Fatigue behaviour of sintered stainless steels with different level of porosity
Sintered components are gaining more and more applications, their success towards the most traditional technologies is due to the possibility of low cost manufacturing of parts having complicated shape coupled with restricted tolerances, to the very high yield of the utilisation (>95 %) of the raw material, as well as to the availability of a large choice of powders with a wide range of chemical composition. The use of structural sintered parts under cyclic loading conditions is now a day very important and is stimulating an intense research activity to well understand the influence of the porosity on the performances of sintered components and to improve their fatigue behaviour. From this point of view, the control of the level and of the shape of pores is very important, because the morphology of the porosity controls the opening and the propagation of fatigue cracks. It is possible to improve the fatigue life through the sintering process, as well as by means of suitable heat treatments. The wide range of available compositions of alloyed iron powders allows the design and the manufacturing of parts having very high performances and among the different materials stainless steels occupy a prominent position. However, porosity, beside the mechanical properties, tends to reduce their corrosion resistance properties too and many efforts are in course in order to reduce the porosity level of sintered stainless steels.