Tungsten carbide micro-tool wear when micro milling UNS S32205 duplex stainless steel

Abstract

In conventional machining operations, tool wear is an important aspect of machining with many relevant discussions in the literature. However, in the micromachining process, very little is known about tool wear and wear mechanism compared to conventional machining. Some considerations for tool wear from a macro machining point-of-view may not be valid for micromachining processes because of reduced geometry of the tools and the so called size effect, which affects the kinematics of micromachining and chip formation mechanism. A small wear land on a micro-tool can eliminate half of its edges, and could double the size of the shear force at the other edges of the tool. Therefore, it is necessary to discuss the types of wear and their mechanisms for tools used in micromachining to characterize end-of-life criteria. In this sense, the main goal of this work is to analyze the evolution of wear land of a carbide micro-mill tool when cutting UNS S32205 duplex stainless steel. Experiments were performed to produce micro channels using a 3-axis CNC micro milling machine and TiN coated tungsten carbide tools with diameter 0.381 mm. Previous experiments were performed in order to choose the most appropriate cutting conditions for the evaluation of tool wear. The tools were examined before and after each experiment using a scanning electron microscope. The results show that the major forms of wear encountered during machining are nose and flank face wear, with adhesion being the most clearly observed wear mechanism. The wear land as a function of machined length showed similar behavior to macro machining operations with three defined regions of wear. Taylor's tool life equation was obtained and the resultant coefficients are similar to results from literature for macro machining operations.