Experimental Evidences of New Nitrogen-Containing Phases in Nitrided Steels (original) (raw)
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Surface analysis by GXRD and XPS in the austenitic steel DIN by nickel ions
Heliyon, 2020
The composition changes in the close to surface of the austenitic stainless steel DIN 1.4981 irradiated at high doses. Theoretical simulations using the SRIM-2013 program show that the damage due to Nickel cation [Ni 2þ ] ions irradiation of 3.66 MeV extends to up 2 μm deep in the steel under study. Then the applications of Grazing incidence X-ray Diffraction (GXRD) and X-ray Photoelectron Spectroscopy (XPS), Gallium cation [Ga 3þ ] ions sputtering assisted, were necessary to detect respectively, any compositional changes with the depth. GXRD differences were recorded in the intensity and it's Full Width at Half Maximum (FWHM), of the austenite (111) diffraction peak, at different depths in the Irradiate Zone (IZ). Through XPS was found that Nickel [Ni], Niobium [Nb], and Manganese [Mn] were depleted it is important to highlight Chromium [Cr], and Molybdenum [Mo] were improved at the irradiated surface; such behavior was contrary to the element migration under irradiation reported for austenitic stainless steels irradiated at low doses.
Microstructure of a Nitrided Steel Previously Decarburized
Journal of Materials Engineering and Performance, 2006
In this study the effects of a surface-controlled decarburization on the structure of a nitrided steel are analyzed. Samples of a quenched and tempered 42CrMo4 steel were decarburized by heating in air at different depths and submitted to gaseous nitriding. After decarburization and nitriding, the microstructure of surface layers was investigated by optical microscopy (OM) and scanning electron microscopy (SEM). The nitrogen and carbon profiles in the diffusion layers were determined by SEM equipped with a wavelength dispersive spectrometer (EPMA-WDS) and by glow discharge optical spectrometry (GDOS). The effect of nitriding was determined by microhardness measurements. Our results indicate that a previous decarburization only slightly affects the surface hardness, but reduces the conventional nitriding depth. The decarburization also favors the nitrogen take-up and produces increased nitrogen concentrations in the compound layer and in the narrow zone beneath it.
Influence of Surface Roughness on the Properties of Nitrided Layer on 42CrMo4 Steel
Materials
A crucial factor of a nitriding process of treated parts is surface roughness. Eight samples of 42CrMo4 steel were used to investigate the parameter represented by Ra. In the study, the innovative combined microhardness profiles were used to present results within the compound zone and diffusion layer. Therefore, two loads were applied in the compound zone, 5 gf, and diffusion layer, 500 gf. Observation with SEM and chemical analysis of the investigated samples showed a correlation between microstructure, nitrogen concentration and microhardness of the compound zone. XRD diffraction was used to identify the phase composition. Moreover, the X-ray photoelectron spectroscopy technique was also applied in the study. No distinct correlations between compound zone morphology and the Ra parameter were observed. The thickness value of the structure was constant and fluctuated around 20 µm in the vast majority of the examined cases. However, analysis of the results revealed a dependence betw...
Structural surface characterization of ion nitrided AISI 4340 steel
Materials & Design (1980-2015), 2012
In this work,AISI 4340 steel samples were plasma nitrided in a mixture of 50%N 2-50%H 2 process gas at 470°C temperatures for different nitriding times of 1, 4 and 8 h. Prior to nitriding, the specimens were normalized at 850°C for 30 min. Nitrided samples were characterized using optical microscopy (OM), scanning electron microscopy (SEM), X-Ray diffraction (XRD) and microhardness testing. The thickness of diffusion and compound layers was determined by using cross-sectional OM & SEM micrographs and microhardness profiles. Residual stresses in diffusion layers were determined using XRD g-method. The results showed that compound layers of 4.5-7 m thick consisting of Fe 4 N (γ) and Fe 2-3 N (ε) phases are formed on samples surface. The thickness of the diffusion layer increases from 90m to 240 m with increasing plasma nitriding time. The surface and cross-sectional hardness are also increased with increasing nitriding time and the maximum surface hardness of 750 HV obtained after 8 h plasma nitriding. All samples contain compressive residual stress and the highest compressive residual stress of 260 MPa is obtained for sample nitrided.
Surface and Coatings Technology, 1994
TiN coatings on metals are mainly used when good coating adhesion to the substrate material can be obtained. However, if the same treatment is carried out on different types of steel, marked differences in coating adhesion are observed. Thus, to optimize the coating adhesion, it is necessary to know what phases and contamination are present on the substrate prior the coating, and how these are affected by the deposition process. Implantation of nitrogen at doses ranging between 1 and 5 x 10" N+cmm2 is used to form the nitride in austenitic steels 304 and 310. Preliminary results are presented on the phases obtained with different plasma nitriding processes, measured using nuclear reaction analysis and X-ray diffraction techniques.
Surface Characterization of a Decarburized and Nitrided Steel
Microscopy and Microanalysis, 2006
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~800-9008C! 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.
Surface and Coatings Technology, 2002
Three types of steels with different Cr and Ni contents were ion nitrided by means of 100 Hz glow discharge in a N -H gas 2 2 mixture using a special reactor installed in the SAXS beamline of the National Synchrotron Light Laboratory (LNLS), Campinas, Brazil. The studied materials were austenitic (AISI 304 and DIN WNr 1.4882) and ferritic (SAE HNV3) steels. The experimental setup allowed the study of the structural evolution in situ and in real time of steel surfaces during the ion nitriding process itself, using the X-ray diffraction technique. The use of a well-collimated and intense X-ray beam of the synchrotron radiation source allowed successive short exposure diffraction patterns to be taken. A very fast ion nitriding process was verified for the three studied steels. The measurements concerning the nitriding kinetics of both austenitic steels indicated the formation of an S phase. Nevertheless, while in the AISI 304 steel, the S phase was later replaced by a compound layer of g9-Fe N, in the DIN WNr 4 1.4882 steel, the S phase remained until the end of the nitriding process. In both cases, CrN was formed during the process. Instead, in the ferritic SAE HNV3 steel, the S and CrN phases were not observed. ᮊ
Contribution to X-ray analysis of carbo-nitrided steel layers
Journal of Applied Crystallography, 2001
The non-destructive X-ray diffraction method is used to analyse carbo-nitrided steel layers after wear testing. These measurements are carried out on the two major phases of the material,i.e.the martensite and the retained austenite. Such measurements are particularly difficult for three reasons. First, strong gradients exist across the wear track. Second, the diffraction peaks obtained for the martensite are broadened, as a result of the overlap of different reflections of the tetragonal structure. Third, the studied material is multiphase. Its major phases are martensite and austenite, but it also contains carbide and nitride clusters, which lead to incoherent scattering of X-rays. A new quantitative phase analysis method is thus proposed to define the volume fractions of these different constituents of the material. This method accounts for the evolution of the background level during wear. A micro-mechanical model is then developed to process the diffraction peak positions obtai...
Journal of Materials Research and Technology, 2017
Plasma nitriding processes are widely used to improve surface properties of several steels and alloys. In this work, the formation of nitrides in the surface of plasma nitrided IF steels as a function of the temperature was investigated. Three cold-rolled IF steel plates were nitrided for 4 h after shot peening at three different temperatures: 450 • C, 475 • C, and 500 • C. The resultant nitrided layers were then characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Rietveld method, and hardness measurements. Through SEM images, it was possible to visualize two main sublayers: a compound layer and a diffusion zone. Through XRD, two phases were identified in the compound layer, which were-Fe 2-3 N and ␥-Fe 4 N. The diffusion zone presented a ferritic matrix with fine precipitates, possibly ␣-Fe 16 N 2. By Rietveld, the calculated quantity of ␥-Fe 4 N was 68 wt.% for the sample treated at 475 • C and 58 wt.% for the one treated at 500 • C. These values were consistent with the hardness measurements. Thus, it is suggested that higher nitriding temperatures facilitate the decreasing of ␥-Fe 4 N and, consequently, the increasing of-Fe 2-3 N in the compound layer.