Collaborative Impact of Cryo-Treated Cutting Tool and Hybrid Milling Environment Towards Improved Sustainable Milling of ASTM F2063 Ni55.6Ti44.4 Alloy

Abstract

Abstract Shape memory alloys are mainly used in medical devices and surgical implants due to their biocompatibility. Machining these alloys into intricate patterns can be challenging due to their poor thermal conductivity which could lead to a poor surface finish. The poor surface finish causes a release of toxic elements such as Nickel, leading to contact allergies and thus deteriorating its biocompatibility. Using the right cooling technology can help improve their machinability and overcome issues related to surface integrity. The current study investigates the effect of milling parameters (cutting-speed, feed rate, and depth of cut) and different cooling strategies (flood coolant, cryogenic liquid nitrogen, and a hybrid approach) on the surface integrity of F2063 Ni55.6Ti44.4 shape memory alloy. In addition, the effect of cryogenically treating the cutting tool for further enhancement of surface finish was investigated. A considerable modification on the milled surfaces was observed when using the hybrid cooling/milling approach and cryo-treated tools in terms of morphological, chemical compositional, crystallographic, and microhardness. In addition, this modified surface had a noticeably improved bioactivity due to enhanced hydrophobicity (with contact angle 92°) and surface topography (Ra: 341.69 nm), which favoured cell adhesion and proliferation. The results indicate that the modified Ni55.6Ti44.4 alloy surface might be adequate for use in medical applications.