Production of NiAl-matrix composites by reactive sintering

This work was devoted to the development of NiAl-matrix composite and its production by reactive sintering powder metallurgy. Various types of reinforcement (aluminium oxide, silicon and tungsten carbides, titanium silicide) were tested. The best chemical compatibility and the highest hardness and wear resistance were achieved by Al2O3 fibres. Electroless nickel plating pretreatment of Al2O3 fibres improves both distribution of fibres and hardness of the composite. However, it strongly reduces the wear resistance, probably due to phosphorus content in the nickel coating. In situ formation of NiAl-Al2O3 composites by reactive sintering of a pressed powder mixture of Ni, Al and NiO was unsuccessful. Only a small amount of cubic gamma-Al2O3 was detected after reactive sintering and hence no significant hardness increase was observed.