Sintering process of M2-H$S feedstock reinforced with carbides

摘要

Metal matrix composites (MMCs) based on M2 HSS (High Speed Steel) are processed using a metal injection moulding route. Different types of reinforcement are added to the mixture and the effect in the sintering behaviour has been analysed. An optimised feedstock of M2 with carbides based on polyethylene and paraffin wax has been designed. The mixing procedure and the moulding conditions have been optimised to obtain parts without defects. A debinding schedule of thermal treatment has been established to partially eliminate the binder in order to promote the presence of some residual carbon into the parts. Finally, the sintering was studied under N2-H2 atmosphere. Density and microhardness measurements and SEM microstructures were used to determine the optimum sintering temperature and the sintering window of each system. This research has demonstrated that the addition of carbides produces an important reduction in the sintering temperature. Grain growth and coarsening of the grains are inhibited by the effect of the addition of the reinforcements. Although the addition of carbides reveals some general secondary effects in both cases, the addition of different reinforcement shows particular effects depending on which reinforcement is used. The mixture of carbides (WC+TiC+TaC+NbC) produces an important enlargement of the sintering window and the addition of VC produces an important reduction in the optimum sintering temperature.