Development of powder metallurgy T42 high speed steel for structural applications

Water atomized T42 high speed steel powders have been processed by a powder metallurgy (PM) route in order to obtain a fully dense material suitable for valve seat inserts (VSI) in diesel engines. Two different heat treatments (isothermal annealing and multitempering) were designed leading to the targeted hardness value (50 HRC). Microstructural characterisation of the heat-treated material was carried out using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Fracture strength and fracture toughness have also been investigated. The wear behaviour was evaluated through pin-on-disc tests at service temperature (360 °C). The obtained results demonstrated the excellent wear resistance of the VSI material without severe wear of the countermaterial (valve).