Fabrication of a novel Al 2 O 3 -Ti(C 0.7 N 0.3 )-cBN composite with excellent performance in the turning of difficult-to-machine stellite alloys

A novel Al2O3-Ti(C0.7N0.3)-cBN composite was designed and prepared for the first time by hot pressing. The addition of cBN was found to be very effective in simultaneously enhancing the hardness and toughness of the Al2O3-Ti(C0.7N0.3) ceramics. The optimum cBN content of the Al2O3-Ti(C0.7N0.3)-cBN composite was determined to be 5 vol%. The optimal properties were achieved by sintering at 1400 degrees C for 20 min under 40 MPa , and the Vickers hardness, bending strength, and fracture toughness were 20 GPa, 548 MPa, and 5.3 MPa m(1/2), respectively. When turning stellite 3 using the Al2O3-Ti(C0.7N0.3)-cBN insert, the longest cutting length achieved at a cutting speed of 117 m/min was 5122 m, 73% and 45% longer than those of the Al2O3-Ti(C0.7N0.3) and commercial A66N inserts, respectively. This indicates that the Al2O3-Ti(C0.7N0.3)-cBN composite is a promising tool material for the turning of stellite alloys.