Results of Cyclic-Strength Investigation of Developed Cutting Ceramic

The results of an investigation of the cyclic strength of cutting ceramics are presented: replaceable multifaceted insert, developed at NSTU, and VOK-60 cutting ceramic for working hardened steel piece made of KhVG steel (45 HRC) with two opposing grooves. Turning continued until the cutting edge of the plates was destroyed. A HITACHI S3400N electron microscope was used to investigate the structure of the destroyed surface layer; the mechanism effecting the destruction of the cutting edge of tool inserts made of cutting ceramics was determined. It was established that developed cutting ceramic has a higher resistance to fracture under conditions of intermittent turning of hardened steel compared to VOK-60 grade steel. Under intermittent turning conditions, the low performance of cutting inserts made of developed ceramic is mainly caused by chipping of the cutting edge due to the formation of microcracks at grain boundaries. A characteristic feature of the mechanism effecting brittle fracture of the cutting ceramic is intergranular extraction and chipping of large grains of Al 2 O 3 .