Influência de diferentes preparações de aresta de corte de um inserto de Al2O3-MgO no torneamento de um aço endurecido

Abstract

The cutting edge geometry has a great influence on the temperatures and forces developed during metal cutting processes, as well as on tool life. Aiming at obtaining high quality components and high productivity, proper edge preparation is essential. Within this context, the applicability of Al2O3-MgO ceramic cutting inserts with different edge geometries was investigated in hard turning. Such brittle materials must have a resistant edge to resist the impact without breaking. As it is a recently developed material and there is no information available, this work serves as a first investigation on this topic and has the goal of determining the most appropriate edge preparation regarding tool life and workpiece surface quality. For this, cutting inserts of the mentioned material had their edges prepared with four different geometries through grinding process and were applied with constant parameters in turning of hardened AISI 4140 steel (50 HRC). To analyze wear types and mechanisms, the used tools were observed in an optical microscope. From the obtained results, it was verified that the microgeometry with form factor K = 2 was the most effective in terms of tool life. In contrast, the insert with a single chamfer machined lower material volumes and fractured at the end of the tests. Tools with K = 1 and unprepared cutting edge allowed the machining of intermediate volumes. Regarding tool wear mechanisms, abrasion, adhesion, and chipping were predominant, in addition to tool breakage, which occurred in 75% of the experiments. Furthermore, in all cases, increased tool wear led to increased surface roughness, due to possible variations in microgeometry.