Effect of the Si Additions on the Mechanical Behaviour and High-Temperature Performance of Hydrogen Sintered 434L Stainless Steels

摘要

Non-commercial, 434L ferritic stainless steel powders prealloyed with 2% of Si wereuniaxially compacted at 700 MPa and sintered in 100% H2 atmosphere for 30 min at three differenttemperatures (1225, 1250 and 1275 °C). For comparison, standard, commercial 434L powders weresintered in the same conditions, and 434L+2%Si powders were also sintered in vacuum. Theporosity and grain size of the 9 sintered stainless steels were measured by image analysis methods.Tensile strength and Vickers hardness tests show that the steels with 2% of Si exhibit highermechanical properties. Oxidation tests were carried out in air at 800 and 900 °C. H2-sintered 434Lsteels prealloyed with Si exhibit higher weight gains per unit of apparent surface than 434L steelssintered in the same conditions, due to the higher porosity of the former. The sintering atmosphereaffects the nature and morphology of the scales observed by XRD and SEM. Vacuum sintering of434L+2%Si stainless steels promotes the formation of more protective scales and lower mass gains(for identical porosity volume) than H2 sintering.