Preparation and characterization of cBN-based composites from cBN-Ti3AlC2 mixtures

摘要

Cubic boron nitride (cBN)-based composites were prepared at similar to 5.5 GPa and similar to 1350 degrees C with different mass ratios of cBN-Ti3AlC2 mixtures as starting materials. Ti3AlC2 decomposed and reacted with cBN during high pressure and high temperature (HPHT) sintering. TiC, TiC0.7N0.3, TiB2, and AlN were then formed. The bending and compressive strengths of cBN-based composites first increased and then decreased when the Ti3AlC2 content increased from 5 wt.% to 40 wt.%; hardness was determined by both the compactness and binder content. cBNbased composites sintered with 20 wt.% Ti3AlC2 possessed the highest bending strength (422.45 MPa), compressive strength (3969.14 MPa), and hardness (3381.58 HV); they also had the most compact microstructure. The initial oxygenation temperature of the cBN-based composites sintered with 20 wt.% Ti3AlC2 was about 850 degrees C. After isothermal oxidation at 1200 degrees C for 1200 s, titanium and aluminum oxides formed on the surface with pores and cracks. The isothermal oxidation process of the cBN-based composites could be described by a parabolic law. (C) 2016 Elsevier B.V. All rights reserved.