Study On The Blade Materials Fabricated By The Solid-solution Ti(C,N)-based Cermets

The Ti（C,N）-based cermets are expected to partly replace the hard alloys to make blades as they have a high red hardness,a better resistance to high-temperature oxidation and an excellent self-lubricating performance.However,their potential applications in the field of cutting tools are restricted by low strength and toughness.The solid solution powders are synthesized with carbothermal-reduction and nitridation（CRN）method in this paper.（Ti,W,Mo,Nb,Ta）(C_0.7,N_0.3)-Co-Ni based solid solution cermet（SSA）and（Ti,W,Mo,Nb,Ta）(C_0.5,N_0.5)-Co-Ni based solid solution cermet（SSB）are fabricated by vacuum sintering using the solid solution powders.By controlling reduction temperature,time and atmosphere,carbon and nitrogen content,lattice constant and particle size of the solid solution powders will change.The sintering temperature and time play an important role in the mechanical properties,relative densities and the microstructure to SSA and SSB.The strengthening and toughening mechanisms have been researched as follow.1.（Ti,W,Mo,Nb,Ta）（C,N）solid solution has been synthesized by CRN at 1500℃for 3 hours in the nitrogen atmosphere of 2 KPa in pressure.And the particle size is around 200 nm,the carbon and nitrogen content are 9.6wt.%and 6.5wt.%,respectively.The solid solubility of Molybdenum,Tungsten,Tantalum,Niobium and other metal atoms in Ti（C,N）is in a difficult order of Ta≈Nb>W≈Mo.2.SSA is sintered at 1450℃for 1 hour in vacuum,while SSB is sintered at a temperature of 1350℃for 5 hours in vacuum.Compared with SSB,the relative density,flexural strength,hardness and fracture toughness of SSA have increased by 2.72%,11%,11.2%,10.5%,respectively.Both SSA and SSB contain white-core and grey-rim structure,while SSA contains more white-core and grey-rim structure,SSB contains more black-core and grey-rim structure.SSA and SSB both will be transgranular fractured and intergranular fractured.As sintering temperature and time increase,the grain sizes grow gradually.SSA and SSB will be intergranular fractured rather than transgranular fractured.Grain-boundary strengthening is the primary strengthening mechanism of SSA and SSB.Crack deflection,crack-bridging and fine grain mechanism correlate to cement toughness.Due to the higher relative density,finer grain and thinner rim,the strength and toughness of SSA are better than those of SSB.