Microstructural Evolution and Densification of Co-Based Alloy Powder by Spark Plasma Sintering for High-Hardness Applications

This work presents the densification of Co-based alloy powders by a spark plasma sintering process. The densification process was carried out at a temperature range of 800 °C to 1100 °C in order to obtain sintered coupons and study their microstructure and mechanical properties. The shrinkage behaviour of the sintered coupons was studied, and an optimal densification temperature was defined. The microstructural analysis showed a reduction in porosity with temperature increment along with the development of a fine microstructure comprised of cobalt-molybdenum-chromium-silicon-based intermetallic laves phases, which are dispersed in a softer cobalt-based alloy matrix. X-diffraction analysis showed that these crystalline phases were well-dispersed, with a lattice parameter corresponding to a hexagonal system. The obtained high Vickers hardness values were attributed to the preservation of a fine microstructure and to the precipitation of Co-Mo phases. Three-point bending tests were performed in order to identify the strain path concerning the densification of the sintered coupons.