Study in durability of Cr₂O₃-based ceramic cutting tools

Abstract

The research was performed in the context of feasibility examinations of chromia application as cutting tool materials. In the paper, a study on the Cr2O3 –based ceramic cutting tools is presented from the perspective of structural features and durability under various machining parameters. Comparative analysis was performed using alumina-based ceramic cutting inserts. Microstructure was examined using scanning and transmission electron microscopy (SEM and TEM), LEO1455 VP (ZEISS) and MIRA3 TESCAN, respectively. It was found that Cr2O3 –based ceramic with AlN additions after electroconsolidation exhibited more fine structure with evenly distributed AlN inclusions and small amount of spherical pores, below 2%. The cutting durability tests were performed with both hardened NC11LV and non-hardened C45 (1.0503) steels, using multiedge cutting inserts of dimensions 14.75 mm × 14.75 mm × 4.75 mm, made of respective ceramics. The machine tool Mazak QTE was used for the tests, and the wear criterion was 0.4 mm notch wear value, assessed with Keyence microscope. It was demonstrated that a pure alumina cutting tool exhibited 3 times larger wear than Cr2O3–AlN one after 25 minutes of work. On the other hand, Cr2O3–AlN cutting edge reached the same wear rate at 175 m·min-1 as Al2O3 –based tools at just 50 m·min-1. For the same cutting speed of 150 m·min-1, the chromia-based ceramic insert worked over 30 minutes, two times longer than alumina ones. The increased wear resistance and durability can be attributed to the fine-dispersed structure obtained not only by certain proportion of components, but also by the electroconsolidation technique with specific parameters.