

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    Process-microstructural features for tailoring fatigue strength of wire arc additive manufactured functionally graded material of SS904L and Hastelloy C-276
    (Elsevier B.V., 2020) Kannan, A.; Subramaniyan, S.; Pravin Kumar, N.; Siva Shanmugam, N.; Vishnu, A.S.; Palguna, Y.
    Many engineered components on subjecting to critical environments require properties that slightly differs with location in the fabricated part. The inadequate understanding of wire arc additive manufacturing (WAAM) process-microstructural features correlation brings interests on the structural reliability of functionally graded materials (FGM), which limits the extensive use of this cutting edge technology. Gas metal arc welding (GMAW) based WAAM process was adopted to fabricate the FGM of super austenitic stainless steel SS904L and Hastelloy C-276 with excellent bonding. The micrographs revealed that the WAAM processed FGM was mainly composed of columnar and equiaxed dendrites and had noticeable inhomogeneous features along the built direction. Tensile test results of sample along the built direction revealed a yield strength of 311.08 MPa and tensile strength of 680.73 MPa. Cyclic loading results depicted that the WAAM processed FGM has a fatigue resistance of 156 Mpa after sustaining 2 × 106 cycles. As a result of the varying microstructural characteristics along the built direction, the failure was initiated and fractured at the SS904L weaker region. © 2020 Elsevier B.V.
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    Tribological performance of wire arc additive manufactured 347 austenitic stainless steel under unlubricated conditions at elevated temperatures
    (Elsevier Ltd, 2020) Duraisamy, R.; Subramaniyan, S.; Kannan, A.; Siva Shanmugam, N.; Sankaranarayanasamy, K.; Ramesh, M.R.
    Wire Arc Additive Manufacturing (WAAM) is an effective metal additive manufacturing process. In this research, 347 Austenitic Stainless Steel (ASS) walls were manufactured with ER347 consumable material. The microstructure of the WAAM processed 347 plate is entirely heterogeneous with changing grain morphology along the building direction and this is attributed to the complex cyclic thermal history during WAAM process. The microstructure is composed of columnar, cellular and equiaxed structures at various regions. The hardness decreased gradually from bottom to top along the building direction. The volume fraction of ferrite ranged from 0.5% to 4.2% at various regions and the presence of niobium carbide (NbC) was confirmed. The aim of the current work is to provide an outline of the WAAM processed 347 steel under dry sliding conditions at elevated temperatures. The elevated temperature wear mechanism has mild oxidative wear characteristic due to the formation of tribo-oxides on the wearing and sliding surfaces. However, the average coefficient of friction (COF) is lower for the WAAM processed 347 compared to 347 substrate. In all cases after initial running-in, the wear debris from the wearing and sliding surface forms mechanically mixed composite layer of tribo-oxides (Fe2O3, Fe3O4 and Al2O3). The worn surface at 200 °C presents different wear behavior compared to the samples at 400 °C and 600 °C. The wear at 200 °C is a typical adhesive wear, while the wear at 400?600 °C is mild oxidative wear. The increase in the percentage of Fe3O4 helps to heal the wear surface by forming a mechanically mixed composite layer. The characteristics of mild oxidative wear were elucidated. © 2020 The Society of Manufacturing Engineers