Development and characterisation of high-speed steel matrix composites gradient materials

Powder metallurgy (P/M) offers the advantage to obtain a composite material with a high content of reinforcement and, consequently, with a big hardness as well as the possibility of changing the composition as a function of the requirements. The materials developed in this work are constituted by a high-speed steel (HSS) matrix core and composite materials with this matrix and gradient concentration of NbC reinforcement, from the core to the surface, through different steps. Composite powders of different content in NbC were produced through high energy milling in order to obtain the gradient composition. These powders were characterised in their morphology and microhardness. The materials were processed through conventional P/M techniques, pressing and sintering. The behaviour of the final materials was studied by means of the microhardness profile and bending strength, showing a high increment in this one by means of the gradient composition.