Growth kinetics of cubic carbide free layers in graded cemented carbides

Abstract

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.

Mineralogical Characteristics and Isothermal Oxidation Kinetics of Ironsand Pellets

“…For a long time, vanadium-titanium magnetite has been used as an essential raw material in sintering and pelletizing processes for ironmaking. The use of vanadium-titanium magnetite not only helps alleviate the crisis of iron ore resources [7][8][9], but also contributes to prolonging the furnace life due to the deposition of Ti(C x , N 1−x ) at the surface or crack of the firebricks on the hearth [10,11]. Therefore, the effective activation and utilization of vanadium-titanium magnetite in sintering and pelletizing processes are of interest.…”