In situ formation of titanium carbide in titanium powder compacts by gas–solid reaction

Porous titanium compacts of fine and coarse sponge titanium powders were reacted with methane gas to produce Ti–TiC in situ composites. The kinetics of titanium carbide formation during the reaction were studied in relation to powder size, reaction temperature and time, and methane flow rate. The titanium carbide was initially formed as a layer around each titanium powder and the rate of formation was found to be diffusion-controlled. Titanium hydride was also formed during the reaction but was easily removed by post-vacuum annealing. A significant reduction of chlorine content in the compact also resulted during the processing. High temperature vacuum sintering could densify the reacted compacts to over 95% theoretical density and, at the same time, alter the layered titanium carbide phase into rounded particles. It was possible to produce fully dense titanium base composites containing up to 30 vol% by the present gas–solid reaction-based processing.