Machining and mechanical characterisation of PM materials for valve seat inserts

This article shows some fabrication aspects related to the obtention of sintered valve seat insert. This insert was made of a mixture of high-speed steel powders and iron powders plus NbC. This is a new development aiming the substitution of Co alloys currently used for valve seat inserts. The physical properties, mechanical properties and machining behaviour are discussed. The machining characteristics in terms of tool wear, cutting forces and chips morphology of the insert was compared to available commercial insert. The machining results indicate that the material under development has potential for commercial application and shows good machining evidences, in terms of equivalent cutting forces for ceramic tool. In addition, the machining using hard metal tool was susceptible to hardness variation observed for the material under development. Therefore, the machining tests point out the necessity for a microstructure homogenisation of the obtained material.