Estimation of adhesion energy of alumina scales on FeCrAl alloys: effect of the TiO

In this experimental work, the effect of sol-gel TiO2 coating on adhesion energy of alumina scales formed on FeCrAl alloys was investigated. The adhesion energy was evaluated by means of a tensile test in the SEM chamber for the samples oxidized in air at 850 and 950°C during 72 h. In addition, the spallation rate of alumina scales was studied as a function of the imposed longitudinal strain

Estimation of adhesion energy of alumina scales on FeCrAl alloys: effect of the TiO2 sol-gel coating

In this experimental work, the effect of sol-gel TiO2 coating on adhesion energy of alumina scales formed on FeCrAl alloys was investigated. The adhesion energy was evaluated by means of a tensile test in the SEM chamber for the samples oxidized in air at 850 and 950°C during 72 h. In addition, the spallation rate of alumina scales was studied as a function of the imposed longitudinal strain

Growth kinetics of the compound layers: Effect of the nitriding potential

AbstractThe aim of this work is to study the effect of the nitriding potential on development of the compound layers during the gas nitriding of Armco Fe and XC38 carbon steel. The gas nitriding experiments were realized in an atmosphere of partially dissociated gas ammonia (NH3) at 520∘C under a variable nitriding potential (from 0.25 to 3.5atm−0.5) for 2 h.Using XRD analysis and SEM observations of the cross-sections of the treated samples, it was shown that the compound layer was composed of γ′ iron nitride after exceeding a critical value of the nitriding potential that depends on the substrate’s nature. A linear semi-logarithmic relationship relating the nitriding potential to the experimentally measured layer thickness for the γ′ phase was used to evaluate the critical nitriding potential giving rise to its formation on the material substrate. It was found that the required value of the critical nitriding potential for XC steel is greater than that of Armco iron

Surface Characterization of a Nitrided Low Alloy Steel

The 32CrMoV13 low alloy steel was gas nitrided at 550°C, for three time durations (6.5, 13 and 20 h) and under a variable nitriding potential (1, 2.2 and 6 atm-0.5). The generated nitride layers were characterized by SEM observations, XRD and GDOS analyses as well as microhardness testing. The XRD analysis indicates that the compound layer was composed of and iron nitrides and CrN phase. The surface hardness (inside the compound layer) was found to be dependent on the nitriding potential value, its value increases as rises. It was shown by GDOS analysis that the upper and lower nitrogen concentrations at the (compound layer / diffusion zone) interface are approximatively: 4 and 0.88 wt. % N, respectively.</jats:p

Determination of the Diffusion Coefficients of Boron in the FeB and Fe₂B Layers Formed on AISI D2 Steel

In the present work, a diffusion model was applied to estimate the boron diffusion coefficients in the FeB and Fe₂B layers during the pack-boriding of AISI D2 steel in the temperature range of 1223-1323 K during a variable exposure time between 1 and 8 h. The mass balance equations were formulated at each growing interface by considering the effect of boride incubation times. The estimated values of boron activation energies in the FeB and Fe₂B layers were compared with the literature data. Validation of the present model was made by comparing the experimental thickness of each boride layer, taken from the literature data, with the predicted values. In addition, a simple equation was suggested to estimate the required time to obtain a single Fe₂B layer by diffusion annealing