Evaluation of Wire Electro-Discharge Machining Performance Characteristics of Ti49.4Ni50.6 Shape Memory Alloy and SS316L for Orthopedic Implant Application

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Adik Mahadev Takale N.K. Chougule

Abstract

Ti49.4Ni50.6 (at. %) shape memory alloy (SMA) and AISI SS316L are two commonly used materials for the biomedical orthopedic implant. The surface characteristics of the biomedical implants play a significant role in the biocompatibility. Apart from biological factors, the bone healing process strongly depends on the mechanical properties of the implant applied. In order to adapt the orthopedic implant, Ti-Ni SMAs and SS-316L based implants exhibit a variable middle piece was developed. Ti-Ni SMAs and SS316L based implants were manufactured by using wire electro-discharge machining (WEDM). WEDM of Ti49.4Ni50.6 and SS316L have been performed and various performance attributes such as surface topography, migration of materials, recast layer, micro-hardness and residual stresses of the machined components have been evaluated. The smooth surface with consistency suitable surface integrity parameters like less deposition of material, minimum recast layers thickness, consentaneous amount of surface hardness and less affecting subsurface residual stresses were found for Ti49.4Ni50.6 SMA. The Young’s modulus of Ti49.4Ni50.6 SMA (55.63 GPa) is low compared to SS316L (145.45 GPa), this results in a lower bending stiffness compared to SS316L. Shape recovery ability near wire electro-discharge machined surface has been investigated for Ti49.4Ni50.6 SMA from the biocompatible point of view. Heat treatment like annealing is found to be a most suitable process to recover shape memory effect of WEDMed samples.

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