RETRACTED ARTICLE: Experimental and simulation studies on grain growth in TiC and WC-based cermets during liquid phase sintering

Abstract

The grain growth behaviors of TiC and WC particles in TiC-Ni, TiC-Mo2C-Ni, WC-Co and WC-VC-Co alloys during liquid phase sintering were investigated for different Ni or Co contents and compared with the results of Monte Carlo simulations. In the experimental study, TiC-Ni and WC-Co alloys had a maximum grain size at a certain liquid volume fraction, while the grain size in TiC-Mo2C-Ni and WC-VC-Co alloys increased monotonically with an increasing liquid volume fraction. These results mean that the grain growth of these alloys cannot be explained by the conventional mechanisms for Ostwald ripening, namely diffusion or reaction controlled processes. Monte Carlo simulations with different energy relationships between solidliquid interfaces predicted the effect of the liquid volume fraction on grain size similar to the experimental results. The contiguous boundaries between solid (carbide) particles appear to influence the grain growth behavior in TiC-and WC-based alloys during liquid phase sintering.Keywords : cemented carbides, cermets, tungsten carbide, titanium carbide, grain growth, simulation, Monte Carlo method, liquid phase sintering, Ostwald ripening ~TRODUCTIONIt is well known that many systems in ceramics and cermets can be densified by liquid phase sintering [1,2] and the mechanical properties of these materials are strongly affected by the microstmcture, especially the grain size. It is therefore very important to understand the grain growth behavior and its mechanism in order to produce high-performance materials. The grain growth of a solid phase in a liquid phase via a solution-reprecipitation process is called Ostwald ripening, and has often been studied from a theoretical viewpoint [3][4][5].TiC-and WC-based cermets that are widely used as cutting tool materials are fabricated by liquid phase sintering. Grain growth of the carbide particles in these cermets during the sintering occurs by mass transport through a liquid phase. In previous studies on the grain growth of these cermets [6][7][8], an Ostwald ripening mechanism controlled either by diffusion or by a reaction process has often been proposed to explain the grain growth behavior. However, the grain growth mechanism in these cermets is not yet understood in detail yet, especially the effect of the liquid phase content. The classical theory of Ostwald ripening is not sufficient to explain the grain growth mechanism of these cermets, particularly when considering the small amount of liquid used to sinter materials for real applications.The present study examines the grain growth behavior in the presence of a liquid phase for TiC-Ni, WC-Co, TiCMo:C-Ni and WC-VC-Co alloys by varying the liquid phase content over a wide range. In addition to experiments, computer simulation using the Monte Carlo method was performed to examine grain growth in the presence of a liquid phase. Monte Carlo simulation of grain growth [9][10][11][12] is very useful for understanding the grain growth in complicated systems in which solid/liquid interfaces and solid/solid...

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