Microstructure and Mechanical Properties of CrN-Based Composites with the Combined Addition of ZrO_2(3Y) and Al_2O_3

摘要

Chromium nitride (CrN) powder consisting of granular particles of approx 2 mu m has been prepared by self-propagating high-temperature synthesis (SHS). SHS was conducted under a nitrogen pressure of 12MPa using commercially available Cr powder. Dense monolithic CrN ceramics and CrN-based composites with the combined addition of 70 vol percent ZrO_2(3Y)/30 vol percent Al_2O_3 have been fabricated by hot isostatic pressing for 7.2ks at 1573K and 196MPa. The former ceramics composed of pure CrN (approx 9.8 mum) exhibit a bending strength (sigma_b) of 400 MPa and a fracture toughness (K_(IC)) of 3.3 Mpa centre dot m~(1/2). In the latter composites almost all the ZrO_2(3Y)(0.1-0.2 mum) and Al_2O_3(0.3-0.6 mu m) grains are located at the grain boundaries of CrN (2-3mum). The high values of sigma_b (1090MPa) and K_(Ic)(5.0Mpa centre dot m~(1/2)) are obtained in the composites with 40 vol percent combined addition.