An experimental study of influence of wire electro discharge machining parameters on surface integrity of TiNiCo shape m
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Shape memory alloys (SMAs) are unique class of smart materials with excellent physical, mechanical and biomedical properties, which have wide applications in several fields such as aerospace, robotics, biomedical, and dental etc. These alloys are well known for exhibiting shape memory effect (SME) and pseudoelasticity (PE), it is a well-established fact that they are required to be processed into functioning parts. The conventional machining affects the internal properties of shape memory alloys and hence, it is reported that nonconventional machining techniques are more suitable. Wire electro discharge machining (WEDM) is one of the nonconventional machining processes for machining complicated shapes without hampering the internal properties of such type of materials. In the present experimental investigation, wire electro discharge machining of Ti50Ni40Co10 shape memory alloy (SMA) has been carried out and machining performances such as surface roughness (SR), and material removal rate (MRR) have been evaluated. Experimental results exposed that pulse on time, pulse off time and servo voltages are most influential process parameters on the responses. The machined surface has been characterised with respect to microstructure, microhardness, and phases formed.
I. INTRODUCTION
Shape memory alloys are smart materials due to their excellent properties such as shape memory behavior, super elasticity, corrosion resistance, and biocompatibility, and these properties makes them suitable to be used in the robotics, aerospace, and biomedical applications.1 In addition to these properties SMA exhibits SME and PE, high specific strength, greater ductility, and elastic modulus.2,3 To further expand their use in several other specific applications, additional alloying elements are to be used. Adding third element in NiTi alloys by replacing Ti or Ni has an extensive effect on their phase transformation behavior and properties of the material.4,5 Rui and Fu studied the effect of Co addition as a substitute for Ni on the phase transformation behavior and mechanical properties with different percentages of Co 2, 4, 6, 8, and 10 in TiNi alloy.6 From the literature it was found that Ti50Ni40xCox (x 5 2–10%) exhibit two step phase transformation and exhibited good ductility with a lower stress plateau because of stress–induced martensite and martensite reorientation at room temperature deformation. The addition of Co in TiNi results in increased loading and unloading plateaus and workability as
compared to TiNi alloy.1 Conventional machining of these materials creates poor surface finish, burr formation, low dimensional accuracy of the machined product and high tool wear rate caused due to the characteristic property of the material. Therefore, non-conventional techniques such as laser machining, electrochemical machining, and wire electro discharge machining are suitable for machining of these alloys.7–9 MRR and SR are most important parameters of all machining processes; these output parameters exhibit the qualities of machining proce
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