• V SENTHILKUMAR

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    • Experimental investigations on cryo-machining of Hastelloy C-276 with tool wear characteristics

      J KESAVAN V SENTHILKUMAR

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      The super alloy exhibits great strength and fatigue behaviour when nickel (Ni) is present in major quantities. Moreover, it possesses good corrosive resistant behaviour at high temperatures. However, these alloys are very difficult to machine under normal machining conditions due to their great strength and low heat dissolution. In this work, machining was performed on Hastelloy C276 under various machining conditions (speed, feed and depth) and environments (dry and cryogenic). Liquid nitrogen was used as a coolant in themachining region. The machinability of Hastelloy C276 was investigated with machining forces, temperature, surface roughness and hardness under different cutting conditions. Turning experiments that resulted from passing LN2 drastically reduced temperature by up to 40%. Machining forces were minimal under cryogenic machining due to its effective lubrication property. Surface finish of the machined area improved by about 26% under cryogenic conditions. Both dry and cryogenic machining improved the hardness of the work material. Thehigh cooling efficiency of LN2 improved hardness of the machined surface was about 8-15%. Chip width and side-flow of chip material were reduced under cryogenic cooling. Moreover, adhesion and abrasion wear wereobserved minimally in cryogenic machining compared to dry machining. But no significant difference was observed in notch wear for both types of machining. Machinability of Hastelloy C276 significantly improved when LN2 used as a cutting fluid.

    • Experimental investigation on microstructural characterization of machined Ti-6Al-4V using abrasive water jet machining

      S RAMAKRISHNAN D LENIN SINGARAVELU V SENTHILKUMAR C VELMURUGAN

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      Titanium (Ti) alloys are mainly used in medical implants and aerospace applications where high fatigue strength is significant. Most of the titanium based components are subjected to unconventional machining to get the final shape of the product. Because, Ti based alloys are very challenging to machine usingconventional processes. In this work, the unconventional technique of abrasive water jet machining (AWJM) was carried out on Ti6Al4V under variation of the machining parameters such as water jet pressure (WJP), abrasive flow rate (AFR) and standoff distance (SOD). The surface integrities such as roughness, microstructural characterization and residual stress were investigated on the machined surface of Ti6Al4V. The orientation dependence of the compressive deformation in the polycrystalline Ti6Al4V alloy was investigated on the basal(0001)α, prismatic (1010)α and pyramidal (2110)α planes. The AWJM has induced the mechanochemical oxidation on the machined surface of Ti6Al4V alloy. The grain boundary network is the complex structure in the polycrystalline material; though, an attempt has been made in the present study to analyze the induced grain boundary, phase (α/β) fraction, dislocation, and oxide formation during the AWJM. The experimental results exhibited that the grain boundary dislocation density and average misorientation angle were increased and thegrain size was reduced with increasing the water jet pressure (WJP). Moreover, the compressive deformation was induced the residual stress on the machined region of Ti6Al4V. The β-phase of the Ti alloy has been transformed to α-phase when WJP was increased together with the oxygen content.

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