“…2, the maximum Mo distribution peak near the surface can be attributed to the diffusion of Mo atoms from the matrix to the interface, gradually to the oxide layer through the grain boundary and precipitated phases, and from the oxide layer to the surface to form the continuous Mo-rich layer. Thus, a dense (Fe, Cr) 2 O 3 oxide layer with the Mo-rich oxide layer acts as a barrier to protect the matrix from further oxidation within short time periods, but the protective effect gradually diminishes for an extended period >5 h because of the shedding as noted in previous works 21, 22 .Figure 3The cross-sections morphology of the specimens after oxidation at 900 °C for 1, 3, and 5 h ( a – c ) and the SEM–EDS line profile ( d–f ).
…”
A combined experimental and first-principle study on the oxidation mechanism of super austenitic stainless steel S32654 at 900 °C for a short time period ( Super austenitic stainless steels S32654 are primarily used in applications where increased pitting and crevice corrosion resistances are required, such as marine and offshore applications, seawater handling systems, nuclear power plant condenser tubes, waste incineration systems, and chemical-processing equipment [1][2][3] . Their extensive use is because of their superior corrosion resistance, enhanced mechanical property, formability, and weldability 4, 5 . However, the high Mo and Cr concentrates in S32654 steels may promote the segregation of the elements and formation of precipitated phases such as σ, χ, and Laves phase 3, 6-8 . Recently, many reported investigations on S32654 mainly focused on the hot deformation behaviour, precipitation behaviour, and corrosion resistance [9][10][11] .In recent years, many studies have examined the high-temperature oxidation mechanism of the lower-Mo-content stainless steels [12][13][14][15][16] . Yun et al. 13 examined the effect of Mo on the oxidation resistance of Fe-22Cr-0.5Mn ferritic stainless steel at 800 °C and confirmed that the lower Mo addition (<4 wt.%) effectively enhanced the oxidation stability at the initial oxidation stage up to 300 h. Buscail et al. 14 demonstrated that Mo could restrain the outward diffusion of Fe and decrease the growth rate of the oxide layer, which enhanced the oxidation stability of the AISI 316 L stainless steel at 900 °C. Mo contents below 3 wt.% in the ferritic stainless steel could reduce the absorption of O 2 , prevent the outward diffusion of the metal cations and inward diffusion of anions, and enhance the oxidation resistance 16 . Furthermore, alloys with high Mo contents sustain the heavy oxidation at high temperatures because of the formation of volatile MoO 3 species [17][18][19][20] investigated the effect of Mo on the oxidation behaviour of AISI 304 and discovered that Mo could accelerate the oxidation rate because the evaporation of volatile MoO 3 damaged the Cr 2 O 3 layer. However, for high-Mo-content austenitic stainless steels such as S32654 steels, the effect of Mo on the high-temperature oxidation behaviour is inadequate. Therefore, the investigation on the high-temperature oxidation behaviour of S32654 steels is useful.Moreover, our previous work 21 mainly investigated the oxidation behaviour of S32654 steels at 900 °C, 1000 °C, and 1200 °C in air. At 900 °C, the samples exhibit excellent oxidation resistance because the MnMoO 4 layer and
“…2, the maximum Mo distribution peak near the surface can be attributed to the diffusion of Mo atoms from the matrix to the interface, gradually to the oxide layer through the grain boundary and precipitated phases, and from the oxide layer to the surface to form the continuous Mo-rich layer. Thus, a dense (Fe, Cr) 2 O 3 oxide layer with the Mo-rich oxide layer acts as a barrier to protect the matrix from further oxidation within short time periods, but the protective effect gradually diminishes for an extended period >5 h because of the shedding as noted in previous works 21, 22 .Figure 3The cross-sections morphology of the specimens after oxidation at 900 °C for 1, 3, and 5 h ( a – c ) and the SEM–EDS line profile ( d–f ).
…”
A combined experimental and first-principle study on the oxidation mechanism of super austenitic stainless steel S32654 at 900 °C for a short time period ( Super austenitic stainless steels S32654 are primarily used in applications where increased pitting and crevice corrosion resistances are required, such as marine and offshore applications, seawater handling systems, nuclear power plant condenser tubes, waste incineration systems, and chemical-processing equipment [1][2][3] . Their extensive use is because of their superior corrosion resistance, enhanced mechanical property, formability, and weldability 4, 5 . However, the high Mo and Cr concentrates in S32654 steels may promote the segregation of the elements and formation of precipitated phases such as σ, χ, and Laves phase 3, 6-8 . Recently, many reported investigations on S32654 mainly focused on the hot deformation behaviour, precipitation behaviour, and corrosion resistance [9][10][11] .In recent years, many studies have examined the high-temperature oxidation mechanism of the lower-Mo-content stainless steels [12][13][14][15][16] . Yun et al. 13 examined the effect of Mo on the oxidation resistance of Fe-22Cr-0.5Mn ferritic stainless steel at 800 °C and confirmed that the lower Mo addition (<4 wt.%) effectively enhanced the oxidation stability at the initial oxidation stage up to 300 h. Buscail et al. 14 demonstrated that Mo could restrain the outward diffusion of Fe and decrease the growth rate of the oxide layer, which enhanced the oxidation stability of the AISI 316 L stainless steel at 900 °C. Mo contents below 3 wt.% in the ferritic stainless steel could reduce the absorption of O 2 , prevent the outward diffusion of the metal cations and inward diffusion of anions, and enhance the oxidation resistance 16 . Furthermore, alloys with high Mo contents sustain the heavy oxidation at high temperatures because of the formation of volatile MoO 3 species [17][18][19][20] investigated the effect of Mo on the oxidation behaviour of AISI 304 and discovered that Mo could accelerate the oxidation rate because the evaporation of volatile MoO 3 damaged the Cr 2 O 3 layer. However, for high-Mo-content austenitic stainless steels such as S32654 steels, the effect of Mo on the high-temperature oxidation behaviour is inadequate. Therefore, the investigation on the high-temperature oxidation behaviour of S32654 steels is useful.Moreover, our previous work 21 mainly investigated the oxidation behaviour of S32654 steels at 900 °C, 1000 °C, and 1200 °C in air. At 900 °C, the samples exhibit excellent oxidation resistance because the MnMoO 4 layer and
“…The S31254 super austenite stainless steel (SASS) has a high content of Cr, Ni, Mo, and N, providing steel with excellent corrosion resistance. Hence, SASS has applications in diverse fields such as seawater treatment systems, chemical processing equipment, flue gas desulfurization systems, incinerators, and nuclear industries . However, due to a high Mo and Cr content in severe conditions, the brittle second phases such as sigma, chi, and laves phase easily precipitate in the S31254 stainless steel, which can have a negative influence on its performance .…”
The second phases in the S31254 super austenitic stainless steel is easily precipitated, and the solution treatment plays an important role on the microstructure and performance. In this work, the solution treatment is performed on S31254 steel at 1180, 1200, and 1220 C for 1, 2, and 4 h, respectively. Given the grain size and precipitation of second phase, the 1200 C for 4 h or 1220 C for 2 h may be suitable as the solid-solution parameters. The corrosion resistance and impact toughness of the steel after solution treatment at 1200 C are further investigated by means of microstructural analysis and electrochemical experiments. The sample after solution treatment for 4 h, where no second phase can be observed, exhibits a lower corrosion rate and a better mechanical properties, compared to that after annealed for 1 or 2 h. The electrochemical impedance spectroscopy, Mott-Schottky, and XPS results indicate that the passive films of the samples, with a significantly decreased donor and acceptor densities and increased Cr 2 O 3 and Mo-riched oxides, may be responsible for the improvement of corrosion resistance. The impact toughness results show that the samples after solution treatment for 4 h has the highest impact energy among the studied samples.
“…Molybdenum can improve the oxidation of steel up to 900°C for 10 h, but it has a catastrophic influence after 10 h and above 900°C. 6 High Mo steels are prone to segregations and the formation of intermetallic phases such as s, g and Laves phases above 900°C, which lower the oxidation resistance and make them vulnerable to cracking during hot working. [6][7][8][9] Steels with higher Mo content typically face oxidation complications above 900°C due to MoO 3 formation.…”
Section: Introductionmentioning
confidence: 99%
“…6 High Mo steels are prone to segregations and the formation of intermetallic phases such as s, g and Laves phases above 900°C, which lower the oxidation resistance and make them vulnerable to cracking during hot working. [6][7][8][9] Steels with higher Mo content typically face oxidation complications above 900°C due to MoO 3 formation. [10][11][12] Since we studied oxidation below 900°C the Mo should improve the oxidation resistance.…”
Hot-work tool steels have very good mechanical properties, especially strength, hardness and wear resistance at high temperatures. Therefore, hot-work tool steels are used for different applications, such as the high-pressure die casting of light alloys, the extrusion of polymers and forging. Since all these processes are operating at high temperatures, the main focus of this research was to investigate the high-temperature oxidation resistance of tool steels. We investigated the high-temperature oxidation at two different temperatures: 500°C and 700°C. The following tool steels were analyzed: HTCS-130, W600, RavnexHD and Dievar. Tests were made in an air atmosphere, while the heating and cooling were made in a controlled argon atmosphere. Simultaneous thermal analysis (STA 449 C Jupiter), scanning electron microscopy (SEM and EDS) and X-ray diffraction were used as the investigation methods. The results showed that during high-temperature oxidation at 500°C Dievar steel has the best oxidation resistance, followed by RavnexHD, HTCS-130 and W600. However, at 700°C the results were different, HTCS-130 had the best oxidation resistance, followed by Dievar, W600 and RavnexHD.
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