MICRO-MACHINING OF A BIO-COMPATIBLE MATERIAL FOR PROSTHESIS PRODUCTION: 99.9% PURITY TANTALUM

Abstract

During the last decades, micromilling has been widely researched for a wide variety of materials. However, the behavior of many materials has not yet been studied in the micro-machined area. Among these materials we can highlight those that have wide applications in industries such as aerospace, nuclear and biomedical. Within these last ones those biocompatible materials are the focus of this work. Thanks to its high melting point and its high resistance to corrosion, tantalum can have diverse applications in the above mentioned areas. In this paper we present the study of the cutting forces, mainly in the feed direction, and the acoustic emission in the micro-milling of 99.9 % purity tantalum with cemented carbide tools without coating and with two different coatings, (Ti,Al)N and DLC. The diameter of the tools was 500 µm, the cutting speed and the cutting depth of the test were kept constant with values of 63 m/min and 40 µm respectively, while 6 feed rates were in order to observe the influence of the critical undeformed chip thickness in the micro-milling operation. The recorded emission acoustic results allowed to identify the value of minimum chip thickness for each tool, while the power spectrum density results allowed to identify dominant frequencies of machining for different feeds per tooth. Regarding the feed force, it was possible to identify a minimum value for each tool as function of feed rate and the specific cutting force values showed the typical nonlinear behavior of the size effect. Keywords: micro-milling, tantalum, acoustic emission, cutting forces, specific cutting force.