The Preparation And Research On The Microstructure&Properties Of Ti（C,N）-based Cermets Based On Ni₃Al Binder Phase

This paper first reviews the present research of performance improvement measuresin Ti(C,N)-based cermets field from hard phase to binder phase, and then elicits theadvantages of intermetallic compound Ni3Al as a bonding phase in the cermetsapplications as while as describing some preparation methods of Ni3Al. The purpose andthe significance and main conten of the research are then proposed on this basis.In situsynthesis of Ni3Al powder by heating in vacuum is carried out and then the hard phase andother raw materials are mixed with Ni3Al by powder metallurgy process and vacuumsintering technique for preparing cermets. Finally Ni3Al powder and cermets sample areanalyzed and characterized of their phase,mechanical properties,microstructure andmicro-component.A complete single phase Ni3Al can be obained after mixing Ni, Al and little B rawmaterial powder with a tiny pressing of2MPa and heating at1000℃for90min.Bymechanical crushing and pulverizing powder Ni3Al can be got.Comparative study of microstructures and mechanical properties of TiC/Ni3Alcermets by two different methods show that the two different cermets having a core/rimstructure but different mechanical properties.Mo addition can improve the wettability ofTiC and Ni3Al and optimize mechanical properties.Ti(C,N)-based cermets by adding different single Ni3Al binder are studied and theirmicrostructure and mechanical properties are compared to the same components but withsingle Ni binder phase.The results show that with the increasing of Ni3Al content, theoverall trend of hardness and bending strength are inversely related but with good fracturetoughness.Cermets with Ni3Al content at about30wt%have both relatively goodperformance and microstructure and the main mechanical properties at this time are:bending strength is1045±80MPa, Rockwell hardness is HRA89.7±0.25, KICis14.26MPa·m1/2.Mechanical properties and microstructure of cermets by adding different Ni/Ni3Alranging from0.6-7are studied and compared to the same components but with Ni binderphase. The results show that when the mass ratio of Ni and Ni3Al is3, cermets show the most uniform microstructure and smallest grain size.At this time bending strength is up to1630±20MPa, Rockwell hardness is up to HRA89.7±0.2, and fracture toughness KICisup to15.07MPa·m1/2. It is much better than Ti(C,N)-based cermet with Ni binder phaseprepared using the same raw materials and procedure.