Shinroku Saito

On the Sintering Process of the Cermets of TiC System

An apparatus for measuring the shrinkage of cermet in hydrogen atmosphere was designed, and was used successfully for following up the process of sintering. Also the close examinations under the optical and electron microscopes have added some useful informations. The results may be summarized in the following outline.1) The velocities of shrinkage under different conditions, and the mode of approaching to an equilibrium value at a certain temperature as well as the subsequent shrinkage by the repeated heating at higher temperatures have revealed that the sintering was governed mainly by temperature but not by holding time. It may, therefore, be concluded that the heating schedule of very short holding time at higher temperature is by far better than the usual one.2) Sintering started by the thermal diffusion of the materials along the contact surface between the particles which were pressed strongly by the forming process. The increase of the path of diffusion brought about of the decrease of the distance between the particles, and the shrinkage of the mass was observed. When the temperature was too high the perspiration of metal bonding was observed.3) Sintering by an instantaneous heating, i.e. so called flash sintering method showed no sign of grain growth.4) Observations under electron microscope have revealed that the rupture of TiC cermets occured in two ways, viz. trans-crystal and inter-crystal, according to tha heating temperature.

On the Numerical Solution of the One Dimentional Transiental Phenomena of Heat Conduction in a Furnace Wall

Since the heat conduction in a furnace wall may be regarded as a stochastic process, any boundary or initial condition may be represented by the sum of instantaneous heat sources coming out at the surface or inside of the wall with corresponding temperatures and phase differences.Therefore, if the probability function of an instantaneous heat source having unit temperature (θ=1), being in existence at the surface or inside of the wall in question, be calculated, the given condition at any point may easily be worked out by the process of simply multiplying the distribution function by the corresponding temperature and superposing the products taking into account of the phase difference and the variation of the temperature.This paper concerns mainly with the method of getting the probability distribution function mentioned above for the problems of one dimensional right angle coordinates, and the graphical and numerical methods were compared with those of Schmidt, Tanazawa and Takahashi.This process was also extended to the method of getting the distribution function of unit temperature at any point, making use of the solution of steady heat source problem, and to this end it was proved that the solution of steady boundary conditions may be used to get the corresponding distribution function of instantaneous heat source having unit temperature irrespective of the form of the expression, functional form, empirical form, or any other forms.

Studies on TiC-Co Cermets Sintered in a Hydrogen Molybdenum Furnace

The cermets of TIC-Ni system containing 5 to 30% metallic nickel as a bond were studied. As the technical processes of producing TiC-Co cermets apply almost unmodified to the present case, the authors have limited their attention mainly to the effects of the forming process and the sintering temperature. The compacting pressure, however, was increased to 6ton/cm2 as the higher pressure has proved to give the better results in the sintering shrinkage, and the transverse rupture strength of the sintered psecimens.The general trends which the TiC-Ni system showed in the process of production as well as in the properties of the finished products were found to be the same as in the case of the TiC-Co cermets. Although the former is easier to handle it is less resistive to aerial oxydation than the latter. The study of the micro-photographs of the specimens of TiC-Ni cermets revealed that the grain growth of TiC was accelerated considerably with the increasing Ni content, which is the cause that brings to the lower transverse rupture strength of the finished products.