title: Surface characterization of a decarburized and nitrided steel.
abstract: This article describes the effects of surface controlled decarburization on the structure of a nitrided steel. Samples of quenched and tempered 40CrMo4 steel were decarburized by air heat treatment (800-900 degrees C) at different depths and submitted to gaseous nitriding. The microstructure of surface layers after decarburization and nitriding were investigated by optical (OM) and scanning electron microscopy (SEM). The nitrogen and carbon profiles in the diffusion layers were determined by a scanning electron microscope equipped with a wavelength dispersive spectrometer (EPMA-WDS). The effect of nitriding was determined by microhardness measurements. The increasing of time and temperature of decarburization slightly affect the surface hardness values, while case hardness depths decrease. In all the specimens, the nitriding depth, as determined by the WDS nitrogen profile, is larger than the one determined by the hardness profile.
authors.affiliation: Department of Innovation in Mechanics and Management (DIMEG), University of Padova, Via Marzolo 9, IT-35131 Padova, Italy. irene.calliari@unipd.it
authors.forename: Irene
authors.initials: I
authors.lastname: Calliari
authors.forename: Manuele
authors.initials: M
authors.lastname: Dabalà
authors.forename: Marzia
authors.initials: M
authors.lastname: Zanesco
authors.forename: Enrico
authors.initials: E
authors.lastname: Bernardo
authors.forename: Filippo
authors.initials: F
authors.lastname: Olmi
authors.forename: Gloria
authors.initials: G
authors.lastname: Vagelli