TiC-reinforced 304L-stainless steel-matrix composites via reactive sintering

Stainless steel (304L) matrix composites reinforced with TiC particles were produced by reactive sintering. Powder blends were prepared from 304L, Ti and C (graphite) powders corresponding to composites consisting 304L, mixed 20, 30, 40, or 60 volume percent (v%) TiC particles along with monolithic 304L and TiC end members. Green compacts were produced from the composite powder blends by die pressing and the compacts were vacuum sintered at 1200 degreesC for 15 minutes. The influence of heating rate (2 and 15 degreesC/min) on the composite microstructure and hardness was examined. In general, the reactive sintered composites were porous, as the measured sintered densities decreased with increasing TiC content. Composites sintered at the slower heating rate were more dense than corresponding composites sintered at faster rate. This was attributed to the slower heating rate allowing more time for the evolution of impurities from the powder surfaces prior to the volatilization of these species at the onset of the SHS-type reaction. Although the composites were porous they were significantly harder than the relatively dense unreinforced monolithic 304L matrix.