Kinetics of thermal dewaxing of injection‐molded silicon carbide

Abstract

Powder injection molding is a near-net shape, high-speed fabrication process that has been studied only lightly with silicon carbide (SiC) as the powder. The addition of nanoparticles to the monomodal powder to form a bimodal powder increases the solid fraction in the feedstock but may also adversely affect other properties. In this paper, the kinetic properties of thermally dewaxed SiC mono-and bimodal feedstocks by three models were compared to solvent-dewaxed SiC and thermally dewaxed powder metal from other studies. The activation energy E a of pyrolytic dewaxing was graphically estimated by the master dewaxing curve model as ~80 kJ/mol for monomodal and ~60 kJ/mol for bimodal SiC powder size distributions, a little higher than the ~50 kJ/mol by solvent dewaxing of the same compositions. The E a in the Flynn-Wall model was 64 kJ/mol for monomodal and 53 kJ/mol for bimodal. The E a was 49 kJ/ mol for monomodal and 42 kJ/mol for bimodal SiC powder by the Kissinger thermal analysis model. The lower E a of the bimodal feedstock was attributed to its increased nucleation sites. These results provide the basis for dewaxing models-part of the rate-limiting step in powder injection molding-for SiC powder-binder systems. K E Y W O R D Sactivation energy, dewaxing, kinetics, powder injection molding, silicon carbide 86 | CHINN et al. How to cite this article: Chinn RE, Enneti RK, Kate KH, Atre SV. Kinetics of thermal dewaxing of injection-molded silicon carbide. Int J Ceramic Eng Sci. 2019;1:85-91. https ://doi.