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The resistance to chloride-induced stress corrosion cracking was investigated on a high-strength CrNiMnMoN austenitic stainless steel in the hot-rolled and in different cold-drawn states. The resistance against chloride-induced stress corrosion cracking was determined by slow strain rate tests in different chloride containing solutions at elevated temperatures. A fracture analysis was carried out using scanning electron microscopy. Improved resistance is obtained by the formation of deformation-induced twins. In addition, synchrotron X-ray diffraction measurements show full austenite stability during all cold-drawing steps. [ABSTRACT FROM AUTHOR]

Material selection for thermal cracking processes of anthropogenic resources is challenging. H2S and HCl are formed, and corrosion occurs at high temperatures. Several steels were investigated in the past. In all cases, corrosion layers were characteristically structured. On top, large chromium sulfide crystals are located, followed by a Cr2O3 layer, followed by a layer enriched in chlorine and nickel. In this paper, we propose a model on the course of the corrosion reactions. By considering the water-gas shift reaction as well as the influence of H2S, the layer formation can be explained. As an example S31400, 240 h corrosion time at 680 °C was chosen. [ABSTRACT FROM AUTHOR]

The effects of gaseous hydrogen chloride and hydrogen sulphide on the high‐temperature corrosion of the austenitic SS. S31400 and the duplex steel S32205 were investigated in an atmosphere without molecular O2. The testing gas atmosphere consisted of 3.8 vol% HCl, 1.9 vol% CO2, 0.3 vol% CO, 2.8 vol% H2, 0.02 vol% H2S, bal. N2. It showed a similar composition, which is present in the thermal cracking of anthropogenic resources. Tests were performed between 480 and 680 °C for 1, 3 and 10 days. Mass loss measurements were done for all experiments. After the reaction times the samples showed non‐adherent and porous layers of corrosion products, which were investigated by SEM/EDX and XRD. Metallographic cross sections of the corroded samples were prepared by water‐free polishing to investigate the microstructure of the corrosion products. Both materials formed large chromium sulphide crystals on top of a chromium oxide layer and a chlorine‐containing layer beneath the oxide. The ferrite phase of the duplex steel is selectively attacked, while the austenite phase remained without severe corrosion. Steel S31400 showed a uniform corrosion. [ABSTRACT FROM AUTHOR]

A new high-nitrogen austenitic stainless steel with excellent mechanical properties was tested for its resistance to stress corrosion cracking. The new conventional produced hybrid CrNiMnMoN stainless steel combines the excellent mechanical properties of CrMnN stainless steels with the good corrosion properties of CrNiMo stainless steels. Possible applications of such a high-strength material are wires in maritime environments. In principle, the material can come into direct contact with high chloride solutions as well as low pH containing media. The resistance against chloride-induced stress corrosion cracking was determined by slow strain rate tests and constant load tests in different chloride-containing solutions at elevated temperatures. Resistance to hydrogen-induced stress corrosion cracking was investigated by precharging and ongoing in-situ hydrogen charging in both slow strain rate test and constant load test. The hydrogen charging was carried out by cathodic charging in 3.5 wt.% NaCl solution with addition of 1 g/L thiourea as corrosion inhibitor and recombination inhibitor to ensure hydrogen absorption with negligible corrosive attack. Slow strain rate tests only lead to hydrogen induced stress corrosion cracking by in-situ charging, which leads to total hydrogen contents of more than 10 wt.-ppm and not by precharging alone. Excellent resistance to chloride-induced stress corrosion cracking in 43 wt.% CaCl2 at 120 °C and in 5 wt.% NaCl buffered pH 3.5 solution at 80 °C is obtained for the investigated austenitic stainless steel. [ABSTRACT FROM AUTHOR]

Austenitic stainless steel 1.4435, a candidate material for high-pressure tubing for hydrogen applications, was investigated in two different stages of cold deformation (0 and 27 %) regarding its hydrogen embrittlement tendency. The determination of effective diffusion coefficients revealed slightly increased diffusion kinetics at 60°C for the cold-reduced material (8.0 · 10−15 m²/s) compared to the solution annealed one (5.0 · 10−15 m²/s). High-pressure gaseous hydrogen charging shows no differences regarding the degree of cold deformation with a maximum hydrogen concentration of 112 wt.-ppm. Furthermore, a significant ductility loss expressed by the ratio of the reduction of area was observed. • Cold drawn material shows enhanced diffusion kinetics than solution annealed state. • Hydrogen contents of up to 112 wt.-ppm are present after gaseous charging. • No failure occurred in constant load tests at 90 % of the yield strength. • SSRTs show no significant decrease in fracture elongation due to hydrogen charging. • 1.4435 is applicable for hydrogen tank systems within the tested conditions. [ABSTRACT FROM AUTHOR]

• High temperature corrosion of austenitic steel and nickel based alloy in HCl and H 2 S atmosphere. • Layered structure of the corrosion products was observed. • Corrosion behavior of materials changed when going to lower temperatures. • Supporting effect of nickel on corrosion resistance could not be observed at lower temperatures. In this paper the corrosion behavior of high temperature corrosion resistant alloys is investigated in a gas atmosphere containing HCl and H 2 S at 480 °C and 680 °C. By considering the vapor pressures of the metal chlorides and the water gas shift reaction, as well as the influence of H 2 S, the different corrosion behavior at 480 °C compared to 680 °C can be explained and a model of the course of corrosion is proposed. Corrosion tests were performed for 240 h with the austenitic stainless steels S31400 (20 wt% Ni) and N08811 (30.4 wt% Ni) and with the Ni-based alloy N06600 (72.5 wt% Ni). It could be shown that with increasing Ni-content in the alloy, the corrosion rate at high temperatures decreased, but this effect could no longer be observed at lower temperatures. While for N08811 and N06600 the mass loss was lower at 680 °C, it increased at temperatures of 480 °C. In the case of S31400 the mass loss increased with rising temperature. [ABSTRACT FROM AUTHOR]

Hydrogen uptake and embrittlement characteristics of a cold-drawn austenitic stainless steel wire were investigated. Slow strain rate testing and fracture surface analysis were applied to determine the hydrogen embrittlement resistance, providing an apparent decrease in resistance to hydrogen embrittlement for a 50% degree of cold deformation. The hydrogen content was assessed by thermal desorption and laser-induced breakdown spectroscopy establishing a correlation between the total absorbed hydrogen and the intensity of near-surface hydrogen. The sub-surface hydrogen content of the hot-rolled specimen was determined to be 791 wt.ppm. • TDS combined with LIBS was applied to quantify H-diffusion profiles. • Critical hydrogen concentrations for brittle fracture were obtained. • The degree of cold-drawing was correlated to hydrogen-induced damage. [ABSTRACT FROM AUTHOR]