Effect of N2 Partial-Pressure Sintering Time on Ultrafine-Grained Ti(C,N)-Based Cermets
In view of the easy denitrification of the sintered body and the decomposition of N during the preparation of ultrafine-grained Ti(C,N)-based cermets by vacuum sintering,ultrafine-grained Ti(C,N)-based cermets are prepared by partial-pressure sintering with 130 Pa of nitrogen at 1 450℃ during the holding stage of the liquid phase,and the influence of the time of partial-pressure sintering under nitrogen on the microstructures and mechanical properties of cermets is investigated.The experimental results show that partial-pressure sintering under nitrogen can improve the uniformity of the internal structure of the sample.Under the influence of nitrogen,a Ni-rich layer will be formed in the outermost layer of the sample,and a TiN layer will be formed in the near-surface layer of the material.At the beginning of the partial pressure,the outermost layer of the sample is only the Ni-rich layer.With the increase in the partial pressure time,the black core phase in the near-surface layer of the organization dissolves under the influence of nitrogen,and the size of the black core phase decreases.The size of the annular phase increases until the black core phase gradually disappears,forming a Ti-rich(Ti,W)(C,N)solid solution,which is formed into the solid solution layer by merging the grown solid solution,As the partial-pressure time increases,the titanium-rich solid solution reacts with N to form a TiN layer in the near-surface layer of the sample.The comprehensive mechanical properties of the sample are the best when the partial-pressure sintering time reaches 40 min,and its bending strength increases by 20%to 2 350 MPa.The Vickers hardness increases by 13.9%to 1 635 HV30,and the fracture toughness is not significantly improved.
Ti(C,N)-based cermetspartial-pressure sintering under nitrogenmicrostructuremechanical propertiesnitriding layer
NETL
NSTL
万方数据
维普
