Development and machinability evaluation of MgO doped Y-ZTA ceramic inserts for high-speed machining of steel

In current high productivity manufacturing era, it is necessary to develop non-conventional newer tool materials. Here, an attempt has been made for developing MgO doped zirconia-toughened alumina (Mg-ZTA) using powder metallurgy process route. The 3 mol% yttria stabilized zirconia (YSZ) (10 wt%), alumina (Al2O3) (90 wt%) with varying percentage of magnesium oxide (MgO) (0-1 wt%) are mixed to study the phase transformation and uniaxially pressed into square inserts with 0.8 mm nose radius and sintered at 1,600oC for 1 h in pressure less condition. The maximum hardness of 17.04 GPa, fracture toughness of 5.09 MPa m(1/2) and flexural strength of 502 MPa, respectively, has been reached at 0.6 wt% of MgO due to more metastable tetragonal phase. The performance of the insert has been evaluated by machining AISI 4340 steel (radius 75 mm) in lathe. The performance with respect to flank wear, cutting force and surface roughness is quite impressive at different cutting speed even after 20 min of machining. It can be inferred that MgO doped ZTA insert can be used for medium to high-speed machining in current manufacturing scenario and is very promising to replace carbide or coated carbide inserts in coming days.