A new fracture-resistant binder phase for use with AlMgB_(14) and other ultra-hard ceramics

摘要

A new ductile binder phase alloy, Co-17 at. percent Mn, has been developed for producing cermet composite cutting tools using ultra-hard AlMgB_(14) grit. Metallography, X-ray diffraction, tensile test, and recrystallization studies indicate that the Co-17 at. percent Mn alloy has a two-phase (FCC/HCP) structure with an ultimate tensile strength of 670 MPa and 40 percent elongation. The recrystallization temperature is approximately 620 deg C. The plane strain fracture toughness (K_(IC)) for AlMgB_(14) was estimated using the Palmquist method, both with and without the Co-Mn binder phase alloy. Results show that the fracture toughness of the monolithic boride without binder ranges from 3 to 4 MPa √m, which is increased to 7-9 MPa √m upon addition of the binder. The high ductility and tensile strength of the Co-Mn solid solution alloy, combined with its excellent wettability on boron-based compounds is expected to make this binder composition compatible with other boride ceramics.