Microstructure and Wear Properties of a Low Carbon Bainitic Steel on Plasma Nitriding at Different N2-H2 Gas Mixtures

Abstract

For the first time, the influence of gas mixture on first damage resistance of a plasma nitrided DIN 18MnCrSiMo6-4 bainitic steel was investigated. Samples were nitrided at 500 °C with three different N 2 -H 2 gas mixtures, containing 5, 24, and 76 vol.% N 2 . Samples were characterized concerning the resulting roughness, microstructure, compound layer's phase composition, residual stresses in the diffusion zone, and surface hardness. Tribological ball-on-flat tests were carried out in reciprocal mode using zirconia as ball material for friction coefficient and the compound layer resistance until the first damage. The test results were evaluated statistically by analysis of variance (ANOVA). As the amount of nitrogen in the gas mixture decreases, the ε-Fe 2-3 (C)N content in the compound layer decreases. A γ'-Fe 4 N monophasic compound layer was achieved at 5 vol.% N 2 gas mixture. The diffusion zone as expected presented compressive residual stresses with the highest values near the surface. In the tribological tests, better results were obtained for 5 and 24 vol.% N 2 in the gas mixture as higher amounts of γ'-Fe 4 N were formed. The 76 vol.% N 2 gas mixture led to a brittle behavior, due to the biphasic compound layer (γ'-Fe 4 N and ε-Fe 2-3 (C)N) with a predominant content of ε-Fe 2-3 (C)N.

An investigation on the suitability of different welding recovery procedures for cold stamping punches in VF800AT steel

“…Interaction plots of the hardness in the regions of the weld metal, heat affected zone and base metal with the heat treatments were generated. The data was then submitted to an analysis of variance (ANOVA) [29,30], using the statistical program (SISVAR), following the Tukey'sb post hoc test [31], in order to evaluate the statistical significance of the experiments. To compare the means was used with a 4x3 factorial experimental design, with different repetitions and a confidence level of 95% (significance level of 0.05).…”

Plasma Electrolytic Nitrocarburizing of SAE 1045: Electro-chemical Slurry Erosion Wear Analysis

“…However, as expected, the surface hardness of the samples with the nitrocarburized layer has a substantially higher microhardness than the substrate. At the first measurement point (3 µm from the surface), the coating showed a maximum hardness of approximately 1040 HV, which is associated with the phases: ε -Fe 2 -3 N, γ' -Fe 4 N and Fe(Fe(C 9 N) 6 ) 3 detected in the XRD analysis (Figure 1C) 31,32 . As shown in Figure 1B, the coating has a thickness ranging from 16 µm to 25 µm.…”

“…Therefore, the presence of these phases suggests that the concentration of carbon and nitrogen in the surface layers was so high that it had exceeded the solubility limits of carbon and nitrogen in iron, forming this protective coating on the samples surfaces 30 . It is known that the formation of ε -Fe 2 -3 N makes it possible to increase the hardness of the coating formed and increase the wear resistance 31,32 . It should be noted that in other works involving nitrocarburizing, carbon could be associated with the nitrides formed, generating the ε-Fe 2-3 (C,N) and γ'-Fe 4 (C,N) phases 33,34 .…”

Influence of the pressure on the interaction between stearic acid and Ar-O2 in inductively coupled radio frequency plasma

“…This contamination can hinder the efficiency of surface treatments. Even on a laboratory scale, the cleanness of the surface is mandatory to achieve the best thermochemical treatment performance [1]. During the cleaning processes, non-biodegradable or even toxic compounds are used, which can be harmful to the environment.…”