Growth kinetics of cubic carbide free layers in graded cemented carbides

Liu-yong Shi1,2), Yi-min Liu1), Ji-hua Huang1), Shou-quan Zhang3), and Xing-ke Zhao1) 1) School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China 2) College of Mechanical and Electrical engineering, Hainan University, Danzhou 571737, China 3) Xiamen Golden Egret Special Alloy Co. Ltd., Xiamen 361006, China

摘 要：In order to reveal the formation mechanism of cubic carbide free layers （CCFL）, graded cemented carbides with CCFL in the surface zone were fabricated by a one-step sintering procedure in vacuum, and the analysis on microstructure and element distribution were performed by scanning electron microscopy （SEM） and electron probe micro-analyzer （EPMA）, respectively. A new physical model and kinetic equation were established based on experimental results. Being different from previous models, this model suggests that nitrogen diffusion outward is only considered as an induction factor, and the diffusion of titanium through liquid phase plays a dominative role. The driving force of diffusion is expressed as the differential value between nitrogen partial pressure and nitrogen equilibrium pressure essentially. Simulation results by the kinetic equation are in good agreement with experimental values, and the effect of process parameters on the growth kinetics of CCFL can also be explained reasonably by the current model.

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